This article introduces the concept of load aggregation,which involves a comprehensive analysis of loads to acquire their external characteristics for the purpose of modeling and analyzing power systems.The online ide...This article introduces the concept of load aggregation,which involves a comprehensive analysis of loads to acquire their external characteristics for the purpose of modeling and analyzing power systems.The online identification method is a computer-involved approach for data collection,processing,and system identification,commonly used for adaptive control and prediction.This paper proposes a method for dynamically aggregating large-scale adjustable loads to support high proportions of new energy integration,aiming to study the aggregation characteristics of regional large-scale adjustable loads using online identification techniques and feature extraction methods.The experiment selected 300 central air conditioners as the research subject and analyzed their regulation characteristics,economic efficiency,and comfort.The experimental results show that as the adjustment time of the air conditioner increases from 5 minutes to 35 minutes,the stable adjustment quantity during the adjustment period decreases from 28.46 to 3.57,indicating that air conditioning loads can be controlled over a long period and have better adjustment effects in the short term.Overall,the experimental results of this paper demonstrate that analyzing the aggregation characteristics of regional large-scale adjustable loads using online identification techniques and feature extraction algorithms is effective.展开更多
Rain-on-snow(ROS)events involve rainfall on snow surfaces,and the occurrence of ROS events can exacerbate water scarcity and ecosystem vulnerability in the arid region of Northwest China(ARNC).In this study,using dail...Rain-on-snow(ROS)events involve rainfall on snow surfaces,and the occurrence of ROS events can exacerbate water scarcity and ecosystem vulnerability in the arid region of Northwest China(ARNC).In this study,using daily snow depth data and daily meteorological data from 68 meteorological stations provided by the China Meteorological Administration National Meteorological Information Centre,we investigated the spatiotemporal variability of ROS events in the ARNC from 1978 to 2015 and examined the factors affecting these events and possible changes of future ROS events in the ARNC.The results showed that ROS events in the ARNC mainly occurred from October to May of the following year and were largely distributed in the Qilian Mountains,Tianshan Mountains,Ili River Valley,Tacheng Prefecture,and Altay Prefecture,with the Ili River Valley,Tacheng City,and Altay Mountains exhibiting the most occurrences.Based on the intensity of ROS events,the areas with the highest risk of flooding resulting from ROS events in the ARNC were the Tianshan Mountains,Ili River Valley,Tacheng City,and Altay Mountains.The number and intensity of ROS events in the ARNC largely increased from 1978 to 2015,mainly influenced by air temperature and the number of rainfall days.However,due to the snowpack abundance in areas experiencing frequent ROS events in the ARNC,snowpack changes exerted slight impact on ROS events,which is a temporary phenomenon.Furthermore,elevation imposed lesser impact on ROS events in the ARNC than other factors.In the ARNC,the start time of rainfall and the end time of snowpack gradually advanced from the spring of the current year to the winter of the previous year,while the end time of rainfall and the start time of snowpack gradually delayed from autumn to winter.This may lead to more ROS events in winter in the future.These results could provide a sound basis for managing water resources and mitigating related disasters caused by ROS events in the ARNC.展开更多
Based on the hourly precipitation data at 176 observational stations over south China and the hourly ERA5reanalysis data during the 40-yr period of 1981-2020, we analyzed the universal characteristics of moisture tran...Based on the hourly precipitation data at 176 observational stations over south China and the hourly ERA5reanalysis data during the 40-yr period of 1981-2020, we analyzed the universal characteristics of moisture transport and their associated background circulations for four types of regional extreme precipitation events(REPEs) over south China. Main findings are shown as follow.(i) The wind that transported moisture for the REPEs over south China featured a notable diurnal variation, which was consistent with the variations of the precipitation.(ii) Four types of REPEs could be determined, among which the southwest type(SWT) and the southeast type(SET) accounted for ~92%and ~5.7%, respectively, ranking the first and second, respectively.(iii) Trajectory analyses showed that the air particles of the SWT-REPEs had the largest specific humidity and experienced the most intense ascending motion, and therefore their precipitation was the strongest among the four types.(iv) South China was dominated by notable moisture flux convergence for the four types of REPEs, but their moisture transport was controlled by different flow paths.(v)Composite analyses indicated that the background circulation of the four types of REPEs showed different features,particularly for the intensity, location and coverage of a western Pacific subtropical high. For the SWT-REPEs, their moisture transport was mainly driven by a lower-tropospheric strong southwesterly wind band in the low-latitude regions. Air particles for this type of REPEs mainly passed over the Indochina Peninsula and South China Sea. For the SET-REPEs, their moisture transport was mainly steered by a strong low-tropospheric southeasterly wind northeast of a transversal trough. Air particles mainly passed over the South China Sea for this type of REPEs.展开更多
Changes of extreme events due to greenhouse effects (2 × CO<SUB>2</SUB>) over East Asia, with a focus on the China region as simulated by a regional climate model (RegCM2), are investigated. The model...Changes of extreme events due to greenhouse effects (2 × CO<SUB>2</SUB>) over East Asia, with a focus on the China region as simulated by a regional climate model (RegCM2), are investigated. The model is nested to a global coupled ocean-atmosphere model (CSIRO R21L9 AOGCM). Analysis of the control run of the regional model indicates that it can reproduce well the extreme events in China. Statistically significant changes of the events are analyzed. Results show that both daily maximum and daily minimum temperature increase in 2 × CO<SUB>2</SUB> conditions, while the diurnal temperature range decreases. The number of hot spell days increases while the number of cold spell days decreases. The number of rainy days and heavy rain days increases over some sub-regions of China. The 2 × CO<SUB>2</SUB> conditions also cause some changes in the tropical storms affecting China.展开更多
This study examined regional prolonged low temperature (PLT) events in China from the observational station data for the period 1960–2008 using the new criteria. The new definition of a site PLT event is that the d...This study examined regional prolonged low temperature (PLT) events in China from the observational station data for the period 1960–2008 using the new criteria. The new definition of a site PLT event is that the daily minimum temperature does not exceed the 10th percentile threshold of the local daily minimum temperature climatology for at least 5 days at a station. The regional PLT event is defined as at least five adjacent stations exhibiting site PLT simultaneously for 5 d. Under the new definition, 552 regional PLT events were identified, and three indices: duration, extent, and intensity, as well as a comprehensive index (CI) were used to quantify the event severity. In addition, geographical patterns and temporal variations of regional PLT events were investigated using three event categories: strong, moderate, and weak. Spatially, strong events were mainly located in the north of Xinjiang and along the Yangtze River to the south of the Yangtze River; moderate events occurred in Xinjiang and south of the Yangtze River; and weak events occurred south of the Yellow River. The variation for the annual frequency of regional PLT events in China in the last 49 years showed a significant decreasing trend with a rate of-1.99 times per decade, and the significant transition decade was the 1980s.展开更多
The spatiotemporal variations of the site and regional droughts in China during 1960–2009 were analyzed by applying a daily composite-drought index (CDI) to 722 stations in China's Mainland. Droughts frequently...The spatiotemporal variations of the site and regional droughts in China during 1960–2009 were analyzed by applying a daily composite-drought index (CDI) to 722 stations in China's Mainland. Droughts frequently happened in a zone extended from Southwest China to the Yellow River, North China, and the southwestern part of Northeast China, with two centers of high frequency in North China and Southwest China. In Southwest and South China, droughts tend to happen during the winter. In North China and along the Yellow River, droughts mainly occur during the winter and during May–June. During the past 50 years, the geographical distribution of site drought events showed high frequencies (0.9–1.3 times per year) in the upper Yellow River basin and North China, comparing with moderate frequencies (0.6–0.9 times per year) in Southwest China and the southwestern part of Northeast China and with lower frequencies over the middle and lower Yangtze River basin. And the frequencies increased over China's Mainland except for the upper reaches of the Yangtze River. A regional drought (RD) event is a widespread and persistent event that covers at least five adjacent sites and lasts for at least 10 days. There were 252 RD events in the past 50 years—five times per year. Most RD events lasted for 100 days and covered 100 stations, but the longest and largest RD event lasted for 307 days from 6 September 1998 to 9 July 1999 and covered 327 stations from North to Southwest China.展开更多
A new technique for identifying regional climate events, the Objective Identification Technique for Regional Extreme Events(OITREE), was applied to investigate the characteristics of regional heavy rainfall events i...A new technique for identifying regional climate events, the Objective Identification Technique for Regional Extreme Events(OITREE), was applied to investigate the characteristics of regional heavy rainfall events in China during the period1961–2012. In total, 373 regional heavy rainfall events(RHREs) were identified during the past 52 years. The East Asian summer monsoon(EASM) had an important influence on the annual variations of China's RHRE activities, with a significant relationship between the intensity of the RHREs and the intensity of the Mei-yu. Although the increase in the frequency of those RHREs was not significant, China experienced more severe and extreme regional rainfall events in the 1990 s. The middle and lower reaches of the Yangtze River and the northern part of South China were the regions in the country most susceptible to extreme precipitation events. Some stations showed significant increasing trends in the southern part of the middle and lower reaches of the Yangtze River and the northern part of South China, while parts of North China, regions between Guangxi and Guangdong, and northern Sichuan showed decreasing trends in the accumulated intensity of RHREs.The spatial distribution of the linear trends of events' accumulated intensity displayed a similar so-called "southern flooding and northern drought" pattern over eastern China in recent decades.展开更多
The regional characteristics of dust events in China has b een mainly studied by using the data of dust storm, wind-blown sand and floating dust from 338 observation stations through China from 1954 to 2000. The resul...The regional characteristics of dust events in China has b een mainly studied by using the data of dust storm, wind-blown sand and floating dust from 338 observation stations through China from 1954 to 2000. The results of this study are as follows: (1) In China, there are two h igh frequent areas of dust events, one is located in the area of Min feng and Hotan in the South Xinjiang Basin, the other is situated in the area of Minqin and Jilantai in the Hexi Region. Furthermore, th e spatial distributions of the various types of dust events are diffe rent. The dust storms mainly occur in the arid and semiarid areas co vering the deserts and the areas undergoing desertification in northern China. Wind-blown sand and floating-dust not only occur in the areas where dust storms occur, but also extend to the neighboring areas. The range of wind-blown sand extends northeastward and southeastward, b ut floating-dust mainly extends southeastward to the low-latitude region such as the East China Plain and the area of the middle and lower reaches o f the Yangtze River. Compared with wind-blown sand, the floating-dust seldo m occurs in the high latitude areas such as North Xinjiang and North east China. (2) The affected areas of dust storms can be divided into seven sub-regions, that is, North Xinjiang Region, South Xinjiang Reg ion, Hexi Region, Qaidam Basin Region, Hetao Region, Northeastern China Region and Qinghai-Xizang (Tibet) Region. The area of the most freque nt occurrence of dust storms and floating-dust is in South Xinjiang Region, and of wind-blown sand in the Hexi Region. In general, the frequency of d ust events in all the seven regions shows a decreasing tendency from 19 54 to 2000, but there are certain differences between various dust events in d ifferent regions. The maximum interannual change and variance of dust events during this time happened in South Xinjiang Region and Hexi Re gion. The dust events generally occur most frequently in April in most pa rts of China. The spring occurred days of dust events occupied 60-70% of the whole year in Hetao Region and Northeastern China Region. However, in South Xinjiang Region and North Xinjiang Region, which was less affec ted by monsoon climate, dust events may occur at any time of the year, le ss than 50% of the events in this region occur during spring. In the remaining three regions 50-60% of the dust events occur in spring of a year.展开更多
An extreme (weather and climate) event does not only mean that an extreme occurs at a location, but more generally it can impact a certainarea and last a certain period of time, which is defined as a regional extrem...An extreme (weather and climate) event does not only mean that an extreme occurs at a location, but more generally it can impact a certainarea and last a certain period of time, which is defined as a regional extreme event (REE) with a certain impacted area and duration. The conceptof REE has been defined to allow mainly objective assessment of the events without a pre-determined boundary and duration. This paper reviewsthe studies on REEs published during the past 20 years, especially recent years. Mainly in view of methodology, these studies can be divided intothree types studies focusing on spatial simultaneity, studies focusing on temporal persistence, and studies identifying REEs. The methodsidentifying REEs include two kinds, e.g., type-I methods stressing REE's temporal persistence within a relatively certain area and type-IImethods focusing on catching a complete REE. Identification methods proposed in this paper could provide valuable information for variouspurposes, such as real-time monitoring, estimating long-term changes, mechanism diagnosis, forecasting study and even attribution analysis.Research on REEs is important for objectively defining extreme weather and climate events, which depends on the spatial and temporal scales ofinterest. Such an objective definition will support ongoing climate monitoring and improve the assessment of how regional extreme events havechanged over time.展开更多
In this paper, the changes in temperature and precipitation extremes over the next 20-30 years (2021-2050) in relative to the present day (1986-2005) under the Intergovernmental Panel on Climate Change (IPCC) Special ...In this paper, the changes in temperature and precipitation extremes over the next 20-30 years (2021-2050) in relative to the present day (1986-2005) under the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A1B scenario are analyzed based on a high-resolution climate change simulation performed by a regional climate model (the Abdus Salam International Center for Theoretical Physics (ICTP) RegCM3). The extreme indices of summer days (SU), frost days (FD), and growing season length (GSL) for temperature and simple daily intensity index (SDII), number of days with precipitation ≥10 mm d-1 (R10), and consecutive dry days (CDD) for precipitation are used as the indicators of the extremes. The results show that the indices simulated by RegCM3 in the present day show good agreement with the observed. A general increase in SU, a decrease in FD, and an increase in GSL are found to occur in the next 20-30 years over China. A general increase in SDII, an increase in R10 over western China, and a decrease in R10 in north, northeast, and central China are simulated by the model. Changes in CDD are characterized by a decrease in the north and an increase in the south and the Tibetan Plateau.展开更多
The middle-lower Yangtze area underwent a series of complex tectonic evolution, such as Hercynian extensional rifting, Indosinian foreland basining, and Yanshanian transpression-transtension, resulting in a large dist...The middle-lower Yangtze area underwent a series of complex tectonic evolution, such as Hercynian extensional rifting, Indosinian foreland basining, and Yanshanian transpression-transtension, resulting in a large distinctive Cu-Fe-Au metallogenic belt. In the tectonic evolution, large-scale migration and convergence of fluids toward foreland basins induced during the collisional orogeny of the Yangtze and North China continental blocks were of vital importance for the formation of the metallogenic belt. Through geological surveys of the middle-lower Yangtze area, three lines of evidence of large-scale fluid migration are proposed: (1) The extensive dolomitic and silicic alteration penetrating Cambrian-Triassic strata generally occurs in a region sandwiched between the metallogenic belt along the Yangtze River and the Dabie orogenic belt, and in the alteration domain alternately strong and weak alteration zones extend in a NW direction and are controlled by the fault system of the Dabie orogenic belt; it might record the locus of the activities of long-distance migrating fluids. (2) The textures and structures of very thick Middle-Lower Triassic anhydrock sequences in restricted basins along the river reveal the important contribution of the convergence of regional hot brine in restricted basins and the chemical deposition or their formation. (3) Early-Middle Triassic syndepositional iron carbonate sequences and Fe-Cu-Pb-Zn massive sulfide deposits alternate with anhydrock sequences or are separated from the latter, but all of them occur in the same stratigraphic horizon and are intimately associated with each other, being the product of syndeposition of high-salinity hot brine. According to the geological surveys, combined with previous data, the authors propose a conceptual model of fluid migration-convergence and mineralization during the Dabie collisional orogeny.展开更多
In earlier studies,objective techniques have been used to determine the contribution of tropical cyclones to precipitation(TCP)in a region,where the Tropical cyclone Precipitation Event(TPE)and the Regional Heavy Prec...In earlier studies,objective techniques have been used to determine the contribution of tropical cyclones to precipitation(TCP)in a region,where the Tropical cyclone Precipitation Event(TPE)and the Regional Heavy Precipitation Events(RHPEs)are defined and investigated.In this study,TPE and RHPEs are combined to determine the Typhoon Regional Heavy Precipitation Events(TRHPEs),which is employed to evaluate the contribution of tropical cyclones to regional extreme precipitation events.Based on the Objective Identification Technique for Regional Extreme Events(OITREE)and the Objective Synoptic Analysis Technique(OSAT)to define TPE,temporal and spatial overlap indices are developed to identify the combined events as TRHPE.With daily precipitation data and TC best-track data over the western North Pacific from 1960 to 2018,86 TRHPEs have been identified.TRHPEs contribute as much as 20%of the RHPEs,but100%of events with extreme individual precipitation intensities.The major TRHPEs continued for approximately a week after tropical cyclone landfall,indicating a role of post landfall precipitation.The frequency and extreme intensity of TRHPEs display increasing trends,consistent with an observed positive trend in the mean intensity of TPEs as measured by the number of daily station precipitation observations exceeding 100 mm and 250 mm.More frequent landfalling Southeast and South China TCs induced more serious impacts in coastal areas in the Southeast and the South during 1990-2018 than1960-89.The roles of cyclone translation speed and"shifts"in cyclone tracks are examined as possible explanations for the temporal trends.展开更多
An objective identification technique is used to detect regional extreme low temperature events (RELTE) in China during 1960-2009. Their spatial-temporal characteristics are analyzed. The results indicate that the l...An objective identification technique is used to detect regional extreme low temperature events (RELTE) in China during 1960-2009. Their spatial-temporal characteristics are analyzed. The results indicate that the lowest temperatures of RELTE, together with the frequency distribution of the geometric latitude center, exhibit a double-peak feature. The RELTE frequently happen near the geometric area of 30°N and 42°N before the mid-1980s, but shifted afterwards to 30°N. During 1960-2009, the frequency~ intensity, and the maximum impacted area of RELTE show overall decreasing trends. Due to the contribution of RELTE, with long duratioh and large spatial range, which account for 10% of the total RELTE, there is a significant turning point in the late 1980s. A change to a much more steady state after the late 1990s is identified. In addition, the integrated indices of RELTE are classified and analyzed.展开更多
Large-scale atmospheric information plays an important role in the regional model for the forecasts of weather such as tropical cyclone(TC).However,it is difficult to be fully represented in regional models due to dom...Large-scale atmospheric information plays an important role in the regional model for the forecasts of weather such as tropical cyclone(TC).However,it is difficult to be fully represented in regional models due to domain size and a lack of observation data,particularly at sea used in regional data assimilation.Blending analysis has been developed and implemented in regional models to reintroduce large-scale information from global model to regional analysis.Research of the impact of this large-scale blending scheme for the Global/Regional Assimilation and PrEdiction System(CMA-MESO)regional model on TC forecasting is limited and this study attempts to further progress by examining the adaptivity of the blending scheme using the two-dimensional Discrete Cosine Transform(2D-DCT)filter on the model forecast of Typhoon Haima over Shenzhen,China in 2016 and considering various cut-off wavelengths.Results showed that the error of the 24-hour typhoon track forecast can be reduced to less than 25 km by applying the scale-dependent blending scheme,indicating that the blending analysis is effectively able to minimise the large-scale bias for the initial fields.The improvement of the wind forecast is more evident for u-wind component according to the reduced root mean square errors(RMSEs)by comparing the experiments with and without blending analysis.Furthermore,the higher equitable threat score(ETS)provided implications that the precipitation prediction skills were increased in the 24h forecast by improving the representation of the large-scale feature in the CMA-MESO analysis.Furthermore,significant differences of the track error forecast were found by applying the blending analysis with different cut-off wavelengths from 400 km to 1200 km and the track error can be reduced less than by 10 km with 400 km cut-off wavelength in the first 6h forecast.It highlighted that the blending scheme with dynamic cut-off wavelengths adapted to the development of different TC systems is necessary in order to optimally introduce and ingest the large-scale information from global model to the regional model for improving the TC forecast.In this paper,the methods and data applied in this study will be firstly introduced,before discussion of the results regarding the performance of the blending analysis and its impacts on the wind and precipitation forecast correspondingly,followed by the discussion of the effects of different blending scheme on TC forecasts and the conclusion section.展开更多
Climate sequences can be applied to defining sensitive climate zones, and then the mining of spatio-temporal teleconnection patterns is useful for learning from the past and preparing for the future. However, scale-de...Climate sequences can be applied to defining sensitive climate zones, and then the mining of spatio-temporal teleconnection patterns is useful for learning from the past and preparing for the future. However, scale-dependency in this kind of pattern is still not well handled by existing work. Therefore, in this study, the multi-scale regionalization is embedded into the spatio-temporal teleconnection pattern mining between anomalous sea and land climatic events. A modified scale-space clustering algorithm is first developed to group climate sequences into multi-scale climate zones. Then, scale variance analysis method is employed to identify climate zones at characteristic scales, indicating the main characteristics of geographical phenomena. Finally, by using the climate zones identified at characteristic scales, a time association rule mining algorithm based on sliding time windows is employed to discover spatio-temporal teleconnection patterns. Experiments on sea surface temperature, sea level pressure, land precipitation and land temperature datasets show that many patterns obtained by the multi-scale approach are coincident with prior knowledge, indicating that this method is effective and reasonable. In addition, some unknown teleconnection patterns discovered from the multi-scale approach can be further used to guide the prediction of land climate.展开更多
The city is facing the unprecedented pressure with the rapid development and the moving population. Some hidden knowledge can be found to service the social with human trajectory data. In this paper, we define a state...The city is facing the unprecedented pressure with the rapid development and the moving population. Some hidden knowledge can be found to service the social with human trajectory data. In this paper, we define a state-ofthe-art concept on fluctuant locations with PCA method and discover the same attribute of fluctuant locations called event with topic model. In the time slice, locations with the same attribute are called event region. Event regions aim to understand the relationship between spatial-temporal locations in the city and to early-warning analyze for the city planning, construction, intelligent navigation, route planning and location based service. We use GeoLife public data to experiment and verify this paper.展开更多
In this study, regional persistent haze events(RPHEs) in the Beijing–Tianjin–Hebei(BTH) region were identified based on the Objective Identification Technique for Regional Extreme Events for the period 1980–201...In this study, regional persistent haze events(RPHEs) in the Beijing–Tianjin–Hebei(BTH) region were identified based on the Objective Identification Technique for Regional Extreme Events for the period 1980–2013. The formation mechanisms of the severe RPHEs were investigated with focus on the atmospheric circulation and dynamic mechanisms. Results indicated that:(1) 49 RPHEs occurred during the past 34 years.(2) The severe RPHEs could be categorized into two types according to the large-scale circulation, i.e. the zonal westerly airflow(ZWA) type and the high-pressure ridge(HPR) type. When the ZWA-type RPHEs occurred, the BTH region was controlled by near zonal westerly airflow in the mid–upper troposphere.Southwesterly winds prevailed in the lower troposphere, and near-surface wind speeds were only 1–2 ms^-1. Warm and humid air originating from the northwestern Pacific was transported into the region, where the relative humidity was 70% to 80%, creating favorable moisture conditions. When the HPR-type RPHEs appeared, northwesterly airflow in the mid–upper troposphere controlled the region. Westerly winds prevailed in the lower troposphere and the moisture conditions were relatively weak.(3) Descending motion in the mid-lower troposphere caused by the above two circulation types provided a crucial dynamic mechanism for the formation of the two types of RPHEs. The descending motion contributed to a reduction in the height of the planetary boundary layer(PBL), which generated an inversion in the lower troposphere. This inversion trapped the abundant pollution and moisture in the lower PBL, leading to high concentrations of pollutants.展开更多
Based on a new multi-source dataset (GLDP-V1.0) recently developed in China Meteorological Administration, we employed precipitation indices including percentile-based indices of light (below the 50th percentile), mod...Based on a new multi-source dataset (GLDP-V1.0) recently developed in China Meteorological Administration, we employed precipitation indices including percentile-based indices of light (below the 50th percentile), moderate (between the 50th and 90th percentile), and intense (above the 90th percentile) precipitation, maximum 1-day, 3-day, and 5-day precipitation amounts (RX1DAY, RX3DAY, and RX5DAY, respectively), and consecutive wet and dry days (CWDs and CDDs) to analyze variations in extreme precipitation events in the Hindu Kush Himalayan (HKH) during 1961e2012. The main results are presented as follows. Firstly, there was a significant increase in the amount of light and moderate precipitation and number of associated days over various parts of India and northern Tibetan Plateau during 1961e2012; but the intensity of light precipitation decreased significantly in the Hindu Kush and central India, and the regional average intensity also decreased. Secondly, the amount and frequency of intense precipitation mostly increased significantly on the Tibetan Plateau, but there was a heterogeneous change over the remainder of the HKH, and regional average annual intense precipitation amount and frequency significantly increased over the HKH during 1961e2012. Thirdly, regional average RX1DAY, RX3DAY, and RX5DAYall showed significant upward trends during 1961e2012, and there was a significant increased tendency of consecutive wet-days in most parts of the study region; however, trends of consecutive dry-days were mostly opposite to those of consecutive wet-days, with regional averaged consecutive dry-days showing no noticeable trend.展开更多
Based on an objective identification technique for regional low temperature event(OITRLTE), the daily minimum temperature in China has been detected from 1960 to 2013. During this period, there were 60 regional extr...Based on an objective identification technique for regional low temperature event(OITRLTE), the daily minimum temperature in China has been detected from 1960 to 2013. During this period, there were 60 regional extreme low temperature events(ERLTEs), which are included in the 690 regional low temperature events(RLTEs). The 60 ERLTEs are analyzed in this paper. The results show that in the last 50 years, the intensity of the ERLTEs has become weak; the number of lasted days has decreased; and, the affected area has become small. However, that situation has changed in this century.In terms of spatial distribution, the high intensity regions are mainly in Northern China while the high frequency regions concentrate in Central and Eastern China. According to the affected area of each event, the 60 ERLTEs are classified into six types. The atmospheric circulation background fields which correspond to these types are also analyzed. The results show that, influenced by stronger blocking highs of Ural and Lake Baikal, as well as stronger southward polar vortex and East Asia major trough at 500-h Pa geopotential height, cold air from high latitudes is guided to move southward and abnormal northerly winds at 850 h Pa makes the cold air blow into China along diverse paths, thereby forming different types of regional extreme low temperatures in winter.展开更多
基金supported by the State Grid Science&Technology Project(5100-202114296A-0-0-00).
文摘This article introduces the concept of load aggregation,which involves a comprehensive analysis of loads to acquire their external characteristics for the purpose of modeling and analyzing power systems.The online identification method is a computer-involved approach for data collection,processing,and system identification,commonly used for adaptive control and prediction.This paper proposes a method for dynamically aggregating large-scale adjustable loads to support high proportions of new energy integration,aiming to study the aggregation characteristics of regional large-scale adjustable loads using online identification techniques and feature extraction methods.The experiment selected 300 central air conditioners as the research subject and analyzed their regulation characteristics,economic efficiency,and comfort.The experimental results show that as the adjustment time of the air conditioner increases from 5 minutes to 35 minutes,the stable adjustment quantity during the adjustment period decreases from 28.46 to 3.57,indicating that air conditioning loads can be controlled over a long period and have better adjustment effects in the short term.Overall,the experimental results of this paper demonstrate that analyzing the aggregation characteristics of regional large-scale adjustable loads using online identification techniques and feature extraction algorithms is effective.
基金funded by the National Natural Science Foundation of China(42171145,42171147)the Gansu Provincial Science and Technology Program(22ZD6FA005)the Key Talent Program of Gansu Province.
文摘Rain-on-snow(ROS)events involve rainfall on snow surfaces,and the occurrence of ROS events can exacerbate water scarcity and ecosystem vulnerability in the arid region of Northwest China(ARNC).In this study,using daily snow depth data and daily meteorological data from 68 meteorological stations provided by the China Meteorological Administration National Meteorological Information Centre,we investigated the spatiotemporal variability of ROS events in the ARNC from 1978 to 2015 and examined the factors affecting these events and possible changes of future ROS events in the ARNC.The results showed that ROS events in the ARNC mainly occurred from October to May of the following year and were largely distributed in the Qilian Mountains,Tianshan Mountains,Ili River Valley,Tacheng Prefecture,and Altay Prefecture,with the Ili River Valley,Tacheng City,and Altay Mountains exhibiting the most occurrences.Based on the intensity of ROS events,the areas with the highest risk of flooding resulting from ROS events in the ARNC were the Tianshan Mountains,Ili River Valley,Tacheng City,and Altay Mountains.The number and intensity of ROS events in the ARNC largely increased from 1978 to 2015,mainly influenced by air temperature and the number of rainfall days.However,due to the snowpack abundance in areas experiencing frequent ROS events in the ARNC,snowpack changes exerted slight impact on ROS events,which is a temporary phenomenon.Furthermore,elevation imposed lesser impact on ROS events in the ARNC than other factors.In the ARNC,the start time of rainfall and the end time of snowpack gradually advanced from the spring of the current year to the winter of the previous year,while the end time of rainfall and the start time of snowpack gradually delayed from autumn to winter.This may lead to more ROS events in winter in the future.These results could provide a sound basis for managing water resources and mitigating related disasters caused by ROS events in the ARNC.
基金National Key Research and Development Program of China(2019YFC1510400)National Natural Science Foundation of China(42075002)。
文摘Based on the hourly precipitation data at 176 observational stations over south China and the hourly ERA5reanalysis data during the 40-yr period of 1981-2020, we analyzed the universal characteristics of moisture transport and their associated background circulations for four types of regional extreme precipitation events(REPEs) over south China. Main findings are shown as follow.(i) The wind that transported moisture for the REPEs over south China featured a notable diurnal variation, which was consistent with the variations of the precipitation.(ii) Four types of REPEs could be determined, among which the southwest type(SWT) and the southeast type(SET) accounted for ~92%and ~5.7%, respectively, ranking the first and second, respectively.(iii) Trajectory analyses showed that the air particles of the SWT-REPEs had the largest specific humidity and experienced the most intense ascending motion, and therefore their precipitation was the strongest among the four types.(iv) South China was dominated by notable moisture flux convergence for the four types of REPEs, but their moisture transport was controlled by different flow paths.(v)Composite analyses indicated that the background circulation of the four types of REPEs showed different features,particularly for the intensity, location and coverage of a western Pacific subtropical high. For the SWT-REPEs, their moisture transport was mainly driven by a lower-tropospheric strong southwesterly wind band in the low-latitude regions. Air particles for this type of REPEs mainly passed over the Indochina Peninsula and South China Sea. For the SET-REPEs, their moisture transport was mainly steered by a strong low-tropospheric southeasterly wind northeast of a transversal trough. Air particles mainly passed over the South China Sea for this type of REPEs.
基金Thanks are due to CSIRO in Australia and the Institute of Botany,Chinese Academy of Sciences,National Climate Center of China , for providing the data sets of the GCM and the vegetation coverThis research was supported by the National Natural Science Foundation of China under Grant No, 40125014National Key Programme for Developing Basic Sciences (G1998040900-part 1).
文摘Changes of extreme events due to greenhouse effects (2 × CO<SUB>2</SUB>) over East Asia, with a focus on the China region as simulated by a regional climate model (RegCM2), are investigated. The model is nested to a global coupled ocean-atmosphere model (CSIRO R21L9 AOGCM). Analysis of the control run of the regional model indicates that it can reproduce well the extreme events in China. Statistically significant changes of the events are analyzed. Results show that both daily maximum and daily minimum temperature increase in 2 × CO<SUB>2</SUB> conditions, while the diurnal temperature range decreases. The number of hot spell days increases while the number of cold spell days decreases. The number of rainy days and heavy rain days increases over some sub-regions of China. The 2 × CO<SUB>2</SUB> conditions also cause some changes in the tropical storms affecting China.
基金supported jointly by the National Natural Science Foundation of China (GrantNo. 40975039)the Key Technologies R&D Program(Grant No. 2009BAC51B00)
文摘This study examined regional prolonged low temperature (PLT) events in China from the observational station data for the period 1960–2008 using the new criteria. The new definition of a site PLT event is that the daily minimum temperature does not exceed the 10th percentile threshold of the local daily minimum temperature climatology for at least 5 days at a station. The regional PLT event is defined as at least five adjacent stations exhibiting site PLT simultaneously for 5 d. Under the new definition, 552 regional PLT events were identified, and three indices: duration, extent, and intensity, as well as a comprehensive index (CI) were used to quantify the event severity. In addition, geographical patterns and temporal variations of regional PLT events were investigated using three event categories: strong, moderate, and weak. Spatially, strong events were mainly located in the north of Xinjiang and along the Yangtze River to the south of the Yangtze River; moderate events occurred in Xinjiang and south of the Yangtze River; and weak events occurred south of the Yellow River. The variation for the annual frequency of regional PLT events in China in the last 49 years showed a significant decreasing trend with a rate of-1.99 times per decade, and the significant transition decade was the 1980s.
基金supported jointly bythe National Natural Science Foundation of China (GrantNo. 40975039)the Key Technologies R&D Program(Grant No. 2009BAC51B04)+1 种基金the Chinese COPES Project (Grant No. GYHY201006018)The CDI data was provided by the Key Technologies R&D Program (GrantNo. 2007BAC29B06).
文摘The spatiotemporal variations of the site and regional droughts in China during 1960–2009 were analyzed by applying a daily composite-drought index (CDI) to 722 stations in China's Mainland. Droughts frequently happened in a zone extended from Southwest China to the Yellow River, North China, and the southwestern part of Northeast China, with two centers of high frequency in North China and Southwest China. In Southwest and South China, droughts tend to happen during the winter. In North China and along the Yellow River, droughts mainly occur during the winter and during May–June. During the past 50 years, the geographical distribution of site drought events showed high frequencies (0.9–1.3 times per year) in the upper Yellow River basin and North China, comparing with moderate frequencies (0.6–0.9 times per year) in Southwest China and the southwestern part of Northeast China and with lower frequencies over the middle and lower Yangtze River basin. And the frequencies increased over China's Mainland except for the upper reaches of the Yangtze River. A regional drought (RD) event is a widespread and persistent event that covers at least five adjacent sites and lasts for at least 10 days. There were 252 RD events in the past 50 years—five times per year. Most RD events lasted for 100 days and covered 100 stations, but the longest and largest RD event lasted for 307 days from 6 September 1998 to 9 July 1999 and covered 327 stations from North to Southwest China.
基金supported jointly by the National Natural Science Foundation of China (Grant No. 41175075)the Major State Basic Research Development Program of China (973 program) (Grant No. 2010CB950501)
文摘A new technique for identifying regional climate events, the Objective Identification Technique for Regional Extreme Events(OITREE), was applied to investigate the characteristics of regional heavy rainfall events in China during the period1961–2012. In total, 373 regional heavy rainfall events(RHREs) were identified during the past 52 years. The East Asian summer monsoon(EASM) had an important influence on the annual variations of China's RHRE activities, with a significant relationship between the intensity of the RHREs and the intensity of the Mei-yu. Although the increase in the frequency of those RHREs was not significant, China experienced more severe and extreme regional rainfall events in the 1990 s. The middle and lower reaches of the Yangtze River and the northern part of South China were the regions in the country most susceptible to extreme precipitation events. Some stations showed significant increasing trends in the southern part of the middle and lower reaches of the Yangtze River and the northern part of South China, while parts of North China, regions between Guangxi and Guangdong, and northern Sichuan showed decreasing trends in the accumulated intensity of RHREs.The spatial distribution of the linear trends of events' accumulated intensity displayed a similar so-called "southern flooding and northern drought" pattern over eastern China in recent decades.
基金National Key Project for Basic Research, No.G2000048703 National Natural Science Foundation of China, No.39990490 Key project of the Chinese Academy of Sciences, No.KZCX1-Y-05
文摘The regional characteristics of dust events in China has b een mainly studied by using the data of dust storm, wind-blown sand and floating dust from 338 observation stations through China from 1954 to 2000. The results of this study are as follows: (1) In China, there are two h igh frequent areas of dust events, one is located in the area of Min feng and Hotan in the South Xinjiang Basin, the other is situated in the area of Minqin and Jilantai in the Hexi Region. Furthermore, th e spatial distributions of the various types of dust events are diffe rent. The dust storms mainly occur in the arid and semiarid areas co vering the deserts and the areas undergoing desertification in northern China. Wind-blown sand and floating-dust not only occur in the areas where dust storms occur, but also extend to the neighboring areas. The range of wind-blown sand extends northeastward and southeastward, b ut floating-dust mainly extends southeastward to the low-latitude region such as the East China Plain and the area of the middle and lower reaches o f the Yangtze River. Compared with wind-blown sand, the floating-dust seldo m occurs in the high latitude areas such as North Xinjiang and North east China. (2) The affected areas of dust storms can be divided into seven sub-regions, that is, North Xinjiang Region, South Xinjiang Reg ion, Hexi Region, Qaidam Basin Region, Hetao Region, Northeastern China Region and Qinghai-Xizang (Tibet) Region. The area of the most freque nt occurrence of dust storms and floating-dust is in South Xinjiang Region, and of wind-blown sand in the Hexi Region. In general, the frequency of d ust events in all the seven regions shows a decreasing tendency from 19 54 to 2000, but there are certain differences between various dust events in d ifferent regions. The maximum interannual change and variance of dust events during this time happened in South Xinjiang Region and Hexi Re gion. The dust events generally occur most frequently in April in most pa rts of China. The spring occurred days of dust events occupied 60-70% of the whole year in Hetao Region and Northeastern China Region. However, in South Xinjiang Region and North Xinjiang Region, which was less affec ted by monsoon climate, dust events may occur at any time of the year, le ss than 50% of the events in this region occur during spring. In the remaining three regions 50-60% of the dust events occur in spring of a year.
文摘An extreme (weather and climate) event does not only mean that an extreme occurs at a location, but more generally it can impact a certainarea and last a certain period of time, which is defined as a regional extreme event (REE) with a certain impacted area and duration. The conceptof REE has been defined to allow mainly objective assessment of the events without a pre-determined boundary and duration. This paper reviewsthe studies on REEs published during the past 20 years, especially recent years. Mainly in view of methodology, these studies can be divided intothree types studies focusing on spatial simultaneity, studies focusing on temporal persistence, and studies identifying REEs. The methodsidentifying REEs include two kinds, e.g., type-I methods stressing REE's temporal persistence within a relatively certain area and type-IImethods focusing on catching a complete REE. Identification methods proposed in this paper could provide valuable information for variouspurposes, such as real-time monitoring, estimating long-term changes, mechanism diagnosis, forecasting study and even attribution analysis.Research on REEs is important for objectively defining extreme weather and climate events, which depends on the spatial and temporal scales ofinterest. Such an objective definition will support ongoing climate monitoring and improve the assessment of how regional extreme events havechanged over time.
基金supported by the National Basic Research Program of China(Grant No.2009CB421407)the China-UK-Swiss Adapting to Climate Change in China Project (ACCC)-Climate Science
文摘In this paper, the changes in temperature and precipitation extremes over the next 20-30 years (2021-2050) in relative to the present day (1986-2005) under the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) A1B scenario are analyzed based on a high-resolution climate change simulation performed by a regional climate model (the Abdus Salam International Center for Theoretical Physics (ICTP) RegCM3). The extreme indices of summer days (SU), frost days (FD), and growing season length (GSL) for temperature and simple daily intensity index (SDII), number of days with precipitation ≥10 mm d-1 (R10), and consecutive dry days (CDD) for precipitation are used as the indicators of the extremes. The results show that the indices simulated by RegCM3 in the present day show good agreement with the observed. A general increase in SU, a decrease in FD, and an increase in GSL are found to occur in the next 20-30 years over China. A general increase in SDII, an increase in R10 over western China, and a decrease in R10 in north, northeast, and central China are simulated by the model. Changes in CDD are characterized by a decrease in the north and an increase in the south and the Tibetan Plateau.
文摘The middle-lower Yangtze area underwent a series of complex tectonic evolution, such as Hercynian extensional rifting, Indosinian foreland basining, and Yanshanian transpression-transtension, resulting in a large distinctive Cu-Fe-Au metallogenic belt. In the tectonic evolution, large-scale migration and convergence of fluids toward foreland basins induced during the collisional orogeny of the Yangtze and North China continental blocks were of vital importance for the formation of the metallogenic belt. Through geological surveys of the middle-lower Yangtze area, three lines of evidence of large-scale fluid migration are proposed: (1) The extensive dolomitic and silicic alteration penetrating Cambrian-Triassic strata generally occurs in a region sandwiched between the metallogenic belt along the Yangtze River and the Dabie orogenic belt, and in the alteration domain alternately strong and weak alteration zones extend in a NW direction and are controlled by the fault system of the Dabie orogenic belt; it might record the locus of the activities of long-distance migrating fluids. (2) The textures and structures of very thick Middle-Lower Triassic anhydrock sequences in restricted basins along the river reveal the important contribution of the convergence of regional hot brine in restricted basins and the chemical deposition or their formation. (3) Early-Middle Triassic syndepositional iron carbonate sequences and Fe-Cu-Pb-Zn massive sulfide deposits alternate with anhydrock sequences or are separated from the latter, but all of them occur in the same stratigraphic horizon and are intimately associated with each other, being the product of syndeposition of high-salinity hot brine. According to the geological surveys, combined with previous data, the authors propose a conceptual model of fluid migration-convergence and mineralization during the Dabie collisional orogeny.
基金supported by the National Key R&D Program of China(Grant No.2018YFC1507703)the National Natural Science Foundation of China(Grant No.41675042)the Jiangsu Collaborative Innovation Center for Climate Change。
文摘In earlier studies,objective techniques have been used to determine the contribution of tropical cyclones to precipitation(TCP)in a region,where the Tropical cyclone Precipitation Event(TPE)and the Regional Heavy Precipitation Events(RHPEs)are defined and investigated.In this study,TPE and RHPEs are combined to determine the Typhoon Regional Heavy Precipitation Events(TRHPEs),which is employed to evaluate the contribution of tropical cyclones to regional extreme precipitation events.Based on the Objective Identification Technique for Regional Extreme Events(OITREE)and the Objective Synoptic Analysis Technique(OSAT)to define TPE,temporal and spatial overlap indices are developed to identify the combined events as TRHPE.With daily precipitation data and TC best-track data over the western North Pacific from 1960 to 2018,86 TRHPEs have been identified.TRHPEs contribute as much as 20%of the RHPEs,but100%of events with extreme individual precipitation intensities.The major TRHPEs continued for approximately a week after tropical cyclone landfall,indicating a role of post landfall precipitation.The frequency and extreme intensity of TRHPEs display increasing trends,consistent with an observed positive trend in the mean intensity of TPEs as measured by the number of daily station precipitation observations exceeding 100 mm and 250 mm.More frequent landfalling Southeast and South China TCs induced more serious impacts in coastal areas in the Southeast and the South during 1990-2018 than1960-89.The roles of cyclone translation speed and"shifts"in cyclone tracks are examined as possible explanations for the temporal trends.
基金supported by the Special Scientific Research Projects for Public Interest(No.GYHY201006021 and GYHY201106016)the National Natural Science Foundation of China(No.41205040 and 40930952)
文摘An objective identification technique is used to detect regional extreme low temperature events (RELTE) in China during 1960-2009. Their spatial-temporal characteristics are analyzed. The results indicate that the lowest temperatures of RELTE, together with the frequency distribution of the geometric latitude center, exhibit a double-peak feature. The RELTE frequently happen near the geometric area of 30°N and 42°N before the mid-1980s, but shifted afterwards to 30°N. During 1960-2009, the frequency~ intensity, and the maximum impacted area of RELTE show overall decreasing trends. Due to the contribution of RELTE, with long duratioh and large spatial range, which account for 10% of the total RELTE, there is a significant turning point in the late 1980s. A change to a much more steady state after the late 1990s is identified. In addition, the integrated indices of RELTE are classified and analyzed.
基金Project of Shenzhen Science and Technology Innovation Commission(KCXFZ20201221173610028)。
文摘Large-scale atmospheric information plays an important role in the regional model for the forecasts of weather such as tropical cyclone(TC).However,it is difficult to be fully represented in regional models due to domain size and a lack of observation data,particularly at sea used in regional data assimilation.Blending analysis has been developed and implemented in regional models to reintroduce large-scale information from global model to regional analysis.Research of the impact of this large-scale blending scheme for the Global/Regional Assimilation and PrEdiction System(CMA-MESO)regional model on TC forecasting is limited and this study attempts to further progress by examining the adaptivity of the blending scheme using the two-dimensional Discrete Cosine Transform(2D-DCT)filter on the model forecast of Typhoon Haima over Shenzhen,China in 2016 and considering various cut-off wavelengths.Results showed that the error of the 24-hour typhoon track forecast can be reduced to less than 25 km by applying the scale-dependent blending scheme,indicating that the blending analysis is effectively able to minimise the large-scale bias for the initial fields.The improvement of the wind forecast is more evident for u-wind component according to the reduced root mean square errors(RMSEs)by comparing the experiments with and without blending analysis.Furthermore,the higher equitable threat score(ETS)provided implications that the precipitation prediction skills were increased in the 24h forecast by improving the representation of the large-scale feature in the CMA-MESO analysis.Furthermore,significant differences of the track error forecast were found by applying the blending analysis with different cut-off wavelengths from 400 km to 1200 km and the track error can be reduced less than by 10 km with 400 km cut-off wavelength in the first 6h forecast.It highlighted that the blending scheme with dynamic cut-off wavelengths adapted to the development of different TC systems is necessary in order to optimally introduce and ingest the large-scale information from global model to the regional model for improving the TC forecast.In this paper,the methods and data applied in this study will be firstly introduced,before discussion of the results regarding the performance of the blending analysis and its impacts on the wind and precipitation forecast correspondingly,followed by the discussion of the effects of different blending scheme on TC forecasts and the conclusion section.
基金Projects(41601424,41171351)supported by the National Natural Science Foundation of ChinaProject(2012CB719906)supported by the National Basic Research Program of China(973 Program)+2 种基金Project(14JJ1007)supported by the Hunan Natural Science Fund for Distinguished Young Scholars,ChinaProject(2017M610486)supported by the China Postdoctoral Science FoundationProjects(2017YFB0503700,2017YFB0503601)supported by the National Key Research and Development Foundation of China
文摘Climate sequences can be applied to defining sensitive climate zones, and then the mining of spatio-temporal teleconnection patterns is useful for learning from the past and preparing for the future. However, scale-dependency in this kind of pattern is still not well handled by existing work. Therefore, in this study, the multi-scale regionalization is embedded into the spatio-temporal teleconnection pattern mining between anomalous sea and land climatic events. A modified scale-space clustering algorithm is first developed to group climate sequences into multi-scale climate zones. Then, scale variance analysis method is employed to identify climate zones at characteristic scales, indicating the main characteristics of geographical phenomena. Finally, by using the climate zones identified at characteristic scales, a time association rule mining algorithm based on sliding time windows is employed to discover spatio-temporal teleconnection patterns. Experiments on sea surface temperature, sea level pressure, land precipitation and land temperature datasets show that many patterns obtained by the multi-scale approach are coincident with prior knowledge, indicating that this method is effective and reasonable. In addition, some unknown teleconnection patterns discovered from the multi-scale approach can be further used to guide the prediction of land climate.
文摘The city is facing the unprecedented pressure with the rapid development and the moving population. Some hidden knowledge can be found to service the social with human trajectory data. In this paper, we define a state-ofthe-art concept on fluctuant locations with PCA method and discover the same attribute of fluctuant locations called event with topic model. In the time slice, locations with the same attribute are called event region. Event regions aim to understand the relationship between spatial-temporal locations in the city and to early-warning analyze for the city planning, construction, intelligent navigation, route planning and location based service. We use GeoLife public data to experiment and verify this paper.
基金jointly sponsored by the National Basic Research Program of China(973 Program)(Grant No.2013CB430202)the National Natural Science Foundation of China(Grant No.41401056)+1 种基金the China Meteorological Administration Special Public Welfare Research Fund(Grant No.GYHY201406001)the Research Innovation Program for College Graduates of Jiangsu Province(Grant No.KYLX15 0858)
文摘In this study, regional persistent haze events(RPHEs) in the Beijing–Tianjin–Hebei(BTH) region were identified based on the Objective Identification Technique for Regional Extreme Events for the period 1980–2013. The formation mechanisms of the severe RPHEs were investigated with focus on the atmospheric circulation and dynamic mechanisms. Results indicated that:(1) 49 RPHEs occurred during the past 34 years.(2) The severe RPHEs could be categorized into two types according to the large-scale circulation, i.e. the zonal westerly airflow(ZWA) type and the high-pressure ridge(HPR) type. When the ZWA-type RPHEs occurred, the BTH region was controlled by near zonal westerly airflow in the mid–upper troposphere.Southwesterly winds prevailed in the lower troposphere, and near-surface wind speeds were only 1–2 ms^-1. Warm and humid air originating from the northwestern Pacific was transported into the region, where the relative humidity was 70% to 80%, creating favorable moisture conditions. When the HPR-type RPHEs appeared, northwesterly airflow in the mid–upper troposphere controlled the region. Westerly winds prevailed in the lower troposphere and the moisture conditions were relatively weak.(3) Descending motion in the mid-lower troposphere caused by the above two circulation types provided a crucial dynamic mechanism for the formation of the two types of RPHEs. The descending motion contributed to a reduction in the height of the planetary boundary layer(PBL), which generated an inversion in the lower troposphere. This inversion trapped the abundant pollution and moisture in the lower PBL, leading to high concentrations of pollutants.
文摘Based on a new multi-source dataset (GLDP-V1.0) recently developed in China Meteorological Administration, we employed precipitation indices including percentile-based indices of light (below the 50th percentile), moderate (between the 50th and 90th percentile), and intense (above the 90th percentile) precipitation, maximum 1-day, 3-day, and 5-day precipitation amounts (RX1DAY, RX3DAY, and RX5DAY, respectively), and consecutive wet and dry days (CWDs and CDDs) to analyze variations in extreme precipitation events in the Hindu Kush Himalayan (HKH) during 1961e2012. The main results are presented as follows. Firstly, there was a significant increase in the amount of light and moderate precipitation and number of associated days over various parts of India and northern Tibetan Plateau during 1961e2012; but the intensity of light precipitation decreased significantly in the Hindu Kush and central India, and the regional average intensity also decreased. Secondly, the amount and frequency of intense precipitation mostly increased significantly on the Tibetan Plateau, but there was a heterogeneous change over the remainder of the HKH, and regional average annual intense precipitation amount and frequency significantly increased over the HKH during 1961e2012. Thirdly, regional average RX1DAY, RX3DAY, and RX5DAYall showed significant upward trends during 1961e2012, and there was a significant increased tendency of consecutive wet-days in most parts of the study region; however, trends of consecutive dry-days were mostly opposite to those of consecutive wet-days, with regional averaged consecutive dry-days showing no noticeable trend.
基金Project supported by the National Natural Science Foundation of China(Grant No.41305075)the National Basic Research Program of China(Grant Nos.2012CB955203 and 2012CB955902)the Special Scientific Research on Public Welfare Industry,China(Grant No.GYHY201306049)
文摘Based on an objective identification technique for regional low temperature event(OITRLTE), the daily minimum temperature in China has been detected from 1960 to 2013. During this period, there were 60 regional extreme low temperature events(ERLTEs), which are included in the 690 regional low temperature events(RLTEs). The 60 ERLTEs are analyzed in this paper. The results show that in the last 50 years, the intensity of the ERLTEs has become weak; the number of lasted days has decreased; and, the affected area has become small. However, that situation has changed in this century.In terms of spatial distribution, the high intensity regions are mainly in Northern China while the high frequency regions concentrate in Central and Eastern China. According to the affected area of each event, the 60 ERLTEs are classified into six types. The atmospheric circulation background fields which correspond to these types are also analyzed. The results show that, influenced by stronger blocking highs of Ural and Lake Baikal, as well as stronger southward polar vortex and East Asia major trough at 500-h Pa geopotential height, cold air from high latitudes is guided to move southward and abnormal northerly winds at 850 h Pa makes the cold air blow into China along diverse paths, thereby forming different types of regional extreme low temperatures in winter.