The Spatiotemporal Distribution Characteristics of Cloud Types and Phases in the Arctic Based on CloudSat and CALIPSO Cloud Classification Products

The cloud type product 2B-CLDCLASS-LIDAR based on CloudSat and CALIPSO from June 2006 to May 2017 is used to examine the temporal and spatial distribution characteristics and interannual variability of eight cloud types(high cloud, altostratus, altocumulus, stratus, stratocumulus, cumulus, nimbostratus, and deep convection) and three phases(ice,mixed, and water) in the Arctic. Possible reasons for the observed interannual variability are also discussed. The main conclusions are as follows:(1) More water clouds occur on the Atlantic side, and more ice clouds occur over continents.(2)The average spatial and seasonal distributions of cloud types show three patterns: high clouds and most cumuliform clouds are concentrated in low-latitude locations and peak in summer;altostratus and nimbostratus are concentrated over and around continents and are less abundant in summer;stratocumulus and stratus are concentrated near the inner Arctic and peak during spring and autumn.(3) Regional averaged interannual frequencies of ice clouds and altostratus clouds significantly decrease, while those of water clouds, altocumulus, and cumulus clouds increase significantly.(4) Significant features of the linear trends of cloud frequencies are mainly located over ocean areas.(5) The monthly water cloud frequency anomalies are positively correlated with air temperature in most of the troposphere, while those for ice clouds are negatively correlated.(6) The decrease in altostratus clouds is associated with the weakening of the Arctic front due to Arctic warming, while increased water vapor transport into the Arctic and higher atmospheric instability lead to more cumulus and altocumulus clouds.

Temporal and spatial variation characteristics of extreme precipitation on the Loess Plateau of China facing the precipitation process

The preceding and succeeding precipitation(PSP)often act together with extreme precipitation(EP),in turn,causing floods,which is an objective component that is often overlooked with regard to summer flood hazards in the arid region of Northwest China.In this study,event-based extreme precipitation(EEP)was defined as continuous precipitation that includes at least one day of EP.We analyzed the spatiotemporal variation characteristics of four EEP types(front EEP,late EEP,balanced EEP,and single day EEP)across the Loess Plateau(LP)based on data acquired from 87 meteorological stations from 1960 to 2019.Precipitation on the LP basically maintained a spatial pattern of"low in the northwest region and high in the southeast region",and EP over the last 10 a increased significantly.The cumulative precipitation percentage of single day EEP was 34%and was dominant for 60 a,while the cumulative precipitation percentage of front,late,and balanced EEP types associated with PSP accounted for 66%,which confirms to the connotation of EEP.The cumulative frequencies of front and late EEP types were 23%and 21%,respectively,while the cumulative frequency of balanced EEP had the lowest value at only 13%.Moreover,global warming could lead to more single day EEP across the LP,and continuous EEP could increase in the northwestern region and decrease in the eastern region in the future.The concept of process-oriented EP could facilitate further exploration of disaster-causing processes associated with different types of EP,and provide a theoretical basis for deriving precipitation disaster chains and construction of disaster cluster characteristics.

Eff ects of environmental factors on the temporal and spatial variations in branch and leaf CO_(2)effl ux of Larix gmelinii var.principis-rupprechtii Mayr

The CO_(2)effl ux of branches and leaves plays an important role in ecosystem carbon balance.Using a carbon fl ux system,the effl ux of Larix gmelinii var.principisrupprechtii(Dahurian larch)was investigated in 27 years(immature),31 years(near-mature),and 47 years(mature)stands at diurnal,seasonal,and spatial scales(direction and height)as well as its connection with environmental factors from May to October 2020.Diurnal variation in effl ux was a single peak,and the maximum occurring between 14:00 and 16:00.Seasonal variation also exhibited a single peak,with the maximum in late July and the minimum in early October.From May to September,effl ux on the south side was the largest among the three stands,and mean values on the south side of 27 year-old,31 year-old,and 47 year-old trees were 0.50,0.97 and 1.05μmol·m^(–2)·s^(–1),respectively.The minimum occurred on the north side.Except for the maximum in July and September in the 27 year-old stand in the middle of the canopy,the maximum effl ux in the upper canopy,and the means in the 27 year-old,31 year-old,and 47 year-old stands were 0.49,0.96 and 1.04μmol·m^(-2)·s^(-1),respectively;the minimum occurred in the lower canopy.Temperatures and relative humidity infl uenced seasonal variations in effl ux.Seasonal variation in temperature sensitivity coeffi cient(Q 10)was opposite that of temperature,increasing with decreasing temperature.At the spatial scale,maximum Q 10 occurred in the mid canopy.With the effl ux and temperature data in diff erent locations,it is possible to better estimate effl ux variations in each stand.

Analysis on temporal and spatial variations of groundwater hydrochemical characteristics in the past decade in southern plain of Beijing, China

Groundwater utilization and protection are crucial for sustainable urban development. This is especially true for Beijing, where groundwater is an important source for urban water supply. In this study, statistical methods, including descriptive statistics, correlation analysis, principal component analysis, and Piper-Tri-linear diagram, were used in analyzing the temporal and spatial variations of the hydrochemical characteristics of groundwater based on monitored data from the southern plain of Beijing, China. Results indicated consistent changes of groundwater's hydrochemical characteristics in different aquifers in the study area. The percentage of HCO_3^-in total anion increased significantly in the groundwater, and hydrochemical water type evolved gradually from Ca-Mg-Cl-SO_4 based to Ca-Mg-HCO_3 based from period 2005-2007 to period 2013-2015. In shallow groundwater, the concentration of Na^+, Ca^(2+), SO_4^(2-), HCO_3^-, and total dissolved solids(TDS) increased from period 2005-2007 to period 2013-2015, and the greatest change came from HCO_3^-, rising from 428.93 to 528.96 mgL^(-1). The changes of main ionic concentrations in the deep groundwater were consistent with those in the shallow groundwater for both periods. However, the variations in deep groundwater were less than those in shallow groundwater. The temporal and spatial variations of hydrochemical characteristics reflect the groundwater quality in the study area. This study could facilitate decision-making process on the protection of groundwater resources to ensure its sustainable utilization.

Temporal and Spatial Variations in the Climate Controls of Vegetation Dynamics on the Tibetan Plateau during 1982–2011

The ecosystem of the Tibetan Plateau is highly susceptible to climate change. Currently, there is little discussion on the temporal changes in the link between climatic factors and vegetation dynamics in this region under the changing climate.By employing Normalized Difference Vegetation Index data, the Climatic Research Unit temperature and precipitation data,and the in-situ meteorological observations, we report the temporal and spatial variations in the relationships between the vegetation dynamics and climatic factors on the Plateau over the past three decades. The results show that from the early 1980s to the mid-1990s, vegetation dynamics in the central and southeastern part of the Plateau appears to show a closer relationship with precipitation prior to the growing season than that of temperature. From the mid-1990s, the temperature rise seems to be the key climatic factor correlating vegetation growth in this region. The effects of increasing temperature on vegetation are spatially variable across the Plateau: it has negative impacts on vegetation activity in the southwestern and northeastern part of the Plateau, and positive impacts in the central and southeastern Plateau. In the context of global warming, the changing climate condition(increasing precipitation and significant rising temperature) might be the potential contributor to the shift in the climatic controls on vegetation dynamics in the central and southeastern Plateau.

Temporal and spatial variations of δ^18O in precipitation of the Yarlung Zangbo River Basin

This paper reveals the temporal and spatial variations of stable isotope in precipitation of the Yarlung Zangbo River Basin based on the variations of δ^18O in precipitation at four stations （Lhaze, Nugesha, Yangcun and Nuxia） in 2005. The results show that δ^18O of precipitation has distinct seasonal changes in the Yarlung Zangbo River Basin. The higher value of δ^18O occurs in spring prior to monsoon precipitation, and the lower value occurs during monsoon precipitation. From the spatial variations, with the altitude-effect and rainout process during moisture transport along the Yarlung Zangbo River Valley, δ^18O of precipitation is gradually depleted. Thus, δ^18O of precipitation decreases gradually from the downstream to the upstream, and the lapse rate of δ^18O in precipitation is approximately 0.34‰/100m and 0.7%J‰/100km for the two reasons. During monsoon precipitation, spatial variation of δ^18O in precipitation is dominated by the amount effect in the large scale synoptic condition.

Spatial and Temporal Variations of Pneumoconiosis in the Pearl River Delta Region in 2006–2015

Pneumoconiosis is a restrictive lung disease mostly caused by occupational exposure to dust,including silica dust,asbestos,and other fibers.Inhalable particles smaller than 10μm can enter the bronchioles,injure lung cells,and induce lung fibrosis.This hard-to-cure disease places a substantial burden on patients and society[1].

Spatial and temporal variations in pH and total alkalinity at the beginning of the rainy season in the Changjiang Estuary, China

The results of field observation carried out in May 2003 were used to examine pH and total alkalinity behaviors in the Changjiang Estuary. It was showed that pH and total alkalinity took on clear spatial variations in values with the minima in the low salinity region. Like salinity, transect distributions of pH and total alkalinity （TA） in a downriver direction had a sharp gradient each. These gradients appeared in such a sequence that the TA gradient was earlier than salinity and pH gradients, and the salinity gradient was earlier than the pH gradient. These distribution characteristics seemed to be strongly influenced by the mixing process of freshwater and seawater, for both pH and total alkalinity had significant linear relationships with salinity and temperature. For pH, phytoplankton activities also had a significant impact upon its spatial distribution. During a period of 48 h, pH and total alkalinity changed within wide ranges for every layer of the two anchor stations, namely, Stas 13 and 20, which were located at the mixed water mass and seawater mass, respectively. For both Stas 13 and 20, pH and TA fluctuation of every layer could be very wide during a 4 h period. As a whole, the data of the two anchor stations showed that neither variations in salinity and temperature nor phytoplankton activities were the main factors strongly influencing the total alkalinity temporal variability on a small time scale. The data of Sta. 20 implied that both salinity variation and phytoplankton activities had a significant influence on pH temporal variability, but the same conclusion could not be drawn from the data of Sta. 13.

Spatial and Temporal Variations in Available Soil Nitrogen—A Case Study in Kobresia Alpine Meadow in the Qinghai-Tibetan Plateau, China

Elucidating the factors that determine the effects of temporal and spatial variation of nutrients is important for analyzing the characteristics of an ecosystem. The goal of this paper was to estimate how values obtained using a particular sampling approach correlated with the actual data for an entire plot. The mesh partition method was employed to divide an integrated observing field (IOF) located at the Haibei National Field Research Station of an alpine grassland ecosystem, China, into 25 subplots. Five of the 25 subplots were randomly selected for soil sampling and to determine the source of variations in soil nutrient content from 2001 to 2012. The results showed that, contributions of temporal and spatial variation in available nitrogen in the 0 - 10 cm soil layer accounted for 47.3% and 52.7%, respectively. The contribution of spatial variance was higher than that of temporal variance especially in the surface soil layers. The available soil nitrogen content in the alpine meadow was not obviously affected by fluctuations in rainfall and temperature. Increasing the number of samples could reduce calculation errors in measuring available soil nitrogen content, while collecting a reasonable number of samples can save time and labor.

Spatial-temporal dynamics of desert vegetation and its responses to climatic variations over the last three decades:a case study of Hexi region in Northwest China

Analysis of spatial-temporal variations of desert vegetation under the background of climate changes can provide references for ecological restoration in arid and semi-arid areas. In this study, we used the Global Inventory Modeling and Mapping Studies （GIMMS） NDVI data from 1982 to 2006 and Moderate Resolution Imaging Spectroradiometer （MODIS） NDVI data from 2000 to 2013 to reveal the dynamics of desert vegetation in Hexi region of Northwest China over the past three decades. We also used the annual temperature and precipitation data acquired from the Chinese meteorological stations to analyze the response of desert vegetation to climatic variations. The average value of NDVImax （the maximum NDVI during the growing season） for desert vegetation in Hexi region increased at the rate of 0.65x10-3/a （P〈0.05） from 1982 to 2013, and the significant increases of NDVImax mainly appeared in the typical desert vegetation areas. Vegetation was significantly improved in the lower reaches of Shule and Shiyang river basins, and the weighted mean center of desert vegetation mainly shifted toward the lower reaches of the two basins. Almost 95.32% of the total desert vegetation area showed positive correlation between NDVImax and annual precipitation, indicating that precipitation is the key factor for desert vegetation growth in the entire study area. Moreover, the areas with non-significant positive correlation between NDVImax and annual precipitation mainly located in the lower reaches of Shiyang and Shule river basins, this may be due to human activities. Only 7.64% of the desert vegetation showed significant positive correlation between NDVImax and annual precipitation in the Shule River Basin （an extremely arid area）, indicating that precipitation is not the most important factor for vegetation growth in this basin, and further studies are needed to investigate the mechanism for this phenomenon.

Temporal and spatial variations of the Huanghe River mouth bars

On the basis of the bathymetric records of 371 survey sections in the present Huanghe mouth area from 1996 to 2001, the temporal and spatial variations of the Huanghe mouth bars were studied by using GIS technology. The variation of the mouth bars is closely related to the water and sediment discharges from the Huanghe River to the sea that has been decreasing drastically in recent years, and to coastal hydrodynamic regimes. The characteristics of the mouth bars are unique in contrast with those of other estuaries in the world. (1) The mouth bars of the Huanghe River consist of many small sandbars. Usually the sandbars are of ellipse-shape with the long axis of about 1~6 km, and short axis of about 1~4 km. The long axis is parallel to the principal direction of tidal current, and the short axis is variable, depending on the local dynamics. The crest of the sandbars is only about 0.4 m below the water surface at low tide. They are distributed within an area of 20 km2, not far from the river mouth area. The present mouth bars are in small-medium size, quite different from the large one formed during the 1970s and 1980s, when the river sediment discharge was several times larger than that after 1996. (2) The scale of a river mouth bar is related to the river discharge of that year. In 1997 sediment discharge from the Huanghe River was 42 Mt, and the mouth bar consisted of several small scattered sandbars. In 1998 the size of mouth bars was much larger than that in 1997, as the sediment discharge from the Huanghe River increased to 363 Mt. Variation of the mouth bars largely depends on the sediment discharge with a correlation coefficient of 0.78. The calculation of the volume of the mouth bar area shows that about 30%~40% of the river's into-sea sediment is deposited in the mouth bar area. (3) Compared with other large estuaries in the world, the Huanghe mouth bars have three unique features in responding to its high sediment concentration: small size, steep slope gradient and shallow crest depth.

The temporal and spatial variations in the Pacific wind and wave fields for the period 2002–2011

The temporal and spatial variations in the wind and wave fields in the Pacific Ocean between 2002 and 2011 are analyzed using a third-generation wave model（WAVEWATCH III）. The model performance for a significant wave height is validated using in situ buoy data. The results show that the wave model effectively hindcasts the significant wave height in the Pacific Ocean, but the errors are relatively large in the mid- and low-latitude regions. The spatial distributions and temporal variations in a wind speed and the significant wave height in the Pacific Ocean are then considered after dividing the Pacific Ocean into five regions, which show meridional differences and seasonal cycles. Regional mean values are used to give yearly average time series for each separate zone. The high latitude region in the Southern Hemisphere had a stronger significant wave height trend in the model results than regions at other latitudes. The sources and sinks of wave energy are then investigated. Their regional mean values are used to quantify variations in surface waves. Finally, the spectral analyses of the daily mean wind speeds and the significant wave heights are obtained. The significant wave height and the wind speed spectra are found to be connected in some ways but also show certain differences.

Spatial and temporal variations of Synechococcus and picoeukaryotes in the Taiwan Strait,China

The size-fractionated phytoplankton biomass, and the spatial and temporal variations in abundance of Synechococcus (SYN) and picoeukaryotes (PEUK) were measured in the Taiwan Strait during three cruises (August 1997, February-March 1998, and August 1998). The results show that picophytoplankton and nanophytoplankton dominate the phytoplankton biomass, in average of 38% and 40%, respectively. SYN and PEUK varied over time in abundance and carbon biomass, greater in summer than in winter, in range of (7.70–209.2)×106 and (0.75–15.4)×106 cells/cm2 in the abundance, and 1.93–52.3 and 1.57–32.4 μgC/cm2 in the carbon biomass, for SYN and PEUK, respectively. The horizontal distributions of both groups were diurnal but heterogeneous in abundance, depending on the groups and layer of depths. Temperature is the key controlling factor for picophytoplankton distribution (especially in winter) in the Strait.

The Spatial and Temporal Variation Characteristics of CH₄and CO₂Emission Flux under Different Land Use Types in the Yellow River Delta Wetland

The Yellow River Delta Wetland is one of the youngest wetlands, and also the most complete, extensive wetlands in China. The wetland in this delta is ecologically important due to their hydrologic attributes and their roles as ecotones between terrestrial and aquatic ecosystems. In the study, the spatial and temporal variation characteristics of CH4 and CO2 emission flux under five kinds of land use types in the wetland were investigated. The results indicated that the greenhouse gas emission flux, especially the CO2 and CH4, showed distinctly spatial and temporal variation under different land use types in the wetland. In the spring, the emission flux of CO2 was higher than that of CO2 in the autumn, and appeared negative in HW3 and HW4 in the autumn. CH4 emission flux of HW4 and HW5 was negative in the spring and autumn, which indicated that the CH4 emission process was net absorption. Among the five kinds of land use types, the CO2 emission flux of HW4 discharged the largest emission flux reaching 29.3 mg.m-2.h-1, but the CH4 emission flux of HW2 discharged the largest emission flux reaching 0.15 mg.m-2.h-1. From the estuary to the inland, the emission flux of CO2 was decreased at first and then appeared increasing trend, but the emission flux of CH4 was contrary to CO2.

Analysis on the Temporal and Spatial Characteristics and Causes of Cold Wave in Qinhuangdao

[Objective] The aim was to study the temporal and spatial characteristics and causes of cold wave in Qinhuangdao.[Method] Based on temperature data from five surface meteorological stations in Qinhuangdao from 1970 to 2009 and the latest standards issuing cold wave early warning signal,statistical analysis on the temporal and spatial distribution of cold wave was carried out,and the causes were discussed preliminarily.[Result] From 1970 to 2009,the frequencies of blue and yellow cold wave in Qinhuangdao region were 2 334 and 105 times respectively,and cold wave occurred most frequently in Qinglong County and least frequently in Lulong County,which was related to the effects of underlying surface,latitude and altitude.Cold wave might happen from September to next May,and the earliest occurrence date was September 9,while the latest end date was May 26.In addition,the frequency of cold wave was the highest in January and lowest in May.From 1970 to 2009,blue cold wave occurred most frequently in 1972 and 1979 and least frequently in 1984,while the frequency of yellow cold wave was the highest in 1979 and lowest in 9 years.From decadal variation,cold wave appeared most frequently in the 1970s and least frequently in the 1990s.With the increase of temperature,the frequency of cold wave showed decrease trend,and the beginning date tended to postpone,while its end date advanced,and it showed that the changes of cold wave was mainly caused by climate warming.[Conclusion] The study could provide theoretical guidance for the meteorological disaster prevention and reduction and local agricultural service.

Analysis on Temporal and Spatial Variation Characteristics of the Precipitation in Hexi Corridor in Recent 58 Years

[ Objective] The research aimed to analyze temporal and spatial variation characteristics of the precipitation in Hexi Corridor in the past 58 years. [Method] Based on monthly rainfall data in Hexi Corridor from 1951 to 2008, by using moving average, wavelet analysis and climate trend coefficient, variation rule of the precipitation in Hexi Corridor in the past 58 years was analyzed. [ Result] Average rainfall in Hexi Corridor in the past 58 years was 130.4 mm. Precipitation mainly concentrated in summer, occupying 59.08% of the annual rainfall. From June to September, it occupied 72.57% of the annual precipitation. Interdecadal change of the precipitation in Hexi Corridor wasn＇t severe. Average rainfall in each dec- ade was from 120.8 to 139.0 mm. The precipitation series had periods of the 5, 10, 21 and 32 years in Hexi Corridor from 1951 to 2008. in the fu- ture, annual, spring, summer and winter precipitation would have small increase tendency. Increase amplitude of the annual precipitation in Shule River basin was the biggest （5.231 -0.062 mm/10 a）. The increase amplitude in the south and southeast of the Heihe River basin was bigger than that in the northwest. The smallest increase amplitude of the annual precipitation was 3.280 -0.098 mm/10 a in Shiyang River basin. [ Conclusion] This research could provide beneficial reference for coordinated development between local social economy and ecological environment.

Investigating spatial and temporal variations of soil moisture content in an arid mining area using an improved thermal inertia model

Mining operations can usually lead to environmental deteriorations. Underground mining activities could cause an extensive decrease in groundwater level and thus a dramatic variation in soil moisture content（SMC）. In this study, the spatial and temporal variations of SMC from 2001 to 2015 at two spatial scales（i.e., the Shendong coal mining area and the Daliuta Coal Mine） were analyzed using an improved thermal inertia model with a long-term series of Landsat TM/OLI（TM=Thematic Mapper and OLI=Operational Land Imager） data. Our results show that at large spatial scale（the Shendong coal mining area）, underground mining activities had insignificant negative impacts on SMC and that at small spatial scale（the Daliuta Coal Mine）, underground mining activities had significant negative impacts on SMC. Trend analysis of SMC demonstrated that areas with decreasing trend of SMC were mainly distributed in the mined area, indicating that underground mining is a primary cause for the drying trend in the mining region in this arid environment.

Analysis on Hydrogeochemical Characteristics and Their Temporal and Spatial Variation in the Karst Catchment of Lianjiang River,Northern Guangdong Province

[ Objective] The study aimed to discuss the hydrogeochemical features and their temporal and spatial variation in the karst catchment of Lianjiang River, northem Guangdong Province. [ Method] Water samples were collected from 10 sub-drainages of Lianjiang River in July of 2012 and January of 2013, and then major chemical ions in tributaries of Xingzi River and Tongguanshui River were analyzed in detail to discuss the hydrochemistry type, spatial and temporal distribution and its causes of formation in Lianjiang River basin. [ Result] Among chemical ions in the wa- ter samples, Ca2. and HCO^- were dominant in Lianjiang River, accounting for over 70% and 80% of total concentrations of cations and anions re- spectively, followed by Mg2＋ and SO24-. The concentrations of most major ions were higher in winter than those in summer except SO4^2- concentra- tion was much higher in summer than that in winter, which was related to anthropogenic factors. From hydrochemical types, it is seen that HCO3-- Ca2＋ type in summer and HCO3--Ca2＋ ~ Mg2. type in winter were dominant in Lianjiang River, followed by the HCO3--SO4^2- · Ca2＋ type, and only two samples of Xingzi River belonged to HCO3--Ca2＋ Mg2· Na＋ type in winter. The spatial distribution regularity of chemical ions was not obvi- ous in the 10 sub-drainages of Lianjiang River. The concentrations of chemical ions changed greatly in the upper reaches but slightly in the lower reaches of Xingzi River catchment. The concentrations of chemical ions were steady in Tongguanshui River catchment with a smaller area, and it was a little higher in the upper reaches than those in the lower reaches. [ Conclusion] Natural processes, such as lithological heterogeneities and at- mospheric precipitation, contributed to the chemical composition of Lianjiang River catchment, northem Guangdong Province.

Spatial and Temporal Variations of Blocking and Cyclogenesis in the 1978 / 79 Winter

Complex empirical orthogonal function (CEOF) and Fourier analyses are applied to 500 hPa geopotential height anomaly for two selected latitude belts in the Northern Hemisphere from Dec 1978 through Feb 1979 based on the ECMWF FGGE Hl-b data. The positive anomalies in the three leading CEOFs for the high-latitude belt mainly show the preferred locations for blocking activity in the North Atlantic, the North Pacific and to the west of the Ural Mountains. The negative anomalies in the three leading CEOFs for the mid-latitude belt mainly show the preferred locations for cyclogenesis in the east coasts of Asia and North America, and the Mediterranean; weak cyclogenesis is also seen in the western United States and off the coasts of Spain and Morocco. The travelling components of the positive anomalies in the high-latitude belt mainly propagate westward, weakening as approaching the east side of some mountain chains while intensifying to the west side. On the contrary, the travelling components of the negative anomalies in the mid-latitude belt mainly propagate eastward, intensifying over the lee side of mountain and/or approaching the east coasts of the two continents. These preferred locations for blocking and cyclogenesis are basically consistent with the climatological results, and related to some teleconnection patterns found earlier.The temporal variation of blocking highs seems to relate with the vacillation of the potential vorticity (PV) index defined by Weng (1992). There are two build-up stages of the PV index during the winter. Each build-up stage corresponds to a westward propagation of a large-scale positive anomaly in the high-latitude belt, resulting in the occurrence of a series of blocking highs over the western Eurasia, Scandinavia, Greenland and the Pacific. In general, the temporal variation of cyclogenesis is less reflected by the PV index than blocking highs. The duration of a PV index cycle of build-up and break-down is about 30-50 days. Within this low-frequency envelope, there is a global quasi-two-week vacillation of the PV index, reflecting one of the preferred time scales of mid-latitude cyclone and anticyclone activity in some preferred locations during the 1978 / 79 winter.

Comparison of temporal and Spatial Characteristics of Ozone Pollution at Ground Level in the Eastern China

Monitoring data from ozone(O3) automatic stations in three typical cities with different climatic areas in the southern and northern parts of eastern China are used to analyze temporal and spatial characteristics of ozone pollution at ground level. The results show that ozone pollution level has distinct regional differences and the concentration in the suburbs is higher than that in the urban areas. The seasonal variation of ozone concentration in different climatic areas is greatly affected by the variation of precipitation. Ozone concentration in Shenyang and Beijing , in the temperate zone, has one perennial peak concentration, occurring in early summer, May or June. Ozone concentration in Guangzhou, in sub-tropical zone, has two peak values year round. The highest values occur in October and the secondary high value in June. The ozone season in the south is longer than that in the north. The annual average daily peak value of ozone concentrations in different climates usually occur around 3 pm. The diurnal variation range of ozone concentration declines with the increase of latitude. Ozone concentration does not elevate with the increase of traffic flow. Ozone concentration in Guangzhou has a distinct reverse relation to CO and NOx. This complicated non-linearity indicates that the equilibrium of ozone photochemical reaction has regional differences. Exceeding the rate of Beijing’s 1h ozone concentration is higher than that of Guangzhou, whereas the average 8h ozone level is lower than that of Guangzhou, indicating that areas in low latitude are more easily affected by moderate ozone concentrations and longer exposure. Thus, China should work out standards for 8h ozone concentration.