Atmospheric Sulfur Deposition on Farmland in East China

Atmospheric sulfur deposition onto typical farmland in East China was investigated using both field measurements and numerical modeling. The field measurements were conducted at the Experiment Station of Red Soil Ecology, Chinese Academy of Sciences, 10 km from Yingtan, Jiangxi Province, East China, between November 1998 and October 1999, and at the Changshu Ecological Experiment Station, Chinese Academy of Sciences, in a rapidly developing region of Jiangsu Province, East China, between April 2001 and Marc…

Influence of Arctic Oscillation on winter climate over China

In this study the relationship between the Arctic Oscillation (AO) and climate in China in boreal winter are investigated. Correlation analysis for the last 41 years shows that the winter temperature and precipitation in China change in phase with AO. High positive correlation (>0.4) between temperature and AO appears in the northern China. High correlation coefficients between precipitation and AO cover the southern China (close to the South China Sea) and the central China (between 30 o -40 o N and east of ~100 o E), with the values varying between +0.3 and +0.4. It is found that during the past several decades the precipitation was strongly affected by AO, but for the temperature the Siberian High plays a more important role. At the interdecadal time scale the AO has significant influence on both temperature and precipitation. Multivariate regression analysis demonstrates that AO and the Siberian High related variance in temperature and precipitation is 35% and 11% respectively. For precipitation, however the portion is rather low, implying that some other factors may be responsible for the changes in precipitation, in addition to AO and the Siberian High.

Relationship between SSTA in the northwestern Pacific and winter climate anomaly in China

The relationship between sea surface temperature anomaly (SSTA) in the domain from the northwest of the Pacific to China seas (NWP-CS) and climate (precipitation and surface temperature) anomaly in winters over east of Chinese Mainland (ECM) are investigated with composite analysis. The results suggest that (1) SSTA in NWP-CS usually appears as 'seesaw' pattern, i.e., sign of SSTA in the northwest of the Philippines is positive (negative) while in the southeast it is negative (positive), defined as SSTA 'seesaw' positive (negative) pattern. When SSTA 'seesaw' positive (negative) pattern appears, the surface temperature in ECM is higher (lower) than the normal winters but the precipitation anomaly is not distinct ; (2) there are two anomalous anticyclones (cyclones) locating in the northwest Pacific and east of the Philippines at 850 hPa level and an anomalous anti-Hadley (Hadley) circulation, which descends (ascends) south of 18oN, ascends (descends) north of 18oN; (3) heat flux anomaly from ocean into atmosphere is weaker (stronger) in the northwest of the Philippines but stronger (weaker) in the southeast of the Philippines than the normal winters, because the weaker (stronger) northerly prevails in the northwest of the Philippines and stronger (weaker) northeaster in the southeast of the Philippines induced by anomalous anticyclones (cyclones).

High-frequency atmospheric variability over South China Sea as depicted by TRMM and QuikSCAT

By using the TRMM and QuikSCAT datathe characteristics of the 2–8 day high frequency atmospheric variability over the South China Sea are studied in this paper.It’s found that： （1） the 2–8 day high frequency signals are significant not only during the periods of the South China Sea Summer Monsoon （SCSSM）,but also after the retreat of the SCSSM.It reaches its peak around July to August;（2） the 2–8 day high frequency signals exhibit strong intermittent features;（3） During El Nino years,the 2–8 day high frequency signals are active only in the periods of the SCSSM.During La Nina years,the 2–8 day high frequency signals are obviously not only in periods of the SCSSM,but also after the retreat of the SCSSM.During the SCSSM periods,the 2–8 day high frequency signals in El Nino years are much stronger than that in La Nina years;（4） During spring to early summer,most of 2–8 day signals propagate southward and eastward,during midsummer to autumn,however,most of 2–8-day signals propagate northward and westward;（5） The 2–8 day northward and westward propagation signals is probably related to the activities of high-frequency vortex over the SCS.

Three-dimensional hydrodynamic model of Xiamen waters

A semi-implicit and Eulerian - Lagrangian finite difference method for three-dimensionalshallow flow has been extended to a more complete system of equations incorporating second-moment turbulence closure model and transport equations of salinity and temperature. The simulation for flooding and drying of mudflats has been improved. The model is applied to Xiamen waters. Based on extensive survey data, water level elevation, temperature and salinity field along the eastern open boundary and at the Jiulong River inlets and runoffs are analyzed, specified and calibrated. The computed results show good agreement with the measured data, reproduce flooding, emergence of large and complex mudflat region.

Atmospheric Sulfur Deposition for a Red Soil Broadleaf Forest in Southern China

A two-year study in a typical red soil region of Southern China was conductedto determine 1) the dry deposition velocity (V_d) for SO_2 and particulate SO_4^(2-) above abroadleaf forest, and 2) atmospheric sulfur fluxes so as to estimate the contribution of variousfractions in the total. Using a resistance model based on continuous hourly meteorological data,atmospheric dry sulfur deposition in a forest was estimated according to V_d and concentrations ofboth atmospheric SO_2 and particulate SO_4^(2-). Meanwhile, wet S deposition was estimated based onrainfall and sulfate concentrations in the rainwater. Results showed that about 99% of the drysulfur deposition flux in the forest resulted from SO_2 dry deposition. In addition, the observeddry S deposition was greater in 2002 than in 2000 because of a higher average concentration of SO_2in 2002 than in 2000 and not because of the average dry deposition velocity which was lower for SO_2in 2002. Also, dry SO_2 deposition was the dominant fraction of deposited atmospheric sulfur inforests, contributing over 69% of the total annual sulfur deposition. Thus, dry SO_2 depositionshould be considered when estimating sulfur balance in forest ecological systems.

Regional characteristics of dust events in China

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.

The influence of 30~60 d oscillation on the development of the South China Sea summer monsoon

Using the National Center for Enviromental Prediction/National Center for Atmospheric Research (NCEP/NCAR)reanalysis data and NOAA satellite-observed outgoing long-wave radiation (OLR) data, the development of theSouth China Sea (SCS) summer monsoon and intraseasonal (30~60 d) oscillation (ISO) have been examined. Theresults show that there exists obvious interannual variability of intraseasonal oscillaiton. Using the 16 a time series offiltered OLR averaged over the SCS, an index is defined to define onset events over the SCS on the ISO time scales.Of the 16 a examined here, 10 shows a strong ISO signal in the onset of monsoon convection over the SCS. In thesecases, the ISO initially suppresses the seasonal development of southwesterly and cyclonic circulation over the SCSbefore the ISO onset. As the ISO propagates northeastward, the low frequency cyclonic circulation anomaly occursin the SCS and the low frequency southwesterly wind and convection over here dramatically intensify. The northeastprogression of the ISO anomaleis plays a role in the initial suppression and then acceleration of the seasonal cycle ofthe SCS summer monsoon.

THE TEMPORAL AND SPATIAL CHARACTERISTICS OF MOISTURE BUDGETS OVER ASIAN AND AUSTRALIAN MONSOON REGIONS

Apparent moisture sink and water vapor transport flux are calculated by using NCAR/NCEP reanalyzed daily data for water vapor and wind fields at various levels from 1980 to 1989.With the aid of EOF analysis method,temporal and spatial characteristics of moisture budgets over Asian and Australian monsoon regions are studied.The results show that there is apparent seasonal transition of moistrue sink and water vapor transport between Asian monsoon region and Australian monsoon region.In winter,the Asian monsoon region is a moisture source,in which three cross-equatorial water vapor transport channels in the 'continent bridge',at 80°E and 40°E～50° transport water vapor to the Australian monsoon region and southern Indian Ocean which are moistrue sinks.In summer,Australian Monsoon region anmd southern Indian Ocean are moistrue sources and by the three cross-equatorial transport channels water vapor is transport to the Asian monsoon region which is a moisture sink.In spring and autumn,ITCZ is the main moisture sink and there is no apparent water vapor transport between Asian monsoon region and Australian monsoon region.

草原生态动力学模式及其实际检验

基于物理定律、数学分析以及一些生态和气候学的简化,建立了一个草原生态系统动力学模式.该模式包括相互作用的3个变量,即青草量、枯落物量和土壤水分.主要生物及物理过程均用参数化方法表示,而参数可由实测得到的宏观量反推出来.用试算方法,并用内蒙古草原的一些资料,对模式参数先作标定;然后用模式做计算,结果与实况相吻合,例如:草原的存在要求年降水量大于一临界值(约 300 mm),产草量与年降水量有对应关系,放牧过度会导致荒漠化等.特别是,青草和枯落物遮阴可以降低地表温度和减少蒸发,这对维持草原、减少土壤水分损失是很重要的。

Typical severe dust storms in northern China during 1954—2002

Based on China抯 available daily observation data from 681 national meteorological stations from 1954 to 2002, a time series of typical severe dust storms in northern China is constructed in terms of the weather process, and the temporal and spatial distribution, and their evolution ten-dency is analyzed. The results indicate that there were 223 relatively typical severe dust storms in northern China from 1954 to 2002, among which the event on April 10—12, 1979 had the largest affected area. Closely associated with the geographical distribution of deserts, sandy lands and the tracks of strong cold air outbreaks, severe dust storms mainly occurred in the Tarim Basin, the eastern part of Northwest China and the northern part of North China. The season with the most frequent severe dust storms was spring, in which the frequency accounts for 82.5% in the whole year, while the least occurrence was in summer and autumn. Dur-ing the past 49 years, the highest frequency of severe dust storms occurred in the 1950s and the lowest was in the 1990s with a general descending tendency, but during 2000—2002 the occurrence was relatively increasing. On the average, the duration of severe dust storms was shortest in the 1990s, about 0.5—1 h shorter than that in the other 4 decades.

The experiment of monthly mean circulation prediction using the analogy-dynamical model

Based on the past related research work,a new analogy-dynamical monthly predic- tion model is established with the operational dynamic extended-range forecast model T63L16 (hereafter T63) as a dynamic kernel.The monthly mean circulation predicition with T63 is considered as a control experiment,and the prediction with the analogy-dynamical model as a contrast one.It is found that the anal- ogy-dynamical model has more precise forecast skill than the T63 model through monthly mean numerical prediction experiment.

Arctic Oscillation influence on daily temperature variance in winter over China

The relationship between the Arctic Oscillation (AO) and daily temperature variance of 150 Chinese stations are investigated in the present study for wintertime (1 No-vember through 31 March) in the period of 1954-2001. Re-sults show that the temperature variance significantly de-creases during the high AO years, and increases in low AO cases. A key factor connecting them is the Siberian High, particularly the high-frequency fluctuations of the High. Within the seasonal time scale, the frequency of low-temperature extremes (daily temperature anomaly below 2σ,σ is the standard deviation of daily temperature for a given winter and a given station) displays an odd relation to the variance: a larger (smaller) variance is found to be asso-ciated with smaller (greater) frequency o low-temperature events. That is due to the non-normal distribution of the temperatures, and also influenced by the hhases of AO. Dur-ing the last 50 years or so, AO experiences a significant increasing trend, meanwhile the variance of daily sea level pressure (SLP) in the central region of Siberian High has decreased at a rate of 10.7%/10 a. These result in a signifi-cant weakening of the daily temperature variance in China with a trend of 4.1%/10 a, and a significant increaswe in the intra-seasonal low-temperature extremes at a rate of 0.16d/10 a.

Analyzing global trends of different cloud types and their potential impacts on climate by using the ISCCP D2 dataset

The International Satellite Cloud Climatology Project (ISCCP) D2 dataset is used to study the global dis- tribution of low, middle and high cloud amounts and their trends of 1983—2001. Evidences have shown that global warming has accelerated over the past 20 a and the 1990s was the warmest decade in the instrumental records since 1861. Trends of various clouds amounts over this period are analyzed by employing the linear regression method. The results show that global mean total cloud amounts, in general, have tended to reduce over the past 20 a. But there are slightly increasing by about 2% before 1987 and decreasing by about 4% since then. Cloudiness trends of both low and high clouds decrease while increase for the middle cloud. And there exist remarkable discrepancies in different regions. The preliminary analyses suggest that it is likely that the cloud change occurring over the past 20 a is a positive feed- back to global warming.

Characteristics of distribution and seasonal variation of aerosol optical depth in eastern China with MODIS products

The accuracy of MODIS aerosol products from the NASA Terra Satellite is validated in comparison with the results of sun-photometer observations in Beijing and Hong Kong. By analyzing the MODIS aerosol products within the period of August 2000 to April 2003, it is believed that human activities are the main source of aerosols in the eastern part of China. This is based on the facts that all areas with relatively high values are consistent with regions of dense population and fast economic development, such as the North China Plain, the Sichuan Basin and the Pearl River Delta. It is also supported by the distribution of 舗gstr鰉 exponents showing that most aerosols in the eastern part of China are closely related to human activities, excepting the strong sandstorm episodes occurring in spring, fall and winter. In contrast to developed countries, the 舗gstr鰉 exponent of urban area in China is lower than its surroundings, indicating that the contribution of local floating dust and soot attributed to human activities is significant. Results presented in this paper provide important data for further research on climatic change and environmental study.

Assimilation analysis of Rammasun typhoon structure over Northwest Pacific using satellite data

The kinetic and thermodynamic structure of typhoon Rammasun (No. 0205) over the Northwest Pacific has been analyzed, using NOAA-16 polar orbiting Advanced Microwave Sounding Unit (AMSU) data collected on 2 July, 2002. The three-dimensional variational (3DVAR) assimila-tion technology is used to assimilate the satellite observation. The results show that the characteristics of the 3D typhoon structure can be more reasonably described from the assimi-lated data. The warm-cored structure of the typhoon is en-hanced in the analyzed field, which corresponds to strong typhoon. The typhoon cyclonic circulation in the middle and lower layers is apparently strengthened, and the strong anti-cyclonic circulation appears at the top of the typhoon. The water vapor and its supply in the typhoon are enhanced. The microwave assimilation data may be used to supply the lack of the conventional observation data over the tropical ocean.

An estimation of ozone flux in a stratosphere-troposphere exchange event

A new method based on mass fluxes and observed ozone profiles was developed to estimate crosstropopause ozone flux. Using this method, we estimated the cross-tropopause ozone flux in a stratospheric-tropospheric exchange event that occurred over East Asia in March 2001.The result revealed that the ozone flux across the tropopause in this event was an order of magnitude higher than the global and hemispheric average. Compared to the traditional method using a linear relationship between ozone mixing ratio and potential vorticity near the tropopause, the cross-tropopause ozone flux evaluated with ozonesonde data was somewhat higher, although the orders of the two values were the same.

Localized 3D-structural features of dynamic-chemical processes of urban air pollution in Beijing winter

The Beijing City Air Pollution Observation Field Experiment (BECAPEX) is described with emphases on the 損oint-surface?research approach and composite analysis. The analysis results of measurements from four observation sites across the Beijing urban area from January to March indicate that the overall impact of urban emission sources in the heating season is significant, and the staggered impact of urban emission sources has different features at observation sites over different parts of Beijing in both heat-ing and non-heating seasons. The pollutants NOx, SO2 and CO in the urban boundary layer have the in-phase variation features over a large area. O3 concentrations at different sites have the same variation trend but its change is reversed phases with above pollutants. The pollutants over the urban area in heating and non-heating seasons also have the syn-chronous variation trend. The comprehensive sounding of BECAPEX indicates that pollutants and aerosol vertical profiles are closely correlated to the vertical structure of the large-scale inversion layer in the urban boundary layer over the urban area. The localized 3D-structural features of local urban polluting processes associated with the peripheral areas are discussed with a 損oint-surface?comprehensive sounding technique.