Statistical-Dynamic Features Of Interdecadal Spatial-temporal Evolution Of Regional Climate In East Asia Under Global Change Background

Under global warming background, the impacts of climate change on environment, water resource,agriculture, industry and people's life are becoming more and more remarkable and drawing more andmore attention. In order to study the change laws and their causes of regional climate in China and EastAsia monsoon (EAM) in recent 40 years, it is very necessary and urgent to disclose the spatial structureand its interdecadal change (IC) features of climatic basic factors. In virtue of the statistic-dynamicsynthetical methods such as climatic trend turning discriminating model (PLFIM), correlation analysis,EOF-SVD compositive analysis, this paper analyzes the ICs and trend turning characteristics of climatemodes in China, with emphases on the researches of spatial-temporal features of the ICs of EAM andthe heterogeneous thermal structure in East Asia under global warming and the correlation of ICsbetween EAM and the sea–land thermal difference in East Asia–West Pacific (SLTD). In addition, wealso studied the IC characters of meteorologic factors, such as sunshine duration and low cloud cover(LCC) etc. in East China and discussed the relations between IC of EAM and regional climate effect ofaerosol. Finally, the RegCM3 is used to investigate the influence effects of the changes of SLTD.The confidence of NCEP/NCAR reanalysis data: The seasonal characters and spatial differencesof the confidence of NCEP/NCAR reanalysis data in China are studied by using varied statisticalmethods, such as normalized root mean square (RMS), correlation analysis and empirical orthogonalfunction analyze (EOF) etc. Viewed from time, the confidence of reanalysis wind data in spring,summer and autumn is preferable, but that in winter is worse. The confidence of surface air temperature(SAT) data is best in winter and worst in summer. Viewed from space, the confidences of reanalysiswind and SAT data in eastern China are better than those in western China. Along with the heightincreases, the confidence of reanalysis wind data is better.The spatial structures of interdecadal turning of climate modes: Using climatic trend turningdiscriminating model (PLFIM), the interdecadal turnings of climate modes (CMIT) in winter andsummer of varied stations and sub-regions in China during 1961?2000 have been investigated. Resultsshow that the stations with close occurrence years of CMIT and coincident trends after the turningsexhibit a zonal distribution, indicating a notable regional "in-phase" feature. The test results of stationsand sub-regions show that the occurrence time of interdecadal trend turning (ITT) of temperature fromdecrease to increase in northern China is earlier than that in southern China in winter, while theoccurrence time in northern China is later than that in southern China in summer. The warming trendafter turning in northern China is more significant than that in southern China in both winter andsummer. The last ITTs of summer precipitation mostly occur in 1980s;afterwards, summer precipitationincreases in southern China and decreases in northern China except in Northwest China, exhibiting anotable "south-flooding and north-drought" trend.The interdecadal change characteristics of spatial structures of regional climate and EAM:The temporal and spatial distributions of the IC of EAM and SLTD in recent 40 years and theirrelationship are studied based on NCEP/NCAR reanalysis data and monthly observational data in China,such as SAT and precipitation, and using some statistic methods, such as running mean, correlationanalysis and EOF-SVD compositive analysis. Results suggest that the first eigenvector of interdecadalcomponent (FEIC) of sea level pressure (SLP) in winter displays a "negative in north and positive insouth" spatial structure, and its time coefficient (TC) happens a turning from negative to positive in thelast 1970s, reflecting the weakening and southward extending of East Asia winter monsoon (EAWM).The FEIC of SAT in winter exhibits a spatial distribution with distinctive warming over northern landand little change over southern land and sea, and its TC occurs a turning from negative to positive in theearly 1980s, suggesting the change of SLTD with decreasing in north and increasing in south. Theinterdecadal spatial-temporal changes (ISTC) of the above two meteorological elements are inaccordance, indicating the close correlation between the IC of EAWM and the ISTC of SAT in winter.Using SVD, it is found that the interdecadal correlation between SLP and SAT in winter over land ismore significant than that over sea, suggesting the IC of EAWM may be a regional response of theclimate in East Asia to the heterogeneous spatial structure of global warming. According to the analysisresults of ISTC of SAT in spring and 850hPa wind in summer and their correlation, it is discovered thatthe southerly at 850hPa over eastern China weakens decade by decade. The FEIC of 850hPa windexhibits the northerly or east-northerly anomalies in the eastern of East Asia, South China Sea and theeastern of Bay of Bengal, suggesting the weakening of East Asia summer monsoon (EASM). The year1978 is the turning point when its TC turns from negative to positive;that is to say, the EASM becomesweak after this year. The FEIC of SAT in spring displays a spatial structure with "positive in north andnegative in south" over land and positive over sea, indicating the decreasing of SLTD in spring. Its TCalso occurs a turning from negative to positive in 1978, suggesting that on the interdecadal time scale,SLTD between the south of East Asia and the West Pacific is characterized by two periods with differentintensity and they are consistent with the two periods with varied intensity of EASM. The results bySVD also show that there exists an important relation between the interdecadal weakening trend ofEASM and the ISTC of SAT in spring. As a whole, the interdecadal weakening trend of EASM isclosely correlated to the heterogeneous spatial structure of SAT over East Asia-West Pacific in spring.The spatial evolution of aerosol and its regional climatic effects: The primary discussion onaerosol influence domains and their regional climatic effects in Beijing and its peripheral in winter andEast China in summer half year in recent about 20 years are performed, and the viewpoint that aerosolregional climatic effect have a certain spatial range is proposed in this paper. Results show that thereexists an aerosol influence domain in Beijing and its south peripheral and the IC of sunshine duration,LCC and fog days show a distinctive difference within and out of the aerosol influence domain inwinter. The regional climate changes including decreasing sunshine duration, increasing LCC and fogdays exist in Beijing and its south peripheral, which are consistent with such trend that aerosol opticaldepth (AOD) in this region increases in recent 20 years. It is found in further investigation that thecorrelation coefficient fields of AOD with sunshine duration and SAT in summer half year in easternChina show a "south negative and north positive" distribution and the significant negative correlationregion is located in the south of eastern China that is also the significant positive correlation regionbetween AOD and LCC, which is similar to the marked interdecadal increasing region of summerprecipitation. It denotes that the regional climatic effects including increasing LCC and precipitation butdecreasing sunshine duration and SAT in summer half year might be caused by increasing aerosol in thesouth of eastern China. It also suggests that in summer half year, the aerosol influence domain overeastern China is located in its south. By calculating the correlation coefficients of AOD with verticalvelocity and meridional wind in summer half year in eastern China, it is found that the regional climaticeffects of aerosol have some impacts on the EASM.The response of regional climate to the change of SLTD: Shown for the sensitivityexperiments by RegCM3, it will cause reduction of east-west direction SLP difference and weakeningof low level northerly wind if winter long wave cooling rate over the northeast of East Asia is decreasedin RegCM3, which indicates that the regional climatic response to greenhouse effect is a possiblereason of the weakening of EAWM. In RegCM3, decreasing SAT over the southeast China andincreasing SAT over the ocean to south of China will lead to the weakening of the intensity of WestPacific subtropical high and leaning to south of its location in summer, as well as the weakening ofEASM. Furthermore, it will cause the "south-increasing and north-decreasing" distribution of summerprecipitation in East China. It is similar to the simulation result of the sensitivity experiment withdecreasing solar heating rate over the south of eastern China in spring and summer. These resultssuggest that the regional climatic response to the change of SLTD associated with aerosol influenceeffect is related to the variety of EASM intensity. These simulation results of sensitivity experimentsreasonably validate the diagnosis results of the ISTC of EAM.