The East Asian Monsoon Simulation with IAP AGCMs-A Composite Study

Ｔｈｅ　Ｅａｓｔ　Ａｓｉａｎ　Ｍｏｎｓｏｏｎ　Ｓｉｍｕｌａｔｉｏｎ　ｗｉｔｈ　ＩＡＰ　ＡＧＣＭｓ－Ａ　Ｃｏｍｐｏｓｉｔｅ　ＳｔｕｄｙＷａｎｇＨｕｉｊｕｎａｎｄＢｉＸｕｎｑｉａｎｇ（ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＰｈｙｓｉｃｓ（ＩＡＰ），...     

近10年我国降水的QBO分析

近10年来我国东部地区降水分布趋势的年际变化具有QBO特征，双年的降水为中部地区少南北多，单年的降水为中部多南北少，其中江淮流域的降水变化最明显。分析表明，降水QBO的特征与西太平洋副高和冷空气活动有关，一般双年副高偏北、亚洲纬向环流发展，雨带偏北；单年相反，副高偏南、亚洲经向环流发展，雨带偏南，江淮流域降水较多。     

Simulation of East Asian Summer Monsoon by Using an Improved AGCM

The IAP 2-L AGCM is modified by introducing a set of climatological surface albedo data into the model for substituting the model’s original surface albedo parameterization. The comparison between the observations and the simulation results by the modified model shows that the general features of the East Asian summer monsoon can be well reproduced by the modified IAP 2-L AGCM. Especially for the simulation of monsoon precipitation, the modi-fied model can well reproduce not only the monthly mean features of the summer monsoon rainfall over East Asia, but also the stepwise advance and retreat of the East Asian summer monsoon rainbelt. Analysis results demonstrate that the good simulation of the monsoon rainfall is closely related to the reasonable simulation of the large scale gen-eral circulation over East Asian region, such as the western Pacific subtropical high, Asian monsoon low and the low level flows. The good performance of the modified model in the rainfall simulation shows its great potential to serve as a useful tool for the prediction of summer drought / flood events over East Asia.     

亚洲夏季风活动激发的北半球大气环流遥相关型

亚洲季风区是全球热力变化最为显著的区域，亚洲夏季风活动必定会对其它环流系统产生影响。本文通过夏季风指数与北半球环流的相关计算以及强、弱季风候北半球环流异常合成的分析发现，亚洲夏季风的活动会激发北半球夏季大气环流遥相关型，其主要相关中心均出现在季风区的下游地区，即从亚洲经太平洋至北美洲一带，除了表现出正负中心交替出现的波列状结构外，该遥相关型在太平洋地区还表现为一对南北向的偶极子异常型，我们将这一遥相关型称为亚洲太平洋北美（ＡＰＮ）型。     

Correlation of climatic events between East Asia and Norwegian Sea during last deglaciation

Using a high resolution¹⁴C chronology, β¹³C values and organic carbon content, from loess/paleosol and peat profiles in China, we can demonstrate century scale warm-cold East Asian monsoon paleoclimatic fluctuation events and significant precipitation variability within the last deglaciation. The major climatic events recognized are the Bolling (1 300-12 500 a B.P.), Older Dryas (12 500-11 750 a B. P.), Allerod (11 750-11 200 aB.P.) and Younger Dryas (11 200-10 000 aB.P.). The stratigraphic structure of the last deglaciation sediments is characterized by frequent changes in sedimentation phases reflecting climatic instability. These high frequency, rapid climatic events can correlate with fluctuations recorded by sea surface temperatures in the Norwegian Sea. This indicates a pale-oclimate teleconnection between polar, high latitude areas and East Asian monsoon areas through westerlies and the related atmospheric pressure system. Project supported by the National Natural Science Foundation of China, the Foundation of Chinese Academy of Sciences and the National Science Foundation of U.S.A.     

Latent and sensible heat fluxes under active and weak phases of the summer monsoon of 1986

An analysis of the meteorological data collected by the research vessel ORV Sagarkanya for the mean latent and sensible heat fluxes over the Arabian Sea has indicated appreciable changes between active and weak phases of the southwest monsoon of 1986. We suggest that: (a) the presence of a core of low level winds associated with the Somali jet and its southward shift during the season, along with (b) a ridge in surface pressure over the central Arabian Sea could be responsible for the deficit in monsoon rainfall along the west coast of India in 1986.     

Oxygen and hydrogen isotopic ratios in groundwaters and river waters from India

A comprehensive set of measurements of oxygen and hydrogen isotopic ratios in groundwaters as well as waters from rivers, lakes, hot springs etc. taken from a variety of locations in India has been carried out for the first time. Isotopically the most depleted samples occur in the high altitude precipitations in the Himalayas e.g. in the lakes of Bhutan and the source water of the Ganga. The shallow groundwater data display a continental effect where the heavy isotope content decreases with distance from the coast (about 4 to 6 per mil decrease in δ¹⁸O per 1000 km). The δ D and δ¹⁸O of these fresh waters are linearly related and an analysis of this relation vis-a-vis the meteoric water line shows the unambiguous effect of enrichment due to evaporation from soils.     

Interannual and long-term variability of the summer monsoon and its possible link with northern hemispheric surface air temperature

Some statistical properties of the summer monsoon seasonal rainfall for India during the last 100 years (1881–1980) are presented. The most recent decade of 1971–1980 shows the lowest value of standard-decadal average monsoon rainfall (86.40 cm) and is also characterised by the second highest value of coefficient of variation in monsoon rainfall (12.4 %). The combined last two standard-decadal period of 1961–1980 was the period of the largest coefficient of variation and the lowest average monsoon rainfall for India. The possible influence of global climatic variability on the performance of the monsoon is also examined. Analyses of correlation coefficient show that a statistically significant positive relationship with a time-lag of about six months exists between monsoon rainfall and northern hemispheric surface air temperature. A cooler northern hemisphere during January/February leads to a poor monsoon. All the major drought years during the last 3 decades had much cooler January/February periods over the northern hemisphere—1972 having the coldest January/February with a temperature departure of −0.94°C and the most disastrous monsoon failure.     

Interannual and long-term variability of Indian summer monsoon rainfall

Analysis of summer monsoon (June to September) rainfall series of 29 subdivisions based on a fixed number of raingauges (306 stations) has been made for the 108-year period 1871–1978 for interannual and long-term variability of the rainfall. Statistical tests show that the rainfall series of 29 sub-divisions are homogeneous, Gaussian-distributed and do not contain any persistence. The highest and the lowest normal rainfall of 284 and 26 cm are observed over coastal Karnataka and west Rajasthan sub-divisions respectively. The interannual variability (range) varies over different sub-divisions, the lowest being 55 and the highest 231% of the normal rainfall, for south Assam and Saurashtra and Kutch sub-divisions respectively. High spatial coherency is observed between neighbouring sub-divisions; northeast region and northern west and peninsular Indian sub-divisions show oppositic correlation tendency. Significant change in mean rainfall of six sub-divisions is noticed. Correlogram and spectrum analysis show the presence of 14-year and QBO cycles in a few sub-divisional rainfall series.     

盛夏中国北方的超强区域性持续暴雨

将“６３．８暴雨”与“７５．８暴雨”的天气学特征作了系统的对比分析。研究表明：尽管这两次暴雨相隔１２年,主要暴雨落区相距５００ｋｍ以上,发生暴雨的低气压系统分别来自西南与东南等差别,而形成暴雨的基本天气学过程是非常相似的。概括这两次暴雨的环一种盛夏出现在中国北方的超强区域在气的概念模型。