The Configurable Relationships Between Warm-Cold And Dry-Wet In Cliamte Change Over China

The monthly data set of self-Calibrated PDSI from 1951to 2004 over Chinese 160 stations is derived using historical precipitation and temperature data provided by China Meteorological Administration (CMA). The temporal-spatial distributions of the configurable relationships between warm-cold and dry-wet in Chinese climate change are studied using PDSI, historical precipitation and temperature data, especially their inter-decadal characteristic and climatic shifts. Then we specifically focus on the impacts of some climate factors of ENSO, East Asian monsoon and global warming to the configurable relationships. The result shows that there are large spatial difference and inter-decadal change characteristic in the configurable relationships between warm-cold and dry-wet in climate change over China. Over North China the climate shifts from the wet-cold pattern during 1950s-1970s to the warm-dry pattern from 1980s to present, moreover the trend of climatic shift to warm-dry is the most serious over China. In north-east China the regional climate also changes from the wet-cold pattern to the warm-dry pattern, but not so typical as North China. In the west regions of northwest China the regional climate has happened a prominent inter-decadal climatic shift, the regional climate was characterized basically by the wet-cold pattern during 1950s and was under the dry-cold or dry-warm pattern from 1960s to 1986, but after 1987 was mainly under the warm-wet pattern. The trend of climatic shift to warm-wet is very notable in the west regions of northwest China. In the middle regions of northwest China the climatic pattern only becomes wet slightly, and warming is more notable weting. In the most east area of northwest China the climatic pattern shifts from cold-wet to warm-dry,from 1950s to 1986 the climate is mainly the cold-wet pattern, but after 1987 is mostly the warm-dry pattern. South-east China is another noticeable region, the climate shifts from the cold-dry or cold-wet pattern to warm-wet pattern, during 1951-1986 only one year of 1953 is the warm-wet pattern, but the latest 10 years are all under the warm-wet pattern. Through the analysis of the mechanism, it is found that there is one good relationship between ENSO and the variations of warm-cold and dry-wet in China. An EOF analysis of the PDSI reveals a fairly linear trend resulting from trends in precitation and surface temperature and an ENSO-induced mode of mostly interannual variations as the first leading pattern. The ENSO EOF shows that during the typical warm phase of ENSO , surface conditions are drier in most regions of China ,especially the north China, however wetter than normal in the southern regions of Changjiang river. During the typical cold phase of ENSO ,these anomalies reverse sign. The time scale of the relationships mentioned above are mainly 4-8 years.There is also one decadal change, during 1951-1961 and 1976-2000 the relationships are good, but bad from 1962 to 1975. The research also shows that the recent climate changes over China, especially the north China's drying and northwest China's weting, are closely relate to the shift in ENSO towards more warm events since the late 1970s. It is also found that there is one very good relationship between east Asian summer/spring monsoon and the temporal-spatial distributions of the dry-wet variations in Chinese climate change. The EOF analysis of the PDSI also reveals that the temporal and spatial patterns of the first PDSI's EOF are highly correlated with EASM and April-May 850hpa meridinal winds , suggesting that EASM has a great impact on the temporal-spatial distributions of the dry-wet variations in Chinese climate change. The recent 20-30 years climate changes of north China's drying and northwest China's weting are closely relate to the inter-decadal change of EASM. It is also found the April-May 850hpa meridinal winds over the region of EASM are also highly relate to the dry-wet variations in Chinese climate change, it will exbit a great significance for predicting summer droughts and wets in China. Under the global warming ,surface air temperature in recent 20-30 years has been increasing rapidliy in most parts of China, which has made a great impact on the dry-wet variations in Chinese climate change. In recent 30 years warming bring on that surface conditions are more drier in drying regions, e.g, north China, northeast China and eastern northwest China , less wetter in wetting regions for southeast China. At the same time, it is also found that warming is benefit to the wetting of western northwest China. In fact, the warming by the end of the 20th century results in increases or decreases of 0.5-2 of PDSI over most parts of China. These changes are very significant considering that a PDSI of less than –0.5is classified as dry or drought conditions by Palmer(1965).