Alternation Of Dry And Wet Climate Zone And Its Cause Analysis In China In Last 50 Years

Climate regionalization is conducive to the understanding of regional differences in climate and regional climate characteristics from a systematic point of view, and is of practical significance to the healthy and sustainable development of agriculture, the reasonable utilization of climate resources and the evaluation and protection of the ecological environment in China. This paper takes 1961-2010 years as the research time, collects nearly 50 years of conventional ground meteorological observation data, NOAA/AVHRR data and basic geographic information data, selects two kinds of wet and dry indexes as the annual precipitation and annual dry index, discusses the spatial distribution of dry and wet zones in China and ten basins, the variation law of wet and dry regions, the variation law of wet and dry influence factors and The dominant factors of dry and wet climatic changes in the last 50 years. This paper mainly completed the following aspects of the work:(1) Spatial distribution and area distribution of dry and wet zones in two kinds of dry and wet indexes of annual precipitation and annual dry index on the three time scales of multi-year average, different decades and different years show that the spatial distribution of drought is gradually increasing from the southeast to the northwest and climate zone presents a northeast-southwest angle tilt strip in China. The area of dry and wet area is sorted as follows:semi-humid area> humid area> arid area> semi-arid area. The area of arid area and semi-humid area are decreasing, and the area of semi-arid area is increasing.(2) The changes of dry and wet climate zone are classified, and the spatial distribution and change trend of dry region, variable wet region and invariant region are analyzed. Also change trend of area increase, area reduction and overall rate according to different dry and wet zones are analyzed. The results show that the line between semi-humid area and semi-arid area has the most obvious fluctuations, which causes the most significant change in dry and wet area. On the whole, the wet area is more than the dry area, and the wet area is increasing. The rate of increase or decrease of the area of semi-arid area and semi-humid area is much larger than that of wet and dry regions.(3) Different time scales analysis of wet and dry factor trends and its dominant factor show that dryness mainly shows an upward trend in the Chinese area in 1960s and 1970s, mainly caused by the decline in annual precipitation. Dryness mainly shows an upward trend in 1990s, mainly caused by the increase of annual potential evapotranspiration. Dryness mainly shows a downward trend in 1980s and 2000s, mainly caused by the increase in annual precipitation. But it’s the most common that the change trend of dryness is caused by the interaction in potential evapotranspiration and precipitation.(4) The interannual analysis of dry and wet factor trends and its dominant factor show that drying mainly shows a downward trend in nearly 50 years in the Chinese area, mainly caused by the decline in potential evapotranspiration. In terms of different river basins, dryness mainly shows an upward trend in Songhua River Basin, Liaohe River Basin and the Yellow River Basin, mainly caused by the decline in annual precipitation. The Haihe River Basin, Huaihe Basin, Yangtze River Basin, Pearl River Basin and the Southwest River Basin have the similar situation, with the whole Chinese area, mainly caused by the decline in annual potential evapotranspiration. Dryness in the Southeast and Northwest River Basin follows descending trend, mainly caused by the rising trend of annual precipitation effect.