Study Of Climatic Disaster On Drought In Gansu Province And Its Responses To Climatic Change

The global warming has been and will have extensive and meaningful effects on the climate and ecosystem in the Northwest of China. The issue on arid climate change in the Northwest of China has been received a great deal of recent attention and become a subject of extensive research. As one of important region in the Northwest of China, the arid climatically disaster in Gansu province becomes severer and severer.The climatic observed data which had been provided by National Climate Center were used, these data had been recognized by our Project Team (2005DIB3J10- 0).The relating literature ancient books were consulted, and the natural and the humanities factors which had probably leaded to the arid climate disaster in Gansu Province were analyzed , the precipitation characteristic in Gansu Province had been studied, what's more , the summer drought and flood characteristic in Gansu Province which had major impact on the agricultural production had been researched. Finally, the response of arid disaster to the climatic change was analyzed.The main conclusions are as follow:(1)It is Gansu Province being far away from the sea that make the water vapor transporting limited, scarce precipitation is extremely uneven distribution in the whole country; most of the natural landscape is desert and Gobi, the vegetation is sparse, surface albedo is high, water conservation capacity is low, the evaporation rate is far greater than precipitation rate; the farmlands raising by the rain share absolute advantages in arable land, these are the natural factors ;since the past 50 years, the population have been increasing, the large area of forest destructing, grassland degradation from overgrazing, these have been resulting in declining on vegetation cover and water conservation capacity, serious soil erosion, land desertification intensified, serious deterioration of the ecological environment, these are the human factors; such non-rational behaviors as ancient frequent wars, over-picking denudation, over-grazing retreated the forest, land desertification, water resources drying up is the historical factors. Human factors plays a role of promoting on the development of drought disaster.(2)Precipitation is increasing from northwest to southeast in Gansu province, the stability is increasing according to precipitation increasing. There are such three models as large-scale consistent, northwest being contrary to southeast and the central districts opposing the northwest and southeast districts representing the spatial distribution of precipitation, the province can be mainly divided into four regions of precipitation; finally, there are different turning points of precipitation in different temporal scales. (3)As a whole system, the percentage of drought in summer is more than the flood's and as a single month, the frequency of flood is equal to the drought's in 6-7 months, but the normal frequency is poorer, and the frequency of bigger drought is also more than the bigger flood's in 7-8monthes.There are three models representing the spatial distribution of flood-drought, Gansu province can be mainly divided into four regions of flood-drought. There are different jumping points of flood-drought in different temporal scales, the inter-annual variable trends of flood-drought is arid in large scale and periodic characteristics every four year is distinct.(4)The warming and drying trend of climate in Gansu Province is clearly in recent 50 years. Drought disaster is a significant growing trend. Drought disaster is a reflection of arid climate change. The annual mean temperature and the lowest highest temperature in Gansu province have been displaying the extremely warming tendency, the lowest temperature's increasing rate is higher than the annual mean highest temperature obviously, the four seasons temperature change is most remarkable by spring winter warming, but the temperature's increasing rate in summer is not obvious. The yearly average precipitation overall displays a declining trend, the season characteristic performance of precipitation is as below: The summer winter precipitation has increased slightly, spring and autumn is reverse instead, but the relevance is not big. The precipitation reducing in autumn and Spring is bigger than the share increasing in summer, and this causes the entire province precipitation to a declining trend. The dry disaster in Gansu province has been distinct positive correlation to the temperature moment even (winter exception), but displayed the remarkable negative correlation with the yearly precipitation, and the precipitation in spring has affected on the Gansu Province arid disaster significantly.