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Study On Arid Climate Change In The Northwest Of China And Its Response To Global Warming

Posted on:2006-12-19Degree:DoctorType:Dissertation
Country:ChinaCandidate:L C SongFull Text:PDF
GTID:1100360152983144Subject:Science of meteorology
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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.In this paper, using a longer climate dataset we establish a precipitation series of recent 100 years in the Northwest of China, analyze the observing fact of arid climate change and sandstorm change, and diagnose the possible reasons based on atmospheric circulation which result in variation of arid year and wet year. We also simulate the response of temperature and precipitation under the situation of CO2 × 2. The main results show as following:l.The precipitation change indicates that there is moderate confidence in decrease during the last century in the Northwest of China and the bottommost point in the 1960s-1970s.The inter-decadal trends of precipitation between the East and the West of the Northwest of China show a contrary variation. The annual precipitation has decreased from 1980 in its eastern part, especially in autumn, but increased in its western part with significant confidence in summer and autumn. 2.The monthly temporal-spatial distribution of sandstorms indicates the sandstorms occur most frequently in the Tibetan Plateau and arid and semi-arid areas in northern China. The center of sandstorms is in the Tibetan Plateau and gradually moves northward from December to March and the most areas of sandstorms happen in April. In winter and spring the majority of KOSA(yellow sand) in Japan, and Korea derive from the Tibetan Plateau and northern China. The dust is transported by the vortex system in lower levels and by the planet westerly in upper levels. 3.The sandstorm is a response to Arctic Oscillation (AO) and frozen soil. The results show that when the Arctic Oscillation is negative episode, correspondingly, the zonal circulation index exhibits negative anomaly and the westerly flow in middle and high latitudes weakens, which makes cold air in polar areas to transport southwards and the Siberia High to strengthen, thus results in frozen soil deepening and sandstormincreasing such as in 1960s and 1970s in the Northwest of China. The oppositesituations happen in 1980s and 1990s.4. When drought occurs in the eastern part of the Northwest of China low frequencyteleconnection shows EAP and AIA patterns, and the curves of 500 hpa high field inmost areas represent large-frequency and long-period. Australia High becomes muchweaker while Mascarene High, cross-equatorial flow, Somali jet and southwestmonsoon become much stronger.5.The surface temperature will increase 2.87°C and annual precipitation will increase27.4% under the situation of CO2 X 2 in the Northwest of China.
Keywords/Search Tags:Drought in the Northwest of China, Climate change, Diagnosis, Numerical experiment
PDF Full Text Request
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