| Under the background of global climate change, the intensity and frequency of dro ught events occurred in the eastern agricultural region of Qinghai province have change d. Based on the precipitation, temperature and other meteorological data(from 1960 to 2005) of 12 meteorological stations of eastern agricultural province of Qinghai, 12 stati ons’ comprehensive meteorological drought index CI and standard precipitation index SPI were calculated in this paper, annual and seasonal drought characteristics of the study area in recent 45 years were analyzed, and the applicability of SPI index and CI inde x in the study area were evaluated. With ENSO events representing by the Sea Surface Temperature Anomaly(SSTA) and SOI respectively, changing of temperature and preci pitation in the study area in different years and seasons were analyzed, and the relation ship between temperature, ENSO events and regional drought events were analyzed as well. The results show that:(1) The intensity of drought in eastern agricultural area of Qinghai province has inc reased, the frequency of drought in southern region is slightly higher than that of the eas tern region, the drought events in research region of the southern were more frequent tha n that of in the eastern region, the duration of drought of arid area in the south area is slightly longer than that of in the northern region, effects of drought on southern study area would be more serious.(2) The spring drought intensity in the study area was heavy, the diversity of spring drought intensity in different years was obvious, spring drought intensity has increase d year by year; drought frequency in the central region of the study area were slightly h igher than that of the northeast, drought events in the central region were more frequen t than that of the northeast. The summer drought intensity in the study area were slightl y lower than that of the spring, summer drought frequency and their duration of the stu dy area in the south area were higher than that of in the north area, the impact on the drop in the study area would be heavier. The intensity of autumn drought in the study area has increased; autumn drought events in the south of study area were more frequent than that of the northern region, the duration of drought in the south was slightly lo nger than that of the northern region. Winter drought events intensity were low, drought event in the winter of the central of the study area were more frequent than that of t he northern and the duration of the southern and central regions were slightly longer th an that of northern region, the effects of winter drought in central and southern of the s tudy area would be larger.(3)The data in the standardized precipitation index SPI is simple, easy to obtain a nd calculate, comparing with that of the comprehensive meteorological drought index CI.The CI index is more sensitive to mild drought and moderate drought, while the SPI in dex is more sensitive to extreme drought. The consistency of CI index and SPI index in t he defined drought intensity value in this region is good, level consistent rate in the nort hwest part of the site is higher than that of the southeast part. In the actual drought oc currence, the defined drought intensity in the two index were slightly different, howeve r, the defined drought level of the two index is coincides with the actual conditions on the whole.(4) The months of Sea Surface Temperature Anomaly SSTA defined by ENSO eve nts are more than that of it defined by Southern Oscillation Index SOI, there is a negat ive correlation between the big SSTA and SOI index. The study area temperature shows an obvious upward trend in the annual changes, while the precipitation of region sho ws an obvious downward trend; regional temperature and precipitation changes during the year had a great change, and had obvious seasonal feature. Monthly precipitation of the study area and monthly mean temperature have significant correlation.(5) Monthly average temperature of the study area and SPI index correlation coeffi cient are regional, the correlation coefficient in the southwest is high, while in the centra l and northeast, the monthly average temperature and SPI index correlation coefficient is small, the correlation coefficient of months average temperature and the in summer and winter is high. ENSO events have different influence on SPI index in the study area of each site, the months of La Ni?a event’s occurrence defined by SOI index delay 2 m onths; it has a nice negative correlation with SPI, correlation of which is significant.(6)Spectrum analysis of 12 sites’ the SPI average number and ENSO events shows that there are common significant periods. The drought cycle in the eastern agricultural region of Qinghai province is shorter than ENSO period, but they are very close, indica ting that they have significant correlation. Influence of El Ni?o event and La Ni?a event on drought in the eastern agricultural area in Qinghai province is basically the same, El Ni?o event has greater influence on drought in eastern agricultural areas of Qinghai province. |
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