The Impact Of ENSO Events To Droughts And Floods In Qinghai Province

Supported on the precipitation data, temperature data, NOAA sea surface temperatureanomaly (SSTA) Index and Southern Oscillation Index (SOI), using Mann-Kendall trendanalysis, empirical orthogonal function (EOF) decomposition method, correlation analysisand Z-index analysis on droughts and floods, combined with ArcGIS spatial analysistechniques, the papers discussed the climate change law, variation of extreme precipitationevents and variation of droughts and floods in Qinghai Province, and we discussed the impactlaw of ENSO events to climate change and droughts and floods disasters in Qinghai Province.It is beneficial to understanding the climate change of Qinghai Province on the large-scale.The results have showed as follows:(1) In the passed47years (from1959to2005), the increasing trend of precipitation isnot obvious, but the increasing trend of temperature is significant, so the climate in QinghaiProvince is becoming more and more warm and dry; the spatial variation of annualprecipitation and temperature showed decreasing trend from east to west and the variationtrend of each site was unanimous, the time variation showed a significant inter-annualchanges; the annual precipitation in the eastern agricultural area had the greatest change, andthe annual temperature in the farming and pastoral areas had the greatest change; the annualprecipitation changed greatly in the1970s and1990s, Annual temperature changes greatly inthe late20th century.(2) The spatial variation of extreme strong (weak) precipitation threshold showing adecreasing trend from southeast to northwest; each site of the annual extreme strong (weak)precipitation variation was inconsistent, and the time variation showed inter-annual changes;the annual extreme strong precipitation had a greatest change in the eastern agricultural areaand southeastern pastoral areas, and the annual extreme weak precipitation had a greatestchange in the eastern agricultural area; the contribution rate of extreme strong precipitation toregional floods was showed a increasing trend from southeast to northwest, with the oppositeto the distribution of Qinghai precipitation, so the impact of extreme strong precipitationevents to the northwest area’s floods could not be ignored. (3) The calculation results of Z-index on droughts and floods showed as follows,meteorological drought and waterlogging disasters in Qinghai Province occurred in4-10months in every years, and the meteorological drought trend to frequent; the meteorologicaldrought occurred in the Northwest areas, waterlogging disasters occurred in the Northeastareas and the heavy flood disasters occurred in the southern area, it is closely linked to thedistribution of precipitation.(4) The correlation analysis between climatic factors and ENSO events eigenvalues(SSTA, SOI) in the entire time series showed, with time growth, the impact of ENSO eventsto precipitation and temperature reducing, but the sphere of influence increasing, and thesphere of influence to climate increasing to maximum in the lagged period of2months.(5) The number of occurrences of EI Nino/La Nina events was counted, the resultsshowed that the EI Nino events tend to frequent, and it is consistent with the trend of globalwarming; the impact degree and range of EI Nino/La Nina events to precipitation andtemperature increased to maximum in the lagged period of1months; and the impact of EINino/La Nina events to temperature was larger than precipitation.(6) The impact of ENSO events to the extreme strong precipitation showed reducingtrend from east to west, and the impact of EI Nino events to the extreme strong precipitationwere larger; the impact degree and range of EI Nino/La Nina events to extreme weakprecipitation increased to maximum in the lagged period of1months.(7) The impact of ENSO events to meteorological drought was larger in the full areas inQinghai Province, the impact to waterlogging disasters was larger in part of the QinghaiProvince; the impact range of ENSO events to meteorological drought and severe droughtdisasters were both larger, and the impact of EI Nino events was larger than the La Ninainfluence; the ENSO events had a larger influence to the Waterlogging disasters of theNorthwest areas, and had a smaller influence to the Southeast areas, the La Nina influence toWaterlogging disasters was larger than EI Nino influence.