Circulation Anomalies of Interannual and Interdecadal Changes in Summer Precipitation over the Tarim River Basin
The interdecadal and interannual changes in summer precipitation in the Tarim River Basin(TRB)were analyzed by using the NCAR/NCEP reanalysis data in summer(June-August)from 1961 to 2020 and precipitation data from 38 meteorological stations.A 5-year running average was employed to distinguish between interdecadal and interannual changes.Typical dry and wet years,as well as dry periods(1963-1986)and wet periods(1989-2018)with interannual variations,were identified.Furthermore,the atmospheric circulation anomalies related to these two time-scale changes were investigated.The analysis reveals distinct differences in the changes between interdecadal and interannual patterns of precipitation.Moreover,the atmospheric circulations influencing these changes also exhibit dissimilarities.The interdecadal variations in atmospheric circulation anomalies primarily manifest as alternating anticyclonic and cyclonic anomalies in the tropospheric geopotential height fields of the Atlantic and Eurasia,extending from northwest to southeast.During the wet period,the anticyclone and cyclone intensify in Mongolia and Central Asia,respectively.Noticeable easterly and southwesterly wind anomalies occur in the eastern and western regions of the basin,respectively.Additionally,the increased water vapor mainly originates from the northwest Pacific Ocean and the Indian Ocean.Conversely,during the dry period,the opposite conditions prevail.The primary atmospheric circulation anomalies influencing the interannual variations are as follows:during wet years,significant anticyclonic anomalies occur outside the TRB in the northwest and northeast regions of the troposphere,while cyclonic anomalies dominate in the western part of the TRB.Moreover,the eastern region of the basin experiences an intersection of anticyclonic and cyclonic anomalies.The transport of water vapor from the north and south to the TRB increases,with the north wind water vapor flux anomaly exhibiting greater transport to the basin.Conversely,the south wind water vapor flux anomaly is smaller and concentrated primarily in the western part of the basin.The increased water vapor primarily originates from the Arctic Ocean and the Indian Ocean.Conversely,during dry years,the opposite conditions prevail.
precipitationinterdecadal and interannual changesatmospheric circulation anomaliesTarim River Basin
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