Land-sea Temperature Difference And Its Association With Summer Precipitation In Eastern China

The temporal and spatial characteristics of the land and sea surface temperatureanomalies were analyzed based on the observed summer land surface temperature andprecipitation datasets from355stations in eastern China and HadISST reanalysis data for1957to2010. Then the relationship between the zonal and meridional land sea temperaturedifference and the summer precipitation was discussed. Furthermore, the lower atmosphericcirculation changes in the period of1989to2000were simulated using a regional climatemodel. The main conclusions are as follows:(1)The regions where the land surface temperature changed significantly are located inthe lower reaches of the Yangtze River and Northeast China. The areas of sea surfacetemperature greatly changed are in the East China Sea and its adjacent seas (including theYellow Sea and the northern East China Sea) and the Japan Sea. Regional zonal andmeridional land-sea temperature difference index were established according to the key areaswhere land and sea surface temperature changed significantly. The wavelet analysis resultsshow that the index of zonal temperature difference had an interdecadal periodicity about13years after the mid-1970s and a6~9years interannual periodicity before the mid-1970s,andthere are a6~8years interannual periodicity and a27~30years interdecadal periodicity formeridional index. Further analysis indicates that the zonal indices continued to fall since early1970s and began to rise around2000.(2)The correlation analysis results indicate that both of the two indices have significantlyrelationships to summer precipitation in eastern China. Specifically, there is a positivecorrelation area which is located in northeast China in June, in the middle and lower reachesof the Huang River and a negative correlation area in the middle and lower reaches ofYangtze River in July between zonal index and summer precipitation in eastern China. On theother hand, the negative regions are located in the middle and east of Northeast China in Juneand southeast of Northeast China in July and some areas of north China in august. While thepositive regions were South China in July and the lower reaches of Yangtze River in August. (3)The atmospheric circulation composite analysis results suggest that: there is ananomalous anti-cyclonic circulation in China offshore area in high index years for the zonalland-sea temperature difference, while an anomalous cyclonic circulation appears in the sameposition during the low index years. And the atmospheric circulation presents evidentdifferent patterns mostly in the northeast China in high and low index years for themeridional cases.(4)The numerical experiment results show that an anomalous anti-cyclonic loweratmosphere circulation appear over eastern China and its adjacent coastal waters and thesummer rainfall is below the normal in most south area of the middle and lower reaches ofYangtze River, and the rainfall is above normal in most of north China, when the SST ineastern China Sea and its adjacent seas decreases, i.e., zonal land-sea temperature differenceis relatively higher. Conversely, lower atmospheric circulation performed for an anomalouscyclonic and the precipitation is basically contrary, when the SST in eastern China Sea and itsadjacent seas increases, i.e., zonal land-sea temperature difference is relatively lower.