Simulation Of The Effect Of Anomalous Plateau Snow Cover And SSTA On Summer Climate Of Northwest China

The effect of Plateau snow cover and SSTA(Sea-Surface temperature anomaly)on summer climate of Northwest China, are studied and analyzed respectively byusing the latest Regional climate model RegCM3. First, summer climate ofNorthwest China in 1997 is simulated to test the simulating ability to NorthwestChina. Following, we design 2 parts experiments: one part is about the sensitivity ofNorthwest China summer climate to winter Plateau snow cover, contains 5 differentscenarios, normal snow cover scenario named SCV1(30mm snow water equivalent)two snow cover increasing scenarios named SCV2(60mm), SCV3(100mm), and twosnow cover decreasing scenarios named SCV4(15mm), SCV5(5mm). The other partis about the sensitivity of Northwest China summer climate to summer SSTA of WestPacific Ocean, contains 2 different scenario named SSTI(2℃higher than normalSST) and SST2(2℃lower than normal SST). Then comparing the model results withNNRP2 data and 160 stations data of china, do statistic tests also.It indicates that RegCM3 simulate precipitation and temperature pattern ofNorthwest China well. Adding of snow cover make results more accurate.Experiments about snow cover indicate that:Comparing with normal snow cover, precipitation deviation in Northwest Chinais changed from negative to positive along with time in snow cover increasingscenario. Precipitation bias is changed from positive to negative in snow coverdecreasing tests.Comparing with normal snow cover, 700hPa air temperature is lower in snowincreasing experiments. But in snow decreasing experiments, 700hPa temperatureover Plateau is higher while it is lower in other place of Northwest China.The F and t tests indicate that the difference of summer mean rain betweenanomalous snow scenario and normal snow one is not obvious, so is 700hPatemperature. On the contrast, the differences of their variances are much moreremarkable.SSTA experiments indicate that:Summer precipitation bias in SST1 and SST2 is similar in trend. Comparing with control experiment, their effect on summer rain are transformed from negativeand not obvious to positive, and the deviation degree in SST2 is greater than that ofSST1. The F and t tests indicated that the difference of summer mean rain betweenanomalous SST scenario and control experiment is little, the difference of theirvariances are much more remarkable.Temperature in 200hPa is almost higher and lower only over Plateau in SST1,but that of SST2 is positive mainly. The F and t tests indicate that the difference ofsummer 200hPa air temperature between anomalous SST scenario and controlexperiment is little, but more continuous than that of summer rain. On the contrast,the differences of their variances are much more remarkable, and difference oftemperature field variances is larger than difference of rain variances.Relations between rain, temperature change and snow anomaly, SSTA are notlinear simply.