利用1951～2000年我国西北干旱、 半干旱区地温、 气温和表面风场逐日4个时次 (02、 08、 14和20时) 的台站观测资料, 计算并分析了我国西北干旱、 半干旱区春、 夏季感热的年代际变化特征。分析结果表明: 中国西北干旱、 半干旱区春、 夏季感热输送出现相反的年代际变化特征, 春季感热从20世纪70年代中期开始增强, 而夏季感热却减弱了。并且还分析了中国西北干旱、 半干旱区4月感热与中国夏季降水的相关关系, 其结果表明了中国西北干旱、 半干旱区的春季感热输送与中国夏季降水有很好的相关关系, 其中正相关区分别位于东北地区和长江中下游地区, 而负相关区分别位于华北地区和西南地区。作者还利用欧洲中心 (ECMWF) 1958～2000年再分析资料分析水平和垂直环流的年代际变化特征, 在1977～2000年期间, 中国西北地区春季感热增强, 使此地区上升气流增强, 华北地区上空下沉气流增强, 不利于华北地区夏季降水偏多, 并出现持续性干旱, 而长江流域的上升气流增强有利于长江中下游地区夏季降水增多, 出现洪涝。因此, 西北地区春季感热异常可以作为我国夏季降水的一个预报因子。
The characteristics of interdecadal variability of sensible heat are analyzed by using the observed daily data of surface temperature, surface air temperature and surface wind field from 1951 to 2000. The analysis results show that an obvious interdecadal variability of the sensible heat appears in Northwest China. Before the late 1970s, spring (MAM) sensible heat anomalies were negative, but its anomalies became largely positive from the late 1970s to 2000. Summer (JJA) sensible heat anomalies were positive before 1977, but its anomalies became largely negative from the late 1970s to 2000. The correlations between summer precipitation in whole China and the April sensible heat averaged for 38 stations show that the positive correlation regions are in Northwest China, Northeast China and the Yangtze River basin, but the negative correlation regions are in the east of North China and Southwest China. Moreover, the characteristics of interdecadal variability of zonal and meridional circulation are analyzed by using the ERA-40 reanalysis data from ECMWF from 1958 to 2000. The analysis results show that the descent flow occurred over North China, but ascent flow occurred over Northwest China and the middle and lower reaches of the Yangtze River. The results also show that enhanced sensible heat causes ascent flow strengthening over Northwest China, and descent flow strengthening over North China, which maybe resulted in summer precipitation decreasing and persistent drought occurring in North China and summer precipitation increasing and flood in the middle and lower reaches of the Yangtze River. Therefore, the spring sensible heat anomalies in Northwest China may be a forecast factor for summer rainfall in North China.