ERA-Interim中的中国地区水分循环要素的时空演变特征分析

Spatial and temporal characteristics of moisture cycle factors over China analyzed with ERA-Interim reanalysis data

本文利用1979—2011年欧洲中期天气预报中心(ECMWF)的再分析资料(ERA-Interim),运用经验正交函数展开(EOF)和相似系数等方法,对中国地区水分循环诸要素的时空特征进行了计算与分析.研究结果表明:在空间分布特征上,蒸发量、纬向水汽通量和经向水汽通量均与大气可降水量的空间分布最相似,大气可降水量和降水量均与蒸发量的空间分布最相似,降水量与纬向水汽通量的相似系数略大于其与经向水汽通量的相似系数;在时间演变上:年降水量在1979—2002年间,呈现非常显著的上升趋势;在2002—2011年间,呈现显著的下降趋势.年蒸发量在该两个时段的变化趋势与年降水量一致,但均比年降水量明显;年蒸发量在1979—2011年间呈现非常显著的上升趋势,其年际变化明显小于年降水量.可降水量和水汽通量散度在1979—2011年间的长期变化趋势不明显,但可降水量的年际变化呈阶段式增大,水汽通量的年际变化一直较大.纬向与经向水汽通量均存在2—3年为周期的年际变化;此外,纬向水汽通量在1979—2011年间还存在显著的下降趋势.春、秋季的水汽通量都存在显著下降的长期变化趋势,夏、冬季的长期变化趋势不明显.四季都存在2—3年为周期的年际变化.此外,夏季还存在明显的年代际转折.

In this paper, we analyze the spatial and temporal characteristics of different moisture cycle factors over China by using the ERA-Interim data supplied by the European Centre for medium-range weather forecasts （ECMWF）. The methods used in this paper include mainly the empirical orthogonal function （EOF）, similarity coefficients, one-dimensional linear regression and so on. Results show that the spatial distribution of evaporation, zonal and meridional moisture flux are all extremely similar to that of precipitable water. While the spatial distribution of precipitable water and precipitation are both very similar to that of evaporation. The similarity coefficient between precipitation and zonal moisture flux is a little larger than that between precipitation and meridional moisture flux. In terms of temporal characteristics, it is shown that precipitation has an obvious upward trend during 1979-2002 and an obvious downward trend during 2002-2011. The trend of evaporation is the same as that of precipitation during the same period, but the former is more obvious than the latter. Besides, evaporation also shows an obvious upward trend during 1979-2011. Both of precipitable water and moisture flux divergence show a slightly downword trend. Zonal and meridional moisture flux change in a period of 2-3 years. Further, zonal moisture flux has an obvious downward trend during 1979-2011. The vapor flux has an obvious downward trend both in spring and autumn, and changes in a period of 2-3 years for all four seasons. Besides, the vapor flux in summer presents a decadal transition.