长江中下游1998年夏季梅雨期降水再循环研究

Research on Precipitation Recycling during Meiyu Season over Middle-Lower Reaches of Changjiang River in 1998

改进了Eltahir的降水再循环率计算模式，引入水汽变化量，使其可用于小于月际时间尺度的降水再循环评估。并利用1998年6～8月间长江中下游162个测站的旬蒸发和降水资料，结合NCEP／NCAR的高空逐日再分析资料，对长江中下游1998年梅雨期的降水再循环率做了计算。分析发现：1998年夏季暴雨时期长江中下游的降水平均约有三成来自当地的蒸发。区域蒸发的水汽在安徽南部和湖北东部对降水的贡献最大。区域平均再循环率的旬变化强烈，最高可达67．8％，最小只有0．8％。表明地表水文敏感，地-气相互作用不稳定。

The Eltahir calculation model is improved by considering the derivatives of water vapor to adapt to the under-monthly scale assessment of precipitation recycling ratio. By using the ten-day precipitation and evaporation data and NCEP/NCAR daily pressure level reanalysis data, the precipitation recycling ratio over the middlelower reaches of the Changjiang River during Meiyu season in 1998 is estimated. It is found out that about 30 % of precipitation in the research area is contributed by local evaporation during continual heavy rainfall summer in 1998. The greatest contribution is over the southern Anhui and eastern Hubei provinces. The ten-day precipitation recycling ratio varies frequently, The highest value is 67, 8%, while the lowest is just 0,8%. That indicates the high sensibility of land surface hydrology and the instability of land-atmosphere interaction.