Seasonal changes in radiation and evaporation implied from the diurnal distribution of rainfall in the Lower Mekong
Seasonal changes in radiation and evaporation implied from the diurnal distribution of rainfall in the Lower Mekong
复制标题
湄公河下游降雨日分布暗示辐射和蒸发的季节性变化
DOI：
10.1002/hyp.6935
复制
发表时间：
2008
影响因子：
3.2
通讯作者：
T. Mitsuno
中科院分区：
文献类型：
--
作者：
K. Tsujimoto;T. Masumoto;T. Mitsuno
太阳辐射是许多估算蒸发量的经验公式的重要输入，由于热带季风气候的高蒸发势，这反过来又在湄公河下游流域的水文循环中发挥着重要作用。然而，湄公河下游流域几乎没有适当的气象数据，该地区的气象条件，包括辐射和蒸发的季节变化，也没有得到澄清。本研究收集了位于湄公河下游不同土地利用类型(市区、水稻区和湖泊)的三个观测站的地面逐时水文气象资料。对这些数据进行了分析，以研究与降雨量日分布有关的辐射和蒸发的季节变化。与一般预期相反，我们的结果显示，湄公河下游流域雨季和旱季的太阳辐射量几乎相同，这是因为(1)雨季有相对较大的外星辐射量；(2)雨季近一半的日子没有降雨；(3)雨天的太阳辐射量达到非雨天的88%。第三个因素是晚间雨量较多。此外，这种降雨-辐射关系意味着，由于太阳辐射的减少率低和长波入射辐射的增加，雨季有大量的净辐射。因此，雨季有很高的蒸发势。此外，对于这一地区盛行的雨水灌溉的稻田来说，雨季充足的辐射对水稻生长将是一大优势。版权所有©2008 John Wiley&Sons，Ltd.
Solar radiation is an important input to many empirical equations for estimating evaporation, which in turn plays an important role in the hydrologic cycle in the Lower Mekong River Basin due to the high evaporation potential of the tropical monsoon climate. Few proper meteorological data exist for the Lower Mekong River Basin, however, and the region's meteorological conditions, including seasonal variation in radiation and evaporation, have not been clarified. In this study, ground‐based hourly hydrometeorological data were collected at three observation stations located in different land‐use types (urban district, paddy area, and lake) in the Lower Mekong River Basin. These data were analysed to investigate the seasonal variation in radiation and evaporation related to the diurnal distribution of rainfall. Contrary to common expectations, our results showed that rainy and dry seasons had nearly the same amount of solar radiation in the Lower Mekong River Basin because (1) rainy seasons had a relatively larger amount of extraterrestrial radiation; (2) no rain fell on nearly half of the days during rainy seasons; and (3) the amount of solar radiation on rainy days reached 88% of that on non‐rainy days. The third factor was attributed to the high frequency of evening rainfall. Furthermore, this rainfall–radiation relationship meant that rainy seasons had a large amount of net radiation due to the low reduction ratio of solar radiation and an increase in long‐wave incoming radiation. Accordingly, rainy seasons had a high evaporation potential. Moreover, for the rain‐fed rice paddies that prevail in this region, sufficient radiation during the rainy season would be a great advantage for rice growing. Copyright © 2008 John Wiley & Sons, Ltd.