干旱区凝结水评估及对水量平衡方程影响

A new water balance equation introducing dew amount in arid area

凝结水是大气中水汽通过凝结作用向地表输送的水分,在水量平衡计算中常被忽略。本文利用西北干旱区黑河水文气象观测网9个站点2016年涡度相关观测数据,计算评估了相应站点范围的凝结水发生情况、凝结水量量级以及相应的能量闭合度情况。结果表明,黑河流域凝结水现象普遍发生,各站点产生凝结水的天数占全年天数75%以上;各站点年凝结水量最大25.13 mm、最小6.56 mm、平均15.47 mm;各站点总凝结水量与总蒸散发量相比,最大28.82%、最小0.77%、平均6.61%;与总降水量相比,最大63.25%、最小3.02%、平均18.54%;各站点能量闭合度平均为0.69,本文估算的凝结水量或低于实际凝结水量。可以认为,凝结水在干旱区水量平衡中不容忽视。基于此,本文提出在干旱区水量平衡方程中,宜显式表达凝结水过程和凝结水项。引入凝结水的水量平衡分析表明,新水量平衡方程在纳入凝结水这一局地水循环因子后,水量平衡方程闭合度明显提高。

Dew,defined as water transported from atmosphere to certain surface due to condensation,was often ignored in water balance calculation. In this study,observation data from nine stations of Heihe Hydrometeorological Observation Network in 2016 was used to calculate and evaluate dew quantity and duration. The results indicated that condensation was common in Heihe river basin that dew was monitored on more than 75% days in all stations. Dew amount of nine stations in 2016 ranged from 6.56 mm to25.13 mm,while the mean value was 15.47 mm. Calculating the ratio of dew to evapotranspiration,average ratio was 6.61%,while the maximum and minimum ratios were 28.82% and 0.77%,respectively. Ratio of dew to precipitation is 18.54% in average, while the maximum and minimum ratios were 63.25% and3.02%,respectively. The mean energy balance closure is 0.69. These percentages showed that condensed water in arid areas could not be ignored in water balance. Based on above analysis,this paper proposed that dew should be considered in water balance equation of the arid area. The new water balance calculation in desert showed the new water balance equation effectively increased the closure of water balance equation and improved the accuracy of the water balance equation.