青藏高原湖泊蒸发估算方法的比较研究——以纳木错为例

基于青藏高原纳木错湖面2012-2014年日尺度气象观测数据,运用五类水面蒸发模型中的9种经验式估算湖面蒸发量,分别与涡动相关实测值对比分析,优化各公式的参数,进而评价、比较优化后各式的精度和适用性。优化后的Dalton系列估算式精度最高,但要求日尺度数据,且所需参数较多,因而其应用受限;组合模型精度近似Dalton系列公式,适合在气象资料较全时使用;温度-辐射模型和温度-日长模型的精度能达到较高要求,且所需参数少,因而经济简便,是利用常规气象资料估算湖泊蒸发的优良选择;温度模型估算式的精度较差。纳木错季风气候明显,需分季风期和非季风期分别对水面蒸发进行估算,两个时段经验估算式的参数有差异。还分析了纳木错湖面观测点与周边地区四个气象站(当雄、申扎、班戈和那曲)之间常规气象因子的相关关系。其中,太阳总辐射、气温和比湿等存在着较好的线性关系,因而可以在通过线性订正后用于湖泊蒸发估算,不会产生大的误差;但风速的相关性差。

A comparison of the formulas for estimation of the lake evaporation on the Tibetan Plateau: taking Lake Nam Co as an example

Based on the meteorological data from Lake Nam Co during the observation periods of 2012 to 2014,lake evaporation was calculated using nine different empirical formulas of the five groups.The results were compared with the eddy covariance (EC) data,and then the parameters of each formula were optimized.The optimized formulas were further evaluated on their accuracy and applicability.It is shown that the formulas of the Dalton group are the most accurate ones and yet they require daily data of more meteorological elements,which limits its wide application.The formula of the combination group is nearly as accurate as the Dalton's,but it also requires more meteorological elements.The formulas of both the temperature-radiation group and the temperature-daylength group require less meteorological elements,but can acquire estimates with good accuracy.Due to this low cost and high effectiveness,these two groups are considered to be good choices for lake evaporation estimation when conventional meteorological data is only available.The formula of the temperature group was proved to be less accurate.As the monsoon climate is very strong at Lake Nam Co,the parameter optimation for all of the nine formulas was performed separately in terms of monsoon and non-monsoon seasons.Correlations of the conventional meteorological elements were also analyzed between Lake Nam Co and four other weather stations in the surrounding regions (Damxung,Shenzha,Bangor and Nagchu).Of the four meteorological elements,global radiation,air temperature and specific humidity are shown to have good linear relations in between the stations,which suggests that after linear calibration they can be well used in the calculations of lake evaporation without bringing large errors.However,the linear correlation is weak for wind speed.