太湖辐射和能量收支的时间变化特征

湖泊的辐射和能量收支的观测研究对于气象学和水文学研究都具有重要的意义。于2012年采用涡度相关系统和小气候观测系统观测太湖表面的辐射平衡、湖泊与大气之间的感热和潜热通量、水温廓线和常规气象要素数据,分析太湖表面辐射及能量收支的时间变化特征以及环境控制因子。结果表明:(1)太湖2012年辐射收支四分量(向下短波辐射、向上短波辐射、向下长波辐射和向上长波辐射)的年均值分别为146.5、9.4、359.7和405.4 W/m~2,反照率的年均值为0.06,各辐射分量日变化和季节变化特征明显;(2)净辐射和热储量日变化趋势相同,正午最高,午夜最低;湍流能量通量的日变化幅度较小;不同天气条件下能量分配具有一定差别:晴天条件下能量分配以潜热通量为主,阴天净辐射能量主要被水体吸收转换为热储量;(3)通过分析湍流能量通量与环境因子的相关性发现:感热通量变化最主要的相关因子是风速与湖–气界面温度差的乘积;风速与湖-气界面水汽压的乘积是潜热通量的主要驱动因子。本研究结果能为边界层气象学、全球能量和物质循环以及湖泊生态环境治理等研究提供理论基础和数据支持。

TEMPROAL VARIABILITY OF RADIATION AND ENERGY BUDGETS OVER LAKE TAIHU

Observation on radiation and energy budget over lakes are important for meteorological and hydrological studies. Based on the eddy covariance and micrometeorological system, the radiation budget over lake surface, sensible and latent heat flux between lake and atmospheric interface, water temperature and meteorological variables were observed in 2012. Temporal variability of radiation and energy budgets and the environmental controlling factors were analyzed. The results indicated that:(1) Annual mean of the four components of radiation balance in Lake Taihu in 2012 (i.e., downward and upward shortwave radiation, downward and upward longwave radiation) were 146.5 W m-2, 9.4 W m-2, 359.7 W m-2 and 405.4 W m-2, respectively. Annual mean albedo was 0.06. There were obvious diurnal and seasonal variations for each radiation budget. (2)The diurnal pattern of water heat storage was similar to that of net radiation with maximum and minimum values at noon and midnight, respectively. With comparison to net radiation and water heat storage, the diurnal variation amplitude of turbulent energy flux was smaller. The energy distribution is different between sunny and cloudy days:latent heat flux dominates an sunny days, while water heat storage dominate on cloudy days. (3) Correlation analysis between turbulence energy flux and environmental variables indicated that sensible heat flux was mainly controlled by the product of the wind speed and temperature difference at the interface between lake and air; and the product of wind speed and water vapor pressure at their interface was the main driving factor for latent heat flux. This study can provide scientific reference to understanding the mechanism of lake-atmospheric interaction and to identify the contribution of lake in global energy budgets.