利用静止卫星估算青藏高原全域地表潜热通量

Estimation of Land Surface Latent Heat Flux over the Tibetan Plateau Using Geostationary Satellite Data

青藏高原全域高时间分辨率潜热通量变化对定量理解高原能量和水分循环过程尤其是其日变化过程至关重要。为此,利用中国最新一代静止气象卫星Fengyun-4A上搭载的多通道扫描成像辐射计数据,结合中国区域高时空分辨率地表气象驱动数据集,基于陆面能量平衡系统模型估算得到青藏高原全域的地表潜热通量,卫星估算值与青藏高原观测研究平台站点实测值的均方根误差和平均偏差分别为76.05和17.33 W/m^(2)。结果表明,青藏高原地表潜热通量呈现显著的季节变化、昼夜分野和区域差异:4月高原潜热整体上略低于感热,而7月高原西部、中部和东部的潜热均高于感热;潜热通量昼夜相差极大,4月的昼间、夜间和昼夜平均值分别为74.22、3.09和38.66 W/m^(2),而7月的相应值分别为122.75、6.49和64.62 W/m^(2)。青藏高原地表热通量的空间分布具有经向区域差异,其中,净辐射通量与感热通量在高原西部和中部的数值明显高于高原东部,而潜热通量正好相反,在高原东部数值较高。研究结果可为青藏高原地表蒸散与大气热源的定量分析提供参考。

Variations of land surface latent heat flux with high temporal resolution are essential to the quantitative understanding of the energy and water transfer processes,especially their diurnal cycles over the Tibetan Plateau(TP).Therefore,the Advanced Geostationary Radiation Imager onboard the up-to-date Chinese geostationary meteorological satellite Fengyun-4 A was utilized,with the China Meteorological Forcing Dataset in combination,for the estimation of land surface latent heat flux over the entire TP based on the SEBS model.The root mean square error and mean bias for the satellite estimations against the in situ measurements of the Tibetan Observation and Research Platform were 76.05 and 17.33 W/m^(2),respectively.Results showed that land surface latent heat flux over the TP exhibited distinct seasonal variation,day/night discrepancy and regional difference.In April,the plateau-scale latent heat flux was slightly lower than the sensible heat flux overall;while in July,the latent heat flux was higher than the sensible heat flux in all of the western,central,and eastern TP.The daytime,nighttime and daily-mean latent heat flux values in April were 74.22,3.09,and 38.66 W/m^(2),while those in July were 122.75,6.49 and 64.62 W/m^(2),respectively,depicting a clear diurnal variability.Additionally,the spatial distributions of land surface heat fluxes over the TP presented longitudinal regional differences:both the net radiation flux and sensible heat flux were stronger in the western and central TP,while conversely the latent heat flux was stronger in the eastern TP.The above results may provide information for the quantitative analysis on the surface evapotranspiration and the atmospheric heat source in future studies.