海河流域不同下垫面上大孔径闪烁仪观测显热通量的时空特征分析

基于海河流域密云站、馆陶站和大兴站2008-2009年大孔径闪烁仪的观测数据,结合涡动相关仪和自动气象站的同步观测,经过数据筛选、质量评价、数据处理及插补等步骤,得到了3个站点不同时间尺度的显热通量和蒸散量.首先分析了3个站点1月、4月、7月、10月不稳定状态下大孔径闪烁仪通量观测的空间代表性及源区内不同下垫面的通量贡献率,并结合下垫面作物生长状况比较分析了3个站点不同季节大孔径闪烁仪观测显热通量与净辐射的月平均日变化趋势,不同下垫面上两者变化趋势一致,且馆陶站的显热通量在各月中都为最低,1月、7月密云站的显热通量与大兴站较为接近.同时3个站点2008-2009年9:00～15:00显热通量日平均值的季节变化趋势表明,相对于密云站单峰状的季节变化,源区内下垫面的植被类型和植被生长状况导致馆陶站和大兴站的显热通量都表现出明显的三峰变化.最后,以馆陶站大孔径闪烁仪和涡动相关仪观测的30 min显热通量数据为例,结合涡动相关仪的能量闭合率,大孔径闪烁仪和涡动相关仪通量足迹源区的重叠程度和非重叠部分的地面非均一性,对不同尺度显热通量观测的差异原因进行了讨论.

Temporal-spatial Characteristics Analysis of Area-averaged Sensible Heat Fluxes by Large Aperture Scintillometer over Hai River Basin

Combined with the measurements of Eddy Covariance (EC) system and Automatic Weather Station (AWS) and after a series steps including data screening, quality assessment, data processing and gap filling, the sensible heat fluxes of Large Aperture Scintillometer (LAS) H_LAS and evapotranspiration (ET) were calculated based on the LAS measurements in Miyun, Guantao and Daxing sites over Hai River Basin during 2008-2009. The spatial representation and flux contribution of different land use under unstable conditions were analyzed in January and July over Miyun, Guantao and Daxing sites. Combined with the footprint and the crop phenological phase, the seasonal variation of Hlas over the three sites were compared with Rn in the same period, where Guantao site had the lowest value each month, Hlas in Miyun and Daxing were closed in January and July. Meanwhile, daily Hlas between 9:00 and 15:00 were discussed over the three sites from 2008-2009. Compared to the single peak variation of Miyun site, both Guantao and Daxing sites both had three peak values because of the alternation of crops. Finally, according to the energy closure ratio of EC measurement, the different footprint overlapping ratio between LAS and EC measurements, as well as surface heterogeneity of their non-overlap source area, the difference between Hlas and Hec in Guantao site was discussed.