洱海湖滨农田下垫面土壤热通量特征分析

CHARACTERISTICS ABOUT SOIL HEAT FLUX ON THE UNDERLYING SURFACE OF FARMLAND NEARBY ERHAI LAKE

为深入了解洱海湖滨地区的陆面过程和能量交换特征,基于大理国家气候观象台2007—2020年近地层通量观测系统资料,详细分析了土壤热通量的日、季节和年际变化及其与净辐射通量、感热和潜热通量的相关性。结果表明:洱海湖滨农田下垫面4 cm、10 cm、20 cm深处的土壤热通量日变化均呈现“S”形,随着土壤深度的增加,土壤热通量日较差逐渐减小,日变化峰值的时间有一定延迟,延迟速率随季节发生变化。不同深处的土壤热通量年内变化呈现倒“U”形,4 cm深处土壤热通量5月达到最大值,而10 cm、20 cm深处均在6月出现最大值。由浅至深各层土壤热通量多年平均值分别为-0.7 W·m^(-2)、-0.9 W·m^(-2)、-0.6 W·m^(-2)。不同时间尺度的土壤热通量与净辐射通量和潜热通量均有较高的相关性,而与感热通量的相关性较低,这表明土壤热通量的大小主要受净辐射通量的影响,而土壤热通量对潜热通量的影响较为明显。

In order to understand the characteristics of land surface process and energy exchange nearby Erhai Lake,based on the observational data of surface layer flux observing system at Dali National Climate Observatory from 2007 to 2020,the diurnal,seasonal,and interannual variation of soil heat flux and its correlation with net radiation flux,sensible heat and latent heat flux are analyzed in detail.The results show that the diurnal variation of soil heat flux at the depth of 4 cm,10 cm,20 cm on the underlying surface of farmland nearby Erhai Lake presented an“S”shape.With the increase of soil depth,the diurnal range of soil heat flux gradually decreased,the time of diurnal variation peak was delayed,and the delay rate changed with the seasons.The annual variation of soil heat flux in each depth presented an inverted“U”shape.The soil heat flux at the depth of 4 cm reached its maximum value in May,while the soil heat flux at the depth of 10 cm and 20 cm reached the maximum value in June.The normal values of accumulated year for soil heat flux from shallow to deep layers wer-0.7 W·m^(-2)、-0.9 W·m^(-2)、-0.6 W·m^(-2),respectively.The soil heat flux in the different time scales had a significant correlation with net radiation flux and latent heat flux,but a low correlation with sensible heat flux,indicating that soil heat fluxes in the surface energy balance equation was mainly affected by net radiation flux,while soil heat flux had an significant affection on latent heat flux.