摘要
利用兰州大学半干旱气候与环境观测站(SACOL)2008年夏季的观测资料,分析了陇中黄土高原地表能量不平衡特征及其影响机制,计算了地表和5 cm深处土壤热通量板之间的热储存,并对地表能量不平衡特征重新进行了计算和评价。当把土壤热储存作为地表能量收支的一部分考虑后,不平衡差额绝对值平均降低了23 W.m-2,能量不闭合度平均减小了0.104,利用最小二乘法(OLS)进行线性回归得到的平均不闭合度减小了0.085。从白天和晚上的能量不闭合度频率分布也能够看出,土壤热储存对地表能量收支平衡有很大改善。但即使考虑了土壤热储存项,地表能量不闭合仍然很明显。除了土壤热储存,边界层大气不同形式的输送能力作为对地气能量通量交换过程中的重要因素,对能量不平衡也会产生深远影响。结果显示,地表能量不闭合度分别与垂直速度w、水平风速u和对流速度尺度w*有较密切的关系。涡动相关法通量计算中常通过坐标旋转强迫垂直速度变为零,然而非零的垂直速度和垂直平流是真实存在的,忽略垂直平流热量输送是产生地表能量不平衡的重要原因。
Characteristics of the surface energy unbalance and its effect mechanism in the Loess Plateau in the middle part of Gansu were analyzed based on the observed data at the Semi-Arid Climate and Environment Observatory of Lanzhou University（SACOL） in the summer of 2008.The soil heat storage between the ground surface and heat flux plate at 5 cm depth was calculated from some soil thermal parameters,and the condition of surface energy inbalance was reestimated.When the soil heat storage as an energy budget component is taken into the equation of surface energy balance,the mean absolute value of surface energy balance residual decreases 23 W·m^-2 and the mean unclosure of energy balance is reduced by 0.104.Moreover,the unclosure of energy balance obtained by using OLS（Ordinary Least Squares） linear regression method decreases 0.085.Overall,the storage term can improve the surface energy budget condition and makes a large contribution to the unclosure of energy balance,which can also be seen from the frequency distributions of the unclosure of surface energy during the day time and night time.However,even if the soil heat storage is taken into account,the surface energy imbalance still exists and it remains apparent.Except for the soil heat storage,different forms of atmospheric transport capacity as factors affecting land-air energy exchange process,also have an impact on the surface enegy imbalance.The results indicate that the relationships are obvious among the unclosure of surface energy and three velocity scale parameters including vertical velocity,wind speed and convective velocity scale,respectively.Vertical advection is neglected by rotating the coordinate system,however non-zero values of vertical velocity and vertical advection are realistic.The neglect of vertical advection heat transfor is to result in an important reason of surface energy imbalance.
出处
《高原气象》
CSCD
北大核心
2010年第5期1153-1162,共10页
Plateau Meteorology
基金
国家自然科学基金重点项目"黄土高原陆面过程观测与试验研究"(40830957)资助
关键词
陇中黄土高原
地表能量不平衡
土壤热储存
垂直速度
对流速度尺度
Loess Plateau in the middle part of Gansu
Surface energy imbalance
Soil heat storage
Vertical velocity
Convective velocity scale
