Atmosphere-Land Surface Interaction Over A Midwest Watershed: CASES-97

这一更新项目旨在了解地表和大气之间的相互作用。报告继续对1997年春季进行的为期一个月的实地考察所收集的数据进行分析。该项目的总体目标是观察地面过程对大气边界层在24小时周期(日循环)过程中演变的影响。该项目虽然是观测性的，但与正在进行的大气边界层模拟和大尺度模式中边界层效应的参数化方面的工作密切相关。它在几个方面是独一无二的：(A)它集中在地形中等复杂的中尺度分水岭(堪萨斯州)；(B)它侧重于没有低层云和零星卷云的晴朗天气情况；(C)密集观察期涵盖4个完整的和2个部分日循环，土壤水分和植物成熟程度各不相同。具体地说，目前的目标是：o将两个密集观察期(IOP)的大气感热和水汽收支计算从早上扩展到晚上，并包括来自边界层顶部的大气夹带。o完成其余IOP的预算计算，并调查观测到的土壤湿度和土地覆盖变化的影响。o将蒸散算法与测量的5厘米土壤湿度和涡旋相关蒸发进行比较。o研究夜间边界层的特征。通过与大气模型人员的相互作用，这一观测项目将有助于改进大型大气模型内的边界层参数。

This renewal project seeks to understand the interaction between the land surface and the atmosphere. It continues the analysis of data collected in a month-long field expedition conducted in the spring of 1997. The overall objective of this project is to observe the effect of surface processes on the evolution of the atmospheric boundary layer over the course of a 24-hr period (diurnal cycle). Though observational in nature, the project is closely allied with on-going work in atmospheric boundary layer modeling and parameterization of boundary layer effects in large-scale models. It is unique in several respects: (a) it concentrates upon a mesoscale watershed with moderately complex terrain (Kansas); (b) it focuses upon fair weather situations with no lower clouds and only scattered cirrus; (c) intensive observing periods covered 4 complete and 2 partial diurnal cycles with varying degrees of soil moisture and plant maturity. Specifically, the current objectives are: o Extend atmospheric sensible heat and moisture budget computation for two intensive observing periods (IOP) from the morning period to the evening period and include entrainment from the atmosphere on top of the boundary layer.o Complete budget computations for the rest of the IOPs and investigate the effect of' observed variations in soil moisture and land cover.o Compare an evapotranspiration algorithm to measured 5-cm soil moisture and eddy correlation evaporation.o Investigate the characteristics of the nocturnal boundary layer. Through interaction with atmospheric modelers, this observational project will contribute to the improvement of boundary layer parameterizations within large atmospheric models.