The Impact of Spatial and Temporal Variability of the Landscape on Atmosphere-Land Surface Interactions at the Mesoscale

作为美国国家科学基金会先前调查（EAR-9105059）的一部分，研究表明，与蒸发蒸腾水有效性水平梯度产生的中尺度环流相关的亚网格尺度热量和动量通量对大尺度大气数值模式（例如gcm）模拟的大气过程有重大影响。然而，这些通量可能比湍流（即微尺度）通量强三倍，在这些模型中没有得到表示。本文提出的研究是先前研究的延续，其重点是在中尺度上由景观不连续产生的云和降水及其与土壤水分、蒸散发和其他地表通量的水平分布的相互作用。拟议的研究包括三个主要任务，预计将在三年内完成（每年一项任务）：(i)对与陆地-大气相互作用有关的云和降水微物理参数化中最重要的参数进行敏感性分析；（ii）有系统地分析地表蒸散发水量对云和降水的影响；（三）大尺度大气模式中地表非均质性产生的中尺度大气通量（包括湿润过程）的参数化。为了有效地开展这项基于数值分析的研究，采用精细的云物理和陆地水文参数化模型是非常重要的。此外，它应该具有在大范围空间尺度上进行模拟的灵活性。因此，科罗拉多州立大学（CSU）区域大气模拟系统（RAMS），一个最先进的模拟系统，旨在支持大气科学的基础研究，将被用于这项调查。这项研究将为中尺度陆地-大气相互作用的复杂水文气象过程提供新的见解，预计将对GEWEX和其他国家和国际计划所支持的研究活动特别相关和有益。

9415441 Avissar As part of a prior NSF investigation (EAR-9105059), it was demonstrated that subgrid-scale heat and momentum fluxes associated with mesoscale circulations generated by horizontal gradients of water availability for evapotranspiration, have a significant impact on the atmospheric processes simulated with large-scale atmospheric numerical models (e.g., GCMs). However, these fluxes, which can be three times stronger than turbulent (i.e., microscale) fluxes, are not represented in such models. The research proposed here is a continuation of this prior investigation, which concentrates on clouds and precipitation generated by landscape discontinuities at the mesoscale and their interactions with the horizontal distribution of soil moisture, evapotranspiration, and the other surface fluxes. The proposed research includes three major tasks, which are expected to be accomplished within three years (one task a year): (i) a sensitivity analysis of which parameters are most important in the parameterization of cloud and precipitation microphysics relevant to land-atmosphere interactions; (ii) a systematic analysis of the impact of water availability for evapotranspiration at the ground surface on clouds and precipitation; and (iii) a parameterization of mesocale heart fluxes (including moist processes) generated by land-surface heterogeneity for large-scale atmospheric models. To perform efficiently this research, which is based on numerical analysis, it is very important to adopt a models that has refined parameterizations of cloud physics as well as land hydrology. Furthermore, it should have the flexibility to produce simulations on a broad range of spatial scales. Thus, the Colorado State University (CSU) Regional Atmospheric Modeling System (RAMS), a state-of-the-art modeling system designed to support basic research in the atmospheric sciences will be used for this investigation. This research, which will provide new insights in the complex hydrometeorological processes in volved in land-atmosphere interactions at the mesoscale, is expected to be particularly relevant and beneficial for the research activity endorsed by GEWEX and other national and international programs.