A Parameterization of Subgrid-Scale Land-Atmosphere Interactions for Atmospheric Models

在大气的计算机模型中，计算是按水平间隔进行的。这样，计算就代表了一个区域，其中自然变化的细粒度细节被抹去了。模型中包含的公式，试图至少在某种统计意义上解释这些细节的重要热和动态影响，被称为“参数化”。特别是陆地表面，通常在典型尺度（从中尺度模式的10平方公里到全球范围模式的100万平方公里）的模式网格正方形内包含显著的地形、植被覆盖、湿度和热特征的水平变化。目前最先进的参数化中使用的两种方法要么没有考虑复杂生物物理机制的亚网格尺度异质性，要么忽略了已知的亚网格尺度陆地-大气相互作用的影响，如坡谷风、湖风和其他由不同植被覆盖引起的热循环。在改进当前模型计算机算法之前，评估这些变化在不同空间尺度上对模型行为的影响是很重要的。Avissar建议进行这样的评估，通过结合使用一个非常灵活的（在可选的分辨率方面）和经过良好测试的计算机模型（科罗拉多州立大学-区域大气模拟系统），以及通过飞越丘陵，裸露，农业，在过去的两个观测项目中。中国气象局以前在边界层和农业气象方面的研究，以及在开发区域大气模式方面的研究，将有助于在这一问题领域取得进展，并应用于改进短期、中期和长期预报，以及区域和全球尺度上的气候变化研究。

In computer models of the atmosphere, calculations are carried out at horizontal intervals. Thus a calculation is representative of an area in which the fine-grain detail of natural variations is smeared out. Formulas included in the model that attempt to account for important thermal and dynamic effects of such detail, at least in some statistical sense, are referred to as "parameterizations". The land surface, in particular, norm- ally contains significant horizontal variations in topography, vegetative cover, moisture, and thermal characteristics within a model grid square of typical dimensions (ranging from 10 sq km in mesoscale models to 1 million sq km in models of global extent). The two approaches used in current state-of-the art parameter- izations either do not account for subgrid-scale heterogenity of complex biophysical mechanisms, or neglect the effects of known subgrid scale land-atmosphere interactions such as slope-valley winds, lake breezes, and other thermal circulations caused by varying vegetative cover. Before improvements in current model computer algorithms are implemented it is important to assess the impact of such variations on the models' behaviour at differing spatial scales. Avissar proposes to carry out such assesments, by using a combination of a very flexible (in terms of optional resolution) and well-tested computer model (the Colorado State University- Regional Atmospheric Modelling System), and detailed low-level measurements made by flight transects over hilly, bare, agricultural, and forested areas in two past observational programs. The PI's prior research in boundary-layer and agricultural meteorology as well as in developing regional models of the atmosphere will contribute to advances in this problem area, which has application to improvement of short, medium and long- term forecasting, as well as research in climate change on regional and global scales.