Mallard Megan S, Spero Tanya L
National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina.
J Geophys Res Atmos. 2019 Oct 3;124(16):9117-9140. doi: 10.1029/2018JD029755.
The representation of land use (LU) in meteorological modeling strongly influences the simulation of fluxes of heat, moisture, and momentum; affecting the accuracy of 2-m temperature and precipitation. Here, the Weather Research and Forecasting (WRF) model is used with the Noah land surface model to compare a mosaic approach, which accounts for subgrid scale variability of LU types, to the default option which only considers the dominant category in each grid cell. Three-year historical dynamically downscaled WRF simulations are generated using a 12-km domain over the contiguous U.S. to assess the sensitivities to using mosaic LU and to changes to parameters associated with LU and soil categories. Compared to dominant LU, mosaic LU features decreased coverage of forest and agricultural types and increased low-density urban LU throughout much of the eastern and central U.S. However, highly urbanized areas show the opposite trend, as mosaic LU represents partial greenspace within areas that are exclusively urban within dominant LU. Mosaic LU results in widespread increases in sensible heat fluxes and 2-m temperatures, with reductions in latent heat flux, 2-m mixing ratio, and monthly precipitation across the central and eastern U.S. These changes exacerbate an existing warm bias found with dominant LU but reduce overestimations of precipitation. Highly urbanized areas in the eastern U.S. tend to have cooler, more realistic temperatures with mosaic LU relative to dominant LU. A pair of runs with updated surface parameters corroborates these results. Overall, differences between the simulations are largely attributable to their representations of urban LU.
气象模型中土地利用（LU）的表示方式对热量、水分和动量通量的模拟有很大影响，进而影响2米温度和降水的准确性。在此，将天气研究与预报（WRF）模型与诺亚陆面模型一起使用，以比较一种考虑LU类型亚网格尺度变异性的镶嵌方法与仅考虑每个网格单元中主导类别的默认选项。使用美国本土12公里的区域生成了为期三年的历史动态降尺度WRF模拟，以评估使用镶嵌LU以及与LU和土壤类别相关参数变化的敏感性。与主导LU相比，镶嵌LU的特征是美国东部和中部大部分地区森林和农业类型的覆盖面积减少，低密度城市LU增加。然而，高度城市化地区呈现相反趋势，因为镶嵌LU代表了主导LU中完全城市化区域内的部分绿地。镶嵌LU导致感热通量和2米温度普遍增加，而美国中部和东部的潜热通量、2米混合比和月降水量减少。这些变化加剧了主导LU存在的暖偏差，但减少了降水的高估。相对于主导LU，美国东部高度城市化地区使用镶嵌LU时往往具有更凉爽、更现实的温度。一对更新了地表参数的运行结果证实了这些结果。总体而言，模拟之间的差异很大程度上归因于它们对城市LU的表示方式。
