地形起伏对模式地表长波辐射计算的影响

初步探讨了数值模式中次网格区地形起伏(高度、坡度)对长波辐射计算的影响。结果表明,地形高度的次网格变化对辐射计算结果的影响较小,其相对误差一般<2%,但不同分辨率的地形高度场会产生不同的坡度计算误差,低分辨率地形资料所计算的坡度分布相差不大,但坡度的量级存在较大偏差。地形的分辨率越高,实际计算结果的偏差越小。而高分辨率地形资料计算实例表明,地形坡度引起的区域相对辐射误差可达到10%以上。因此,在数值模式中,网格区地表长波辐射计算结果对地形起伏的敏感性应给予足够的重视。

The Effect of Terrain Fluctuation on the Computed Surface Long-Wave Radiation in the Models

The effect of orographic fluctuation(including height and slope) on the calculation of surface long-wave radiation in numerical modelsis elementarily explored in this paper.The results show that the effect of subgrid terrain height change on computed long-wave radiation is not obvious,with a relative error commonly less than 2%.Digital elevation modelwith different resolutions may lead to different slope calculation errors.Slope distributions calculated by using low resolution terrain data have only a little deviationcomparing with that in the high resolution data,but the slope calculation has larger difference in magnitude.The higher the terrain resolution is,the less the error of the real calculation is.While case calculation using high resolution terrain data shows that the regional relative radiation error caused by terrain slope can reach up to above 10%.Thus,in the surface long-wave radiation calculation of numerical model,the more attention should be paid to the effect of orographic fluctuation on the subgrid scale.