中文摘要：

对云层垂直结构的准确参数化描述是数值天气预报模式准确计算长短波辐射通量、辐射加热率廓线、云反射率、云辐射效应等参数的重要基础,但地基观测数据无法对模式预报的云层垂直分层情况进行验证。文章基于卫星资料Collection5版本的MODIS云产品MOD06,利用国际上能够较准确判别云层垂直分层的一个新算法,以反演的高、中、低云发生频率和云顶气压结果,评估美国国家环境预报中心（NCEP）北美中尺度模式NAM的云层垂直结构。2006年7～10月北美地区（153°～48°W,12°～62°N）的评估结果表明：①卫星反演和模式预报的高、中、低云的云量区域分布比较相似,尤其是高云。热带太平洋地区模式预报高云量大于卫星反演值。模式预报的低云在墨西哥及北美大陆、大西洋地区更多。②卫星反演和模式预报中云发生频率的差异最小,模式预报高云和低云发生频率峰值比卫星反演的峰值更大,且云顶出现的高度更高。③模式预报中云量和低云量的纬度平均值比卫星反演的高,尤其是低云量。NAM的云参数化有待于进一步改进。

英文摘要：

Accurate description of the cloud vertical layer structure is of primary importance for the Numerical Weather Prediction Model to get accurate parameters like longwave,shortwave radiation fluxes,radiation heating rate profile,cloud reflection,cloud radiation effect.However,the cloud vertical structure can not be validated by the data observed on the ground.The occurrence frequencies of high,middle,low clouds and cloud top pressure retrieved from a up-to-date algorithm（classifying cloud vertical layer structure）,applied with MODIS cloud product MOD06（Collection 5）,are used to evaluate the results from the NCEP North American Meso-scale model（NAM）.The evaluation results from the scope of（153° to 48°W,12° to 62°N）,July to October,2006 show：（1）The distribution patterns of high,middle,and low clouds retrieved from satellite products and model are similar,especially for high clouds.Over the tropical Pacific,the model shows greater high cloud amount than the satellite scene.The model data shows much more low cloud cover over Mexico,the North American continent,and the Atlantic Ocean,and the middle cloud cover is less than high cloud cover.（2）There is the least difference in the occurrence frequencies of middle clouds between satellite retrieval and model results.Peaks for high and low clouds seen in NAM outputs are sharper and higher than those from the satellite retrieval.（3）The latitude-mean middle and low cloud amounts from the model are greater than those generated form the satellite retrieval and more noticeably for low clouds.The cloud parameterization in NCEP NAM needs to be improved.