A comparison of cloud and boundary layer variables in the ECMWF forecast model with observations at Surface Heat Budget of the Arctic Ocean (SHEBA) ice camp
A comparison of cloud and boundary layer variables in the ECMWF forecast model with observations at Surface Heat Budget of the Arctic Ocean (SHEBA) ice camp
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ECMWF 预报模型中的云层和边界层变量与北冰洋表面热量收支 (SHEBA) 冰营观测结果的比较
DOI：
10.1029/2000jd900079
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发表时间：
2000
影响因子：
--
通讯作者：
T. Uttal
中科院分区：
文献类型：
--
作者：
J. A. Beesley;C. Bretherton;C. Jakob;E. L. Andreas;J. Intrieri;T. Uttal
将欧洲中期天气预报中心（ECMWF）预报模式的云和边界层变量与1997年11月和12月在北冰洋冰营（SHEBA）的地面仪器和向上观测的8毫米波长雷达和激光雷达的测量结果进行了比较。模式预报的降水积累、近地面风和地面向下长波辐照度与示巴观测值吻合较好。然而，当模式和观测中存在低云时，地表向下长波辐照度平均被低估了10 W m−2。该模式在预测示巴上空的云量和垂直范围方面显示出相当大的能力，但有高估1公里以下云量频率的倾向。根据ECMWF模式变量估计的合成雷达反射率与8mm波长雷达测量值进行了比较。只有在假定的谢巴地区的雪花大小分布中，大雪花所占比例小于之前在低纬度地区的研究中发现的比例时，这两者才大致一致。ECMWF模式假定云凝结物在水和冰之间的分配依赖于温度。SHEBA的激光雷达去极化测量表明，整个冬季，液态和冰相云的温度范围很广，液态云的温度低至239 K。观测到的液态水云比ECMWF模式预测的要大得多。ECMWF模式与观测值之间最大的差异是地表温度（高达15 K）和湍流感热通量（高达60 W m−2）。这似乎至少部分是由于ECMWF的海冰模型，该模型不允许表面温度对观测到的大气条件变化做出快速反应。
Cloud and boundary layer variables from the European Centre for Medium-Range Weather Forecasts (ECMWF) forecast model were compared with measurements made from surface instruments and from upward looking 8 mm wavelength radar and lidar at the Surface Heat Budget of the Arctic Ocean (SHEBA) ice camp during November and December of 1997. The precipitation accumulation, near-surface winds, and surface downward longwave irradiance predicted by the model were in good agreement with SHEBA observations during this period. However, surface downward longwave irradiance was underestimated by 10 W m−2 on average when low clouds were present in the model and observations. The model demonstrated considerable skill in predicting the occurrence and vertical extent of cloudiness over SHEBA, with some tendency to overestimate the frequency of clouds below 1 km. A synthetic radar reflectivity estimated from the ECMWF model variables was compared with 8 mm wavelength radar measurements. The two were broadly consistent only if the assumed snowflake size distribution over SHEBA had a smaller proportion of large flakes than was found in previous studies at lower latitudes. The ECMWF model assumes a temperature-dependent partitioning of cloud condensate between water and ice. Lidar depolarization measurements at SHEBA indicate that both liquid and ice phase clouds occurred over a wide range of temperatures throughout the winter season, with liquid occurring at temperatures as low as 239 K. A much larger fraction of liquid water clouds was observed than the ECMWF model predicted. The largest discrepancies between the ECMWF model and the observations were in surface temperature (up to 15 K) and turbulent sensible heat fluxes (up to 60 W m−2). These appear to be due at least partially to the ECMWF sea ice model, which did not allow surface temperatures to respond nearly as rapidly to changing atmospheric conditions as was observed.