Use of ship mean data for validating model and satellite flux fields during the FETCH experiment
Use of ship mean data for validating model and satellite flux fields during the FETCH experiment
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DOI：
10.1029/2001jc001207
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发表时间：
2003-03
影响因子：
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通讯作者：
L. Eymard;A. Weill;D. Bourras;C. Guérin;P. Borgne;J. Lefèvre
中科院分区：
文献类型：
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作者：
L. Eymard;A. Weill;D. Bourras;C. Guérin;P. Borgne;J. Lefèvre
[1]在地中海西北部进行的FETCH试验期间（1998年3月和4月），在一艘研究船上和一个系泊浮标上测量了表面通量。为了提供中尺度的海洋表面强迫，收集了三个气象模型（欧洲中期天气预报中心（ECMWF）和法国气象局ARPEGE和ALADIN）的输出场以及卫星数据。为了评估模型场的一致性，我们比较船舶测量预测的辐射和湍流表面通量和湍流通量来自使用散装公式的分析。我们首先分析的质量的船舶散装通量方面的可能影响的流动畸变和固有的变异性作为积分时间的函数。在船上的气流畸变被发现显着影响通量，但在实验的平均通量保持不变，因为由于不同的表观风向的正负误差之间的补偿。通过对船舶时间序列的谱分析以及对1 ~ 90 min的几种平均时间所得通量的比较表明，计算船舶通量的最佳尺度为20 min左右，以保证与总阻力和交换系数的推导一致。这些通量然后被作为与模式和卫星进行比较的参考。没有一个预测的辐射通量是一致的船舶测量。模式的湍流通量各不相同，其主要原因是模式与观测大气特征的差异。在强风条件下，由于热通量的不同通量参数化，预测通量和船舶通量之间存在很大的差异。因此，模型散装通量比预测通量，特别是在中期的实验船比较好。相反，气象卫星派生的向下辐射通量与船舶数据相当，它们的高时间采样使我们能够描述太阳加热的日周期。它们既可以在瞬时尺度上使用（将0.1° × 0.1°的卫星平均通量与10分钟平均船舶通量进行比较），也可以在更大的尺度上使用（0.3° × 0.3°，1小时）。它示出的表面潜热通量，来自组合的特殊传感器微波成像仪（SSMI）的亮度温度和海表面温度（SST），从红外传感器（高级甚高分辨率辐射计（AVHRR））获得的，是一个质量类似或更好的模型批量通量。
[1] During the FETCH experiment in NW Mediterranean Sea (March and April 1998), surface fluxes were measured on board a research vessel and on a moored buoy. To provide the ocean surface forcing at the mesoscale, output fields of three meteorological models (European Centre for Medium-Range Weather Forecasts (ECMWF) and Meteo-France ARPEGE and ALADIN) were gathered as well as satellite data. To evaluate the consistency of model fields, we compare ship measurements to the predicted radiative and turbulent surface fluxes and to turbulent fluxes derived from analyses using a bulk formula. We first analyze the quality of the ship bulk fluxes in terms of possible effects of the flow distortion and of intrinsic variability as function of the integration time. The airflow distortion over the ship is found to significantly affect fluxes, but the mean fluxes over the experiment remain unchanged because of compensation between positive and negative errors due to the varying apparent wind direction. Spectral analysis of the ship time series as well as comparison of fluxes obtained by using several averaging times from 1 to 90 min show that the optimal scale for computing ship fluxes is about 20 min, ensuring consistency with the derivation of bulk drag and exchange coefficient. These fluxes are then taken as reference for the comparison with models and satellites. None of the predicted radiative fluxes is consistent with ship measurements. Model turbulent fluxes differ from each other, and the main reason is the discrepancy between modeled and observed atmospheric features. Large discrepancies are found between predicted fluxes and ship fluxes in strong wind conditions due to the different flux parameterization for heat fluxes. Model bulk fluxes thus compare better to ship than predicted fluxes, particularly during the middle period of the experiment. On the contrary, the Meteosat-derived downward radiative fluxes are comparable to the ship data, and their high time sampling allows us to describe the diurnal cycle of the solar heating. They can be used either at an instantaneous scale (comparison of the satellite flux averaged over 0.1° × 0.1° with 10 min averaged ship fluxes) or at a larger scale (0.3° × 0.3°, 1 hour). It is shown that the surface latent heat flux, derived from a combination of Special Sensor Microwave Imager (SSMI) brightness temperatures and sea surface temperature (SST), as obtained from IR sensors (Advanced Very High Resolution Radiometer (AVHRR), is of a quality similar or better to model bulk fluxes.