The Impact of Assimilating Sea Surface Wind Aboard QuikSCAT on Sea Fog Simulation
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摘要: 为了评估同化QuikSCAT海面风场资料对海雾模拟的影响,对发生在2006年4月3—5日的海雾过程,首先通过3个敏感性试验,研究了不同边界层参数化方案对海雾模拟的影响,发现YSU边界层参数化方案更适合海雾过程的模拟。然后对2006年4月3—5日平流雾过程和2005年6月23—24日辐射雾过程利用WRF-3DVAR系统将QuikSCAT海面风场资料同化到模式中,并以未同化和同化了QuikSCAT海面风场资料的数据为初始场,应用WRF模式进行模拟预报,同时对模拟预报得到的结果与实况 (卫星云图和地面观测) 进行对比,结果表明:QuikSCAT海面风场资料的三维变分同化能够改善低层其他要素场,对海雾预报有明显的正效应,但对高层的影响相对有限。
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关键词:
- 海雾;
- 三维变分同化;
- 海面风场;
- QuikSCAT资料
Abstract: Sea fog is a kind of disaster weather with strong local characteristics. It has brought more serious losses as people's activities over the sea become more frequent. Therefore, the forecast of sea fog is becoming more and more important. There is no effective method to directly and widely obtain the real data of meteorological fields over the sea at present. However, the microwave scatterometer aboard a satellite is the most popular sensor that provides accurate global sea surface winds which are used widely. At the same time, the progress and popularity of variational assimilation method also make a great deal of unconventional data be used in numerical models, which optimize initial condition of models.To evaluate the impact of assimilating the sea surface wind data aboard QuikSCAT on the sea fog simulation, 3 sensitive experiments are carried out for the sea fog process during 3—5 April 2006. The effect of the different boundary layer parameterization schemes, such as Medium Range Forecast Model (MRF), Yonsei University (YSU) and Mellor-Yamada-Janjic (MYJ) on sea fog simulation are discussed. It is found that YSU boundary layer physical parameterization scheme is more suitable for simulating sea fog, the MRF scheme takes the second place and the MYJ scheme is the worst. Then by the three dimensional variational data assimilation (3DVAR) method based on the Weather Research and Forecast (WRF) model the sea surface wind aboard QuikSCAT is assimilated to investigate an advection fog and a radiation fog occurred over the sea around China, respectively.The results with and without assimilating the QuikSCAT sea surface wind data are used as the initial fields for WRF model to simulate the sea fog, respectively. The simulated results are compared with the satellite nephogram and the ground observation. Preliminary results show that the three dimensions variational assimilation of sea surface wind data by WRF-3DVAR system can make the sea surface wind data affect other element fields at low levels of the model, which have an obviously positive impact on the area forecast of sea fog. In particular, some detailed results are obviously better compared with those of the control experiment without assimilating the sea surface wind data. But for high levels the impact is limited. Since the sea fog data are sparse, results of only two cases are insufficient to generalization, so more cases will be discussed to validate the conclusions in the future. -
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