南海中尺度大气海浪耦合模式及其对该区一次强台风过程的模拟研究

利用中尺度大气模式MM5(V3)和第3代海浪模式WWATCH建立考虑大气-海浪相互作用的风浪耦合模式.在耦合模式中引入考虑波浪影响的海表粗糙度参数化方案,大气模式分量提供海面10 m风场驱动海浪模式分量运行,并利用海浪模式分量反馈的波龄参数计算海表粗糙度.利用耦合模式模拟南海的一次台风过程,通过3组对比试验,检验耦合模式对台风过程的模拟效果并研究大气-海浪相互作用对台风过程的影响.结果表明:耦合模式能够较好地模拟南海的台风过程,与非耦合大气模式相比,其模拟的台风强度略有增强,路径变化不大;耦合模式对台风过程中海表热通量及降水影响显著,在台风充分发展过程中,耦合模式模拟的海表热通量增强,台风螺旋雨带上尤其是台风路径的右侧,耦合模式模拟的降水强于非耦合模式;耦合模式较好地模拟了台风过程海浪场的分布和演变,与非耦合模式相比,其模拟的海浪场增强,与实际更为接近;考虑了海表粗糙度对波浪的依赖关系后,海浪场同时影响海表的动力过程和热力过程,从本次个例看,在台风发展初期,海浪对海表动力作用影响显著,其反馈作用使台风系统减弱,但在台风充分发展后,耦合系统中海表热通量增加,热力作用显著增强,海浪的反馈作用有利于台风系统的发展和维持.

A mesoscale atmosphere ocean wave coupling model and numerical simulations on a strong typhoon process in South China Sea.

Quantitative estimates of liquid water path (LWP) in clouds using satellite measurements are critical to understanding of cloud properties and the assessment of global climate change. In this paper, the relationship between microwave brightness temperature (TB) and LWP in the nonprecipitating clouds is studied by using satellite microwave measurements from the TRMM Microwave Imager (TMI) onboard the Tropical Rainfall Measuring Mission (TRMM), together with a radiative transfer model for microwave radiance calculations. Radiative transfer modeling shows that the sensitivity is higher at both 37.0 and 85.5 GHz horizontal polarization channels for the LWP retrievals. Also, the differences between the retrieved values responding to TBs of various channels and the theoretical values are displayed by the model. Based upon above simulations, with taking into account the factor of resolution and retrieval bias for a single channel, a nonprecipitating cloud LWP in the summer subtropical marine environment retrieval algorithm is formulated by the combination of the two TMI horizontal polarization channels, 37.0 and 85.5 GHz. Moreover, by using TMI measurements (1B11), this algorithm is applied to retrieving respectively LWPs for clear sky,nonprecipitating clouds, and typhoon precipitating clouds. In the clear sky case, the LWP changes from -1 to 1 g m-2, and its mean value is about 10-5 g m-2. It indicates that, using this combination retrieval algorithm, there are no obvious systemic deviations when the LWP is low enough.The LWP values varying from 0 to 1000 g m-2 in nonprecipitating clouds are reasonable, and its distribution pattern is very similar to the detected results in the visible channel of Visible and Infrared Scanner (VIRS) on the TRMM. In typhoon precipitating clouds, there is much more proportion of high LWP in the mature phase than the early stage. When surface rainfall rate is lower than 5 mm h-1, the LWP increases with increasing rainfall rate.