近海与远洋飓风边界层特征高度的差异分析

ANALYSIS ON THE DIFFERENCE OF HURRICANE BOUNDARY LAYER CHARACTERISTIC HEIGHT BETWEEN NEARSHORE AND OFFSHORE

关键词:  飓风边界层  近海与远洋  GPS下投式探空仪

Key words:  hurricane boundary layer  nearshore and offshore  GPS dropsonde

摘要:

使用1998—2016年大西洋40个飓风2 032个GPS下投式探空仪观测数据，以距离海岸线300 km为界分为近海和远洋两组，利用合成分析方法探讨了飓风边界层特征高度的差异。边界层特征高度的定义方法包括最大切向风高度、入流层高度、混合层高度和理查森数法高度。对比分析不同定义方法下近海和远洋边界层高度，结果表明：根据最大切向风和入流层强度定义的边界层高度，近海边界层高度低于远洋边界层高度，且近海边界层高度随径向增加至2倍最大风速半径后趋于稳定；基于混合层定义的边界层高度明显低于动力边界层高度，且近海与远洋混合边界层特征高度无明显差异；近海理查森数边界层高度在最大风速半径内与远洋的无明显差异，而在最大风速半径外略高于远洋的。

Abstract:

Abstract: In this study, 2032 GPS dropsondes around 40 hurricanes over Atlantic basin from 1998 to 2016 were used to investigate the difference of boundary layer characteristic height between nearshore and offshore using composite analysis. The defining methods of the characteristic height of the boundary layer include (1) the maximum tangential wind height, (2) the depth of the inflow layer, (3) the depth of the mixed layer and (4) the height of the bulk Richardson number method. Through comparing the boundary layer heights of the nearshore and offshore areas under these different definition methods, we find that the height of nearshore boundary layer is lower than that of the offshore area under the definition methods of (1) and (2), and the height of nearshore boundary layer increases radially to twice as much as the radius of the maximum wind speed before it tends to be stabilized. The height of boundary layer defined by (3) is lower than dynamical boundary layer heights, and there is no significant difference in the characteristic height of mixed boundary layer between nearshore and offshore area. Within the radius of the maximum wind speed, the height of the Richardson number boundary layer defined by (4) in the nearshore area shows no significant difference from that in the offshore, while it is slightly higher than the offshore outside the radius of the maximum wind speed.