超强台风“鲇鱼”形成过程中的水汽演变特征  

Moisture evolution during the pre-genesis of Super Typhoon Megi(2010)

作　　者：卓立 吴钲 方德贤 方娟[1] Zhuo Li;Wu Zheng;Fang Dexian;Fang Juan(School of the Atmospheric Sciences,Nanjing University,Nanjing,210023,China;Chongqing Institute of Meteorological Sciences,Chongqing 401147,China;Yubei Meteorological Office of Chonging,Chongqing 401147,China)

机构地区：[1]南京大学大气科学学院,南京210023 [2]重庆气象科学研究所,重庆401147 [3]重庆渝北气象局,401147

出　　处：《南京大学学报（自然科学版）》2020年第5期640-652,共13页Journal of Nanjing University（Natural Science）

基　　金：国家重大研究发展计划(2017YFC1501601);国家自然科学基金(41875067)。

摘　　要：基于一次成功的数值模拟和相关的敏感性试验,对超强台风鲇鱼形成过程中的水汽演变以及海气非线性反馈机制-WISHE(wind-induced surface heat exchange instability)机制的作用进行了探讨.在"鲇鱼"台风形成过程中,对流活动具有显著的日变化特征.与之相对应,台风前期扰动中的总水汽含量呈现出振荡式增长的特征.在浅对流活跃阶段,台风胚胎中的总水汽含量逐渐增加,而在深对流爆发和随后的层云阶段,总水汽含量迅速减小.在浅对流活跃阶段,台风前期扰动中总水汽含量的增加是大气中水汽通量辐合和海洋蒸发的结果,其中,前者的贡献远大于后者.在深对流阶段,由于水汽通量辐合以及海洋蒸发所贡献的水汽之和略小于深对流引发的强降水引起的水汽消耗,因此,台风前期扰动中的总水汽含量下降,但这一减少量小于浅对流阶段总水汽含量的增量,正是通过几次这样的周期性变化,台风前期扰动中的总水汽含量呈振荡式增加,最终支持了临近台风形成时刻深对流的爆发,导致了"鲇鱼"台风的生成.上述结果表明浅对流活动对于台风前期扰动的增湿和深对流活动以及台风形成具有重要贡献.数值敏感性试验表明,尽管海洋蒸发贡献的水汽远小于大气中水汽辐合贡献的水汽,但来自海洋的水汽对"鲇鱼"的形成仍然是必不可少的.不仅如此,WISHE机制对于"鲇鱼"的形成也是必要的.在敏感性试验中,WISHE机制被抑制后,"鲇鱼"台风前期扰动发展缓慢,涡度柱一直局限于500 hPa以下,没有形成一个典型的热带低压.This study explores the moisture evolution and the role of the wind-induced surface heat exchange instability(WISHE) mechanism during the formation of Super Typhoon Megi(2010) with a successful high-resolution simulation and related sensitivity experiments. During the genesis of Megi,the convection is quasi-periodically active in pre-Megi disturbance. Corresponding to the convection activities,the column-integrated water vapor(CWV) fluctuates in pre-Megi′s center area. CWV increases rapidly in the shallow convection phases while decreases slightly in the deep convection and subsequent stratiform phases.During the shallow convection phase,both the surrounding atmosphere and the underlying ocean contributes to the humidification of the disturbance,and the contribution from the fomer is most of time larger than that from latter. During the deep convection phase, CWV decreases a little as the water vapor consumed by the intense precipitation accompanying the deep convection exceeds that contributed from the water vapor convergence and the underlying ocean. But such a decrease is smaller than the increase during the shallow convection phase. Such periodical processes lead to the oscillating increase of CWV,which eventually favors the burst of deep intense convection and the genesis of Megi. The above results indicate that shallow convection plays an important role in the humidification of pre-Megi′s disturbance and the genesis of Megi. Even though the mositure from the ocean is much less than that from the atmosphere,the sensitivity experiment indicates that the ocean and the corresponding WISHE mechanism are both important to Megi′s formation. For in the experiment with near-surface wind capped,the spin-up of pre-Megi is much slower than that of the control experiment. And the associated vorticity is confined below 500 hPa. As a result,the disturbance fails to develop into a typical tropical depression.

关 键 词：台风形成 水汽 对流 海洋蒸发 WISHE 

分 类 号：P444[天文地球—大气科学及气象学]