摘要
This study investigated the formation and development of a mesoscale convergence line （MCL） within the circulation of Typhoon Rananim （0414）, which eventually led to torrential rainfall over inland China. The study is based on satellite, surface and sounding data, and 20 km×20 km regional spectral model data released by the Japan Meteorological Agency. It is found that midlatitude cold air intruded into the typhoon circulation, which resulted in the formation of the MCL in the northwestern quadrant of the typhoon. The MCL occurred in the lower troposphere below 700 hPa, with an ascending airflow inclined to cold air, and a secondary vertical circulation across the MCL. Meso-/~ scale convective cloud clusters emerged and developed near the MCL before their merging into the typhoon remnant clouds. Convective instability and conditional symmetric instability appeared simultaneously near Diagnosis of the interaction between the MCL and kinetic energy and positive vorticity for its further the MCL, favorable for the development of convection. the typhoon remnant implies that the MCL obtained development from the typhoon remnant in the lower troposphere. In turn, the development of the MCL provided kinetic energy and positive vorticity at upper levels for the typhoon remnant, which may have slowed clown the decaying of the typhoon.
This study investigated the formation and development of a mesoscale convergence line （MCL） within the circulation of Typhoon Rananim （0414）, which eventually led to torrential rainfall over inland China. The study is based on satellite, surface and sounding data, and 20 km×20 km regional spectral model data released by the Japan Meteorological Agency. It is found that midlatitude cold air intruded into the typhoon circulation, which resulted in the formation of the MCL in the northwestern quadrant of the typhoon. The MCL occurred in the lower troposphere below 700 hPa, with an ascending airflow inclined to cold air, and a secondary vertical circulation across the MCL. Meso-/~ scale convective cloud clusters emerged and developed near the MCL before their merging into the typhoon remnant clouds. Convective instability and conditional symmetric instability appeared simultaneously near Diagnosis of the interaction between the MCL and kinetic energy and positive vorticity for its further the MCL, favorable for the development of convection. the typhoon remnant implies that the MCL obtained development from the typhoon remnant in the lower troposphere. In turn, the development of the MCL provided kinetic energy and positive vorticity at upper levels for the typhoon remnant, which may have slowed clown the decaying of the typhoon.
基金
the National"973"Program of China under Grant No.2009CB421504
the National Natural Science Foundation of China under Grant Nos.40730948,40675033,and 40975032
the Key Project of the Chinese Academy of Meteorological Sciences under Grant No.2008LASWZI01.
