Numerical Prediction of the Heavy Rainfall Vortex Over Eastern Asia Monsoon Region

Abstract

A series of numerical forecasts were carried out to investigate a heavy rainfall event over the monsoon region of Eastern Asia which was caused by a vortex formed over the Tibet Plateau during Summer. The ECMWF global grid point model was capable of predicting the vortex four days in advance.The importance of the moist processes in the development of the vortex was investigated by comparing the results from a moist and a dry (without latent heat) versions of the model. It was found that the low level jet associated with the vortex and the upper level easterlies are more active when the latent heat is included in the model.The ECMWF limited area model with resolution 0.5* of latitude and longitude (*37km at 45*N) was used in order to obtain a more accurate and detailed forecast.Some intermediate scale disturbances were predicted over the Tibet Plateau and verified with satellite pictures and observations. This result is significant for the problem of numerical weather prediction over the Asian Continent.

Multi-scale Features of Baiu, the Summer Monsoon over Japan and the East Asia

“…Several case studies showed that the Baiu rainfalls over Japan are mainly caused by mesoscale organized cloud systems associated with Baiu frontal depressions (e. g., Matsumoto et al, 1970;Akiyama, 1971, 1974;Yoshizumi, 1977;Akiyama, 1978). It has been reported that many vortices form over the Tibetan Plateau during the summer monsoon, and some of them move eastward and bring rainfalls over the central China (Tao and Ding, 1981;Tao and Chen, 1986;Kuo et al, 1986;Chen and Dell'Osso, 1984;Murakami and Huang, 1984;Ma and Bosart, 1987). Ninomiya et al ( , 1989a and Akiyama (1984a, b) studied a long-lived cloud cluster which formed at the eastern foot of the Tibetan Plateau and caused intense rainfalls over China and Japan.…”

Kinetic Energy Budgets of the Low-Level Jet during TAMEX IOP 5.

“…The transverse secondary circulation across the Mei-Yu front is baroclinic in nature and enhanced by convective heating. This view on the LLJ development differs from the mass-momentum adjustment process driven by cumulus convection suggested by several authors (Chen and Dell'Osso 1984;Chou et al 1990;Hsu and Sun 1994;Chen et al 1998). This problem will be investigated quantitatively in this study.…”

“…4d) forecast time as the upper-level trough amplified with a stronger secondary circulation. It is apparent that during 1-2 June 1987, the upper-level circulations during the intensification of the LLJ is not maintained by the thermally direct circulation driven by convective heating as suggested by several authors (Chen and Chang 1980; Chen 1983; Chen and Dell'Osso 1984;and Chou et al 1990). This problem will be discussed further in later sections.…”

“…The LLJ transports warm, moist air from the southwest to generate convective instability (Chen 1983;Chen et al 1994;Li et al 1997). Numerical studies of the LLJ have focused on the massmomentum adjustment process driven by convective heating (Chen and Dell'Osso 1984;Chou et al 1990;Hsu and Sun 1994;Chen et al 1998). The generation of the LLJ in low levels is thought to result from the Coriolis force acting on the lower branch of the thermally direct circulation driven by convective heating.…”

Pattern-based statistical downscaling of East Asian Summer Monsoon precipitation

“…Additionally, baroclinic instability might instigate the generation of SWVs. The front between the warm and moist air from the south Á or more precisely from the Indochinese peninsula and the SCS Á and the cold and dry air from the mid-latitudes preconditions the development of SWVs (Chen and Dell'Osso, 1984). SWVs may take different tracks through China and the adjacent seas.…”