Tao Zuyu

A note on the dynamics of the quasi-stationary Kunming front

SummaryThe quasi-stationary Kunming front is oriented parallel to the north-south running major mountain chains of south-western China and normal to the upper-level westerlies. The front curves towards the east off the mountain. We hypothesize that the shape of the Kunming front is due to ageostrophic flow along the mountains which is induced by westerly flow in the cold air and at upper levels. Eventually the front must become stagnant. This conjecture is supported by numerical experiments with simple models.

A Study of the extratropical transformation of typhoon Winnie (1997)

The complicated evolutive process of how a tropical cyclone transforms into an extratropical cyclone is still an unresolved issue to date, especially one which arises in a weakly baroclinic environment. Typhoon Winnie (1997) is studied during its extratropical transformation stage of extratropical transition (ET) with observational data and numerical simulations. Results show that Winnie experienced its extratropical transformation to the south of the subtropical high without intrusion of the mid-latitude baroclinic zone. This is significantly different from previous studies. Analyses reveal that the cold air, which appeared in the north edge of Winnie circulation, resulted from the precipitation drag and cooling effect of latent heat absorption associated with the intense precipitation there. The cooling only happened below 3 km and the greatest cooling was below 1 km. With the cold air and its advection by the circulation of Winnie, a front was formed in the lower troposphere. The front above is related not only to the cooling in the lower level but also to the warming effect of latent heat release in the middle-upper levels. The different temperature variation in the vertical caused the temperature gradient over Winnie and resulted in the baroclinicity.

Analysis of indian monsoon and associated low-level circulation in 1980 and 1981

In this paper, Indian monsoon of 1980 and 1981 is analysed based on the seasonal and half-month averaged data of 850 hPa of ECMWF analysis. The results show that Indian monsoon is related to Somali jet, the low-latitude easterlies and the mid-latitude westerlies over southern Indian Ocean, which are associated with the stationary wave of Southern Hemisphere. The forces affecting on the low-level flow are diagnosed, which display the relationship between Indian monsoon and the associated low-level flow.