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Using betts-miller-janjic convective parameterization scheme in H14-31 model to forecast heavy rainfall in Vietnam

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In this paper we used the scheme of Betts-Miller-Janjic (BMJ) based on the convective adjustment toward tropical observationally structures in reality instead of Tiedtke in Hl4-31. Statistical verification results and verification using CRA method of Hl4-31 of two CPSs for seperated cases and for three rain seasons (2003-2005) shows that heavy rainfall forecast of Hl4-31/BMJ is better than one of H14-31/TK for Vietnam-South China Sea. | Vietnam Journal of Mechanics, VAST, Vol. 29, No. 2 (2007), pp. 83 - 97 USING BETTS-MILLER-JANJIC CONVECTIVE PARAMETERIZATION SCHEME IN H14-31 MODEL TO FORECAST HEAVY RAINFALL IN VIETNAM Vu THANH HANG, Kmu Tm XIN Vietnam National University of Hanoi Abstract. According to Krishnamurti , improvements of physical parameterizations will mainly affect simulations for the tropics [10] . The study of William A. Gallus Jr . showed that the higher the model resolution and more detailed convective parameterizations, the better the skill in quantitative precipitation forecast (QPF) in general [16]. The quality of precipitation forecast is so sensitive to convective parameterization scheme (CPS) used in the model as well as model resolution. The fact shows that for high resolution regional model like H14-31 CPS based on low-level moisture convergence as Tiedtke did not give good heavy rainfall forecast in Vietnam . In this paper we used the scheme of Betts-Miller-Janjic (BMJ) based on the convective adjustment toward tropical observationally structures in reality instead of Tiedtke in Hl4-31. Statistical verification results and verification using CRA method of Hl4-31 of two CPSs for seperated cases and for three rain seasons (2003-2005) shows that heavy rainfall forecast of Hl4-31/BMJ is better than one of H14-31/TK for Vietnam-South China Sea. CRA verification also shows that it is possible to say that heavy rainfall forecast skill of l-I14-31/BMJ in tropics is nearly similar to the skill of LAPS of Australia. 1. INTRODUCTION Numerical ·weather Prediction (NWP) in general and rainfall forecast in the tropics in particular are difficult problems for meteorologists over the world . Variations in meteorological fields in the tropics are very small in comparison with one in the extratropics so that to show the same forecast skill we need to achieve much higher forecast accuracy in the tropics than in the extratropics. According to Krishnamurti, improvements of .