Development of an integrated vertical-slantwise convective parameterization scheme and its associated numerical experiments |
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Authors: | Jianfang Fei Rongsheng Wu Xiaogang Huang Yuan Wang and Xiaoping Cheng |
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Affiliation: | (1) Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, Pune, Maharashtra, 411 008, India |
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Abstract: | An integrated vertical-slantwise convective parameterization scheme, based on the vertical Kuo-Anthes and the slantwise Nordeng
convective parameterization schemes, is introduced into the MM5 model. By employing the MM5 model with the proposed scheme,
numerical simulations of a snowstorm event that occurred over southern China on 28–29 January 2008 and of Typhoon Haitang
(2005) are conducted. The results indicate that during the snowstorm event, the atmosphere was convectively stable in the
vertical direction but with conditional symmetric instability (CSI) in the lower troposphere, and when the area of CSI developed
and extended to upper levels, strong rising motion occurred and triggered the release of large amount of energy, producing
enhanced convective precipitation with the total precipitation much closer to the observation. The development and strengthening
of CSI corresponded to changes in the intensity of snowfall, convergence, and ascending motions of air, revealing that CSI
was responsible for the initiation and growth of the snowstorm. The results from a 72-h explicit simulation of Typhoon Haitang
indicate that CSI occurred mainly at lower levels with a well-defined spiral structure, and it tended to have a larger impact
on the intensity of typhoon than on its track. The minimum pressure at the typhoon center for the 72-h runs with the integrated
vertical-slantwise convective parameterization scheme was on average 3 hPa (maximum 8 hPa) lower than that from the runs with
only the vertical cumulus parameterization scheme. Introducing the influence of CSI into the model has improved the warm core
structure at the middle and upper levels of the typhoon, with stronger and persistent upward motions causing increased precipitation,
and the latent heat released through convection in turn made the typhoon develop further. |
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Keywords: | snowstorm typhoon conditional symmetric instability (CSI) the integrated vertical-slantwise convective parameterization scheme numerical simulation |
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