The Effects of Different Cumulus Parameterization Schemes on the Intensity Forecast of Typhoon Flo (1990)
2000 Volume 78 Issue 6 Pages 819-833
Details
2000 Volume 78 Issue 6 Pages 819-833
The impact of two cumulus parameterizations on intensity of a simulated tropical cyclone was examined using a limited area numerical model. A moist convective adjustment scheme and Arakawa-Schubert scheme were used as a cumulus parameterization for each numerical experiment. Typhoon Flo (1990) was selected as a case study.
Difference in the cumulus parameterizations had drastic influence on a difference in sea-level pressure averaged over the core region (within the 250km radius from the storm center) of the simulated storm from an early stage of the integration. That is, compared with the experiment with moist convective adjustment, the averaged sea-level pressure with Arakawa-Schubert scheme was relatively low. Central pressure in the latter was also lower than the former, which showed that the latter produced a more intense tropical cyclone consistent with the observation. The difference in central pressure, however, appeared at a later stage, compared with the difference in the averaged sea-level pressure.
Temperature tendency due to a moist convective adjustment was considerably negative in the lower troposphere and so was actual temperature tendency, which resulted in a rapid drop of temperature. Consequently, the total air mass within the inner-core region became greater in the experiment with moist convective adjustment than with the Arakawa-Schubert scheme. On the other hand, the difference in the low-level temperature field between the two experiments results in the difference in radial profile of rainfall, and the radius where the eyewall is located. The difference probably brings about the delayed appearance of the central pressure difference.
Another numerical experiment was conducted with modified moist convective adjustment not to be cool in the lower troposphere. The result confirmed that cooling in the lower troposphere within the inner core-region greatly inhibits intensification of the simulated storm.
