A Contrast Test of the Methods to Remove the Analyzed Typhoon

The theories about removing the analyzed typhoon which used in GFDL hurricane model and MM5 model are introduced in detail. The GFDL model uses a sophisticated filtering scheme, and the filter domain defining the location and extent of the tropical cyclone in the global analysis is determined from the distribution of the low-level disturbance winds. Each level's filter domain is same and there is no correlativity in the fields. The MM5 model modifies the vorticity, geostrophic vorticity, and divergence, then solve for the change in the nondivergent stream function, geopotential and velocity potential and compute a modified velocity field. The MM5 scheme sets the radius same so that the analyzed typhoon features may be removed more or less for various cases. The comparison analysis about ten cases shows that, owing to the error in data and bought from the projection, the location between two levels has big departure for some cases, and make the fields cannot be removed reasonably, such as temperature. So the method seeking the analyzed typhoon center and radius in the average meaning used by GFDL is more advantageous, on the other hand, the harmony of fields is considered in MM5 scheme, and it is more reasonable than GFDL in this facet. The modified method which correcting MM5 scheme through combining these two schemes' advantages is also tested for these cases and the results showed the analyzed typhoon may be removed more reasonably and thoroughly.