Cause Analysis Of Precipitation Differences Associated With Two Landing Typhoons With Similar Track

In this paper,a variety of satellite data (TRMM/PR,TRMM/TMI,MTSAT,FY2C), observationdata(3hours measured rainfall data) and Climate Forecast System Reanalysis data (CFSR) are usedto analyze the precipitation characteristics of two landing typhoon Matsa (0509) and Khanun (0515)in Zhejiang area,which has a similar track and similar center intensity, and gives the reasons for theirprecipitation differences.Based on the comparative analysis, results show that the precipitation in large value areas ofMatsa and Khanun are located on the right side of the moving path after their landing. The Matsaprocess rainfall is significantly greater than Khanun, in addition to the Maximum precipitation zonenear the landing point,there is the other precipitation in large value areas are located on Jiangsueastern coastal areas. The Short-term special heavy precipitation,which means3hours of rainfallgreater than100mm, is more decentralized both in geographical distribution and time distributionduring Matsa landing process,and obvious tropical cyclone remote rainfall Occurred during Matsa atsea. Khanun’’s total precipitation is less than Matsa, but the Short-term special heavy precipitationoccurred at a time and place of the more concentrated,All the21Short-term special heavyprecipitation stations during Khanun process have occurred in the12-hour period before and after itslanding, and are concentrated in developed urban areas of Ningbo, Zhoushan.Using TRMM satellite data and cloud top infrared brightness temperature data found that, atlanding time, cloud development is stronger at the right part of TC than the left part both in Matsaand Khanun,and as a result, right side of the precipitation is larger than the left side; using CFSRdata, found that, over the typhoons body heavy rain region,there is a bimodal structure of thepseudo-equivalent temperature,where there is the extremal area of the horizontal gradient ofpseudo-equivalent temperature nearby, and925hPa moisture flux divergence of negative large valuearea are superimposed on the area; while tropical cyclone remote rainfall area are located on theextremal area of the horizontal gradient of pseudo-equivalent temperature.Because of the absence ofthe warm core structure of the typhoon body,the bimodal structure of the pseudo-equivalent temperature is not obvious. Combined with previous studies of other cases,925hPa moisture fluxdivergence negative big value can be used as a good indicator of the typhoon body rainstorm drop.Topographic effects plays an important role on the distribution of typhoon rainstorm zone bothin Matsa and Khanun, The rainfall area of the large value fall in the following areas: the windwardslope of the the Zhenan hilly terrain and the coast of Zhejiang, where the economy is developed, sowe should pay more attention to prevent the harm caused by typhoons rainstorm.The four reasons for Matsa and Khanun precipitation differences are as follows:1. Moving speed Both at sea and on land, the average moving speed of Kanu must faster thanMatsa.Matsa spent66hours on land,while Kanu spent only30hours, moving slower precipitationmore.2.Wind circle radius Although the intensity is close, both the storm wind radius and gale windradius of Matsa are much larger than Khanun, thereby enabling Matsa at sea to absorb more watervapor and latent heat energy.3. environmental vertical wind shear There is a closer relationship between rainfall andenvironmental vertical wind shear than the relationship with central intensity and rainfall.Weakenvironmental vertical wind shear is conducive to the accumulation of typhoon internal latent heat,and thus conducive to maintaining typhoon strength and precipitation intensity.4. low-level water vapor content and the intensity difference of the convergence low-levelwater vapor content is richer in Matsa than that in Khanun, the same with convergence intensity,and thus the convergence of low-level moisture flux divergence is also stronger, the precipitation ofMatsa is more. Matsa and Khanun,With similar intensity but different rainfall and wind circle radius,the root cause is likely to be the Indian Ocean region through the low-level jet conveyor to the TCinternal water vapor channel is blocked related.