Characteristics Of Cloud Parameter And Precipitation Of Tropical Cyclone In Northwest Pacific Ocean Observed By TRMM PR And VIRS

Western North Pacific (WNP) is the basin where tropical cyclones (TC) frequently occur. The study on the charateristics of cloud parameter and precipitation for tropical cyclone over WNP is crucial for the understanding of developing, evolving and dissipation of TC, which also provides observational evidence for numerical models and ehances the ability for forecasting TC tracks and intensity. On the basis of merged dataset of TRMM Precipitation radar (PR) and visible/infrared scanner (VIRS), TRMM Multi-satellite Precipitation Analysis 3B42, in addition with the TC track data from JAXA and CMA, the characteristics of TC cloud parameter and TC precipitaiton contribution (TCPC), the difference between TCs and non-TCs in precipitation intensity, frequency, profile, deep convection and overshooting are investigated in this study.1 Characteristics of cloud parameters for precipitating clouds and non-precipitaitng clouds in TCsOn the basis of the merged datasets of PR and VIRS, and the retrieved cloud parameter, the characteristics of precipitating clouds (PC) and non-precipitating clouds (NPC) parameter are analyzed. The results indicate:1) the differences of effective radius (Re) between PC and non-precipitating clouds NPC are small. However, the cloud optical thickness (COT) for PC ranges from 40 to 140, which is much larger than NPC (below 40). Similiarly, the cloud water path (CWP) is much larger for PC,120 g/m2 is identified as the critical threshold.2) the relationship between precipitation and cloud parameter show that as the CWP or COT increases, the precipitation probability increases. While as the Re increases, the precipitation probability increases and then dereases; as the CWP is relatively small (<1000 g/m2), the precipitation probability increase as the enhancement of CWP, regardless of the cloud effective radius. As the CWP is above 1000 g/m2, the precipitation probability is in relation to both the CWP and Re; in general, the larger the Re is and the larger the CWP is, the larger the precipitation probability will be.3) the analysis of the method for discriminating PC and NPC by cloud parameter indicates that three indexes (COT greater than 40, CWP greater than 120 g/m2 and COT greater than 40, Brightness temperatre at 10.8μm less than 260K and CWP greater than 120 g/m2) exihibit good performance in discriminating PC, with TS reaches 0.48,0.48, and 0.5, respectively. The threshold methods can be applied for MODIS cloud products in discriminating PC, which provides a new way for discriminating PC through satellite obseravations.2 Characteristics of TC and non-TC precipitation and their infaraed signalsThe TC region and non-TC regions are discrimated using JAXA/EORC Tropical Cyclone Database, and then based on the merged data of PR and VIRS, the characteristics of TC precipitation and non-TC precipitation and their infrared signals were analyzed over East Asia during rainy season from 1998 to 2007. It is found that: 1) the distribution of typhoon rainfall intensity spectrum is much wider, especially for typhoon convective rainfall which ranges from 5-20mm/h.2) The main form of precipitation over East Asia is non-typhoon stratiform precipitation, reaching above 60%; the frequency of TC stratiform and convective precipitation is small, with the largest value only reaching 20% and 5%, respectively.3) the difference of precipitation profile for TC and non-TC is obvious below the freezing layer (-4 km). With the decrease of brightness temperature for TC convective clouds, the rain rate increase as the decrease of height, while non-TC almost stays the same.4) the brightness temperature of TC precipitating clouds is much lower than non-TC precipiting clouds, the difference could reach 15K.3 Characteristics of TCPCOn the basis of TRMM Multi-satellite Precipitation Analysis (TMPA) 3B42 at 3-hourly temporal resolution and 0.25° spatial resolution), in addition with the best track data from China Meteorological Administration (CMA), the seasonal, monthly and annual contribution of tropical cyclone precipitation to the total rainfall (TCPC) are analyzed over the WNP. The results show that 1) TC seasonal (from May to December) rainfall contribution ranges from 4% in inland regions to above 40% in ocean-regions of 15°N-25°N. Moreover, TCs at higher categories contribute much more to the total precipitation.2) On monthly scale, TCs contribute 60% to the total rainfall regionally during whole TC season, which is the maximum contribution. The peak contribution of TC rainfall averaged in multi-months of the ten years occurs in August (28%) over the whole ocean impacted by TC and in December (23%) over the whole land impacted by TC, respectively.3) on annual scale, the maximum contribution of TC precipitation to the total rainfall are in 2004 (-30%) over ocean and in 1998 (-20%) over land, respectively.4) there is a huge difference for TCPC in in El Nino and La Nina years. The contribution of TC precipitation to the total rainfall increases 6%(decreases 6%) in El Nino (La Nina) years compared with neutral years.4 Deep convection and overshooting in TCs and Non-TCsBased on the PR precipitation profile dataset from 1998 to 2011 during June and Sepetember, the difference between deep convection and overshooting in TCs and Non-TCs are studied, and the fraction of TCs to deep convection and overshooting in WNP is estimated. The results indicate that 1) the deep convection and overshooting in TCs mainly occur over ocean, with the maximum frequency in the ocean 15°N-25°N; while in Non-TCs, the deep convection and overshooting mainly occur over land.2) The frequency of deep convection and overshootings in TCs ranges from 0.01%-0.15%,0.005%-0.02%, respectively, while is much smaller than in Non-TCs, with frequency at above 0.15% and above 0.02%, respectively.3) The precipition intensity for TC deep convection and overshooting exceed 14 mm/h and 22 mm/h, respectively, while it is much smaller in Non-TCs, ranging from 10 mm/h (10 mm/h) to 14 mm/h (18 mm/h) for deep convection (overshooting).4) About 2%-30% of deep convection events in NWP are contributed by TCs, and the ratio of TCs to overshooting in NWP increase, with most of the regions reaching 50%.