The Utilization of Satellite Data in Analyzing the Formation of Tropical Cyclones Gin-Rong Liu Dean, Research and Development Office Professor, Center for Space and Remote Sensing Research Institute of Atmospheric Physics Institute of Hydrological Sciences National Central University E-mail : grliu@csrsr.ncu.edu.tw Gin-Rong Liu, Dean/Prof. Research and Development Office Center for Space and Remote Sensing Research Institute of Atmospheric Physics Institute of Hytrological Sciences National Central University E-mail : grliu@csrsr.ncu.edu.tw Ph.D., University of Wisconsin-Madison, Meteorology (Atmospheric and Oceanic Sciences) M.S., University of Wisconsin-Madison, Meteorology (Atmospheric and Oceanic Sciences) B.S., National Taiwan University, Atmospheric Sciences Current Appointments Dean, Research and Development office, National Central University, August 2004 ~ present. Professor, Department of Atmospheric Science, National Central University Professor, Institute of Hydrological Science, National Central University Panel Chair, Nature Science Division, National Science Council (NSC), January 2004 ~ present. Adjunct Professor, Department of Atmospheric Science, National Taiwan University Adjunct Professor, Department of Atmospheric Science, Chinese Cultural University Chief Editor, Journal of Atmospheric Science, ROC(Taiwan) Meteorological Society. Principal Investigator, Taiwan Chung-Li NCU station, Aerosol Robotic Network (AERONET). Responser, Meteorological Satellite Laboratory,NCU Satellite Receiving Systems of CSRSR NCU 13 m Antenna 6.1 m Antenna 3000km CKS International Airport (SPOT) ¾ Meteorological Satellite Laborotary Antenna-GMS Antenna-NOAA Sand Index from GMS-5, March, 2002 NOAA-17 AVHRR, 2004/01/02 Outline .Introduction .Theoretical concepts and Methods .Data Acquirement and Processing .Analysis and Discussion .Conclusion .Introduction ¾ In the research of tropical cyclone formations, Charney and Eliassen(1964) believed that the conditional instability of the second kind (CISK), along with the addition of lowlevel perturbations and the convection of cumulus clouds were considered important factors. ¾ Gray (1968) defined a tropical cyclone genesis parameter as the product of thermodynamic and dynamical terms, where SST and midlevel moisture effects were included in the thermodynamic term, and vertical shear and lowlevel vorticity effects were included in the dynamical term. ¾ Mark et al. employed 3 thermal conditions mentioned previously in computing a “Tropical Cyclone Genesis Parameter”. This parameter was used to analyze the cyclone cases that occurred over the Atlantic Ocean. The results showed that the geopotential parameter trend was strongly associated with the seasonal variation of cyclone formations. ¾ Liu et al.(2000) used SSM/I data to show that the air-sea interaction plays an important role in MCSs’ formations over the ocean. This interaction may also play a similar role in the development of typhoons by providing the required thermal energy. OPI Application (Case study: 1997/06/11) 3 1 2 OPI Application (Case study: 1997/05/16) ¾ Hack and Schubert (1988) suggested that improvements in the system heating efficiency is conducive for the formation of TCs, especially in stronger vorticity areas. Similar results were reached by Ryan et al.(2002), where they employed QuickSCAT data in analyzing the vorticity variations. ¾ This study makes use of SSM/I and QuickScat satellite data in analyzing how the thermal and dynamic conditions-namely the daily air-sea energy flux and near-sea surface vorticity variations-- are related to the formation of TCs over SCS during the TC seasons (May~Oct, 2000~2002). II. Theoretical concepts and Methods ¾ Utilization of Liu and Liu’s method (2002) to derive relevant air-sea parameters – Ts Ta Qs Qa Ws SHF LHF ¾ Using satellite-derived air-sea parameters in deriving the objective thermal and dynamic indices ¾ In estimating air-sea parameters was applied Liu et. al. 2002 . by Sea surface temperature (Ts) Ts=118.186+3.458Tb(19V) -1.799Tb(19H) -2.417Tb(37V)+1.119Tb(37H)+0.414Tb(85V) -0.136Tb(85H) ------ K Near sea surface air humidity (qa) qa=-101.398+0.547Tb(19V)-0.677Tb(37V) +0.078Tb(37H)+0.765Tb(85V)-0.254Tb(85H) ------ g/Kg Near sea surface wind speed (Ws) Ws=96.015+0.162Tb(19V)-0.228Tb(22V) -0.701Tb(37V)+0.527Tb(37H) ------ m/s Near sea surface air temperature (Ta) ⎧ ⎡ ⎪⎪ q (T ) ⎢ Ta = Ts − ⎨0.2 × (qs − qa ) ∗ qa ⎢ ⎪ ⎢ ⎪⎩ ⎣ ⎫ ⎤ ⎪⎪ ⎥ 1 ⎬ ∂q* ⎥ ⎪ ⎥ ∂T ⎦ T −Ta ⎪⎭ Ta: near-sea –surface air temperature qa: near-sea-surface air humidity qs the saturated specific humidity Air sea latent heat flux and sensible heat flux LHF = −lρCe (qs − qa )u SHF = − ρC p Ch (Ts − Ta )u Ch and Ce : bulk coefficients for sensible heat and latent heat flux Subscript s : the field value of sea surface level Subscript a :those of 10m above sea surface level U : the wind speed of 10m above sea surface level. T: temperature, q :humidity, ρ : air density, l : latent heat of evaporation, Cp :specific heat of constant pressure. ¾ To derive the objective thermal and dynamic indices Gaussian fitting of air-sea parameters 2000~2002 VT (Aug) 2000~2002 LHF+SHF (Aug) 0 SHF+LHF 0.5 0 LHA 0.5 Air sea latent heat flux and sensible heat flux LHF = −lρCe (qs − qa )u SHF = − ρC p Ch (Ts − Ta )u 1 Latent heat release (LHR):In estimating latent heat release was applied byAlliss et al.(1992) Rodgers et al.(1994,1995) LHR = Lρ ∫ Rda A L:condensation latent heat( 2.5 ×10 J /)Kg ρ: density of air( 1.0 ×10 Kg / m) R:rainfall rate da:the measure of area increment, A:the area of integration. This shows that the environmental Not conducive for system development atmosphere provides thermal energy to TCs Conducive for system development 6 3 1 3 •SSM/I –Channels Tb19v, Tb19h, Tb22v, Tb37v, Tb37h, Tb85v, Tb85h –Time May-Step. (2000-2002) –Satellites F10, F11, F13 and F14 –Test area 5°N~25°N 110°E~125°E •QuikSCAT –Channel L3 –Time Same as SSM/I –Test area: Same as SSM/I IV. Results and Discussions ¾Analysis of the objective Thermal and dynamic indices of the initial typhoon development stages over the South China Sea (SCS) during 2000-2002. Type I Cimaron (2001) Location of Typhoon Formation 17.1N 119.1E Date 2001.05.11-05.14 Air-sea parameters analysis area 14.1N-20.1N 116.1E-122.1E 2001 05/12 00Z(-1day) 1st typhoon watch announced by JTWC ¾ For Type I typhoons it shows that the objective thermal index increases significantly 2 days before the it’s actual formation Type II Durian (2001) Location of Typhoon Formation 17.5N 114.6E Date 2001.06.30-07.02 Air-sea parameters analysis area 14.5N-20.5N 111.6E-117.6E 2001 06/30 00Z The official time point in the actual typhoon formation announced by JTWC ¾ For Type II typhoons, it also shows an evident increase in the thermal objective index two days prior to the typhoon’s actual formation. However, this phenomena can also be witnessed 4~7 days before the typhoon’s genesis, which make it very difficult to distinguish the specific time point for the typhoon’s formation. Question: Is it more precise if both Thermal and dynamic Parameters are considered? For example, the add of Vorticity information? Type II Durian (2001) ¾The case study of Durian (2001) showed that the vorticity information was Helpful to the determination of typhoon occurring time. Note 1 ¾ Based on the analysis of 15 typhoons cases over SCS during 2000-2002, the results showed that the formation time point for 10 typhoon cases could be determined in advance by the objective thermal index. 4 typhoons cases could be determined with the additional accompaniment of the objective dynamic index. There was only 1 typhoon case--Yutu (2001)– that could not be correctly determined. ¾ In other words, a 93% (14/15) ratio of typhoons showed a significant raise in the objective thermal and dynamic indices 2 days prior to its actual formation. ¾ Monitoring of the variations in the objective thermal and dynamic indices over SCS( 5-25N 110-125E) during the 2002-2003 typhoon seasons T.D. Typhoon ¾Area: 5-25N, 110-125E, time: 2002 Data: SSM/I and QuickScat (resampling to a 0.5X0.5 Degree Grid) Method: (1)Computation of the objective thermal and dynamic Indices (2)Shadowing the areas where the Indices is larger than 0.5. ¾The results show that areas that had more shadow areas, seemed to have a higher occurrence of typhoons. T.D. Typhoon Independent Case(2003) ¾ The result of 2003 showed the same trend like 2002. OB:Objective Potential Index(OPI, Thermal Index) Vt: Vorticity (Dynamic Index) Verification of objective index ¾ Verification of the SCS cases during 2000-2002 ¾ Shadow areas indicate the objective index values are larger than 0.5 0.5X0.5 1.X1. 1.5X1.5 ¾ Different grid resolutions were tested. ¾ It showed that 1X1 degree grid had a better sensitivity, and was capable of removing signal noises Case study of objective index ¾ A 1x1 degree grid was used in the monitoring of tropical cyclones ¾ Case I Nakri Typhoon Lifetime 2002/07/08~13 Location of Typhoon Formation [21.6 N 117.7 E] ¾ Case II Kammuri Typhoon Lifetime 2002/08/03~06 Location of Typhoon Formation [20.7 N 114.6 E] Nakri Nakri Kammuri Kammuri Kammuri Note 2 ¾ Verification of Typhoon Formations in SCS during 2000-2002 2000 Æ 10 : 1(X) 9(O) 2001 Æ 20 : 6(X) 14(O) 2002 Æ 14 : 5(X) 9(O) ¾ Correction= 72.7% (32/44) X: incorrect O: correct .Conclusions ¾ Based on the analysis of typhoons occurring over SCS during 2000-2002, it revealed that the objective thermal index would raise significantly 2-3 days prior to the actual typhoon formation. ¾ From the analysis of the vorticity data from QuickScat satellite, it shows that although the objective thermal indices for some cases increased substantially, but due to weak dynamic conditions, they were unable to evolve into typhoons. 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