NUMERICAL SIMULATION OF A BAY OF BENGAL TROPICAL CYCLONE: A COMPARISON OF THE RESULTS FROM EXPERIMENTS WITH JRA-25 AND NCEP REANALYSIS FIELDS

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1 NUMERICAL SIMULATION OF A BAY OF BENGAL TROPICAL CYCLONE: A COMPARISON OF THE RESULTS FROM EXPERIMENTS WITH JRA-25 AND NCEP REANALYSIS FIELDS Dodla Venkata Bhaskar Rao Desamsetti Srinivas and Dasari Hari Prasad Department of Meteorology and Oceanography Andhra University Visakhapatnam, India Third WCRP International Conference on Reanalysis Tokyo, Japan 28 th January 1 st Febraury 2008

2 Objective Numerical simulation/ prediction of tropical cyclones over Bay of Bengal with high resolution mesoscale models using JRA-25 and NCEP Reanalysis Data

3 JRA-25 Reanalysis Dataset JRA Reanalysis data is available from 1979 to present at 1.25x1.25 degree resolution

4 NCEP Reanalysis Dataset (Kalnay et al. BAMS, 1996) NCEP Reanalysis is available from 1948 to present at 2.5x2.5 degree resolution NCEP-Reanalysis Dataset uses the following Observations: NCEP --- GTS data NOAA/NESDIS --- TOVS data GFDL --- Ocean Reanalysis UKMO --- Global Ice and SST reanalysis for earlier periods JMA --- Cloud track winds, Special Rawinsonde data (not available on GTS) ECMWF --- sea ice database, fill up of data gaps NASA/GLA --- retrievals missing from NCEP archives, especially of 1986

5 JRA-25 and NCEP Reanalysis Used Variables Surface Variables 3-D Profiles Vertical Levels (hpa) JRA-25 T, U, V, Dew point Depression, q, MSLP T,U,V,Φ at 23 levels q at 12 levels Dew point Depression at 8 levels , 925, 850, 700, 600, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20, 10, 7, 5, 3, 2, 1, 0.4 NCEP T,U, V, RH, MSLP SST, SNOW T,U,V,RH, Φ at 17 levels , 925, 850, 700, 600, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20, 10

6 Outline Case Study Description of Orissa Super Cyclone (1999) Model and Data Used Experimental Setup Results

7 Case Study SuCS 15_28 SCS 03_27 CS 03_26 VSCS 15_27 D 06_25 DD 00_26 A case study of the Orissa Super cyclone is chosen as this was the most intense cyclonic system on record over the Bay of Bengal during the last century with an estimated Central Sea level pressure of 912 hpa and associated maximum wind speed of 140 knots. Location and intensity of the Orissa super cyclone as per IMD reports

8 Description of Orissa Super Cyclone (1999) The storm had its genesis over the Gulf of Thailand, located as a low-pressure area on 24 th Oct It attained the different stages of low pressure (24 October), depression (12 UTC of 25 October), cyclonic storm (03 UTC of 26 October), severe cyclonic storm (03 UTC of 27 October), very severe cyclonic storm (15 UTC of 27 October) and super cyclonic storm at 15 UTC of 28 October 1999 The lowest central surface pressure was estimated as 912 hpa with an associated maximum wind speed of 140 knots It moved consistently towards northwest with its landfall near Paradip (20.5 N, 86 E) on the east coast of India between 0430 UTC and 0530 UTC on 29 th October, 1999

9 Model and Data Used for Present Study Model : MM5 (NCAR) Initial conditions at 00 UTC of 25 October 1999 & lateral boundary conditions for the period of integration (i.e.) upto 00 UTC of 30 October 1999 were interpolated from two different data sets (i.e.) JRA Reanalysis data available at 1.25 x 1.25 and NCEP Reanalysis data available at 2.5 x 2.5 Model topography for the 90 and 30 km domain regions are obtained from USGS topography data available at 30 (56 km) and 10 (19 km) resolution Track and intensity observations were taken from IMD to compare model results TRMM 3B42 rainfall was used to compare the model simulated rainfall

10 Experimental Setup Model Name PSU/NCAR MM5 Model V3.7 Model type Vertical resolution Horizontal resolution Domain of integration Primitive equation, Non-hydrostatic 23 sigma levels 90 km 30 km 10 km E E E E E E 4.16 S N 4.46 N N 9.19 N N Radiation scheme Dudhia scheme Surface scheme 5 layer model Convection schemes Kain-Fritsch2 PBL schemes MRF, MY Cloud Microphysics Simple Ice, Mixed Phase

11 Domain Setup 10 km 30 km 90 km Model domains (90, 30 and 10 km)

12 Results The results from an experiment with MM5 with interactive nested two domains of 90 and 30 km resolution and with the options of the parameterization schemes of KF2, MRF and SI for the convection, PBL and explicit moisture processes are presented

13 Model simulated track positions for the experiment with 2 domains of 90 and 30 km and with KF2, MRF and SI schemes IMD JRA NCEP Track positions plotted from 00UTC of 26 October 1999

14 Time series of model simulated Track Errors Time series of Track errors (km) NCEP JRA 450 Track error (km) Time (hrs) NCEP JRA

15 Time series of model simulated CSLP (hpa) Time series of Model simulated CSLP (hpa) Pressure (hpa) NCEP REANL JRA IMD Time (hrs) NCEP JRA IMD

16 Time series of model simulated Max. Wind (m/s) Time series of Model simulated Max. Wind (m/s) Wind speed (m/s) NCEP REANL JRA IMD Time (hrs) NCEP JRA IMD

17 Time series of model simulated Radius of Max. Wind Radius of Maximum wind (km) JRA NCEP Radius (km) Time (hrs) NCEP JRA

18 Model simulated track and intensity For the experiment with 3 domains of 90, 30 and 10 km and with KF2, MY and SI schemes (a) (b) (c) Time series of CSLP (hpa) Time series of max. wind (m/s) IMD JRA Pressure (hpa) IMD KF2MYSI Time (hrs) Wind speed (m/s) Time (hrs) 96 IMD KF2MYSI Fig (a) Model simulated track positions TE (km) CSLP (hpa) WS (m/s) Fig (b) Time series of model simulated CSLP Fig (c) Time series of model simulated Max. wind In the table values in the brackets represents IMD Observations (998) (986) (912) (23) 70 (33) 65 (72) 40

19 Model simulated track and intensity For the experiment with 3 domains of 90, 30 and 10 km and with KF2, MY and MP schemes (a) (b) Time series of CSLP (hpa) (c) Time series of Max. Wind (m/s) IMD JRA Pressure (hpa) IMD KF2MYMP Time (hrs) Wind speed (m/s Time (hrs) 96 IMD KF2MYMP Fig (a) Model simulated track positions TE (km) CSLP (hpa) WS (m/s) Fig (b) Time series of model simulated CSLP Fig (c) Time series of model simulated Max. wind In the table values in the brackets represents IMD Observations (998) (986) (912) (23) 68 (33) 60 (72) 35

20 Surface Pressure Distribution

21 Structure of the Cyclone at Premature stage (a) (b) (c) (d) Structure: (12 UTC of 27 th October 1999) along N (a) Wind speed (m/s) (b) Vertical velocity (cm/s) (c) Relative humidity (%) (d) Temperature Difference (12 UTC27 00UTC25)

22 Structure of the Cyclone at Mature stage (a) (b) (c) (d) Structure: (00 UTC of 29 th October 1999) along N (a) Wind speed (m/s) (b) Vertical velocity (cm/s) (c) Relative humidity (%) (d) Temperature Difference (00 UTC29 00UTC25)

23 Rainfall Distribution 28 Oct Oct Oct 1999 Model TRMM

24 Attempt is made to simulate/predict the movement and intensity of an intense tropical cyclone over Bay of Bengal using NCAR MM5 mesoscale model. The utilization of JRA-25 and NCEP reanalysis data sets has been explored. The experiments indicate that: Summary (1) JRA-25 reanalysis with 1.25 resolution has produced better simulation as compared to NCEP reanalysis data at 2.5 resolution. (2) The combination of the parameterization schemes of KF2, MY and MP for convection. PBL and explicit moisture produce the best result in terms of both the intensity and track errors. (3) The model could produce an CSLP of 890 hpa with the combination of KF2, MY and SI schemes but with track errors up to 474 km at 120 hours, whereas with KF2, MY and MP schemes the simulated CSLP was 940 hpa and the track errors were only 115 km.

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