Indian Journal of Radio & Space Physics Vol 43, February 2014, pp 103-123 Effect of cumulus and microphysical parameterizations on the JAL cyclone prediction M Venkatarami Reddy1,2, S B Surendra Prasad1,2, U V Murali Krishna1 & K Krishna Reddy1,$,* 1Semi-arid-zonal Atmospheric Reseach Centre (SARC), Yogi Vemana University, Kadapa 516 003, Andhra Pradesh, India 2Department of Physics, Acharya Nagarjuna University, Guntur 522 510, Andhra Pradesh, India $E-mail: [email protected] Received 19 August 2013; revised 7 November 2013; accepted 8 January 2014 Weather Research and Forecasting (WRF) model is used to predict the track and intensity of JAL cyclone, which formed during 04-08 November 2010 over the Bay of Bengal. The model has been simulated with numerous experiments using the logical/scientific combination of convection and micro-physics schemes. The model simulations have been conducted with different initial conditions to know the effective track and intensity prediction of JAL cyclone. In addition, the effect of cumulus parameterization schemes at different resolution (27 and 9 km) on the cyclone track and intensity is reported. The model simulated results showed the importance of cumulus schemes and their role at 9 km horizontal resolution. The results indicate that the track predicted by Kain-Fritsch (KF) scheme is in good agreement with the observed track in all the experiments and the land fall error is minimum (~11 km) for the combination of Ferrier and KF scheme with 0000 hrs UTC on 04 November 2010 as initial condition. Strong intensity is produced by KF, New Grell (NG) schemes and weak intensity is produced by Betts-Miller-Janjic (BMJ) scheme with all microphysics parameterization (MP) combinations. Further, the dependency of intensity of cyclone has been studied in terms of surface latent heat flux, divergence and vorticity fields. To validate the model performance, different meteorological parameters are derived from the model simulations over three different regions and are compared with the observed meteorological parameters. The model results are in good agreement with the observed parameters, but variations are observed at the landfall /dissipation of the cyclone. Keywords: JAL cyclone, Weather Research and Forecasting (WRF model), Cumulus parameter, Microphysical parameters, Vorticity, Divergence, Convergence PACS Nos: 92.60.Aa; 92.60.hb; 92.60.Wc 1 Introduction Initially, TC forecast was carried out using a Tropical cyclones (TC) form over Bay of Bengal computer oriented half persistence and half (BOB) with strong winds, torrential rains and tidal climatology technique in India4. Later on, Mohanty & waves1,2 during pre- and post-monsoon season and Gupta5 have used multi-level primitive equation cause a severe damage to lives and property over the models with parameterization of physical processes east coast of India and Bangladesh. The tropical for the prediction of cyclone track. Prasad & Rama storms form and develop over the warm tropical Rao6 have performed numerous sensitive experiments oceans under favourable environmental conditions3. on Quasi-Lagrangian model (QLM) to forecast the The BOB in the Indian Ocean is a potentially track of cyclones. In the last few years, the rapid energetic region for the development of TCs and it advancement of computing power and high resolution contributes about 7% of the global annual tropical mesoscale models are being used to know the TC storms. There is a need to develop a regional weather structure, intensification and movement7-12. Srinivas forecasting system to give the lead time forecast et al.13 explained the importance of boundary layer warnings and to mitigate the disasters. Hence, and convective parameterization in TCs and reported accurate prediction of the track and intensity of the model sensitive studies for the Andhra severe cyclones is essential to minimize the loss of human cyclone in 2003. lives and property damage. Several models and Globally, several studies were carried out using methods have been developed to predict the accurate different numerical models to simulate the structure, position of the cyclone to some extent. The improvement intensity, track of cyclones, hurricanes and typhoons14-21. in prediction helps to issue the appropriate cyclone The high resolution mesoscale models were being warnings to the society and disaster management. used extensively for hurricane sensitivity studies to 104 INDIAN J RADIO & SPACE PHYS, FEBRUARY 2014 know the structure, intensification and movement may not be suitable for other regions. Most of the with different physical processes22,23. Fovell & Su24 studies mainly focused on the prediction of track and showed that the logical combination of microphysics intensity of the cyclones over BOB with resolutions parameterization (MP) and cumulus parameterization greater than 10 km using different physical processes (CP) schemes significantly influenced the track and and few of them performed less than 10 km resolution land fall of Hurricane Rita using WRF model at 30 with different MP and PBL processes. The present and 12 km resolution. They also reported the impact study focused mainly on the prediction of track and of cloud MP schemes on track forecasting. Different intensity of JAL cyclone using WRF model with parameterization schemes have been developed by different CP and MP schemes to find the best set several researchers but all of them have certain of physics options. During the last decade, JAL limitations25-28. cyclone alone passed over the semi-arid region The TC intensity forecast varied with different of India. Hence, the best logical combination of microphysical processes in numerical models. Zhu & parameterization schemes for JAL cyclone was Zhang29 examined the sensitivity of the hurricanes reported and the results compared with observational intensity with different microphysical processes in the meteorological parameters over three regions, viz. MM5 model. The intensity and track forecast of Oceanic (12.8-13.8°N, 80-90.2°E), inland (13-14°N, cyclones depend on the evolution and the distribution 79-80°E) and semi-arid (14-15°N, 78-79°E) at 3 km of the heat rates30, which depends on the release of resolution with and without CP schemes. latent heat flux by the condensation within the system. Deshpande et al.31 studied the track and intensity 2 Brief description of JAL cyclone prediction for cyclone Gonu using MM5 model at A severe cyclonic storm, JAL developed 90 and 30 km resolutions and concluded that (04-08 November 2010) over BOB. It moved track and intensity prediction were highly sensitive west-northwestwards and intensified into severe for convective parameterization schemes than cyclonic storm on 06 November 2010. India other physical parameterization schemes. Loh et al.32 Meteorological Department (IMD) reported41 that the also reported that the planetary boundary layer JAL cyclone moved to the southwest of BOB having parameterization (PBL) schemes did not show much lower ocean thermal energy and high vertical wind impact on the prediction of track and intensity of shear in association with the strong easterlies in the near equatorial typhoons. However, the intensity upper tropospheric level. The strong wind shear led forecast still remains a challenging problem in both to westward shearing of convective clouds from the operational and research communities17,33,34. centre of system and the lower Ocean thermal Even though the CP schemes are important for the energy caused to convection un-sustainability over simulation of TCs, there is a limitation in usage of the region. The severe cyclonic storm, JAL gradually CP schemes in the numerical simulations at high weakened into a deep depression and crossed north resolutions (e.g. less than 10 km grid spacing). Liu Tamil Nadu – South Andhra Pradesh coast, close to et al.35 and Braun et al.36 simulated the TC without the north of Chennai near 13.3°N and 80.3°E around any CP scheme in the high resolution because it is 1600 hrs UTC on 07 November 2010. It continued to not worthy to use CP schemes in the numerical move west–northwestwards and further weakened simulations where the grid horizontal resolution is into well marked low pressure area. The convective less than 10 km. Even though the domain horizontal clouds were sheared to the large extent to west on the resolution is less than 10 km, CP scheme plays date of landfall, i.e. on 07 November 2010. During a key role for the accurate prediction of TC37-39. the last decade, JAL cyclone is the only cyclone, McFarquhar et al.40 used 6 km horizontal resolution which passed over interior parts of Andhra Pradesh domain and reported the change in intensity and track (semi-arid region) and it caused heavy rainfall over prediction of TC with different CP schemes. the coastal region as well as the interior parts of semi- TCs track and intensity simulation are sensitive to arid regions. model resolution, CP, MP and PBL schemes used in the model. However, the best set of parameterization 3 Model description schemes in the model is not same for all the cyclones. The non-hydrostatic compressible WRF model The logical combination of schemes for one region was developed by National Center for Atmospheric REDDY et al.: EFFECT OF CUMULUS AND MICROPHYSICAL PARAMETERIZATIONS ON JAL PREDICTION 105 Research (NCAR)42. It has features like a fully Miller convective adjustment scheme47,48 was commonly compressible, Eulerian non-hydrostatic control used in tropical cyclone simulations35,40. The GD is a equation set, a terrain-following, hydrostatic pressure cloud ensemble scheme with 144 sub-grid members. vertical coordinate system with the constant pressure It uses 16 ensemble members derived from 5 popular surface at the top level of model. The staggered closure assumptions to obtain an ensemble‐mean grid, like Arakawa-C grid, used in the model and a realization at a given time and location49. The third-order Runge-Kutta time integration scheme MP schemes used in the model are WRF Single used for both horizontal and vertical directions.