Jagabandhu Panda

A comprehensive study of surface and upper-air characteristics over two stations on the west coast of India during the occurrence of a cyclonic storm

While qualitative information from meteorological satellites has long been recognized as critical for monitoring weather events such as tropical cyclone activity, quantitative data are required to improve the numerical prediction of these events. In this paper, the sea surface winds from QuikSCAT, cloud motion vectors and water vapor winds from KALPANA-1 are assimilated using three-dimensional variational assimilation technique within Weather Research Forecasting (WRF) modeling system. Further, the sensitivity experiments are also carried out using the available cumulus convective parameterizations in WRF modeling system. The model performance is evaluated using available observations, and both qualitative and quantitative analyses are carried out while analyzing the surface and upper-air characteristics over Mumbai (previously Bombay) and Goa during the occurrence of the tropical cyclone PHYAN at the west coast of Indian subcontinent. The model-predicted surface and upper-air characteristics show improvements in most of the situations with the use of the satellite-derived winds from QuikSCAT and KALPANA-1. Some of the model results are also found to be better in sensitivity experiments using cumulus convection schemes as compared to the CONTROL simulation.

A Qualitative study of Some Meteorological Features During tropical Cyclone PHET Using Satellite Observations and WRF Modeling System

The satellite derived meteorological parameters are quite useful for understanding the genesis of a tropical cyclone. This paper analyses some of the characteristic features of the tropical cyclone (TC) PHET using satellite derived meteorological observations, and numerical model simulations while investigating the performance of various cumulus parameterization schemes using Weather Research and Forecasting (WRF) modeling system. The genesis of the TC is primarily discussed using the observed meteorological parameters including the outgoing long-wave radiation, quantitative precipitation estimate (or rainfall), sea surface temperature, relative vorticity and upper tropospheric humidity. These satellite derived parameters show suitable meteorological condition for the development and propagation of the TC. The qualitative analysis of WRF simulated results indicates that Kain-Fritsch cumulus scheme (Kain and Fritsch, 1990 and 1993; Kain, 2004) performs relatively better in predicting various parameters in relation to the genesis and propagation of PHET.

A New Algorithm to Classify the Homogeneity of ERS-2 Wave Mode SAR Imagette

A new classification parameter is developed using 1535 ERS-2 wave mode synthetic aperture radar (SAR) test imagettes to better differentiate homogeneous and inhomogeneous imagettes. The comparison between the new parameter (Min) and the previous one (Inhomo) (Schulz-Stellenfleth and Lehner, 2004) was done under varied threshold values of Inhomo. It is concluded that the performance of ‘Min’ is much better than ‘Inhomo’ when applying to the 1535 test imagettes. Furthermore, both Min and Inhomo are applied to nearly 1 million imagettes collected for the period from 1 September 1998 to 30 November 2000. The comparisons of the global inhomogeneous distribution between ‘Min’ and ‘Inhomo’ reveal that both the areas and percentage of inhomogeneity calculated by ‘Min’ are larger than that calculated by ‘Inhomo’. By analyzing the low wind speed distribution of HOAPS data, we found that low wind speed over the ocean is one of the key reasons for the inhomogeneity of SAR imagettes.

Monitoring Convective Clouds Over India and Nearby Regions Using Multi-spectral Satellite Observations

Convective clouds are the sources of severe weather and extreme precipitation events which often produce flooding, landslides and other disasters. The physical characteristics of convective clouds influence the distribution of radiative heating/cooling in the troposphere. They play a crucial role in atmospheric circulation and the hydrological cycle. Present study deals with the detection of convective clouds using multispectral observations at split window channels (near 11 and 12 µm) and water vapour absorption channels (near 6.7 µm) from EUMETSAT (Meteosat 7) data. Results are compared with the observations (reflectivity-based threshold) from Precipitation Radar (PR) on-board Tropical Rainfall Measuring Mission (TRMM). The Results have also been validated against convective clouds derived from rain gauge based precipitation product from the IMD data. Validation results show a correlation coefficient (cc) of 0.79 and Root Mean Square Error (RMSE) of 2.61 (%) against rain gauge based observations of convective clouds.

Variability in landfalling trends of cyclonic disturbances over North Indian Ocean region during current and pre-warming climate

Cyclonic disturbances (CDs) are one of the deadliest systems formed over ocean basins in the world. Impact of warming climate over these basins including that of North Indian Ocean (NIO) is quite prominent in terms of enhanced intensity and re-curvature of the cyclonic systems. However, the impact of warming climate on landfall activity is not yet studied for the NIO basin. Therefore, the current study is performed by dividing the climate into current and pre-warming periods based on sea surface temperature (SST) anomaly variation. The study reveals that Bangladesh, Andhra Pradesh (AP), and Tamil Nadu (TN) are more vulnerable to severe cyclones formed over Bay of Bengal (BOB) during the current warming climate. Gujrat is prone to severe cyclones and Arabian Peninsula countries are vulnerable to cyclonic storms formed over the Arabian Sea during the current warming climate as well. During CWP, Bangladesh and Arakan are more vulnerable to CD landfall in pre-monsoon season, whereas in post-monsoon months, AP, TN and Bangladesh are more prone coastal areas of BOB. Gujrat and IAA are more vulnerable coastal areas of AS irrespective of seasons considered. The enhanced genesis over southern and middle sector of BOB is mainly responsible for more landfall over AP, TN and Bangladesh. In addition, change in wind direction from NW to N-NW and increased meridional SST over BOB are found to be encouraging the landfall activity near AP and TN coasts. The W-SW and zonally distributed SST supports landfall over Gujrat. There is less impact of change in genesis location over AS landfalling CDs. Over AS near to 12° N, a well-organised wind circulation is observed enhancing the dissipation of the cyclonic systems over the basin during current warming period.

Validating quantitative precipitation forecast for the Flood Meteorological Office, Patna region during 2011–2014

In order to issue an accurate warning for flood, a better or appropriate quantitative forecasting of precipitation is required. In view of this, the present study intends to validate the quantitative precipitation forecast (QPF) issued during southwest monsoon season for six river catchments (basin) under the flood meteorological office, Patna region. The forecast is analysed statistically by computing various skill scores of six different precipitation ranges during the years 2011–2014. The analysis of QPF validation indicates that the multi-model ensemble (MME) based forecasting is more reliable in the precipitation ranges of 1–10 and 11–25 mm. However, the reliability decreases for higher ranges of rainfall and also for the lowest range, i.e., below 1 mm. In order to testify synoptic analogue method based MME forecasting for QPF during an extreme weather event, a case study of tropical cyclone Phailin is performed. It is realized that in case of extreme events like cyclonic storms, the MME forecasting is qualitatively useful for issue of warning for the occurrence of floods, though it may not be reliable for the QPF. However, QPF may be improved using satellite and radar products.