Campaign mode observation of tropical convection using ground-based radar systems

Tropical convection plays an important role in enhancing rainfall and also creates uncertainty in the model-based predictions of weather in tropics due to the latent heat released into the troposphere. Ground-based radar systems are important tools available for the effective characterization of convective events. Availability of different radar systems ideally suited to study tropical convection in an area popularly known as the Golden triangle for weather observations in southern part of India, led to the organization of an interagency program for a campaign mode of observations using the different radar systems and associated rain gauges etc. to observe tropical convection during the period Oct-Dec, on a few days when the north east monsoon was prevalent over the east coast of peninsular India. The Golden triangle consists of Sriharikota Island where the Space Launch Complex of ISRO is located at the Satish Dhavan Space Center, the Cyclone Detection Radar site of IMD at Chennai and the National MST Radar Facility (NMRF) at Gadanki in close proximity to the temple city of Tirupati. An indigenously developed S band Doppler weather radar is commissioned at Sriharikota Island on the east coast of India in December 2002, as an interagency program between India Meteorological Department and Indian Space Research Organization. A siphoning type fast response rain gauge and a tipping bucket rain gauge are located within 10 km from the radar. Another S band DWR is located in Chennai, India by IMD. These radars have the capability to measure precipitation and Doppler velocity and provide in real time the 3 base products viz., reflectivity, velocity, and spectral width of the hydrometeors within radar sample volume with good accuracy up to 250 km. From these base products, other meteorological products like rainfall rate, rainfall accumulation, Cappi, echotop etc. are derived. Indian MST radar, a VHF profiler (at 53 MHz) normally used for estimating the winds and turbulence and an L band lower atmospheric wind profiler operating at 1357.5 MHz for estimating the winds, turbulence, and precipitating weather systems in tropical latitudes are operating at NMRF since 1990. Apart from these radar systems, a disdrometer and an optical rain gauge are also located at this faci- lity as collocated instrumentations for the measurement of rainfall rate and rainfall accumulation. All these three locations are geographically located within 80-100 km from each other and form a triangle. These instrumentation systems provide an excellent ground-based network for the characterization of tropical convection. The paper describes the campaign details including the detailed characteristics of the radar systems used and provide intercomparison of the data obtained as the convective systems transited over the terrain which is essentially coastal for Chennai and SHAR and mountainous for Gadanki.