Doppler Weather Radars

The Government proposes to install hi-tech Doppler weather radars in sensitive Himalayan region including Uttarakhand to get early alerts about cloudburst and heavy rain in higher reaches of the region. Based on scientific assessment of the needs of observing system network, comprising Doppler Weather Radars, rain radars, Automatic Weather Stations (AWSs), Automatic Rain Gauges (ARGs), Snow Gauges etc. expansion has been formulated by Earth System Science Organization –India Meteorological Department (ESSO-IMD), under its project Integrated Himalayan Meteorology Programme for Western & Central Himalayas. It covers Jammu & Kashmir, Himachal Pradesh and Uttarakhand. The total budget proposed for the entire project is approximately 117 crores. Weather radar, also called weather surveillance radar (WSR) and Doppler weather radar, is a type of radar used to locate precipitation, calculate its motion, and estimate its type (rain, snow, hail etc.). Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to the intensity of the precipitation. Both types of data can be analyzed to determine the structure of storms and their potential to cause severe weather.Weather radars send directional pulses of microwave radiation, on the order of a microsecond long, using acavity magnetron or klystron tube connected by a waveguide to a parabolic antenna. The wavelengths of 1 – 10 cm are approximately ten times the diameter of the droplets or ice particles of interest, because Rayleigh scattering occurs at these frequencies. This means that part of the energy of each pulse will bounce off these small particles, back in the direction of the radar station. Shorter wavelengths are useful for smaller particles, but the signal is more quickly attenuated. Thus 10 cm (S-band) radar is preferred but is more expensive than a 5 cm C-band system. 3 cm X-band radar is used only for short-range units, and 1 cm Ka-band weather radar is used only for research on small-particle phenomena such as drizzle and fog. Impact of Abnormal Weather Condition Many parts of the country are affected by tsunami, heavy rain, drought and global warming due to abnormal weather conditions. The Government is monitoring the variability of the weather phenomena and development of abnormal weather pattern like drought, flood, flash flood, cyclone, rain induced landslides, heat and cold waves, etc. on a continuous basis. Records of past weather events show that extreme values in respect of heavy rainfall, maximum and minimum temperatures, seasonal rainfall etc. remained unsurpassed in many cases. Areas influenced by the abnormal weather pattern change as per the interannual and intra-seasonal weather and climate variability. Heavy rain events (>10cm/day) over central India are increasing at about 1%/year while weak and moderate events are decreasing at about the same rate over the past 50 years. The extreme rain events which are becoming more intense in recent years are localized and could be part of the natural variability of the monsoon system. No such pattern is discerned in respect of other weather phenomena. Earth System Science Organization –India Meteorological Department (ESSO-IMD) has enhanced its observational network under the modernization plan by installing a network of Doppler Weather Radars (DWR), Automatic Weather Stations (AWS), Automatic Rain Gauge Stations (ARGS), etc. for monitoring abnormal weather patterns and upgraded its forecasting capabilities, so that advance warning can be provided to National Disaster Management Authority (NDMA), Ministry of Home Affairs, and Ministry of Agriculture to tackle the impacts of the adverse and extreme weather phenomena.