Network of Automatic weather stations : Time division multiple access type

Abstract

A network of 550 Automatic Weather Stations (AWS) has been established across India during April 2009 to February 2012 to bridge observational gaps in data sparse regions and augment manned surface observational network. All AWS are equipped with sensors for parameters air temperature, relative humidity, atmospheric pressure, rainfall, wind and global solar radiation. Additional sensors for soil temperature, soil moisture, leaf temperature and leaf wetness have been provided at 127 AWS. The data loggers are programmed for hourly measurement schedule. The satellite telemetry technique called Time Division Multiple Access (TDMA) has been employed for data transmission through Data Relay Transponder (DRT) aboard geo-stationary satellite INSAT – 3A located at 93.5º E to ensure effective channel utilization. The data are received and archived in the central data receiving Earth Station established at Pune. The mean sea level pressure, dew point temperature, pressure tendency, daily maximum and minimum temperature are derived at Earth Station. The data are made available in near real time to end users in WMO code form via WMO Information System (WIS) and at www.imdaws.com.This paper presents technical details of AWS, network plan, features of telemetry system, capabilities of data receiving Earth Station and preliminary results of the performance of network.