Sustenance of Global Climate Observation System Upper Air Network (GUAN) of India Meteorological Department

Abstract

India Meteorological Department (IMD), the National Meteorological / Hydrological system (NMHS) of India, has established GUAN standard radiosounding systems at 6 stations at its regional head quarters namely New Delhi, Mumbai, Kolkata, Chennai, Nagpur and Guwahati using high quality radiosounding system during August 2015. These stations have been equipped with M/s GRAW radiosondes, Germany make, high quality GPS based radiosounding system model No GS-E along with DFM-09 radiosondes. Based on their performance of one year, IMD requested GCOS secretariat through Secretary General, WMO, for inclusion of these station into GUAN network. IMD’s claim was discussed and approved by Atmospheric Observation Panel on Climate (AOPC-22), Exeter, UK, 27-31st March 2017. Since then, the performance has been closely monitored and found that these stations are fully compliant for the commitments to be made by the WMO Member for inclusion of a radiosounding station into the GUAN network. All the 6 stations have achieved minimum observational requirements like Nos. of sounding in a month, soundings observed beyond minimum requirement of 100 hPa level, and in most of the cases approach up to the target requirement of 5 hPa level. The RMS departures in case of geo-potential height, observed temperatures and wind vectors have been found well within the minimum requirements (MRQs) and very near to the target requirements (TRQs)-which establishes the accuracies of observed data. The biases observed in monthly climatological averages are observed within the MRQs and approaching to the TRQs. These stations actually fulfilled the essential minimum requirements of radiosounding observations for a GUAN standard radiosounding station, with respect to all the parameters of observation, and very closely approaching the target requirements of GUAN standard radiosounding observatories continuously. The network has sustained without a break since the establishment, performing well meeting all the standards, and committed for continuation.