Analysis of three unusual severe weather events over Delhi during May-June, 2018 using Dual-Pol Doppler Weather Radar and GNSS data

Abstract

High-impact weather events, such as thunderstorms and dust storms, are aspects of a changing climate that are likely to have an adverse effect on society. A number of such severe weather events struck Delhi and adjoining areas during the months of April, May and June of the year 2018. Three events observed during May-June have been analyzed using observations from C-Band Polarimetric Doppler Weather Radar (DWR) and ground based Global Navigational Satellite (GNSS) receiving system installed at Mausam Bhawan, New Delhi. Here, an attempt has been made to study the data regarding these unusual events from DWR observations especially of polarimetric nature and cross verify it with the data obtained from GNSS receiving system. Reflectivity of more than 60 dbZ was observed in all the events by the DWR system except on 9 June when a squall line formed with maximum reflectivity around 54 dBZ and the wind velocity increased upto 120 knots on the same date on few occasions and generally varied between 45-60 knots during the period of the storms. The height of these storms varied between 12 kms and 13.6 kms except on 9 June when the storm height was observed to be more than 15 kms by the DWR. Though the maximum reflectivity was a bit less on 9th June but the vertical extent of the clouds was greater and therefore the estimated value of IPWV from GNSS had a maximum of 67 mm as compared to the values in the range of 40 to 45 mm for other storm events. Apart from the single-pol DWR observations, the dual-pol products presented a more comprehensive ingredients of the storms in respect of the size, shape and variety of the hydrometeors and also their non-meteorological nature. The information regarding the concentration of hydrometeors has also been a positive point while analyzing through the eyes of a dual-pol radar. These multiple thunderstorms have been discussed to bring out some of their important features and a good amount of agreement has been observed between the data obtained from dual-pol DWR system and GNSS.