Abstract
Geo-stationary satellite images are one of the primary tools for real-time monitoring and intensity analysis of tropical cyclones (TCs) in spite of other complimentary remote sensing sensors like scatterometers, microwave imagers and sounders, mounted on the polar orbiting satellites. The weather activities over the Indian region are continuously monitored by two Indian geostationary satellites, viz. INSAT-3D and INSAT-3DR, for every 15 min in staggered mode. During extreme weather events like TCs, INSAT-3DR is operated in rapid scan operation mode by taking observations over the system in every 4-min interval. These observations are highly useful in understanding the instantaneous structural changes during evolution, intensification and landfall of TC. In this study, an attempt has been made to present the salient observations over the cloud systems by visible, thermal infrared (TIR1) and water vapour imageries of INSAT-3DR satellite during the life cycle of the TC FANI. The rapidly evolving small-scale features inside the inner core of TC FANI in high temporal resolution images are examined. The relationship between TC intensity and inner core TIR1 brightness temperature (BT) and the number of overshooting top clouds in the difference images of TIR1-WV BT have been presented by analysing the sequence of INSAT-3DR imageries. The strong correlation (r2 = 0.74) is obtained between the TC eye temperature and radial distance of the first overshooting cloud top. The 1 km × 1 km visible images of TC were found to have the presence of small-scale mesovortices in the eye region, which are a typical characteristic of intense TC system. Usefulness of high temporal satellite images generated using rapid scan mode is demonstrated for identifying the signatures of TC intensification.
Highlights
The rapid scan images from geostationary satellites have been proven to be useful tools in weather applications like the derivation of atmospheric motion winds, analysis of wildfires, convective initiation nowcasting, and identification of overshooting convective cloud tops (Schmidt et al, 2014; Bedka et al, 2015; Line et al, 2016; Mohapatra et al, 2021)
3.1 Tropical Cyclones (TCs) FANI observed by INSAT-3DR TIR1 Imageries
TCs formed in the North Indian Ocean are monitored by geostationary satellites viz., INSAT-3D and INSAT3DR in addition to the polar satellite based microwave instruments like scatterometer (SCATSAT) and humidity sounder (SAPHIR)
Summary
The rapid scan images from geostationary satellites have been proven to be useful tools in weather applications like the derivation of atmospheric motion winds, analysis of wildfires, convective initiation nowcasting, and identification of overshooting convective cloud tops (Schmidt et al, 2014; Bedka et al, 2015; Line et al, 2016; Mohapatra et al, 2021) These images are useful for monitoring the convective features of storms that evolve on shorter time scales i.e. less than 15 or 30-minutes (Dworak et al 2012; Cintineo et al 2013). The Indian geostationary satellite INSAT3DR is being operated in rapid scan operation mode during high impact weather activities like TCs to capture the images in every 4-minutes interval These satellite observations may be helpful in observing the rapidly changing features over TCs and determining its movement, structure and intensity. The cyclone category based on its intensity is shown in the figure
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