Retrieval and Applications of Atmospheric Motion Vectors (AMVs) derived from Indian Geostationary Meteorological Satellites INSAT-3D/3DR: Present Status at ISRO
Two advanced Indian geostationary meteorological satellites INSAT-3D and INSAT-3DR launched on 26 July 2013 (placed at 820E) and 06 September 2016 (placed at 740E) are providing continuous coverage at every 15-minute over the Indian Ocean region. The different spectral channel data from these satellites has enhanced the scope for better understanding of the different tropical atmospheric processes over this region. The atmospheric motion vectors (AMVs) from INSAT-3D/3DR are derived operationally at Space Applications Centre (SAC), ISRO, Ahmedabad and India Meteorological Department (IMD) New Delhi. The retrieval techniques and accuracy of AMVs has also improved with the availability of improved spatial resolution data along with more options of spectral channels in the INSAT-3D/3DR imager. The different AMV products derived from INSAT-3D/3DR at every 15-minute are used in the numerical model for real-time weather forecast at different operational forecasting centres both in India as well as abroad. It is also noted that from 2019 onwards, experimentally INSAT-3DR is configured in rapid-scan mode (5-minute interval) during the formation of tropical cyclone over the Indian Ocean region for taking frequent observations over cyclones. This experiment gives the enhanced opportunities to understand the extreme weather event using rapid scan observations.
Since IWW-14, two significant improvements have taken place in INSAT-3D/3DR AMV retrieval algorithm, one is retrieval of high-resolution low-level visible AMVs from INSAT-3DR high- resolution (1 km) images and second is retrieval of rapid-scan AMVs (RS-AMVs) from INSAT- 3DR images during tropical cyclones. After successful testing and assessment, the first-one is made operational, while the second one is yet to be operational. In the present study, initial results from both these developments are demonstrated. To assess the initial applications, sensitivity studies have been performed by assimilating the newly retrieved AMVs in the numerical model to understand the impact of high-resolution low-level visible AMVs and RS-AMVs against operational INSAT-3D retrieved AMVs. Results suggest noteworthy improvements in track prediction when RS-AMVs are used for assimilation as compared to operational INSAT-3D AMVs. Also, assimilation of high-resolution visible AMVs has improved the forecast, especially at upper levels.
