Comparative Evaluation of the skill of a Global Circulation Model and a Limited Area Model in simulating Tropical Cyclones in the North Indian Ocean

by G N Mohapatra, V Rakesh, P K Mohanty and S Himesh


Considerable improvement has taken place in forecasting tropical cyclones at 24‐48 hour leads; however, improving accuracy of tropical cyclones forecasts at longer leads is still a major scientific challenge. The major bottleneck in accurate tropical cyclone forecast using limited area models (LAM) comes from the use of artificial lateral boundary conditions, especially at longer leads. Although, global circulation models (GCM) still cannot match the horizontal resolution that can be implemented in a LAM over a smaller domain, it is possible that better representation of scales and thus scale interactions in a global domain can lead to better simulation of tropical cyclones with a GCM even with relatively coarser resolution. This hypothesis is tested in the present work with a GCM and LAM configuration. We consider 30 cyclones over the north Indian Ocean (NIO) that represents different seasons and intensity during 1999‐2012. Analysis of forecast skills at 3 leads (24‐hour, 48‐hour and 96 hour) show that while LAM has better skill compared to GCM at shorter lead (< 48 hour), GCM has significantly higher skill at longer lead (96 hour). The two configurations are found to exhibit somewhat complementary skills in terms of forecast lead and the severity of the cyclones. Therefore, it is suggested that a methodology combining both LAM and GCM can provide more reliable forecasts.



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