Narrow Results

This study assesses the effect of background error length scale (Len_scaling) and variance scale (Var_scaling) factors on the intensity and track prediction of very severe cyclonic storm Nivar over the north Indian Ocean. Multiple data assimilation simulations are performed using the three-dimensional variational data assimilation technique by varying the Len_scaling and the Var_scaling of the background error. L10V08 (keeping Len_scaling constant whereas Var_scaling is reduced by 20%) experiment has shown the best results among all closely followed by L10V10 (Len_scaling and Var_scaling both remain constant). In the L10V08 experiment, the average track error is 45.7 km, whereas the average minimum sea level pressure (maximum sustained wind) error is found 3.4 hPa (2.7 m/s) compared to the observations.