Assimilation of the Surface Precipitation Data with JNoVA using 2-ice Bulk Microphysics Scheme

Abstract

The assimilation of surface precipitation data with the ‘JMA nonhydrostatic model(JMA-NHM)’-based four-dimensional variational data assimilation system (JNoVA) is presented. The tangent linear and the adjoint codes of the 2-ice bulk microphysics scheme of Rutledge and Hobbs (1983) have been recently developed in nearly straightforward manner and the accuracy of the tangent linear model has been investigated. We succeed to assimilate the Radar-Raingauge analyzed precipitation data with the JNoVA using this cloud microphysics with horizontal grid spacing of 10 km and improve the precipitation of the analysis.
The same precipitation data is successfully assimilated with the JNoVA using the simplified moist physics. The comparison of both analyses revealed that the analysis by the JNoVA using the 2-ice bulk scheme is not optimized as much as that by the JNoVA using the simplified physics. From the investigation of the cost functions, the tangent linear approximation of 2-ice bulk scheme is not accurate enough to use in the variational data assimilation system with the horizontal grid spacing of 10 km.