The NCEP Regional Spectral Model: An Update

Abstract
The National Centers for Environmental Prediction (NCEP)/Environmental Modeling Center regional spectral model (RSM) has been improved in several aspects since Juang and Kanamitsu. The major improvements of RSM are its efficiency and functionality. The change of the map factor in the semi-implicit scheme from a mean value to maximal value over the regional domain, the relaxation of the lateral boundary from explicit method to implicit method (or simple blending), and the local diffusion over areas of strong wind allowed the doubling of the model computational time step. The model physics was upgraded with the improvements in the operational global spectral model (GSM) and with an additional explicit cloud scheme. An option to run in either hydrostatic or nonhydrostatic mode has been introduced. Another option to run on a CRAY machine or on a workstation has been fully tested. The nesting process has been changed to provide the capability of nesting into a coarse-resolution RSM, besides the GSM, i... Abstract The National Centers for Environmental Prediction (NCEP)/Environmental Modeling Center regional spectral model (RSM) has been improved in several aspects since Juang and Kanamitsu. The major improvements of RSM are its efficiency and functionality. The change of the map factor in the semi-implicit scheme from a mean value to maximal value over the regional domain, the relaxation of the lateral boundary from explicit method to implicit method (or simple blending), and the local diffusion over areas of strong wind allowed the doubling of the model computational time step. The model physics was upgraded with the improvements in the operational global spectral model (GSM) and with an additional explicit cloud scheme. An option to run in either hydrostatic or nonhydrostatic mode has been introduced. Another option to run on a CRAY machine or on a workstation has been fully tested. The nesting process has been changed to provide the capability of nesting into a coarse-resolution RSM, besides the GSM, i...

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