2.2 Providing operational GSI and EnKF to the research community: 2017 update.

Shao, Hui, National Center for Atmospheric Research (NCAR), Ming Hu, National Oceanic and Atmospheric Administration and Cooperative Institute for Research for Research in Environmental Sciences, Chunhua Zhou, Don Stark, and Kathryn Newman, NCAR

The Developmental Testbed Center (DTC), in partnership with the National Centers for Environmental Prediction (NCEP) and other operational and research institutions, provides operational data assimilation capabilities to the research community and helps transition research advances to operations. Currently, the DTC is supporting the Gridpoint Statistical Interpolation (GSI) system and the National Oceanic and Atmospheric Administration (NOAA) ensemble Kalman filter (EnKF) system for community users. The DTC releases GSI and EnKF code annually.

The GSI system is a variational (Var) data assimilation system, including optional 3DVar, 3D/4D (hybrid) EnVar, 4DVar (only with certain models) techniques. The EnKF system is an ensemble based analysis system with variants of the EnKF technique, including Ensemble Square Root Filter (EnSRF) and Local Ensemble Transform Kalman Filter (LETKF) schemes. Currently, the GSI and EnKF systems are being operated as part of the hybrid EnVar system for NCEP Global Forecast System (GFS) operations. The GSI hybrid system is also used for Weather Research and Forecasting (WRF) model based regional applications operationally, e.g., Hurricane WRF (HWRF), Rapid Refresh (RAP), and High-Resolution Rapid Refresh (HRRR).

This paper will provide an annual update of the GSI and EnKF systems, including new and updated code features and capabilities, as well as associated community support. In addition, some highlights will be included from 4D EnVar tests performed at the DTC in the past year.