NEW GFS MODEL TO GO ACTIVE JAN 14

by **Toot** 2015-01-12, 12:53 pm

The Parallel GFS will take the place of the old GFS this wed

Code:: Effective on or about January 14, 2015, beginning with the 1200 Coordinated Universal Time (UTC) run, the National Centers for Environmental Prediction (NCEP) will upgrade the GFS Analysis and Forecast System as follows: - Changes to the model components - Increases in horizontal resolution - Addition of 0.25 degree gridded output - Addition of new product fields - Change to product naming convention - Changes in product timeliness - Changes to downstream model impacts 1) Model changes to the GFS Global Spectral Model: - Increase horizontal resolution of the first segment of the forecast from Eulerian T574 (~27 km) to Semi-Lagrangian T1534 (~13 km), and extend the length of forecast from 192 hours to 240 hours - Increase horizontal resolution of the second segment of the forecast from Eulerian T192 (~84 km) to semi-Lagrangian T574 (~35 km), and set forecast time from 240 hours to 384 hours - Change from Eulerian dynamics to Semi-Lagrangian dynamics, which uses Hermite interpolation in both vertical and horizontal directions. - Use 5 minute daily Real-Time Global (RTG) Sea Surface Temperature (SST) to replace 1.0 degree Reynolds 7 day SST analysis - Initialize ice at small inland lakes in the northern hemisphere with 4 km Interactive Multi-sensor Snow and Ice Mapping System (IMS) ice analysis data from the National Ice Center. For large water bodies, use 5 minute NCEP/MMAB ice analysis data to replace 30 minute ice data - Use 1982-2012 5 minute SST climatology (replacing 1982- 2001 1 degree SST climatology). - Use 1982-2012 30 minute sea ice concentration climatology (replacing 1982-2001 1 degree climatology). - Replace update of model snow depth by direct insertion of AFWA depth data with a blend of the model first guess depth and the AFWA depth. - Use X-number to prepare spectral transform base functions: X-number is a numerical technique that uses paired numbers to represent real number to avoid computational underflow or overflow that can occur in spectral truncation for wave number larger than T1000. - Use divergence damping in the stratosphere to reduce noise - Add a tracer fixer for maintaining global column ozone mass - Use the Monte-Carlo Independent Column Approximation (McICA) for Rapid Radiative Transfer Model (RRTM) Radiation - Reduce drag coefficient at high wind speeds - Use Hybrid Eddy-Diffusivity Mass-Flux Planetary Boundary Layer (EDMF PBL) scheme and Turbulent Kinetic Energy (TKE) dissipative heating - Re-tune ice and water cloud conversion rates, orographic gravity-wave forcing and mountain block; and reduce background diffusion of momentum - Add stationary convective gravity wave drag - Modify initialization of forecast state variables to reduce a sharp decrease in cloud water in the first model time step - Correct a bug in the condensation calculation after the digital filter is applied - Replace 1.0 degree bucket soil moisture climatology with CFS/Global Land Data Assimilation System (GLDAS) climatology at T574 (~27 km) - Replace 1.0 degree momentum roughness length climatology by using a look-up table based on vegetation type - Add a dependence of the ratio of the thermal and momentum roughness on vegetation type 2) Model changes to the GDAS/GFS Hybrid 3D-VAR Ensemble Kalman Filter (EnKF) Data Assimilation: - Increase EnKF resolution from T254L64 to T574L64 - Assimilate hourly GOES and EUMETSAT atmospheric motion vectors - Update radiance assimilation: - Assimilate SSM/IS UPP LAS and Metop-B IASI radiances - Use enhanced radiance bias correction scheme - Update to version 2.1.3 of the Community Radiative Transfer Model (CRTM). CRTM v2.1.3 improves specification of microwave sea surface emissivities. This, in turn, improves the analysis of near surface temperature over water, especially in the southern oceans. - Use stochastic physics in EnKF ensemble forecasts - Change the dump window for GOES Satellite Wind (satwnd) data from 1 hour to 6 hours. Subtypes will be added for (NOAA/METOP AVHRR SATWIND) infrared cloud motion vector and (NESDIS/GOES 3.9 micron channel) derived cloud motion vector