MEMORANDUM FOR: NCEP Model Implementation Scientific Review Team

Dec. 13, 2016

MEMORANDUM FOR: NCEP Model Implementation Scientific Review Team

FROM: Vijay Tallapragada, Branch Chief

Global Climate and Weather Modeling Branch, NCEP Environmental Modeling Center

SUBJECT:Proposed Implementation of Global Data Assimilation System /Global Forecast System v14.0.0

The Environmental Modeling Center (EMC) has proposed implementation of the Global Data Assimilation System/Global Forecast System (GFS) v14.0.0.

Changes and associated expected benefits of the GDAS/GFS model upgrade include:

Changes to assimilation:

•Introduction of Near-Surface Sea Temperature (NSST) describing near surface oceanicvertical temperature structure due to diurnal warming and sub-layer coolingphysical processes. SST, satellite data assimilation and weather forecasting willbe improved by using advanced GSI data assimilation techniques to analyze SSTtogether with atmospheric analysis variables.

Changes to observations:

•Radiances

–Include Megha-Tropiques SAPHIR radiance assimilation

–Monitor GPM/GMI radiance assimilation

–Changes to land surface type specification for CRTM

–AVHRR radiance and in situ (buoys & ships) sea water temperature observations are added to analyze SST

• SATWND observation changes

–Assimilate VIIRS winds

–Log-Normal wind QC for winds

–Assimilate GOES clear-air water vapor winds

• Other changes

–Assimilate extra GNSS-RO observations

–Fix cloud water increment bug

–Readiness for CrIS Full Resolution Data and add/extend RARS and DBNET capability (JPSS, GOESR)

Forecast model:

•NEMS software superstructure and infrastructure

•SST diurnal variability is resolved with the NSST model.

•Land surface changes

–IGBP 20-type 1 km land classification

–STASGO 19-type 1 km soil classification

–MODIS-based snow free albedo

–MODIS-based maximum snow albedo

–Diurnal albedo treatment

–Unify snow cover, albedo between radiation and land surface model

–Increase ground heat flux under deep snow

•Stability parameter constraint in the Monin-Obukov similarity theoryto prevent land surface and atmosphere from fully decoupling leading to excessive cooling of 2m temperature during sunset. Modification of the roughness-length formulation in the surface layer.

•Changes to cumulus convection

–Scale-aware, aerosol-aware

–Rain conversion rate decreases with decreasing air temperature above freezing level

–Convective adjustment time in deep convection proportional to convective turn-over time with CAPE approaching zero after adjustment time

–Cloud base mass flux in shallow convection as a function of mean updraft velocity

–Convection trigger condition to suppress the unrealistic summertime spotty precipitation over high mountains.

–Convective cloudiness enhanced by suspended cloud condensate in updraft

•Rayleigh damping applied to model layers above 2 hPareduced by 50%.

•Surface reference pressure for the two-time-level semi-implicit semi-Lagrangianscheme changed from 800 hPa to 1000 hPa.

Changes in the land surface and stability parameter should reduce a near surface wintertime cold bias, a rapid temperature drop during sunset and reduce a blockiness apparent in some near-surface fields. Some nighttime warm biases were introduced. Changes in convection should reduce a positive bias in light amounts of precipitation and unrealistic summertime spotty precipitation over high mountains and increase skill in forecasting precipitation. NSST is expected to improve tropical forecasts and may affect mid-latitude oceanic storms. Reducing Rayleigh damping improved wind and temperature forecast in the upper stratosphere. Applying the revised reference pressure reduced model computational noise in the upper atmosphere.

Post processing and products:

•Include bug fixes and enhancement:

–increase IO efficiency to post process on 13 km grid

–post process synthetic satellite and other LSM field for both old and new land surface types

–compute vertical velocity differently because model outputis on grid space

–Specify precipitation rate threshold of 1.0E-6 kg/m^2/s for when to start computing precipitation types for non-NMM models

•Start outputting 1/8 deg output for select fields.

•GFS Flux files will be generated by Unified Post instead of GFS model. Therefore, users will see slight (insignificant) delay in receiving GFS Flux files. In addition,the following changes will be made to new GFS Flux files:

–remove cat rain

–higher precision lat/lon

–change to proper Grib2 parameter IDs

• frozen precipitation
• surface Snow Phase Change Heat Flux
• surface Snow Cover
• soil temperature

•GFS Bufr sounding package has been re-engineered to work for new modeloutput format. The new package will use nearest neighbor interpolation for bothsurface and atmosphere fields.

TINto be produced

Real time parallel data:

A web page for the GFS2017 can be found at:

A VLAB forum for comments comparing the GFS and GFSX can be found at: or This is intended as a site for communication on what evaluators and users see in their comparisons of the GFS and GFSX. EMC plans to respond to the comments if appropriate.

A consistent parallel feed of gridded data isavailable on paraNOMADS for 0.5 degree files. Twenty km files will be added soon.

Gempak .25 and 1 degree files from the experimental GFS are available for the national centers.Files from the real time parallel and 1 degree files from the retrospectives are on WCOSS.

GCWMB real time (prnemsrn) 2016101718-

WCOSS Directory /gpfs/hps/emc/global/noscrub/emc.glopara/archive/prnemsrn

HPSS_GCWMB: /5year/NCEPDEV/emc-global/emc.glopara/WCOSS_C/prnemsrn

GCWMB 2015 Summer retrospective (pr4rn_1505) 2015050100-2016010200 (246 days) (to be completed by 12/31/2016)

WCOSS directory /gpfs/hps/emc/global/noscrub/emc.glopara/archive/pr4rn_1505

HPSS_GCWMB: /5year/NCEPDEV/emc-global/emc.glopara/WCOSS_C/pr4rn_1505

GCWMB 2015 Winter retrospective (pr4rn_1512) 2015121500-2016051518 (151 days) (to be completed by 12/25/2016)

WCOSS directory /gpfs/hps/emc/global/noscrub/emc.glopara/archive/pr4rn_1512

HPSS_GCWMB: /5year/NCEPDEV/emc-global/emc.glopara/WCOSS_C/pr4rn_1512

GCWMB 2016 Summer retrospective (pr4rn_1605) 2016050100-2016103018 (184 days) (to be completed by 12/31/2016)

WCOSS directory /gpfs/hps/emc/global/noscrub/emc.glopara/archive/pr4rn_1605
HPSS_GCWMB: /5year/NCEPDEV/emc-global/emc.glopara/WCOSS_C/pr4rn_1605
monitoring/verification:

GCWMB 2014 Summer retrospective (pr4rn_1405) 2014050100-2014110518 (189 days) (to be completed by 2/5/2017)

WCOSS directory /gpfs/hps/emc/global/noscrub/emc.glopara/archive/pr4rn_1405

HPSS_GCWMB: /5year/NCEPDEV/emc-global/emc.glopara/WCOSS_C/pr4rn_1405

Verification:

Location of the GFS2016 files to compare to the GFS2017:

The current operational GFS was implemented on May 11, 2016 12Z. The experimental runs above should be compared to the following GFS2016 data on WCOSS:

Gyre:/global/noscrub/emc.glopara/archive/gfs2016

For the period 2015041506-201507218 /global/noscrub/emc.glopara/archive/pr4devbs15

For the period 2015070106-2016051906 /global/noscrub/emc.glopara/archive/pr4devb

For the period 2016051112 on /global/noscrub/emc.glopara/global/gfs

Graphical imagery from real time parallel data is available on the Model Analysis and Guidance page at:

and can be compared to the operational gfs at:

Western Region has a side by side display of the operational and parallel GFS for North America and the North Pacific:

Verification of the real time parallel can be found at:

Near the top on the left is a link labelled Precip QPF. This will take you a page where you can find verification plots over CONUS for precipitation forecasts by the operational and experimental (GFSX) GFS for a wide range of dates. If you go to the bottom on the left, there are 2D maps showing the current forecasts from the operational and parallel GFS. By 00z there is a link to ARCH. This will take you to an archive over the past few years for synoptic maps for different regions for the operational and parallel GFS. Note that the parallel GFS is whatever was running that day. The GFS14.0.0 is available from Oct. 25, 2016 onward.These sites are subject to the availability of computers to EMC and may not be up to date every day.

The global branch is doing statistical verification of forecast fields against analyses and observations, precipitation, 2m temperatures and dew points, and 10 m winds over CONUS and Alaska, and hurricane tracks and intensity.

The parallel GFS is plotted as the PRX on:

The verification of the real time parallel is at

The verification of the 2014 summer retrospective will be

The verification of the 2015 summer retrospective is

The verification of the 2015/16 winter retrospective is

The verification of the 2016 summer retrospective is

Plume plots of the GFS and GFSX near surface fields for synoptic stations can be found at:

Plots comparing observed radiosonde soundings to soundings from the GFS are available at Soundings from the GFSX will be available shortly.

The global branch will plot maps for specific cases from the retrospectives and has solicited specific cases and specific fields to look at. Please contact and with specific cases.

**Please note, the parallel GFS may be interrupted by computer outages, production switches and lack of 24/7 monitoring and support.

Request for Evaluation

The Weather Prediction Center (WPC), Aviation Weather Center (AWC), Storm Prediction Center (SPC), National Hurricane Center (NHC), Ocean Prediction Center (OPC), and Climate Prediction Center (CPC) are listed as being primarily responsible for this evaluation. All other Service Centers, government agencies, or private companies not listed above are optional.

EMC and NCO are working on designing the same evaluation strategy as used for evaluating the currently operational GFS during the winter of 2015/16. Unlike in the past, scientific evaluation of model upgrades proposed for implementation will be based on much longer period of realtime, and retrospective experiments conducted by EMC and NCO. The 30-day parallels by NCO will be restricted to IT evaluation and model stability.

The evaluation period for Q3FY16 GFS/GDAS upgrades has begun and run throughJan. 31, 2016. Participants need to complete the attached “Model Implementation Subjective Evaluation Report” form and return it to and no later than Jan. 27, 2016. Please indicate the overall performance of the product, with any additional comments on specific cases with noteworthy positive or negative performance. Please note that EMC requests evaluators to specifically address the benefits stated in the attached form as to whether those benefits were observed or not. Any feedback you wish to provide during the evaluation period should be emailed to .

A final coordination teleconference will be scheduled to review the evaluation and address any outstanding issues. Based on the outcome of that teleconference, EMC, and NCO will prepare a recommendation for the NCEP Director. This teleconference has not yet been scheduled.

Points of Contact

(EMC)

(EMC)

Model Implementation Subjective Evaluation Report

Scientific Review Team Member: ______

Region/Service Center/Company Representing: ______

Proposed Change: Global Data Assimilation System/Global Forecast System v14.0..0.

Model Developer: EMC/GCWMB

Please indicate which period your comments are based on.

Evaluation of expected benefits:

Please respond to the following questions if they are relevant to your mission and note if the proposed changes are beneficial to you.

1. Are the new global forecast systemupgrades beneficial to your organization? Does the new forecast system provide significant improvement to the current model analyses and forecasts? If so, please specify what the improvements are. Do you see more continuity between forecasts?

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2. Do you see overall improvement in precipitation forecasts over the United States? If so, please specify what the improvements are.

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3. Do you see improvements in analyses and forecasts of 2 m temperatures and dewpoints, 10 m winds and CAPE over the United States?If so, please specify what the improvements are.

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4. Are forecasts of hurricane track and intensitysignificantly improved in the Atlanticand Eastern, Central,Western and Southern Pacific basins? Are forecasts of tropical storm genesis improved?

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5. Do you observe significant analysis and or forecast improvement in the stratosphere?

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6. Are days 6-10 and week 2 forecasts improved in the new GFS? If so, how are they improved?

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7. Do you see improvements in sea surface temperatures?Please specify what improvements you observe if any.

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8. Do you see improvements in mid-latitude oceanic weather?Please specify what improvements you observe if any.

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9. Do you see improvements in tropical weather or convection? Please specify what improvements you observe if any.

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10. Do you see improvements in fields used for aviation forecasts? Please specify what improvements you observe if any.

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Any other comments: ______

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Recommendation:

Implement as proposed ___Reevaluate after changes ____

Do not implement ___

Evaluation report signed by: ______