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Xu Li, John Derber

NSST (Near-Surface Sea Temperature) in NCEP GFS. Xu Li, John Derber. Outline. NSST in NWP Impacts of NSST Analysis Forecasting Implementation Preparation. What is NSST?. NSST is a T-Profile just below the sea surface. Here, only the vertical thermal structure

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Xu Li, John Derber

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  1. NSST (Near-Surface Sea Temperature) in NCEP GFS Xu Li, John Derber

  2. Outline • NSST in NWP • Impacts of NSST • Analysis • Forecasting • Implementation Preparation

  3. What is NSST? NSST is a T-Profile just below the sea surface. Here, only the vertical thermal structure due to diurnal thermocline layer warming and thermal skin layercooling is resolved Assuming the linear profiles, then, 5 parameters are enough to represent NSST: Diurnal Warming Profile T Mixed Layer z Thermocline Skin Layer Cooling Profile Deeper Ocean z z 3

  4. NSST Analysis variable Analysis variable : a definedreference temperature, currently the foundation temperature. Observation operators and their Jacobi: Relate the depth dependent data, Satellite: , ch (channel) dependent with skin depth of 0.1 ~ 1.0 mm in sub-layer.In Situ: with depth of 0.2 ~ 15.0+ m, to with CRTM and NSSTM for direct assimilation. Products: The boundary condition for GFS_AM : The boundary condition for CRTM: is used to combine NSSTM and OGCM

  5. Basic Ideas in NSST Development • Assimilation • Use observations more effectively • 6-hourly analysis of NSST in GSI • More observations • NSST Profile • depth dependent observations (realistic) • Improved direct assimilation of radiance • Forecasting • Resolve SST evolution in atmospheric model time step • Cycling • Better Analysis Better Background • Atmospheric & Oceanic • Better Forecasting

  6. NSST and NWP: GFS FCST ANAL IC Atmospheric Forecasting Model (AFM) Atmospheric Analysis (GSI) NSST Analysis (NSSTAN) NSST Model (NSSTM) BG Radiative Transfer Model (CRTM) : Observation operator (relate T-Profile to the radiance) : Jacobi (the sensitivity of the radiance to T-Profile)

  7. Experiments of NSST analysis with NCEP GFS The operational version of NCEP GFS (T576) is used to do the experiments for the period of May 12, 2010 to June 24, 2010. The GDAS analysis is performed 4 times a day. Observed data used in the above two runs Satellite:AVHRR, AIRS, IASI, HIRS, GOES Sounder, MHS, AMSUA, AMSRE, others Conventional: Air: prepbufr & others Sea temperature:modsbufr (Ships, Buoys, Argos…)

  8. New New - Old New - Old Old New SST and Operational SST

  9. SST: Diurnal Variability of NSST at z=0 (05/17/2010 – 06/24/2010)

  10. New New New New New - Old New - Old Old Old Old Old New / Old New / Old New / Old Diurnal Variability of Air temperature (05/17/2010 – 06/24/2010)

  11. Validation of analysis: Histogram of O-B. 05/12/2010 – 06/24/2010 Surface Air T AVHRR_N18 Ch-4 Drifting Buoy Trajectory during these 44 days 50W – 70W, 25N – 35N Sea T OLD (Used) OLD (Used) OLD (Used) OLD (Used) OLD (Used) OLD (Used) OLD (Used) OLD (Used) OLD (All) OLD (All) OLD (All) OLD (All) OLD (All) OLD (All) NEW (Used) NEW (Used) NEW (Used) NEW (Used) NEW (All) NEW (All)

  12. Time series at drifting buoy locations. Northern Mid-Latitude Atlantic, 05/12/2010 – 06/24/2010 OLD (Used) OLD (All) NEW (Used) NEW (All) All OB All OB Used OB (OLD) Used OB (NEW) NEW - OLD

  13. 44 16-day forecasting Initial conditions: GDAS analysis at 00Z RMS: Tropics Temperature

  14. RMS: Tropics Wind

  15. RMS: Northern Hemisphere Geopotential Height

  16. Pattern Correlation: Northern Hemisphere Geopotential Height

  17. Preparation for implementation • NSST is ready for test for implementation in GFS • Improved SST analysis • Resolved diurnal variability • Better fit to buoy • More used data • Improved atmospheric analysis • Better simulation of radiance and more used data • Overall positive weather forecasting impact • Code, observations, scripts ready • Concern • Brand new SST introduced into GFS • SST Climatology used in Relaxation • For CFS (with coupled OGCM) • Combination of NSSTM and OGCM (straightforward) • Other applications of NSST • Regional weather forecasting • Hurricane prediction • Climate prediction • Reanalysis

  18. NSST and NWP: CFS FCST ANAL Atmospheric Forecasting Model (AFM) Atmospheric Analysis (GSI) IC NSST Analysis NSSTM BG OGCM Radiative Transfer Model (CRTM) : Observation operator (relate T-Profile to the radiance) : Jacobi (the sensitivity of the radiance to T-Profile)

  19. Combination of NSSTM: and OGCM:  Tr evolution • Conversion from the first layer mean (10 m) temperature • to foundation temperature during forecasting period: Conversion from foundation temperature to the first layer (10 m) mean temperature at analysis step Get lower thermal boundary conditions over water for AFM and CRTM with Foundation temperature and NSST Profile

  20. Cases the increment/adjustment calculation due to : The thickness of the 1st layer of OGCM : The thickness of diurnal warming layer Case 1 Case 2 z z

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