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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

NSST (Near-Surface Sea Temperature)

in NCEP GFS

Xu Li, John Derber

outline
Outline
  • NSST in NWP
  • Impacts of NSST
    • Analysis
    • Forecasting
  • Implementation Preparation
what is nsst
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

nsst analysis variable
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

basic ideas in nsst development
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
slide6

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)

experiments of nsst analysis with ncep gfs
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…)

slide8

New

New - Old

New - Old

Old

New SST and Operational SST

slide9

SST:

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

slide10

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)

slide11

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)

slide12

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

slide13

44 16-day forecasting

Initial conditions: GDAS analysis at 00Z

RMS:

Tropics Temperature

slide14

RMS:

Tropics Wind

slide15

RMS:

Northern Hemisphere Geopotential Height

slide16

Pattern Correlation:

Northern Hemisphere Geopotential Height

preparation for implementation
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
slide18

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)

slide19

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

slide20

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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