GOV-CLIV-WS-Clemente-Tanajura-June2011

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					  GODAE OceanView / CLIVAR GSOP Technical Workshop on Observing System
           Evaluation and Inter-comparisons, 13-17 June 2011, UCSC


A Sensitivity Study of Short-Range Forecasts
  over the Atlantic METAREA V with HYCOM
  and the Cooper and Haines Scheme Using
         Different Sea Surface Heights

     Jean Oliveira1, João Alvarenga1, Raquel Mello1,
   Ana Freitas1, Lucimara Russo1 , Clemente Tanajura2
    1  Brazilian Navy Center of Hydrography (CHM), Brazil
2Institute of Physics, Federal University of Bahia (UFBA), Brazil


Oceanographic Modeling and Observation Network (REMO)
                 www.rederemo.org
Outline

1. Introduction

2. Goals

3. Methodology

4. Results

5. Other Results

6. Conclusions
1. Introduction
• REMO is a research group in physical oceanography and operational
oceanography established in January 2008
• The members are researchers and students from four Brazilian
universities, the Brazilian Navy and the PETROBRAS research center
CENPES
1. Introduction (cont.)

- Pre-operational short-range ocean forecasts with HYCOM (7 days) and
    ROMS (3 days) using NCEP GFS forcing since Oct ober 2009
- Operational forecasts with HYCOM in the Brazilian Navy CHM with the
    Cooper & Haines scheme (1996) (C&H) since February 2010




    HYCOM 1/4o 21L         HYCOM 1/12o 21L       ROMS 5-13 km 32L
2. Goals
-   Evaluate HYCOM 1/12o Forecasts
-   Investigate the behavior of the model predictability along time
-   Investigate the model sensitivity to different initial conditions
-   Develop routines to validate model simulations and forecasts according
      to GODAE OceanView standards

3. Methodology
- Construct initial condition with u, v, T and S from the HYCOM+NCODA
    system on 00Z 1 Feb 2010 available in z-coordinates at
    www.hycom.org
- 7-day forecasts from 1 Feb 2010 until 31 Mar 2010 using GFS forcing
- HYCOM 1/4o : initial condition from C&H with the 24 h forecast as
    background and SSH from HYCOM+NCODA
- HYCOM 1/12o nested in the HYCOM 1/4o : initial condition from C&H
    with the 24 h forecast as background and SSH from
    HYCOM+NCODA (NRL), Mercator-océan (MERCATOR) and SSH
    analysis (ALONG_TRACK)
3. Methodology (cont.)

- SSH analyses were performed daily with (filtered) along-track SSH
    anomalies (SSHA) from Jason-1 and Jason-2 obtained from AVISO.
- OI was employed to assimilate SSHA according to Ezer & Mellor (1997)
- The background SSHA was obtained from SSHA  SSHb  SSH
                                                   b
- The analysis was calculated from                      model mean

        SSHAa = SSHAb + K(Y  H ( SSHAb ) )
                   K = BH ' (HBH   R) 1
                  B(i, j)   i exp r 2ij / L2 
                                2



 R is diagonal with constant values equal to (0.02 m)2
 L = 170 km
  i 2 is the SSHA model variance at point i
 r 2ij  ( xi  x j )2  ( yi  y j )2 is the distance between point s i and j
3. Methodology (cont.)


                                      Argo profilers
                                   1 Feb - 31 Mar 2010


- 747 Argo profilers with T-S
   were used to evaluate the
   forecasts

- Only the 24 h forecasts were
   investigated

- Temperature and salinity from
    Argo and model were
    interpolated to the standard
    Levitus vertical levels
4. Results

     Mean Temperature Profile        Mean Salinity Profile
   Control                         Control

                                                     Argo
             Argo
                                             Experiments
        Experiments




         - NRL = C&H with HYCOM+NCODA
         - ALONG_TRACK = C&H with SSHA analysis
         - MERCATOR = C&H with Mercator-Océan 1/4º SSH
4. Results (cont.)
- Standard deviations (Std) of the difference between the forescast
    and ARGO data for temperature and salinity were calculated
- Smallest values were obtained for the NRL followed by the
    CONTROL , ALONG_TRACK and MERCATOR experiments

    Mean Temperature and Std (ΔT)          Mean Salinity and Std (ΔS)
        0.2oC < Std (ΔT) < 2.4oC            0.2oC < Std (ΔT) < 2.4oC
      NRL (dashed)

                                                              Argo
                     Argo
                                                           NRL (dashed)
4. Results (cont.)

 Taylor Diagrams
 for Temperature
A – ARGO                         0 – 2000 m
B – NRL
C – ALONG_TRACK
D – MERCATOR
E – CONTROL




                     0 – 100 m           125 – 800 m
4. Results (cont.)

 Taylor Diagrams
 for Temperature
A – ARGO                         0 – 2000 m
B – NRL
C – ALONG_TRACK
D – MERCATOR
E – CONTROL




                     0 – 100 m           125 – 800 m
4. Results (cont.)

 Taylor Diagrams
   for Salinity
A – ARGO                         0 – 2000 m
B – NRL
C – ALONG_TRACK
D – MERCATOR
E – CONTROL




                     0 – 100 m           125 – 800 m
        5. Other results
 - Initial condition: “interpolated” HYCOM+NCODA fields available in z-
     coordinate in www.hycom.org on 00Z 1 Jan 2011
 - 7-day (168 h) Forecasts performed daily with Cooper and Haines, SSH
     from HYCOM+NCODA
 - NCEP GFS forcing

                        Forecast minus PIRATA (8oS. 30oW)                           Forecast minus PIRATA (19oS. 34oW)
Temp. Difference (oC)




                                                            Temp. Difference (oC)
                                                                                                                300 m
                                                  20 m                                                         20 m
                                              300 m
                                                                                                              100 m
                                                 100 m


                                            Solid lines = 24 h forecast
                                            Dashed lines = 168 h forecast
              16/09/10
                                                                        Leonardo Lima; Luiz Gavaza
            5. Other results (cont.)

      - Background: “interpolated” HYCOM+NCODA fields available in z-
          coordinate in www.hycom.org on 00Z 1 Jan 2011
      - Bergthorsson and Doos analysis with 19 profiles of T and S from Argo T
          and S data from surface to 2000 m performed in the Levitus z-levels;
      - Application of Cooper and Haines with SSH from HYCOM+NCODA

                       RMSE for Temperature (oC)     RMSE for Salinity (PSU)



                                        Background
Depth (m)




                                                                    Background
                                  Analysis+C&H
                                                      Analysis+C&H
                       Analysis
                                                        Analysis




            16/09/10
                                                            Davi Mingac; Luiz Gavaza
6. Conclusions
- The system HYCOM 1/12o – initialized with “interpolated”
    HYCOM+NCODA fields on 1 Feb 2010 – restrained daily by Cooper
    and Haines with HYCOM+NCODA SSH produces good agreement
    with Argo data;
- When assimilation of AVISO along-track SSHA data was employed,
    similar (worse) results were obtained;
- The use of SSH from Mercator-Océan produced similar results to the
    control run without Cooper and Haines;
- In another forecast experiment (from 1 Jan 2011 to 31 Mar 2011) the
    24h forecasts for T with respect to PIRATA buoys close to Brazil were
    very similar to the 168h forecasts
- The analysis of vertical profiles of T and S from Argo performed in z-
    coordinates were substantially modified by Cooper and Haines;
- An OI scheme to assimilate synthetic T(z) and ρ(z) is under evaluation
    and a multivariate OI system is being pursued to jointly assimilate
    SSHA, SST, T(z) and layer thickness.
16/09/10
Thanks!

				
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