POLDER, CERES, GERB flux comparisons and information on AMMA and MeghaTropiques Michel Viollier

2004/11/10 GIST 22, Brussels , LMD, M. Viollier 1

POLDER, CERES, GERB flux comparisons

and information on AMMA and MeghaTropiques

Michel ViollierLaboratoire de Météorologie Dynamique,

IPSL/CNRS, Ecole PolytechniquePalaiseau, France

with technical support by Sylvain Lassaut


Outline Information: AMMA, Megha-

Tropiques CERES, POLDER nadir comparison CERES, GERB flux comparison

(January to March 2004) Monthly diurnal cycles from GERB


AMMA (1/3)

African Monsoon Multidisciplinary Analyses(http://medias.obs-mip.fr/amma/index.en.html)

multidisciplinary project on the West African Monsoon and its impacts

Atmospheric Dynamics, Continental Water Cycle, Atmospheric Chemistry, Oceanic and Continental Surface Conditions.

Participation: France, Germany, UK, USA, Africa, …French Agencies: CNES, CNRS/INSU, IRD, and Meteo-France


AMMA (2/3)

Long Term Observation Period : … 2009

Special Observing Period (SOP): various key stages of the rainy season during three periods in 2006: (i) monsoon onset, (ii) peak monsoon and (iii) late monsoon

AMMA-SAT : the satellite data component of AMMA

http://ammasat.lmd.polytechnique.fr/WelcomeE.html

In this project : we promote CERES and GERB data and plan to incorporate their main parameters in the AMMA-SAT database


AMMA-SAT (3/3)

- data-set with multiple satellite products and data

- netcdf format with standard grid, organization and documentation (tools: ferret, live access server)GERB data in AMMA-SAT:- link to GERB archive system?- mirroring the GERB site?- hdf to netcdf transformation (of main parameters)?

Amma-sat regions (globe for coarse grid)


ScaRaB-3 on - Tropiques (Megha-Tropiques)

Joint project between France and India

Stopped last year (CNES budget cuts) New green signal on 2004 End of B phase: 2004 Start of C phase: 2005 Planned to be launched on 2009


Basic Megha-Tropiques Instruments


Megha-Tropiques Orbits


June 2003 – Reflectance vza<20°POLDER minus CERESgrid box method (0.5°)

(Reflectances multiplied by 100) Narrow-to-Broadband ConversionValidation with CERES.


POLDER-CERES along trackand nearest ‘pixel’ method

Collocated POLDER triplets and CERES data (T < 5 mn D <2km) for June 2003 (1, 4, 5, 8, 11, 14, 17, 20, 24, 27, and 30 )


Comparisons between POLDER and CERES radiances Figure 10b radiance over ocean Figure 10c radiance over continent

Comparisons between POLDER and CERES albedoes Figure 11d albedo over ocean Figure 11 albedo over continent

POLDER CERES :radianceand fluxcomparison at nadir


GERB/CERES flux comparisons

- GERB data: ex. G2_SEV1_L20S_20031223_130000_V002.hdf

- CERES : ES8

- 3 periods: Jan 1-5, Feb 15-19, Mar 21-25 2004

- average data over 2.5 x 2.5° regions (and also 1° x 1°)

- keep regions with more than 80 (CERES) and 20 (GERB) observations for 2.5 x 2.5° regions

- compare GERB and CERES flux regional means, coincident ± 2 minutes (however, in the present version, we approximate UTC to the half quarter, i.e. 00:07:30, 00:22:30,.. )


March 2004, 21 - flux

CERES

2.5° grid filled with GERB data


GERB-CERES co-registration


Jan. 2004, 1 to 5 – CERES/Terra GERB

SW LW day LW night


stat2.5 (1.0) degree grid

GERB-Terra %mean difference

GERB-Aqua %mean difference

SW LWday

LWnight

SW LWday

LWnight

Dec23

1.4 -0.57 -1.5

Jan1-5

-3.2-3.1

-2.4-2.4

-2.1-2.4

1.20.2

-2.3-2.6

-2.1-2.2

Feb15-20

-1.8-2.6

-2.2-2.3

-2.5-3.2

-2.07-2.60

-1.9-2.3

-2.2-2.4

Mar21-25

-2.6-3.6

-1.9-2.0

-2.5-2.6

-3.4-3.2

-1.5-1.9

-2.2-2.5

Difference

in sampling ?


CERES/GERB flux intercomparison

LW day LW night SWmean difference < ~2%, (preliminary result for 2003 Dec 23,approximate GERB observation time= 00:07:30, 00:22:30,.. )


Jan. 2004, 1 to 5 – CERES/Aqua GERB

SW LW day LW night


Feb. 2004, 15 to 20 – CERES/Terra GERB

SW LW day LW night


Feb. 2004, 15 to 20 – CERES/Aqua GERB

SW LW day LW night


March 2004, 21 to 25 – CERES/Terra GERB

SW LW day LW night


March 2004, 21 to 25 – CERES/Aqua GERB

SW LW day LW night


Same (March, Aqua) but 1° grid

SW LW day LW night


Diurnal variations using GERB (preliminary) – 2004, January

Ocean, clear and partly cloudy



Land (S. Africa), clear and partly cloudy



Convective Clouds Area



Land (East Africa), clear and partly cloudyCheck our localtime and SZA computation



Valencia, 2.5° area


Conclusion• In a first glance :

• Mean GERB SW and LW fluxes ~ 1 to 3 % low / ES8 CERES (Terra and Aqua)

• No noticeable gap or anomaly in the diurnal cycles

• Future works:

• Compare with SSF fluxes • Evaluation of the POLDER nb-bb conversion with GERB SW

radiances (availability of 2003 data ?, April to October)• Study the n2b conversion of HRI*SEVERI/GERB and the impact of

GEO combination on the CERES Terra monthly means computations • AMMA, A-train, ScaRaB/Megha-Tropiques, EarthCARE

POLDER, CERES, GERB flux comparisons and information on AMMA and MeghaTropiques Michel Viollier

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