GEMS Kick-Off Meeting, Hamburg

Aerosols: WP3

Jean-Jacques Morcrette, Olivier Boucher

With contributions at ECMWF from:

Angela Benedetti: background error statistics

Erik Andersson: Overseeing the assimilation of GEMS observations

GEMS AEROSOL Global Monitoring System Leader: O. Boucher

GEMS Aerosols• AER_1: Implementation of the direct physical aerosol model in the

ECMWF model (O.Boucher, J. Feichter)

> implementation of parametrisations for tropospheric aerosols

> implementation of parametrisations for stratospheric aerosols

> implementation of new emission inventories

> implementation of aerosol optical properties

> production of test simulations

HC-MO, MPI-M, CEA-LSCE, ECMWF, SA-UPMC • AER_2: Refinement of aerosol emission sources (M.Sofiev)

> update and assimilation of the anthropogenic emission inventories of aerosol and its precursors

> assimilation of information on wild fires

> quantification of the wind-blown dust emission from desert areas

> quantification of the wind-blown sea salt emission

> sources of stratospheric aerosols

FMI, CEA-LSCE, MPI-M, SA-UPMC

GEMS Aerosols• AER_3: Aerosol data assimilation (J-J Morcrette)

> adaptation of RT codes for SW and LW radiances in nadir geometry

> preparation and harmonisation of aerosol satellite data sets

> error covariance matrices

> test of a 1D-Var system using aerosol products

> test of a 1D-Var system using aerosol radiances

ECMWF, CEA-LSCE, HC-MO, SA-UPMC

• AER_4: Evaluation of the model and analyses (C.O’Dowd, I. Chiapello)

> assessment of diagnostics and skill scores

> evaluation of aerosol radiative properties and associated radiative fluxes

> evaluation of aerosol physico-chemical properties

> analysis of model results with respect to air quality

NUIG, CNRS-LOA, CEA-LSCE, DWD, ECMWF, MPI-M, RMIB, SA-UPMC

Agency Mission Instrument Parameters Data volumeper day of satellitelife (Mb)

ESA ENVISAT MERIS AerOpDepth @0.865 ~250 maxAngstrom coefficientRadiances 7 WL

ESA ERS-2 ATSR Radiances used in TBDENVISAT AATSR GLOBAER project

EUMETSAT MSG SEVIRI Radiances low/moderateMSG GERB Radiation budget low/moderate

NASA TERRA MODIS AerOpDepth ~600AQUA Type

Size distributionRadiances

NASA AURA HIRDLS AerOptThickn 4 WL low/moderateNASA SAGE-2 AerOptThickn 8 WL low, available from

SAGE-3 AerOptThickn 8 WL Web

GEMS Aerosols: products @ end of contract

• Analysis of aerosol-related observations at ERA40 resolution (TL159 L60 [1.125 deg]2 or better) twice a day

• Total optical thickness at ~0.55 m OCEAN• Angstrom coefficient (or at~ 0.865m) “• Total optical thickness at ~0.55 m LAND

• From model 12-hour forecasts used in assimilation cycle.Up to 15 mixing ratio profiles of aerosols, every 3 hours

sea salt 3 bins 1st stage desert dust 3 bins organic 2 bins 2nd stage black carbon, carbonaceous 2bins sulfate fly ash “stratospheric” .Corresponding 2D-fields for sources and sinks

GEMS-AEROSOL: initial steps at ECMWF

JJMorcrette, A.Benedetti, S.Serrar, A.Beljaars, P.Bechtold, A.Untch

• Introduce aerosol prognostic variables in the Integrated Forecast System and assimilate global aerosol information

• Instruments: MERIS, MODIS x 2, MISR, SEAWIFS, POLDER• R/T 6S• Modelling LMDZ• Sources/Sinks LMD-Inca• Data Assim. 1DVar• Variables , radiances• Validation AERONET

Error covariance matrices• Assumptions: We will deal with unbiased Gaussian distributions,

that can therefore be completely characterized by their covariance functions (or matrices in the discrete case)

• We need to deal with:– Model error covariance, describing covariance between errors in the

model at any two locations and two time instances

– Background error covariance: related to correlation between errors of different model variables (e.g., geostrophic balance introduces a strong correlation between temperature and wind errors)

– Observation error covariance: includes measurement errors, imperfections in the design of the observation operators and representativeness errors (linked to the different scales represented by the model and the observations)

GOALS THIS YEAR (from RD Memorandum by Andersson and Benedetti, http://w3ec2.ecmwf.int/publications/library/do/references/list/3)

1. May 2005: Run IFS with simulated aerosol data a. Establish first ODB format for aerosol total optical depth data (AB, DT) b. Introduce new observed variable in IFS (AB) 2. May 2005: Enable aerosol forecast - no physics a. Introduce aerosol as one of the GFL variables (AU, done) b. Initial data from climatological aerosol in grib (JJM, SS) 3. July 2005: Aerosol appearing in JO-table, simulated data a. Implement an aerosol observation operator, called from hop.F90 (AB) b. Calculate departures for simulated aerosol observations (AB) c. Use new generic GOM-arrays introduced in 29r2 (MH, AB) 4. Sept 2005: Establish an aerosol 1D-Var a. Based on existing cloud/rain 1D-Var (AB) b. To be used intermittently for Jo and Jb testing and validation (AB) 5. Nov 2005: Calculation of aerosol Jb cost function a. Make Jb codes generic for GEMS variables- reproduce current result for ozone (MF, RE) b. Run a set of aerosol forecasts (for Jb calibration), with or without physics and sources/sinks depending on progress with the AER work (AB, JJM) c. Derive Jb statistics, using the lagged forecast approach (NMC-method) (MF, RE, AB) 6. Dec 2005: Functional assimilation test (AB) a. Communication and interpolation of GEMS variables between the job steps of incremental 4D-Var (increments and trajectory) (LI, YT) b. Scripts generalisations for GEMS variables (JH) c. Generalisation of grid-point variables (LI)

AN AEROSOL DATA ASSIMILATION SYSTEM

Observation define FormatBUFR<=>ODB

Observationsinto ODB/IFS

Observation operator

Model and Parameterizati

ons

B-matrix Calculation

(1st estimate)

TL/AD Model and

Parameterizations

Control variable Interface

TL/ADExtend Jb

Nearly completed tasks

Work in progress

BACKGROUND ERROR STATISTICS (1st estimate)

• Use NMC method (differences between 48 and 24h forecasts)

• Three aerosol species (now extended to six species with comparable results): - desert dust - seal salt - continental particulate (- background tropospheric ) (- background stratospheric) (- black carbon)

• Forecasts initialized from climatology

• Thirty days of 5-day forecats for January and July 2001 (now extended to 4 months, with comparable results). Little seasonal differences.

• Parameters computed: vertical and horizontal covariances and error correlations (global fields, zonal fields and integral averages over whole globe, Tropics, Northern Hemisphere and Southern Hemisphere) for total aerosol mixing ratio.

-1.0 -0.6 -0.2 0.2 0.6 1.0Correlations on Aerosol Mixing Ratio

1000

800

600

400

200

Pre

ssur

e le

vel

GlobalTropicsExtra-tropics NHExtra-tropics SH

-1.0 -0.6 -0.2 0.2 0.6 1.0Correlations on Aerosol Mixing Ratio

1000

800

600

400

200

Pre

ssur

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vel

GlobalTropicsExtra-tropics NHExtra-tropics SH

Level 1000 hPa

-1.0 -0.6 -0.2 0.2 0.6 1.0Correlations on Aerosol Mixing Ratio

1000

800

600

400

200

Pre

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GlobalTropicsExtra-tropics NHExtra-tropics SH

Average vertical correlations, January 2001

Level 200 hPa

Level 500 hPa

MODIS observationsMODIS (MODerate Resolution Imaging Spectroradiometer): Provides high radiometric sensitivity in 36 spectral bands from 0.4 µm to 14.4 µm. Resolution varies between 250 m and 1 km, depending on the channel.

Level 2 sample data were downloaded and can be found in

ec:/oparch/gems/modisaerosol/terra[aqua]/200505/05

These files contain retrieved products over ocean and land including optical depth at several wavelengths and Angstrom exponent. The resolution is 10x10 km and the data are grouped in 5-min granules.

Suggested MODIS products for use at ECMWF (assimilation/verification):

• Reflectance over land/ocean

• Aerosol optical depth over land/ocean (all available wavelengths)

• Angstrom exponent

• Satellite/atmospheric parameters (i.e. zenith angle, viewing angle, etc.)

FUTURE PLANS (from RD Memorandum by Andersson and Benedetti, http://w3ec2.ecmwf.int/publications/library/do/references/list/3)

• Q1, Q2 and Q3 2006: Monitoring of real aerosol data and validation

a. Acquire real aerosol data from MODIS (and other sources depending on availability) b. Run with (parts of) aerosol physics depending on progress in AER c. Contribute to model and physics validation, based on comparison with real aerosol data d. Perform data monitoring for a period of time of the main data sources e. Adopt monitoring software (e.g. obstat and SATMON, Metview??) f. Study data quality g. Assess biases

• Q4 2006 and Q1 2007: Preliminary assimilation experiments

a. Implement quality control thresholds b. Decide on data selection, i.e. which data to use actively c. Re-tune, massage and re-calibrate Jb, possibly several times

ITEMS FOR DISCUSSION

• Better definition of collaboration with partners on specific tasks Examples for WP_AER_3 (Aerosol data assimilation):

Task 3.2: Preparation and harmonisation of aerosol datasets: it has been suggested that CNRS-LOA reprocesses MODIS data and ECMWF gets data from LOA. Need to coordinate with ECMWF –specific processing needs.

Task 3.3: Error covariance matrices: from the proposal it appears that error covariance matrices will be specified from partners CEA-LSCE and CNRS-LOA. Great for observational error covariance matrices, caveats for background error covariance matrix – this needs to be tailored to ECMWF assimilation system.

• 6S: Second Simulation of the Satellite Signal in the Solar Spectrum: Vermote et al., 1997, version 4.1– allows the computation of radiances in the shortwave channels of

most of the present satellites: AVHRR, GOES, HRV_spot, METEOSAT, MODIS, POLDER, TM_landsat

– under the proper satellite/sun/target geometry– and various specifications of the surface

• homogeneous vs. inhomogeneous

• without and with directional effect

• with possibly different target and environment characteristics

• with different surface representations: Hapke, Verstraete et al., Roujean et al., Walthall et al., Minnaert, Iaquinta and Pinty, Rahman et al., Kuusk allowing sophisticated descriptions of the surface including structural parameters for the canopy.

Simulating the SW radiances

What still has to be done with the 6S RT code expected before the end of 2005

•Speed-up the direct code

•Develop and test the TL and AD

• Likely problems: vertical distribution– With an assimilation of satellite optical thickness or radiances, only the

total optical thickness (vertically integrated distribution) of aerosols is likely to be available. Is this information enough for the model?

• How to distribute it on the vertical?• How to distribute it between different types of aerosols in terms of:

– amounts– optical properties

Pandora’s box - 1

Pandora’s box - 2• Likely problems: Surface effects

– Surface reflectance: the derivation of total aerosol thickness from satellite observations cannot be properly done without knowledge of the surface directional spectral reflectance below these aerosols. This holds for aerosols over land and over ocean.

– How to make sure that the retrieval of aerosol and surface properties use consistent approaches? Do we need considering a simultaneous variational retrieval of surface and aerosol properties? A particular problem might be that, up to now, the aerosol remote sensing community is quite distinct from the surface albedo remote sensing community.

– Various algorithms have been attempted in the past:

• TOMS: ReUV ~0 , get aer : problem with vertical positioning of aerosol layer within the Rayleigh column (Seftor et al., 1997, JGR)

• MODIS: 2.1m Reaer ~0, get Resurf , from 0.67 and 0.47 m channels, get aer: problem with spectral redistributing of aerosol (and surface) optical properties, particularly for desert aerosols, and over bright surfaces (Kaufman et al., 1997, JGR)

• POLDER: can model polarization by surface, getaer : not all surfaces well represented, and problems with little polarizing by “big” aerosols (Deuze et al., 2001, JGR; Tanre et al., 2001, GRL)

Pandora’s box - 3

• Likely problems: Surface effects – How to make sure that the retrieval of aerosol and surface properties use

consistent approaches? Do we need considering a simultaneous variational retrieval of surface and aerosol properties? A particular problem might be that, up to now, the aerosol remote sensing community is quite distinct from the surface albedo remote sensing community.

ENDthank you for your

attention!