1st Progress meeting ELDAS

The ELDORADO surface radiation system

Bart vd Hurk & Dirk Meetschen et al

(see ELDAS web-page)

1st Progress meeting ELDAS

Principle

• Generating 3-hrly LW & SW surface downward radiative fluxes

• ELDAS grid resolution• Combining METEOSAT data and RT

calculations from the ECMWF model• Simplified data assimilation

technique• Brief verification using routine SW

stations in The Netherlands

1st Progress meeting ELDAS

ELDORADO steps (1)1. Create initial field of cloud cover & liquid water

profile• Continuous simulation using LAM version of

ECMWF model at 0.5, started daily from interpolated ECMWF analysis

• Interpolate cloud fields at 3hrly intervals to ELDAS 0.2 grid

2. Create METEOSAT-derived cloud cover field at ELDAS grid

• METCLOCK cloud mask product• Cloud cover = average mask of 53

METEOSAT pixels surrounding target location

1st Progress meeting ELDAS

ELDORADO steps (2)3. Create METEOSAT net TOA SW radiation at

ELDAS resolution• Sensor irradiance net TOA flux• Extra time/space/month-dependent

calibration factor, derived from monthly averaged clear sky TOA SW flux generated by LAM6UTC 9UTC 12UTC

1st Progress meeting ELDAS

ELDORADO steps (3)4. Reshuffle model columns for relocation of

cloudy/cloud-free atmospheric columns• For each target location, select model

column with the smallest value of:J = a distance + b albedo + c SWnetTOA

5. Adjust total cloud cover to METCLOCK value by scaling cloud cover profile

Cumulative cloud cover

MetClock obs

First guessScaled

scaling factor

heig

ht

1st Progress meeting ELDAS

ELDORADO steps (4)6. Adjust liquid water content similarly in

order to match SWnetTOA

• Non-linear relation: 2 iterations applied• Only applied to cloudy model gridpoints

7. Store and interpolate resulting downward LW and SW surface fluxes as best estimate

• When either METCLOCK or SW-obs are absent: use first guess

• Archived METEOSAT/METCLOCK data covers only part of the ELDAS domain

1st Progress meeting ELDAS

Total cloud cover

1st Progress meeting ELDAS

TOA SWnet

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Surface verification

30 Routine stations in Netherlands

• Only downward shortwave• Daily totals• First guess affected by erroneous daily reset

to cloudfree conditions at 0 UTC: probably little cloud spin-up in morning hours

1st Progress meeting ELDAS

Statistics

April/May 2000this dataset:• first guess: 37 W/m2• ELDORADO: 12 W/m2

Bias of ERA40 overSGP ARM observations(April-May 1999):• clear sky: 31 W/m2• overcast: 26 W/m2• all cond.: 17 W/m2

1st Progress meeting ELDAS

Still to do

• Further validation– BSRN stations (hardly available via www-

service, but Lindenberg-data are ordered)– Validation plan

• Cleaning the archive– Replace missing time slots by first guess– Fill area outside METEOSAT domain with

first guess

• Interpolation to ELDAS grid