Page 1 Met Office © Crown copyright 2007 CAMM model performance assessed during DODO2 Steph...

Met Office © Crown copyright 2007

CAMM model performance assessed during DODO2

Steph Woodward – climate model dust scheme

Glenn Greed – implementation of dust in the CAMM model

– Running of operational forecasts for use in DODO2 flight planning

Mark Harrison – NAME model forecasts

Jim Haywood – Analysis of aircraft data

Sundar Christopher – Satellite retrievals/validation


Description of the CAMM:

Non-hydrostatic

Two-time level semi-implicit semi-Lagrangian scheme

Charney-Philips staggering in the vertical

Arakawa C grid in the horizontal

Data assimilation (4-D var) satellite, sonde, surface, and data from commercial aircraft


Description of the CAMM:

Domain:-

Resolution: 0.18°x0.18° resolution (~20km) 38 levels in the vertical 13 levels in the boundary layer.


Description of the dust scheme:

Dust scheme based on Woodward (2001)

6 size bins in the range 0.03-30μm radius

Dust emission is based on the scheme by Marticorena and Bergametti (1995)

Dust flux a function of: clay, silt, and sand fraction, vegetative fraction, soil moisture, friction velocity threshold, and surface layer friction velocity.

Convection, turbulent mixing, gravitational settling accounted for

Dry and wet deposition


Description of the dust optical properties:

Mie scattering

Spherical particles

6-wavebands in the solar spectrum

9- wavebands in the long-wave

AOD diagnostic developed at 0.55μm


Modifications when moving from climate model:

Soil data set in climate model - Wilson and Henderson-Sellers (1985) at 3.75o replaced by International Geosphere Biosphere Programme (IGBP, Loveland and Belward, 1998) at 1kmx1km.


Additional modifications:

The threshold friction velocities were reduced by 0.15ms-1 and is now defined for all particle sizes spanning 0.06 to 2000μm diameter (rather than 0.06 to 60μm as in W2001).

Horizontal dust flux calculations now include sand particles. The vertical flux is still assumed to consist only of particles between .06 and 60μm.

A correction to the dust uplift code have also been introduced which inhibits emissions of dust from steep slopes.


CASE STUDY – AUG 23rd


The dust forecast from the 21st August


The dust forecast from the 21st August

Tropical storm Debbie

Dust storm within range of

BAe146


A t+9 forecast:

Tropical storm Debbie

Dust storm within range of

BAe146


The problems of model validation are shown by the MISR coverage:


Therefore correlative methods of MISR-OMI are developed (Christopher et al):


Comparison of dust event with Dakar AERONET

0

0.2

0.4

0.6

0.8

1

1.2

1.4

21 21.5 22 22.5 23 23.5 24 24.5 25

Day of August 2006

AO

T a

t 55

0 n

m

AERONET

CAMM


Flight pattern on the 23rd August 2006


Comparison of the vertical profile from aircraft against the CAMM vertical profiles for two aircraft deep profiles.


MONTHLY MEAN COMPARISONS


Can also look at the monthly means:


Monthly mean comparisons:


AERONET monthly means:

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1 6 11 16 21 26 31

Day of August 2006

AO

T a

t 55

0 n

m

AERONET

CAMM


Conclusions:

Case study:

The CAMM model shows SKILL up to (and beyond?) 42hours.

The horizontal position and vertical extent of the dust is well represented

The optical depth is reasonably well represented

Monthly means:

The OMI/MISR comparisons show a reasonable agreement

AERONET shows a reasonable agreement

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