Evaluation of Envisat data using a NWP Assimilation System: A vortex-centred view

Validation by Model Assimilation and/or Satellite Intercomparison - ESRIN 9–13 December 2002

Evaluation of Envisat data using a NWP Assimilation System: A vortex-centred

view

Authors: W.A. Lahoz, S. Migliorini,

R. Bannister, R. Brugge, A. O’Neill

Data Assimilation Research Centre,

Reading, UK

Thanks: ESA, Envisat cal-val teams,

Met Office (UK), CNR.IFAC, BADC


Talk overview

Aims

Methodology

Results

- Qualitative

- Quantitative

Conclusions

Further Work


Aims

Evaluate L2 GOMOS, MIPAS & SCIAMACHY data (AOID 1039)

Height-resolved and total column data

- Temperature

- Ozone

- Water vapour


Methodology

Apply to L2 data (unassimilated): vortex-centred view

Vortex-centred view used to look at UARS MLS water vapour

data (Lahoz et al, JAS 1994; QJRMS 1996)

Self-consistency

Comparison against independent datasets

Qualitative/quantitative comparisons

Later: apply to L2+ data (assimilated into a NWP system)


Results: qualitative

24/Oct/2002

Geopotential

Height: Met Office

12 GMT

1, 10, 100hPa

MIPAS orbit track

18.42 – 19.30 GMT

1hPa 10hPa

100hPa Orbit track

S

E

GMID



24/Oct/2002

Temperature MIPAS (top)

Temperature Met Off (bottom)

Along orbit track

S E

S E

1hPa

10hPa

100hPa

1hPa

10hPa

100hPa



24/Oct/2002

Ozone MIPAS (top)

Water vapour MIPAS (bottom)

Along orbit track

S E

S E

1hPa

10hPa

100hPa

1hPa

10hPa

100hPa



24/Oct/2002

CH4 MIPAS (top)

N2O MIPAS (bottom)

Along orbit track

S E

S E

1hPa

10hPa

100hPa

1hPa

10hPa

100hPa



24/Oct/2002

HNO3 MIPAS (top)

NO2 MIPAS (bottom)

Along orbit track

S E

S E

1hPa

10hPa

100hPa

1hPa

10hPa

100hPa

Day Night



27/Sep/2002

MIPAS v sondes

(Ny Alesund: 78.9N, 11.9E)

Temperature (top; K)

Ozone (bottom; ppmv)

1hPa

1000hPa180 300

1hPa

1000hPa0 15



27/Sep/2002

MIPAS v sondes

(Payerne: 46.8N, 7.0E)



1hPa

1000hPa180 300

0

1hPa

1000hPa15



27/Sep/2002

MIPAS v sondes

(Marambio: 64.3S, 56.7W)



1hPa

1000hPa180 300

1hPa

1000hPa0 15



25/Sep/2002

Total ozone column

SCIAMACHY

& footprint

Total ozone column

analyses (KNMI/

ESA)


Results:quantitative

MIPAS v

Sonde ( x AK)

Jokioinen (60.8N,

23.5E)

18 Sep 2002

Chi-squared test

Temperature (K)

MIPAS Averaging Kernels

Red star: MIPAS

Green diamond: Sonde x AK



MIPAS v

Sonde ( x AK)

Ny Alesund

200hPa->10hPa

September 2002

Ozone (LH)

Temperature (RH)

+1-1 +1-1



MIPAS v

Sonde( x AK)

Several stations

200hPa->10hPa

September 2002

Ozone (LH)

Temperature (RH)


Results: quantitative

23/Sep/2002

Histogram

SCIAMACHY –

KNMI/ESA (Total

ozone / DU)

GOME bias not

removed



24/Sep/2002

Histogram

SCIAMACHY –

KNMI/ESA (Total

ozone / DU)

GOME bias not

removed



25/Sep/2002

Histogram

SCIAMACHY –

KNMI/ESA (Total

ozone / DU)

GOME bias not

removed


Data Assimilation

Struthers, Brugge, Lahoz, O’Neill & Swinbank, JGR 2002

Cal-val:O: Observations, A: Analyses, B: Background/Forecast

- Impact of observations: OSEs

- Stability & Bias: O-A differences

- Normality of Errors: O-B histograms

- Best Linear Unbiased Estimate (BLUE): rms(O-A)

- Comparison against independent data


Conclusions

MIPAS: results suggest:

Consistency between MIPAS data & meteorology

Temperature, ozone vs independent data (sondes x AK):

- temperature better characterised than ozone; unrealistic vertical oscillations in temperature retrieval

- ozone errors too small (systematic error needed); ozone has a positive bias

- MIPAS temperature and ozone errors are close to Gaussian


Conclusions

SCIAMACHY: results suggest:

SCIAMACHY total column ozone data agrees well with GOME analyses (N.B. GOME biases not removed):

- bias magnitude ~6DU (bias can be positive/negative)

- std of differences ~20 DU (Errors are close to Gaussian)

- consistent with GOME analyses bias (see BIRA/IASB web-site)

GOMOS

Air density in GOMOS needed work (Sep); may be OK now


Further Work

MIPAS water vapour data (compare vs balloons)

SCIAMACHY total ozone column biases

GOMOS data (ozone, water vapour)

Assimilation into Met Office system (MIPAS ozone data assimilated for 6 hours & evaluating experiment)

- Cal-val

- Combine limb and nadir geometries: ASSET project

- Averaging kernels/theory

Evaluation of Envisat data using a NWP Assimilation System: A vortex-centred view

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