Predictability study using the Environment Canada Chemical Data Assimilation System

Jean de GrandpréYves J. Rochon Richard Ménard

Air Quality Research DivisionWWOSC conference, MontréalAugust 18th 2014

Outline

• Global/Regional Chemical Data Assimilation

• Ozone predictability and radiative coupling

• Results from CDA cycles with ozone assimilation

• Summary

CDA for improving the Air Quality operational system (RAQDPS)

• GEM-MACH as the core model• Comprehensive on-line tropospheric chemistry • Chemical Data Assimilation: 3D-Var/Envar

• Assimilation of O3, NO2, CO, AOD …• NRT measurements: GOME-2, SBUV/2, IASI, OMPS, MODIS and

surface observations (O3, PM2.5, NO2…)

Comprehensive regional CDA system :

• Model : On-line linearized stratospheric chemistry (GEM-LINOZ)• Assimilation of ozone, AOD and GHGs• Chemical Data Assimilation : 3D-Var/Envar• NRT measurements (GOME-2, SBUV/2, IASI, OMPS…)• Radiatively coupled model (ozone heating)• Use of ozone analyses in the NWP DA system• Produce UV-index forecasting (see poster by Y. Rochon)

Simplified and integrated Global CDA system :

CDA for improving the Global NWP system (GDPS)

The Global Chemical Data Assimilation system

Multi-day Forecast

Model: GEM-LINOZAssimilated observations: GOME-2, SBUV/2, MLS3D-Var Data AssimilationIndependant measurements: ACE-FTS, MIPAS,OSIRIS, OMI, …

6-hr forecast

O3 Analysis

chemObs

6-hr forecast

6-hr forecast

O3 Analysis

O3 Analysis

Multi-day Forecast

Met Analysis

Met Analysis

chemObs

chemObs

Variational chemical data assimilation at EC slide 6 9 December 2011

• GEM-Global (80 levels, lid=.1 hPa, 33km resolution)

• Linearized stratospheric chemistry

• 2 months assimilation cycle [winter 2009]

• 3D-var

Microwave Limb Sounder (EOS-AURA)

Day/night measurements

~3500 profiles per day

~ 2.5 km in the vertical

Vertical range : [215 - .02 hPa]

V2.2 retrievals

Assimilation of ozone from MLS

Anomaly correlation

n

iiicc

n

iiicfcf

i

n

iiccicfcf

MxxMxx

MxxMxxr

1

2,

1

2,

1,,

cos)(cos)(

cos)()(

fx x : Forecast and analysis values,

cx : Climatology

cfM , fx -: ( )cx over the verification area

Ozone predictability

Column Ozone predictability

Temperature anomaly correlation August 11 - Sept 5, 2003

North Hemisphere (20-90N)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2 3 4 5 6 7 8 9 10

Forecast day

3D dyn - 50 hPa

3D chem - 50 hPa

3D dyn - 70 hPa

3D chem - 70 hPa

3D dyn - 100 hPa

3D chem - 100 hPa

3D dyn - 200 hPa

3D chem - 200hPa

Ozone radiative coupling

NRT ozone measurements 6 hr sample (centered about 0 UTC) on 25 July 2008

Nadir UV-visible Spectrometer (MetOp-A)

Total column amounts

Day only and cloud free

v8 (level-2) retrievals

~80 x 40km resolution

~18 000 measurements per day

Nadir Solar Backscatter UV instrument (NOAA-17-18)

20 partial column layers

~3.2km thickness

v8 (level-2) retrievals

Assimilation of Total Column Ozone

δQ = (HBHT + R)-1 (z – Hxb)

δx = BHT δQ

Q : Total column ozone analysis increment at the observation locations

xb : ozone mixing ratio

z : total column ozone measurements

Background error standard deviations

Evaluation of ozone analyses against ozone sondes: O-A (%)

[January-February] MLS vs GOME-2

MLS vs GOME-2

MLS vs GOME-2

Evaluation of ozone analyses against ozone sondes: O-A (%)

[January-February] GOME-2 vs SBUV/2

GOME-2 vs SBUV/2

SBUV/2 Partial column retrievals

V8 Partial column retrievals “y”

δx = K (y – Hxb)

Xb: ozone mixing ratio (80 levels)

y : partial column ozone (DU) (20 levels)

H : vertical integrator

New partial column retrievals “z”

δx = K (z – AHxb)

z : partial column ozone without a priori (DU) (20 levels)

A : Averaging kernels matrix (20 levels)

Sample SBUV/2 averaging kernels at ~45 degrees

Evaluation of SBUV/2 retrievals against ozone sondes: O-A (%) [January-February] With/Without a priori

O-A : SBUV/2 retrievals with/without a priori

SUMMARY/CONCLUSIONS

• Anomaly correlation diagnostic based on total column is a useful metric for evaluating ozone analyses system.

• CDA cycles using GOME-2 total column measurements and MLS observations have been compared. In the NH, O-A and O-F results are generally within 5%. The column ozone predictability for GOME-2 after 10-days is larger by ~½ day.

• CDA cycles using SBUV/2 partial column measurements and GOME-2 have been compared. Results are similar in the NH but significantly worst for SBUV/2 in the SH.

• The impact of using different SBUV/2 retrievals on ozone forecasts is negligible.

Ozone Column (DU)

July, 2008 February, 2009

Observation

LINOZ - Observation

Evaluation of ozone forecast against ozone sondes: O-F(10-days)

[January-February] MLS vs GOME-2

Ozone Column (DU)

July, 2008 February, 2009

SBUV/2 - Observation

LINOZ - Observation

Variational chemical data assimilation at EC slide 25 9 December 2011

Assessment of ozone analyses/forecasts

• Total column ozone (July, 2008)– Relative to OMI

With SBUV/2 assimilation With GOME-2 and SBUV/2

Variational chemical data assimilation at EC slide 26 9 December 2011

Variational chemical data assimilation at EC slide 27 9 December 2011

Variational chemical data assimilation at EC slide 28 9 December 2011

Sample ozone observation distributionTangent point orbit tracks for a 6 hour period

(centered about 0 UTC) on 25 July 2008

1748584

5502

Total column amounts

Thinning: 1 degree separation

Day only cloud free points

165-300 km along track

~ 2.5 km in the vertical

(NRT: 0.2 to 68 hPa)

20 usable partial column layers with ~5 ‘no-impact’ tropo. layers

~3.2 km layers

Day only

Variational chemical data assimilation at EC slide 29 9 December 2011

Sample SBUV/2 averaging kernels at ~45 degrees

July average ozone error standard deviations (%)(before and after adjustment via Desroziers approach and 2Jo/N consideration)

MLS SBUV/2 (NOAA 17) GOME-2: 1% applied

SBUV/2: A priori removed before assimilation. Averaging kernels applied in assimilation.

Variational chemical data assimilation at EC slide 30 9 December 2011

Winter Summer (ppmv) (ppmv)

Background error standard deviations

0.4

0.2

0.6 0.6

0.4

– Initial values set to 5% of ozone climatology (vmr).

– Adjustments to ~3-15% (of vmr) based on the Desroziers approach above =0.7 (from assimilation of MLS and using 30 degree bands).

– Below =0.7: Constant extrapolation in absolute uncertainty up to a maximum of 30%.

0.2

• Prescribed 6 hr ozone background error covariances