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Transcript of Predictability study using the Environment Canada Chemical Data Assimilation System Jean de...
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