Post on 21-Dec-2015
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