Slide 1 Retrospective analysis of ozone at ECMWF Rossana Dragani ECMWF Acknowledgements to: D. Tan, A. Inness, E. Hólm, and D. Dee R. Dragani, SPARC/IOC/IGACO,
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Slide 1
Retrospective analysis of ozone at ECMWF
Rossana Dragani ECMWF
Acknowledgements to:D. Tan, A. Inness, E. Hólm, and D. Dee
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Slide 2
Overview
Reanalysis activity at ECMWF
Science application for reanalysis data
Suitability to assess long-term variability
Ozone analyses in ERA-40 and ERA-Interim
Conclusions and remarks
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Slide 3
Reanalysis at ECMWF:
Reanalysis is based on analysis methods developed to provide initial states for numerical weather prediction.
It applies a fixed, modern data assimilation system to multi-year sets of observations of different types, resulting in more uniform analysis quality.
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
ERA-15: 1979 – 1993ERA-40: 1957 – mid-2002ERA-Interim: 1989 onwards
ORA-S3: 1959 onwardsMACC: 2003 – 2010
ERA-CLIM:European Reanalysis of Global Climate Observations
An EU project to help prepare the next ECMWF reanalysis
ERA-20C: 1900 onwards
Slide 4
The ERA data base: www.ecmwf.int
ERA-Interim reanalysis is continuing in near real-timeProducts are updated monthly
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Slide 5
Science applications that rely on reanalysis data
“Observations” for verification and diagnosis- Development of forecast model, climate model; calibration of seasonal
forecasting systems; use of data assimilation increments for identifying model errors
Input data for model applications- for smaller-scales (globalregional; regionallocal), ocean circulation,
chemical transport, …
Study of short-term atmospheric processes and influences- Polar vortex dynamics,…
Providing climatologies Assessment of the observing system
- providing feedback on observational quality, bias corrections and a basis for homogenization studies; contributing to data reprocessing activities
Study of long-term climate variability and trends
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Slide 6
ERA-40 + ERA-Interim Mid 1957 to the present
Analyses are physically coherent and consistent with observations
A realistic model can propagate information in poorly observed areas as well as moved forward in time.
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Suitability to assess long-term changes:
Geer, Planet Earth Autumn 2004, www.nerc.ac.uk
MIPAS O3 retrievals:
23 Sep 2002 © ESA, 2002.
Ozone fc: D+6 from
17 Sep 2002
Ozone analysis: 12Z 23 Sep 2002
Slide 7
Reanalysis uses a modern, stable and invariant forecasting /assimilation system to reprocess (re-analyse) past observations:
Remove artificial changes introduced by model upgrades
Changes in the observing system and their error characteristics can also produce shifts and spurious trends.
- ERA-Interim used VarBC for all radiances
- ERA-Clim will also use VarBC for all L2 products (O3, WV)
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Suitability to assess long-term changes:From archived weather analyses: From a retrospective analysis:
Slide 8
Ozone reanalyses at ECMWF: Ozone has been reanalysed in ERA-40 and ERA-Interim
- MACC also reanalysed ozone for the period 2003-2010.
Long record: ERA-40 until Dec 1988 + ERA-Interim from Jan 1989.
Main differences between ERA-40 (Cy23r4) and ERA-Interim (Cy31r2):
- Assimilation scheme: ERA-40 used 3D-Var; ERA-Interim used 4D-Var
- Data usage
- Variarional Bias Correction (VarBC) for radiances
- Upgrades in the ozone model
- Horizontal resolution: T159 (125km, ERA-40) T255 (80 km, ERA-Interim)
ERA-40 ozone analyses validated by Dethof and Hólm (2004, QJ). ERA-Interim ozone analyses validated by Dragani (2011, QJ submitted).
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
33333
3 243210 OEQOOOO
O ClccTTcccdt
d
ERA-InterimERA-40
Slide 9
Ozone in ERA-40:
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Dethof & Hólm (2004)
Hohenpeissenberg (1983-1987)
JFM JJA
Neumayer (1992-1995)
SO
SondeERA-40
Hilo (1992-1995)
JFM JJA
Slide 10
Ozone in ERA-Interim:
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
TCO validated against
OMI TCO (TOMS-like);
TCO from Dobson Spectrometers (WOUDC);
TCO climatology created as a 5-year running mean from the NASA merged satellite.
3D O3 analyses (Jan 89-Dec 08) validated against
WOUDC sondes; Satellite data.
V6.2
V5 V2.2
V19
V4V6POAM:
HALOE:
MLS:
SAGE:
Slide 11
Validation of the 3D O3 reanalyses:
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
30 hPa
Matching criteria:
t 3 hrs.
ERA-Interim analyses were interpolated at
the obs locations.
GOME
SAGE HALOEMLS POAM
Sat-AnSat
Slide 12
Summary of the comparisons: 1989-2008
Lat Lev (hPa) SAGE HALOE MLS POAM
30 - 90 N
5 ±5% [0,+5]% [0,+5]% [-25,+5]%
10 [-10,+5]% [-5,+1]% [-5,+3]% [-25,+10]%
30 [0,+20]% [-2,+20]% [0,+20]% [-10,+20]%
65 [-20,+10]% [-2,+10]% [-20,+10]% [-20,+10]%
30S - 30N
5 ±5% ±5% ±5%
10 ±10% ±5% [-5,+8]%
30 [0,+20]% [0,+20]% [0,+20]%
65 [-20,+30]% [-5,+20]% [+5,+25]%
30 - 90 S
5 [-8,+5]% ±2% [-8,+5]% [-40,+1]%
10 [-10,+5]% [-8,+1]% [-10,+3]% [-40,-5]%
30 [0,+20]% [0,+20]% [0,+20]% [-20,+10]%
65 [-20,+20]% [-2,+20]% [0,+20]% [-20,+20]%
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Slide 13
ERA-40 vs. ERA-Interim: Jan 1989 - Aug 200230
-90
N30
S-3
0 N
30-9
0 S
HALOE UARS MLS
403333
ERASATInterimERASAT OORMSOORMSR. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Slide 14
ERA-40 vs. ERA-Interim:Comparisons with ozone sondes
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Pre-GOME(1989-1995)
GOME(1996-2001)
60 – 90 SSep-Oct
30N – 30SJan-Feb-Mar
ERA-InterimERA-40
203 soundings 942 soundings
238 soundings227 soundings
Slide 15
Conclusions
ERA-40 O3 analyses showed general good agreement with
observations, but some problems were seen e.g. at mid-latitudes in winter, and at high latitudes in the SH in spring.
ERA-Interim O3 analyses compare well with observations, and show
departures from SAGE, MLS and HALOE ≤10% in the middle stratosphere, and ≤ 20% in the lower stratosphere.
ERA-Interim better than ERA-40 in the UTLS region before 1996, and over the whole stratosphere afterwards (GOME assimilation).
Planned improvements on ozone:
- Use the Variational Bias Correction (VarBC) scheme with L2 data.
- Revise/improve the assimilation of ozone profiles (e.g. SBUV data)
- Assimilate ozone information from different data type/instruments (ozone-sensitive radiances, L2 ozone data not yet used, e.g. those used for validation).
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Slide 16
Remarks:
What can reanalysis deliver?
- Consistent with observations
- Physically coherent
- Complete, with no gaps
- Comprehensive
- Accurate variability and trends
- Meaningful information about uncertainties
Progress towards climate quality requires open access to all input data.
Progress is iterative and needs regular re-processing.
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
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