Transcript and ERA-Interim
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
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
Slide 2 R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
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.
ERA-15: ERA-40: ERA-Interim: 1979 – 1993 1957 – mid-2002 1989 onwards ORA-S3: MACC: 1959 onwards 2003 – 2010
ERA-CLIM:
European Reanalysis of Global Climate Observations An EU project to help prepare the next ECMWF reanalysis
Slide 3
ERA-20C: 1900 onwards
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
The ERA data base: www.ecmwf.int
Slide 4 ERA-Interim reanalysis is continuing in near real-time
Products are updated monthly R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
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 (global
regional; regional
local), ocean circulation, chemical transport, …
Study of short-term atmospheric processes and influences
-
Polar vortex dynamics,…
Providing climatologies
Assessment of the observing system
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providing feedback on observational quality, bias corrections and a basis for homogenization studies; contributing to data reprocessing activities Slide 5
Study of long-term climate variability and trends R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Suitability to assess long-term changes:
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.
Ozone fc: D+6 from 17 Sep 2002 MIPAS O © ESA, 2002.
3 retrievals: 23 Sep 2002 Ozone analysis: 12Z 23 Sep 2002 Slide 6 Geer, Planet Earth Autumn 2004, www.nerc.ac.uk
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Suitability to assess long-term changes:
From archived weather analyses: From a retrospective analysis:
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.
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ERA-Interim used VarBC for all radiances Slide 7
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ERA-Clim will also use VarBC for all L2 products (O 3 , WV) R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
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) :
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Assimilation scheme: ERA-40 used 3D-Var; ERA-Interim used 4D-Var Data usage ERA-Interim Variarional Bias Correction (VarBC) for radiances
-
Upgrades in the ozone model
d
dt O
3
c
0
c
1
O
3
O
3
c
2
T
T
c
3
O
3
O
3
c
4
EQ
2
O
3 -
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
Ozone in ERA-40:
Hilo (1992-1995) JFM JJA Dethof & Hólm (2004) Hohenpeissenberg (1983-1987) JFM JJA Sonde ERA-40 Neumayer (1992-1995) SO Slide 9 R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Ozone in ERA-Interim:
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 O 3
analyses (Jan 89-Dec 08) validated against WOUDC sondes;
Satellite data.
V6.2
SAGE: MLS: HALOE: POAM: V5 V6 V4 V2.2
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Validation of the 3D O
3
reanalyses:
Matching criteria:
D
t 3 hrs.
ERA-Interim analyses were interpolated at Sat-An Sat the obs locations.
30 hPa
GOME SAGE HALOE MLS POAM Slide 11 R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
Summary of the comparisons: 1989-2008
Lat 30 - 90 N 30S - 30N 30 - 90 S 5 10 30 65 5 10 30 65 5 10 30 65 Lev (hPa) SAGE HALOE MLS POAM ±5% [-10,+5]%
[0,+20]% [-20,+10]%
±5% ±10%
[0,+20]%
[-20,+30]% [-8,+5]% [-10,+5]%
[0,+20]% [-20,+20]%
[0,+5]% [-5,+1]%
[-2,+20]%
[-2,+10]% ±5% ±5%
[0,+20]% [-5,+20]%
±2% [-8,+1]%
[-2,+20]%
[0,+5]% [-5,+3]%
[0,+20]% [-20,+10]%
±5% [-5,+8]%
[0,+20]%
[+5,+25]% [-8,+5]% [-10,+3]%
[0,+20]% [0,+20]%
[-25,+5]% [-25,+10]%
[-10,+20]% [-20,+10]%
[-40,+1]% [-40,-5]%
[-20,+10]% [-20,+20]%
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
ERA-40 vs. ERA-Interim: Jan 1989 - Aug 2002
HALOE UARS MLS
RMS
O
3
SAT
O
3
ERA
Interim
Slide 13
RMS
O
3
SAT
O
3
ERA
40
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011
ERA-40 vs. ERA-Interim: Comparisons with ozone sondes
203 soundings 942 soundings 30N – 30S Jan-Feb-Mar 227 soundings 238 soundings 60 – 90 S Sep-Oct
ERA-Interim
ERA-40 Pre-GOME (1989-1995) Slide 14 R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011 GOME (1996-2001)
Conclusions
ERA-40 O 3 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 O 3 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)
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(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
Remarks:
What can reanalysis deliver?
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Consistent with observations
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Physically coherent
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Complete, with no gaps
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Comprehensive
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Accurate variability and trends Meaningful information about uncertainties
Progress towards climate quality requires open access to all input data.
R. Dragani, SPARC/IOC/IGACO, Geneva, Jan 2011 © ECMWF 2011