Homogenization of TEMP data with innovations from...
Transcript of Homogenization of TEMP data with innovations from...
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Fakultät für Geowissenschaften, Geographie und Astronomie
Institut für Meteorologie und Geophysik
Homogenization of TEMP data with innovations from reanalyses
3rd WCRP Conference on Reanalyses, 31 Jan 2008
Leopold HaimbergerChristine Gruber, Stefan Sperka, Christina Tavolato
FWF, EC6FP, ECMWF, MetOffice
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3rd WCRP Conference on Reanalyses, 31.1.2008
Wind direction biases
Gruber & Haimberger, 2008, MetZ, accepted
Wrong northdirection
y-H(xb)
100 hPa
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3rd WCRP Conference on Reanalyses, 31.1.2008
RAOBCORE, RICH• RAdiosonde OBservation COrrection using REanalyses
• 1) Basic idea:– Analysis of time series of innovations y-H(xb) (obs-bg)
– Break detection with modified Standard Normal Homogeneity Test
• 2) Adjustment of detected breaks with:– mean innovations before/after breaks (Haimberger, 2007 J.Climate)
• Bg used as reference for homogenization
• depends on homogeneity of bg
– or anomaly/innovation differences from neighboring RS stations• independent of bg (RICH, Haimberger et al. 2008, J. Climate)
• Reference built from homogeneous pieces of neighboring time series
• Automatic adjustment schemes for both T and Wind
• Full RS dataset homogenized -> Suitable for reanalyses!
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3rd WCRP Conference on Reanalyses, 31.1.2008
A classicalexample
Gruber & Haimberger 2008, MetZ, accepted
Marion Island
South Africa
12 degree wind direction error
1986, MWR
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3rd WCRP Conference on Reanalyses, 31.1.2008
Global RS-Wind homogenization
Gruber & Haimberger, MetZ, 2008, accepted
Grey=anyinhomogeneity
Black=wind directionerror >3deg
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3rd WCRP Conference on Reanalyses, 31.1.2008
12h-00h-T-difference, 50 hPa
• This trend is spurious, can be removed• Day-night differences – Yes, but daily means?• Compare with MSU data, ERA-40 BG, HadAT• Compare RICH/RAOBCORE
Composite30W-40EEurope/Africa
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3rd WCRP Conference on Reanalyses, 31.1.2008
MSU anomaly differences at Yap
Haimberger et al.2008, J. Clim
MSU4
MSU3
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3rd WCRP Conference on Reanalyses, 31.1.2008
RICH: Anomalies vs. Innovations
Smaller variance with innovations!
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3rd WCRP Conference on Reanalyses, 31.1.2008
Tropical LS and TS comparison
Haimbergeret al. 2008,J. Climate
MSU4
MSU3
1K
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3rd WCRP Conference on Reanalyses, 31.1.2008
Santer et al., in prep.together with P. Thorne
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3rd WCRP Conference on Reanalyses, 31.1.2008
Impact of RAOBCORE adj. in ERA-Interim
0.4K
Difference of assimilation experimentswith/without adjustments
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3rd WCRP Conference on Reanalyses, 31.1.2008
Adjustments of US Vaisala RS (Redder et al. 2004)
IFS CY29Unadj RS
IFS CY30Unadj RS
IFS CY29NASA-ADJ
IFS CY30NASA-ADJ
•Error of VRS 80 operated by NCEP. •Biases removed with physical model(Redder et al., 2004) used in MERRA
•RAOBCORE can be applied on top•Improves bias estimates further in the past(Haimberger, special project report 2007)
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3rd WCRP Conference on Reanalyses, 31.1.2008
Arguez (2007), BAMSAgreement in pre-satellite ERA?
Arguez et al.2007, BAMS
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3rd WCRP Conference on Reanalyses, 31.1.2008
Historical upperair data & pilot
reanalyses
Brönnimann, 2008
SLP basedReanalysisfrom G. Compo
1933-1944
1943/44
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3rd WCRP Conference on Reanalyses, 31.1.2008
Conclusions• Advances made:.
– Improved radiosonde TEMPERATURES and WINDS– Large breaks clearly identifiable– Better agreement with MSU, surface temperatures, GCMs
• Key: Availability of innovations in ERA-40
• RAOBCORE data used in ERA-Interim, MERRA– Positive impact in innovation statistics– Physically based adjustments can be added
• To-do list for ERA-75 reanalysis– Uncertainty estimates with background from JRA25, ERA-Interim– Pre-1979 RS T- data need more attention– Preparation of pre-1958 data c.f. S. Brönnimann– Use surface data reanalysis output for homogenization?
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3rd WCRP Conference on Reanalyses, 31.1.2008
ΔFa=0.3PWATM
OCEAN
Does the energyexport from thetropics change?
AOGCMs:Atmosphere: +3%Ocean: -20%
Held&Soden (2006), J. Climate
Can we find thiswith reanalyses?
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3rd WCRP Conference on Reanalyses, 31.1.2008
12h-00h RS-T differences, 50 hPa
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3rd WCRP Conference on Reanalyses, 31.1.2008
Adjusted 12-00GMT Difference, 50hPa
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3rd WCRP Conference on Reanalyses, 31.1.2008
Tropical MT and LT comparisonMSU2
MSU2LT
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3rd WCRP Conference on Reanalyses, 31.1.2008
Independence of bg
Trappes(France) 12GMT
Stuttgart 00 GMTNo sign of break in bg
Rapa(South Pacific) 00GMT
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3rd WCRP Conference on Reanalyses, 31.1.2008
Station climatology adjustment
bgT
x,y
Mean T of neighbouringhomogenized „reliable“series
Mean T of most recentpart of tested series
Bg used for interpolation
(bg-obs)iobsi
Expected(bg-obs)
actual(bg-obs)
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3rd WCRP Conference on Reanalyses, 31.1.2008
Adjusted 12h-00h T-Difference, 50 hPa
Composite30W-40EEurope/Africa
Composite120E-120WFar East/Pacific/Alaska
T-Difference
T-Difference
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3rd WCRP Conference on Reanalyses, 31.1.2008
RAOBCORE v1.3 – no BG adj.
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3rd WCRP Conference on Reanalyses, 31.1.2008
12GMT-00GMT-Difference, 50 hPa
• This trend had nonclimatic reasons, can beremoved
• Day-night differences – Yes but daily means?• Compare with MSU data, ERA-40 BG, HadAT• Compare RICH/RAOBCORE
Composite30W-40EEurope/Africa
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3rd WCRP Conference on Reanalyses, 31.1.2008
Effect of bg adjustment on bgtrends
V1.4v1,.2, v1.3
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3rd WCRP Conference on Reanalyses, 31.1.2008