An Evaluation of Aspects of Tropical Precipitation Forecasts from the ECMWF & NCEP Model Using CMORPH John Janowiak 1 , M.R.P. Sapiano 1 , P. A. Arkin 1 , F.J. Turk 1 Cooperative Institute for Climate and Satellites (CICS) Earth Systems Science Interdisciplinary Center (ESSIC) University of Maryland, College Park, Maryland, USA 2 Jet Propulsion Laboratory Pasadena, California, USA
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An Evaluation of Aspects of Tropical Precipitation Forecasts
An Evaluation of Aspects of Tropical Precipitation Forecasts from the ECMWF & NCEP Model Using CMORPH. John Janowiak 1 , M.R.P. Sapiano 1 , P. A. Arkin 1 , F.J. Turk 2 1 Cooperative Institute for Climate and Satellites (CICS) Earth Systems Science Interdisciplinary Center (ESSIC) - PowerPoint PPT Presentation
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An Evaluation of Aspects of Tropical Precipitation Forecasts from the ECMWF & NCEP Model Using CMORPH
John Janowiak1, M.R.P. Sapiano1, P. A. Arkin1, F.J. Turk2
1 Cooperative Institute for Climate and Satellites (CICS) Earth Systems Science Interdisciplinary Center (ESSIC) University of Maryland, College Park, Maryland, USA
2 Jet Propulsion Laboratory Pasadena, California, USA
Precipitation from Indian Ocean across the Pacific to Greenwich
Seasonal mean removed
MJO signatures clearly evident
Diagonal lines subjectively drawn to identify axis of MJO (and intervening dry periods) eastward progression
15N-15S
These lines identify westward moving elements within MJO envelope
15N-15S
Case Study:
Mod-Stg MJO
Nov 2007 – Feb 2008
CMORPH
Line are same as previous slides; on model plots, lines represent observed features
~10days
Dec 4-15, 2007
Dec 16 – Jan 3
Jan 5-20, 2008
Difference from Nov 2007 – Feb 2008 Period Mean
Dec 4-15, 2007
Dec 16 – Jan 3
Jan 5-20, 2008
Difference from Nov 2007 – Feb 2008 Period Mean
Difference from Nov 2007 – Feb 2008 Period Mean
A
B
C
Dec 4-15
CMORPHGFS 10 dyECMWF 10 dy
(5 dy smoothed)
Difference from Nov 2007 – Feb 2008 Period Mean
A
B
C
Dec 16-Jan 3
CMORPHGFS 10 dyECMWF 10 dy
(5 dy smoothed)
Difference from Nov 2007 – Feb 2008 Period Mean
A
B
CJan 5-20
(5 dy smoothed)CMORPHGFS 10 dyECMWF 10 dy
0
1
2
3
4567 12
0
8 910
11 13 1415
These show pattern correlations over the region between forecasts and observations for different lags (the different colored lines) and for different forecast lead time (the horizontal axis)
The green line labeled “1” represents the correlation between forecasts initialized one day later than the observations they are compared to
“Interesting if true” – we are working to figure out what this might mean
Conclusions
• GFS precipitation forecasts over the tropical oceans do exhibit a diurnal cycle– But the peak occurs earlier than observations – And the amplitude decreases with forecast lead, at least in the central Pacific
• Both GFS and ECMWF exhibit a reasonably realistic MJO precipitation pattern and variability
– At longer leads, both models lose details and seem to lag behind the observations – Possible that the initialization is imperfect and some spin-up is required to attain a more
realistic precipitation field?
• Results, particularly for ECMWF, indicate that useful skill in predicting MJO-related precipitation is close to being attained