tropical biases in next-generation climate models stefan tulich 1 and george kiladis 2 1 cires,...
TRANSCRIPT
![Page 1: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/1.jpg)
Tropical Biases in Next-Generation Climate Models
Stefan Tulich1 and George Kiladis2
1CIRES, University of Colorado, Boulder CO, USA
2NOAA ESRL, Boulder CO, USA
![Page 2: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/2.jpg)
Coupled climate models are known to suffer from biases
Kim et al. (2008)
“High” = 1-2 deg. horizontal grid spacing (5 models)
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Coupled climate models are known to suffer from biases
Kim et al. (2008)
“High” = 1-2 deg. horizontal grid spacing (5 models)
![Page 4: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/4.jpg)
Uncoupled models too
12 CMIP3 AGCMs run in AMIP mode
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Uncoupled models too
12 AGCMs run in AMIP mode (CMIP3 Archive)
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Tropical variability also poorly simulated
Lin et al. (2004)
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Focus of this talk
Mean climate and variability of 3 “next-generation” climate models:
1)WRF tropical channel model (36-km, 45S-45N, Kain-Fritsch, AMIP-type run: 2000-2005)
2)GFDL AM2.1 (0.5-deg, global, relaxed AS, SST = climatological ann. cycle, courtesy of G. Lau)
3)SP-CAM (2.5-deg, global, 2D CRM, AMIP-type run, courtesy of M. Khairoutdinov)
![Page 8: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/8.jpg)
Annual Rainfall Bias
SPCAM
WRF
AM2.1
![Page 9: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/9.jpg)
Annual Rainfall Bias
SPCAM
WRF
AM2.1
![Page 10: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/10.jpg)
Annual Rainfall Bias
SPCAM
WRF
AM2.1
![Page 11: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/11.jpg)
Annual Rainfall Bias
SPCAM
WRF
AM2.1
![Page 12: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/12.jpg)
Annual Rainfall Bias
SPCAM
WRF
AM2.1
![Page 13: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/13.jpg)
Annual Rainfall Bias
SPCAM
WRF
AM2.1
![Page 14: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/14.jpg)
Annual Rainfall Bias
SPCAM
WRF
AM2.1
![Page 15: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/15.jpg)
Basic Question
• How do these mean rainfall biases (e.g., too much rain off the equator/too little rain near the equator) relate to the space-time variability of rainfall?
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Rainfall Spectra (Symmetric)
TRMM
WRF AM2.1
SPCAM
![Page 17: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/17.jpg)
Rainfall Spectra (Symmetric)
TRMM
WRF AM2.1
SPCAM
![Page 18: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/18.jpg)
Rainfall Spectra (Symmetric)
TRMM
WRF AM2.1
SPCAM
![Page 19: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/19.jpg)
Rainfall Spectra (Symmetric)
TRMM
WRF AM2.1
SPCAM
![Page 20: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/20.jpg)
Rainfall Spectra (Symmetric)
TRMM
WRF AM2.1
SPCAM
![Page 21: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/21.jpg)
Rainfall Spectra (Antisym.)
TRMM
WRF AM2.1
SPCAM
![Page 22: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/22.jpg)
Rainfall Spectra (Antisym.)
TRMM
WRF AM2.1
SPCAM
![Page 23: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/23.jpg)
Summary thus far:
• Kelvin waves generally too weak or non-existent; n = 0 EIG wave non-existent
• Westward-moving waves better represented, but generally too active, especially in a relative sense:
Westward Power (PW) /Eastward Power (PE)
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Ratio of westward- to eastward-moving variance (k =1-25)
SPCAM
WRF
AM2.1
10 5 3.3 2.5
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Maps of westward- minus eastward-moving rainfall variance (k=1-25, 2-96 day)
TRMM SPCAM
WRF AM2.1
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Maps of westward- minus eastward-moving rainfall variance (k=1-25, 2-96 day)
TRMM SPCAM
WRF AM2.1
![Page 27: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/27.jpg)
Maps of westward- minus eastward-moving rainfall variance (k=1-25, 2-96 day)
TRMM SPCAM
WRF AM2.1
![Page 28: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/28.jpg)
Maps of westward- minus eastward-moving rainfall variance (k=1-25, 2-96 day)
TRMM SPCAM
WRF AM2.1
![Page 29: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/29.jpg)
Maps of westward- minus eastward-moving rainfall variance (k=1-25, 2-96 day)
TRMM SPCAM
WRF AM2.1
![Page 30: Tropical Biases in Next-Generation Climate Models Stefan Tulich 1 and George Kiladis 2 1 CIRES, University of Colorado, Boulder CO, USA 2 NOAA ESRL, Boulder](https://reader036.vdocument.in/reader036/viewer/2022062713/56649cb85503460f9497dfeb/html5/thumbnails/30.jpg)
Summary
• Results of this study indicate a linkage between biases in simulated time-mean rainfall and its variability:
– Too much rain at off-eq. latitudes
– Too strong coupling between convection and westward-propagating (rotational) wave disturbances
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Open questions
• Is the westward bias in convective wave activity a consequence or a cause of time-mean biases in rainfall?
• What determines the degree of coupling between convection and rotational (Rossby) vs. divergent (Kelvin, n = EIG wave modes)?
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Proposal
• A test case for measuring the strength of coupling between convection and rotational vs. divergent circulation anomalies
• Basic idea: perturb a large-domain model by imposing 3D rotational vs. divergent circulations anomalies (i.e., a step beyond SCM approaches) – Parameterized vs. explicit– Coarse vs. fine resolution