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CMIP1, CMIP2 and CDAS Comparisons. Vernon E. Kousky December 2007. CMIP1-CDAS Circulation and Temperature Differences. Average 200-hPa wind and 850-hPa temperature were computed for JFM and JJA over the last 50 years of the CMIP1 free run.

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Cmip1 cmip2 and cdas comparisons

CMIP1, CMIP2 and CDAS Comparisons

Vernon E. Kousky

December 2007


Cmip1 cdas circulation and temperature differences
CMIP1-CDAS Circulation and Temperature Differences

  • Average 200-hPa wind and 850-hPa temperature were computed for JFM and JJA over the last 50 years of the CMIP1 free run.

  • The differences between those fields and the 1971-2000 CDAS1 mean fields are used to evaluate the performance of the CFS (CMIP1 run).

  • Differences are considered to be biases in the model climatology.


JFM 200-hPa Wind

  • During JFM, the NH westerlies in the CMIP1 run are shifted poleward with respect to CDAS1.

  • In addition, the NH flow is more zonally symmetric, and the eastern Pacific low-latitude troughs (in both hemispheres) are weaker in CMIP1


JJA 200-hPa Wind

  • During JJA the flow is more zonally symmetric in the SH.

  • Again, the low-latitude troughs are weaker than in CDAS1 over the eastern Pacific.

  • In addition, the westerlies are too strong over the NH subtropics.




JFM 850-hPa Temperature region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.

  • The 850-hPa temperatures, relative to CDAS, are too cold over the central and eastern N. Pacific, southern US, and central North Atlantic, and too warm over the eastern tropical Pacific.

  • The 200-hPa circulation differences, shown in slide 3 are consistent with this pattern.


JJA 850-hPa Temperature region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.

  • During JJA, the 850-hPa temperatures are generally colder in the mid-latitudes than depicted in CDAS1.

  • This pattern is consistent with the 200-hPa circulation differences shown in slide 4.

  • Again, the tropical eastern Pacific is too warm in the CMIP simulation run.


Cmip1 2 cdas 200 hpa wind and v variance differences
CMIP1(2)-CDAS 200-hPa Wind and v-Variance Differences region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.

  • Average 200-hPa winds and v-variance were computed for each month over the last 98 years of the CMIP1, CMIP2 free runs.

  • The differences between those fields and the 1971-2000 CDAS1 mean fields are used to evaluate the performance of the CFS (CMIP1 and CMIP2 runs).

  • Differences are considered to be biases in the model climatology.

  • Both CMIP1 and CMIP2 show nearly identical difference patterns for all months, when compared to CDAS1.


Cmip cdas comparison january
CMIP/CDAS Comparison: January region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip cdas comparison february
CMIP/CDAS Comparison: February region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip cdas comparison march
CMIP/CDAS Comparison: March region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip cdas comparison april
CMIP/CDAS Comparison: April region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip cdas comparison may
CMIP/CDAS Comparison: May region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip cdas comparison june
CMIP/CDAS Comparison: June region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip cdas comparison july
CMIP/CDAS Comparison: July region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip cdas comparison august
CMIP/CDAS Comparison: August region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip cdas comparison september
CMIP/CDAS Comparison: September region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip cdas comparison october
CMIP/CDAS Comparison: October region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip cdas comparison november
CMIP/CDAS Comparison: November region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip cdas comparison december
CMIP/CDAS Comparison: December region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip1 cdas comparison january february
CMIP1/CDAS Comparison: January-February region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip1 cdas comparison march april
CMIP1/CDAS Comparison: March-April region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip1 cdas comparison may june
CMIP1/CDAS Comparison: May-June region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip1 cdas comparison july august
CMIP1/CDAS Comparison: July-August region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip1 cdas comparison september october
CMIP1/CDAS Comparison: September-October region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip1 cdas comparison november december
CMIP1/CDAS Comparison: November-December region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Cmip1 cams opi comparison

CMIP1/CAMS-OPI Comparison region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.


Summary
Summary region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.

  • The CFS has a number of biases when compared to CDAS.

    • The 850-hPa temperatures are too cold over many mid-latitude locations and too warm over the eastern tropical Pacific.

    • The wintertime westerlies are shifted poleward and the east-Pacific low-latitude troughs are too weak in the CMIP runs.

    • The meridional wind variance is too high over the NH middle latitudes during winter and too high over the middle and high latitudes of the SH throughout the year.

    • The summertime upper-level ridge over the SW US is weaker in the CMIP run and low-level flow is too strong from the NW over the region of the Gulf of California, indicating a weaker SW monsoon in the CFS.


Summary region of the Gulf of California during summer, and the easterlies are too weak over the Caribbean.

  • The CFS precipitation has substantial biases when compared to CAMS-OPI.

    • The precipitation in the ITCZ over the North Pacific is too strong.

    • The CFS displays a strong SH ITCZ over the Pacific, which is not evident in the CAMS-OPI analyses.

    • The CFS has too much precipitation over Brazil during the SH summer, and the precipitation pattern over the Equatorial Atlantic is markedly different from that depicted in CAMS-OPI.


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