Tropical East Pacific Synoptic Tropical East Pacific Synoptic Variability in NCEP Reanalyses 1 Variability in NCEP Reanalyses 1

and 2:and 2:Comparisons With TAO WindsComparisons With TAO Winds

Presented byPresented by

Yolande Serra, University of Yolande Serra, University of ArizonaArizona

EPIC Workshop 11-13 May 2005 APL, UW

CMAP 79-02 Amonth: JAS TAO buoys used for this study

180 140W 100W 20W140E 60W

20N

10N

0

10S

20S

In Situ TAO DataIn Situ TAO Data Native 10-min data smoothed to hourly, then sub-Native 10-min data smoothed to hourly, then sub-

sampled to 4xdaily to match NCEP Reanalyses.sampled to 4xdaily to match NCEP Reanalyses. All available wind data from June-November All available wind data from June-November

1990-2003.1990-2003.

NCEP/NCAR and NCEP/DOE NCEP/NCAR and NCEP/DOE ReanalysesReanalyses

2.5°x2.5°, 4xdaily 1000 mb winds2.5°x2.5°, 4xdaily 1000 mb winds June-November 1990-2003 time period to June-November 1990-2003 time period to

match TAO data availability.match TAO data availability. TAO data are incorporated into both TAO data are incorporated into both

products to the extent allowed by the products to the extent allowed by the model data assimilation routine (!)model data assimilation routine (!)

Model Configurations (adopted from Model Configurations (adopted from Hodges et al. 2003)Hodges et al. 2003)

NCEP/NCAR NCEP/DOE

Data assimilation 3DVAR 3DVAR

Satellite NESDIS TOVS NESDIS TOVS

Upper Air Cloud winds, Radiosondes, dropsondes, pibals

Same as NCEP.

Surface Stations, buoy Stations, buoy

Special PAOB, FGGE, TOGA COARE Same as NCEP.

Boundary Reynolds SST, ECMWF sea ice, NESDIS snow

Same as NCEP.

PBL Monin-Obukhov (1974) Hong and Pan (1996)

Radiation Lacis and Hansen (1974) (SW); Fels and Schwarztkopf (1975) (LW)

Chou (1996) (SW)

Convection Arakawa-Schubert Simplified Arakawa-Schubert

NCEP/NCAR (RA1) vs. NCEP/DOE (RA2)

NCEP/NCAR (RA1) vs. TAO - V-wind Power Spectra

NCEP/DOE (RA2) vs. TAO - V-wind Power Spectra

9°N 140°W

2°N 140°W

5°N 140°W 9°N 140°W 5°N 140°W

0°N 140°W

5°S 140°W2°S 140°W 2°S 140°W 5°S 140°W

0°N 140°W2°N 140°W

Cycles per dayCycles per day Cycles per day Cycles per day

4-day

NCEP/NCAR (RA1) vs. NCEP/DOE (RA2)NCEP/NCAR (RA1) vs. TAO -

V-wind Power SpectraNCEP/DOE (RA2) vs. TAO -

V-wind Power Spectra

4-day

8°N 125°W 5°N 125°W

2°S 125°W 5°S 125°W

0°N 125°W2°N 125°W

Cycles per day

Cycles per day8°S 125°WCycles per day

Cycles per day

8°N 125°W 5°N 125°W

2°S 125°W 5°S 125°W

0°N 125°W2°N 125°W

8°S 125°W

NCEP/NCAR (RA1) vs. NCEP/DOE (RA2)

NCEP/NCAR (RA1) vs. TAO - V-wind Coherence2 and Phase

NCEP/DOE (RA2) vs. TAO - V-wind Coherence2 and Phase

9°N 140°W

2°N 140°W

5°N 140°W 9°N 140°W 5°N 140°W

0°N 140°W

5°S 140°W2°S 140°W 2°S 140°W 5°S 140°W

0°N 140°W2°N 140°W

Cycles per dayCycles per day Cycles per day Cycles per day

4-day

NCEP/NCAR (RA1) vs. NCEP/DOE (RA2)

NCEP/NCAR (RA1) vs. TAO - U,V-wind Biases and Correlations

NCEP/DOE (RA2) vs. TAO - U,V-wind Biases and Correlations

9°N 140°W

2°N 140°W

5°N 140°W

0°N 140°W

5°S 140°W2°S 140°W

VU

9°N 140°W 5°N 140°W

2°S 140°W 5°S 140°W

0°N 140°W2°N 140°W

SDOM

VU VU VU

1990-2003 Mean Bias in Eastern 1990-2003 Mean Bias in Eastern Tropical Pacific - Tropical Pacific - rough estimates!rough estimates!

RA1 RA2

U V U V

Mean Bias, m s-1 0.1 0.1 0.4 0.6

SDOM,m s-1 0.1 0.1 0.1 0.1

NCEP/NCAR (RA1) vs. NCEP/DOE (RA2)

850 mb winds regressed onto TD-filtered OLR at 7.5N, 130W, June-November 1979-2002

NCEP/NCAR meridional eddy advection by eddy winds at 1000 mb

∂(v’v’)/∂y [m s-2]

Synoptic-scale u’·Hv’ is ~8x10-5 m s-2

Synoptic-scale u’·Hv’ is ~8x10-5 m s-2

NCEP/NCAR advection of meridional eddy NCEP/NCAR advection of meridional eddy momentum by eddy winds at 1000 mbmomentum by eddy winds at 1000 mb

Momentum gained by eddies

Momentum lost by eddies

Comparison of synoptic waves in AGCMs - Hodges et al (2003)

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Track density distributions of EWs

NCEP/NCAR

NCEP/DOE

Summary of Comparisons with TAOSummary of Comparisons with TAO

Less variance at Less variance at synoptic frequencies.synoptic frequencies.

Large diurnal variability Large diurnal variability at some locations.at some locations.

Significant coherence Significant coherence and in phase with TAO and in phase with TAO at synoptic and lower at synoptic and lower frequencies.frequencies.

Potentially large Potentially large differences in mean differences in mean wind components.wind components.

Greater or equal Greater or equal amount of variance at amount of variance at synoptic frequencies.synoptic frequencies.

Significant coherence Significant coherence but but out of phase by as out of phase by as much as a quarter much as a quarter cyclecycle (~1 day) at (~1 day) at synoptic frequencies.synoptic frequencies.

Potentially large Potentially large differences in mean differences in mean wind components.wind components.

RA1RA1 RA2RA2

NCEP/NCAR (RA1) vs. NCEP/DOE (RA2)

NCEP/NCAR (RA1) vs. TAO - U-wind Power Spectra

NCEP/DOE (RA2) vs. TAO - U-wind Power Spectra

9°N 140°W

2°N 140°W

5°N 140°W 9°N 140°W 5°N 140°W

0°N 140°W

5°S 140°W2°S 140°W 2°S 140°W 5°S 140°W

0°N 140°W2°N 140°W

Cycles per dayCycles per day Cycles per day Cycles per day

4-day