The Effect of Vertical Resolution on Zonal Wind Stress in AMIP Runs

An evaluation of monthly means from Suru Saha’s AMIP runs with observed SST PRX 28 versus 64 levels Validation NCEP Reanalyses CDAS, NCEP2 FSU Stresses SOC flux climatology

SOC Zonal mean Ocean

5S-5N Pacific FSU SOC Time-mean U s

Annual Cycle Pacific SOC FSU

CDAS NCEP2

28 levels 64 levels

28 levels-NCEP2 64-NCEP2

Time-mean zonal wind stress SOC Magnitude of systematic difference

CDAS NCEP2

28 levels 64 levels

CDAS-SOC NCEP2-SOC

28 levels minus SOC 64-SOC

Systematic difference from FSU Mean Tropical Pacific

JJA Time mean zonal wind stress FSU 28 64

JJA Time mean zonal wind stress SOC CDAS NCEP2

28-FSU 64-FSU JJA Time mean zonal wind stress

FSU-SOC FSU-NCEP2 CDAS-NCEP2 JJA Time mean zonal wind stress

Anomaly correlation with FSU--Pacific CDAS NCEP2 28 levels 64 levels

Merid. Wind Stress CDAS NCEP2 28 levels 64 levels Anomaly correlation with FSU merid. Wind stress

The reanalyses correlate better in time with FSU stresses than the AMIP runs, after the time-mean annual cycles are removed. Monthly anomalies Pacific

FSU Standard deviation of monthly anomalies 28 levels 64 levels

Standard deviation of monthly anomalies CDAS NCEP2

28-FSU 64-FSU Difference in standard deviation

CDAS-FSU NCEP2-FSU CDAS-NCEP

64 levels do not produce better zonal wind stress than 28 levels. Reanalyses display more agreement with SOC, FSU than AMIP runs. 64 level AMIP run too strong easterly stress in JJA, too strong westerly stress in JFM.