Preliminary evaluation of Rossby wave in T511 Nature run

July 12 2007Nikki Privé

Standard deviation of 200 mb anomaly v (meridional wind).

Nature Run (top) vs reanalysis (center ECMWF and bottom NCEP). 13-month NR, 12 years of reanalysis data (1989 – 2002).

NR shows similar pattern, but stronger amplitude, esp. in Southern Hemisphere midlatitudes – due to higher spatial and temporal resolution?

StdDev v', DJF StdDev v', JJA

NH (30N-60N) 'ensemble' comparison of 200 mb v' standard deviation

blue = ECMWF

red = NCEP

black = Nature Run

blue = ECMWF

red = NCEP

black = Nature Run

SH (30S-60S) 'ensemble' comparison of 200 mb v' standard deviation

Comparison of zonal mean zonal wind jet maxima, NR and ECMWF only, Northern Hemisphere

blue – ECMWF

green star – Nature Run

blue – ECMWF

green star – Nature Run

Comparison of zonal mean zonal wind jet maxima, NR and ECMWF only, Southern Hemisphere

Amplitude of rossby wave envelopes found via Zimin (2003) using 200 mb v-anomaly field. This panel shows the mean wave envelope amplitude (m/s) for the Nature Run (top), ECMWF reanalysis (center), and NCEP reanalysis (bottom). Patterns similar to that seen in standard deviation of v'.

Wave envelope magnitude, DJF Wave envelope magnitude, JJA

Northern Hemisphere, power spectra decomposition of wave envelope field.

Southern Hemisphere, power spectra decomposition of wave envelope field.

Dominant wavenumber and group velocities of the 200 mb v' field found using power spectra decomposition (a la Hayashi 1971). The wave of greatest power on each latitude band is identified.

Westward propagating waves dominant in the deep tropics, eastward propagating waves dominant in midlatitudes. Diagnostics in agreement with studies using different method (eg. lag-correlation, Chang (1999)).

Dominant waves, DJF Dominant waves, JJA