Kl. Hill et al., Propagation characteristics of extratropical planetary waves observed in the ATSR global sea surface temperature record, J GEO RES-O, 105(C9), 2000, pp. 21927-21945
This paper examines the characteristics of planetary wave signatures that h
ave been found in the Along Track Scanning Radiometer averaged sea surface
temperature (ASST) record for 1991-1996. Longitude-time plots for every lat
itude between 5 degrees and 50 degrees, north and south, reveal westward pr
opagating wave-like patterns at many locations, whose speed decreases with
latitude like baroclinic Rossby waves. A two-dimensional Radon transform me
thod is used to measure the wave speed and its variation with location and
time, which broadly matches the Rossby wave speeds predicted by the most re
cent theory and those measured by TOPEX altimetry, although there are some
discrepancies. At low latitudes the thermally detected speeds are slower th
an expected, a possible consequence of sampling limitations. Wave signature
s are dearest between 25 degrees and 40 degrees S, where the meridional tem
perature gradient is strongest. Here observed speeds are 20-30% greater tha
n theoretical predictions. Planetary wave speed varies considerably with lo
ngitude. In general, it increases toward the west of ocean basins, and dist
inct differences between ocean basins are evident. The propagation characte
ristics of the waves appear to change abruptly at locations consistent with
latitudinal variations in seafloor bathymetry, particularly midocean ridge
s. In addition, eastward propagating signatures are found in the Southern O
cean. The results demonstrate the value of the ASST data set as a tool for
studying basin-scale wave processes as a complement to the use of altimetry
. By observing the thermal signature of Rossby waves the method has the pot
ential to clarify their influence on air sea interaction processes and to c
ontribute to climate modeling studies.