Db. Chelton et al., Satellite observations of the wind jets off the Pacific coast of Central America. Part II: Regional relationships and dynamical considerations, M WEATH REV, 128(7), 2000, pp. 2019-2043
Satellite estimates of winds at 10 m above the sea surface by the NASA scat
terometer (NSCAT) during the 9-month period October 1996-June 1997 are anal
yzed to investigate the correlations between the three major wind jets alon
g the Pacific coast of Central America and their relationships to the wind
and pressure fields in the Inter-American Seas and eastern tropical Pacific
. Comparisons with sea level pressure confirm the conventional view that Te
huantepec wind variations are driven by pressure variations in the Gulf of
Mexico associated with North American cold-air outbreaks. The three jets so
metimes developed sequentially from north to south. Statistically, however,
the Papagayo and Panama jets were poorly correlated with variations of the
Tehuantepec jet over the NSCAT observational period. The Papagayo and Pana
ma jets were significantly correlated with each other and were coupled to c
oherent variations of the trade winds extending from the Caribbean Sea to t
he eastern tropical Pacific.
The detailed structures of the wind fields within the three jets are examin
ed to infer dynamical balances within the jets. After leaving the coast, th
e northerly Tehuantepec and Panama jets turn anticyclonically toward the we
st in manners that are consistent with jets that are inertially balanced at
the coast and become progressively more geostrophically balanced with incr
easing distance from the coast. There is no evidence of anticyclonic turnin
g of the easterly Papagayo jet, suggesting that the winds may remain in app
roximate geostrophic balance through the gap over the Nicaraguan lake distr
ict.
NSCAT observations are compared with operational analyses by ECMWF to inves
tigate the detailed structures of the wind fields over the Gulfs of Tehuant
epec, Papagayo, and Panama. Systematic differences between the NSCAT observ
ations and the ECMWF analyses of the divergent off-axis fanning of all thre
e jets suggest that there may be systematic errors in parameterizations of
boundary layer processes in the ECMWF "first-guess" fields in these data-sp
arse regions.