Satellite observations of the wind jets off the Pacific coast of Central America. Part II: Regional relationships and dynamical considerations

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.