HR: 08:30h
AN: A31D-02    [Abstracts]
TI: Mesoscale Structure and Interannual Variability of Atmospheric Kelvin Waves Over the Eastern Tropical Pacific
AU: * Kiladis, G N
EM: george.kiladis@noaa.gov
AU: Liebmann, B
EM: brant.liebmann@noaa.gov
AB: Atmospheric Kelvin waves are prominent disturbances within the eastern tropical Pacific. Convectively coupled Kelvin waves modulate a substantial portion of the rainfall within the ITCZ. The convective envelopes of these waves move eastward at between 15-18 m/s on average, and are composed primarily of westward propagating features within them. Many of these westward disturbances move too quickly (greater than 20 m/s) to be explained solely by advection, and therefore must also be wavelike. We present evidence that some of these features are likely inertio-gravity waves. Using high temporal and spatial resolution satellite data, we show that Kelvin waves are much more common than previously realized. Many of these events are relatively short-lived, but they can still have a pronounced impact on ITCZ convection. Kelvin waves readily propagate unimpeded across the Andes barrier and control convection over Amazonia, however the connection between the Pacific and South America is strongly influenced on the interannual time scale by the El Nino/Southern Oscillation (ENSO) phenomenon. During warm ENSO events, when sea surface temperature (SST) is high in the eastern equatorial Pacific, the Kelvin wave activity in enhanced along the equator and they propagate readily from the Pacific into South America and on through the Atlantic to Africa. During cold events, the activity is confined to the ITCZ off the equator and the connection between the Pacific and Amazonia is suppressed, but there is still substantial Kelvin wave generation to the east of the Andes. In these cases Kelvin waves are frequently excited by incursions of mid-latitude air into Amazonia, characterized by lower tropospheric high pressure surges trapped along the eastern flank of the Andes. Strong upper tropospheric extratropical wavetrain signatures over the South Pacific precede the development of composite Kelvin waves over both the Pacific and South America, indicating that such events may be predictable in numerical models several days in advance.
DE: 3314 Convective processes
DE: 3329 Mesoscale meteorology
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3364 Synoptic-scale meteorology
DE: 3374 Tropical meteorology
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly