Extended Abstract (1.3M)5.1
Large-amplitude gravity-wave breaking over the Greenland lee and the subsequent formation of downstream synoptic-scale tropopause folding and stratospheric-tropospheric exchange
Melvyn A. Shapiro, NOAA/ERL/ETL, Boulder, CO; and S. Low-Nam, H. Olafsson, J. D. Doyle, and P. K. Smolarkiewicz
On 9-10 November 2001, an extreme orographic flow event occurred over and in the eastern lee of Greenland. Observed surface winds over the Greenland Sea and Iceland exceeded 40 m s-1 as rapid cyclogenesis ensued in the East Greenland coastal zone. The event included the formation of a ~80 ms-1 tropopause-based jet stream at 6-km altitude. The upper jet and associated tropopause fold extended northeast from the Greenland to west of Iceland. The severity of this event warranted its simulation and diagnosis with the MM5 multi-scale prediction system. The simulation was performed as a two-way, interactive, triply-nested mesh, with horizontal resolutions of 90, 30, and 10 km, and 62 levels. Results of the simulation show massive orographically induced gravity-wave breaking, extending continuously over ~500 km along and above the east Greenland lee. The associated hydraulic jump rose from 2 km to above 7 km, with a surface-based, low-level down-slope jet ~60 m s-1. The surface-based jet decelerated to near calm as the isentropic surfaces ascended adiabatically to 7 km in association within the jump. Vertical wave propagation resulted in comparable wave breaking aloft in the layer 10-20 km. The extreme depth of the localized adiabatic cooling associated with the jump gave rise to a ~500 km diameter 10 C cold pool in the layer 2-6 km, that expanded ~1000 km eastward, including strong upper-level frontogenesis, jet stream formation, and tropopause folding and PV banner development downstream from the region of wave breaking. Trajectory analysis, and TOMS satellite and surface ozone measurements show that ozone was extruded from the arctic lower stratosphere and transported into the lower troposphere during this event. The representativeness of the simulation was supported by: i) surface observations from automatic surface stations on the Greenland ice cap and on its western slope and coastline, ii) QUIKSCAT scatterometer satellite surface wind measurements over the Greenland and Norwegian Sea, iii) commercial airline pilot reports, iv) upper-air and surface observations from Greenland and Iceland, v) Satellite multispectoral observations of polar-stratospheric clouds over Greenland at ~20 km (derived from sun-shadow trigonometry and infrred cloud-top temperatures), and vi)TOMS and TOVS satellite ozone anomalies in the region and downwind of wave breaking.
Session 5, Orographically Modified Cyclone Evolution
Tuesday, 18 June 2002, 8:00 AM-9:00 AM
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