Extended Abstract (844K)P2.3
Summertime Low-level jets over the High Latitude Arctic Ocean
Douglas O. ReVelle, LANL, Los Alamos, NM; and E. D. Nilsson
Data taken during the 3 month Arctic Ocean Expedition 1996 (AOE96) expedition on the icebreaker Oden (from 70 - 87.1 deg north latitude) have been carefully examined for the presence of low-level jets. Fully 2/3 of the rawinsoundings taken, exhibit such low-level jet profiles according to definitions developed in Stull (1988) and other references. Although we have assumed a variety of planetary boundary layer forcing mechanisms for understanding these low-level jets, characteristic wavelengths computed for this latitude region range from ~110-215 km for the conditions examined which clearly correspond to processes active on mesoscale meteorological scales. We have assembled statistics from the Oden and from the accompanying Polarstern icebreaker for the presence of such jets in terms of variables such as friction velocity, z/L, aerodynamic roughness length, cloud cover, cloud-base elevation, fog frequency of occurrence, visibility, wind speed at 1, 10 and at 35 m above the intermittent ice flows, vertical wind, standard deviation of the horizontal wind, standard deviation of the vertical wind, key radiation power budget parameters, etc. and will use such statistics to guide the development of a theory for explaining the high probability of occurrence of these summertime Arctic low-level jets. Extensive supporting field data have also been used to properly initialize the period starting on July 27, 1996 (for station 3 on the Oden), a time period when an unusually very well developed low-level jet was present. Using our one-dimensional computer code, BLMARC (Boundary layer, mixing, aerosols, radiation and clouds) quite good temporal agreement was found between observations and one-dimensional theoretical temperature and wind modeling. In fact, power spectra of the observed wind profiles for a 1 month period during the expedition, clearly show the presence of a cycle of almost exactly 12 hours in length which would correspond to the development of an undamped, “nocturnal”, i.e., z/L > 0 , inertial oscillation as originally envisioned by A.K. Blackadar (1957) over middle latitude, continental regions at night. We will also examine how well this forcing hypothesis works for the other low-level jets observed during the AOE-96 expedition compared with several other possible low-level jet forcing mechanisms.
Poster Session 2, Poster Session P2 with Coffee Break
Wednesday, 25 June 2003, 3:30 PM-5:00 PM
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