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Detection and occurrence of low-level jets over Testbed area

Detection and occurrence of low-level jets over Testbed area. T. Roschier A-J Punkka. motivation and goals. Use and evaluation of wind profiler data in low-level jet detection Comparison between sounding and profiler data Low-level jet occurrence (11/2005-10/2006).

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Detection and occurrence of low-level jets over Testbed area

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  1. Detection and occurrence of low-level jets over Testbed area T. Roschier A-J Punkka

  2. motivation and goals • Use and evaluation of wind profiler data in low-level jet detection • Comparison between sounding and profiler data • Low-level jet occurrence (11/2005-10/2006)

  3. definition of low-level jet • Glossary of meteorology: ”A jet stream that is typically found in the lower 2-3 km of the troposphere.” • Climatology of the low level jet (Bonner 1968): ”Criterion 1: The wind at the level of maximum wind must equal or exceed 12 m/s and must decrease at least 6 m/s to the next higher minimum or to the 3 km level.” • LLJ climatology…in the Southern Great Plains (Whiteman et al. 1997): ”Criterion 1: Maximum wind speed greater than 10 m/s in the lowest 3 km and the wind speed must decrease by at least 5 m/s before the 3 km level is reached.” • Definition of Whiteman et al. used in this study.

  4. methods • Primary data source Vantaa soundings (via Researcher’s interface) • Comparisons to Jokioinen and Tallinn soundings (UWyo) and to Malmi wind profiler (RI) • Stages • collecting of cases • statistics of found cases: monthly distribution, wind speed at LLJ core, LLJ core height etc. • comparisons

  5. data problems • irregular soundings from Vantaa • coarse temporal resolution of Jokioinen and Tallinn soundings • bad raw data from Malmi wind profiler • discontinuities in measurements • poor signal quality

  6. Good data from soundings • Profiler data missing ;)

  7. Good wind profiler case ?

  8. what to learn • usability of wind profiler data in LLJ detection • to get very preliminary overview the frequency of occurrence of LLJs

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