Micrometeorological Observations of a Microburst in Southern Finland
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- 作者：Leena J?rvi ; Ari-Juhani Punkka ; David M. Schultz ; Tuukka Pet?j? ; Harri Hohti ; Janne Rinne ; Toivo Pohja ; Markku Kulmala ; Pertti Hari and Timo Vesala
- 关键词：Aerosol particles ; Convective storm ; Microburst ; Micrometeorology ; Trace gases
- 刊名：Boundary-Layer Meteorology
- 出版年：2007
- 出版时间：November, 2007
- 年：2007
- 卷：125
- 期：2
- 页码：343-359
- 全文大小：965 KB
- 刊物类别：Earth and Environmental Science
- 刊物主题：Earth sciences
Meteorology and Climatology
Atmospheric Protection, Air Quality Control and Air Pollution - 出版者：Springer Netherlands
- ISSN：1573-1472
文摘
On the afternoon of 3 July 2004 in Hyyti?l? (Juupajoki, Finland), convective cells produced a strong downburst causing forest damage. The SMEAR II field station, situated near the damage site, enabled a unique micrometeorological analysis of a microburst with differences above and inside the canopy. At the time of the event, a squall line associated with a cold front was crossing Hyyti?l? with a reflectivity maximum in the middle of the squall line. A bow echo, rear-inflow notch, and probable mesovortex were observed in radar data. The bow echo moved west-north-west, and its apex travelled just north of Hyyti?l?. The turbulence data were analysed at two locations above the forest canopy and at one location at sub-canopy. At 1412 EET (Eastern European Time, UTC+2), the horizontal and vertical wind speed increased and the wind veered, reflecting the arrival of a gust front. At the same time, the carbon dioxide concentration increased due to turbulent mixing, the temperature decreased due to cold air flow from aloft and aerosol particle concentration decreased due to rain scavenging. An increase in the number concentration of ultra-fine particles (< 10 nm) was detected, supporting the new particle formation either from cloud outflow or due to rain. Five minutes after the gust front (1417 EET), strong horizontal and downward vertical wind speed gusts occurred with maxima of 22 and 15 m s?1, respectively, reflecting the microburst. The turbulence spectra before, during and after the event were consistent with traditional turbulence spectral theory.