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Low-Level Jets over Utö, Finland, Based on Doppler Lidar Observations.
- Source :
-
Journal of Applied Meteorology & Climatology . Sep2017, Vol. 56 Issue 9, p2577-2594. 18p. 1 Diagram, 1 Chart, 8 Graphs, 1 Map. - Publication Year :
- 2017
-
Abstract
- Over two years of meteorological observations from Utö, a small island in the Finnish outer archipelago in the Baltic Sea, were used to investigate the occurrence and characteristics of low-level jets (LLJs) and the diurnal and seasonal variations in these properties. An objective LLJ identification algorithm that is suitable for high-temporal-and-vertical-resolution Doppler lidar data was created and applied to wind profiles obtained from a combination of Doppler lidar data and two-dimensional sonic anemometer observations. This algorithm was designed to identify coherent LLJ structures and requires that they persist for at least 1 h. The long-term mean LLJ frequency of occurrence at Utö was 12%, the mean LLJ wind speed was 11.6 m s−1, and the vast majority of identified LLJs occurred below 150 m above ground level. The LLJ frequency of occurrence was much higher during summer (21%) and spring (18%) than in autumn (8%) and winter (3%). During winter and spring, the LLJ frequency of occurrence is evenly distributed throughout the day. In contrast, the LLJ frequency of occurrence peaks at night (1900-0100 UTC) during summer and during the evening hours (1700-1900 UTC) in autumn. The highest and strongest LLJs come from the southwest, which is also the predominant LLJ direction in all seasons. LLJs below 100 m are common in spring and summer, are weaker, and do not show a strong directional dependence. [ABSTRACT FROM AUTHOR]
- Subjects :
- *DOPPLER lidar
*ANEMOMETER
*WIND speed
*SUMMER
*DIURNAL variations in meteorology
Subjects
Details
- Language :
- English
- ISSN :
- 15588424
- Volume :
- 56
- Issue :
- 9
- Database :
- Academic Search Index
- Journal :
- Journal of Applied Meteorology & Climatology
- Publication Type :
- Academic Journal
- Accession number :
- 126890292
- Full Text :
- https://doi.org/10.1175/JAMC-D-16-0411.1