Radar Anomalous Propagation Associated with Foehn Winds Induced by Typhoon Krosa (2007)

In this study, unusual radar anomalous propagation (AP) phenomena associated with foehn winds induced by Typhoon Krosa (2007) were documented by using observations from radar, surface stations, and soundings. The AP echoes embedded within rainband areas and exhibited inward motions toward the radar...

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Bibliographic Details
Published in:Journal of applied meteorology and climatology 2011-07, Vol.50 (7), p.1527-1542
Main Authors: Chang, Pao-Liang, Lin, Pin-Fang
Format: Article
Language:English
Subjects:
Acoustic data
Atmosphere
Confined spaces
Downslope winds
Drying
Earth, ocean, space
Echoes
Exact sciences and technology
External geophysics
Foehn
Foehn winds
Humidity
Hurricanes
Light refraction
Meteorology
Propagation
Radar
Radar beams
Radar data
Radar echoes
Radar tracking
Ray tracing
Refractive index
Refractivity
Signal processing
Soundings
Studies
Subsidence
Temperature inversion
Temperature inversions
Typhoons
Weather
Wind
Winds
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Summary:In this study, unusual radar anomalous propagation (AP) phenomena associated with foehn winds induced by Typhoon Krosa (2007) were documented by using observations from radar, surface stations, and soundings. The AP echoes embedded within rainband areas and exhibited inward motions toward the radar site within 2–3 h prior to the occurrences of foehn winds at the radar site, which would interfere with the interpretation of radar data and associated downstream applications. As Typhoon Krosa appeared in the vicinity of the northeastern coast of Taiwan, foehn winds with significant subsidence warming and drying generated by downslope winds were observed in southeastern Taiwan. The foehn winds continuously moved northward within confined areas from the southeastern to eastern–central parts of Taiwan. Before the foehn winds penetrated to the surface, the subsidence warming introduced a temperature inversion layer above the surface and caused the ducting of radar beams. Analyses of refractive index and ray tracing suggested that the occurrence and evolution of the AP echoes during Typhoon Krosa were closely related to the varying inversion heights induced by downslope winds.
ISSN:1558-8424
1558-8432
DOI:10.1175/2011JAMC2619.1