DOI: 10.1029/2012JD018134
论文题名: Why does radar reflectivity tend to increase downward toward the ocean surface, but decrease downward toward the land surface?
作者: Liu C. ; Zipser E.J.
刊名: Journal of Geophysical Research Atmospheres
ISSN: 21698996
出版年: 2013
卷: 118, 期: 1 起始页码: 135
结束页码: 148
语种: 英语
英文关键词: radar reflectivity slope
; rainfall
; TRMM
; updraft
Scopus关键词: Drops
; Freezing
; Radar
; Rain
; Rain gages
; Reflection
; Convective precipitation
; Different slopes
; High reflectivity
; Radar reflectivities
; Surface precipitation
; TRMM
; Tropical rainfall measuring mission precipitation radars
; updraft
; Radar measurement
; cumulus
; land surface
; precipitation (climatology)
; radar
; reflectivity
; relative humidity
; sea surface
; stratiform cloud
; TRMM
; updraft
; Africa
; China
英文摘要: Both ground and space borne radars have shown that radar reflectivity profiles below the freezing level have different slopes over land and ocean in general. This is critical in correctly estimating the surface precipitation rate in the usual situation in which the radar reflectivity cannot be measured as close to the surface as one would like. Using 14 years of Tropical Rainfall Measuring Mission precipitation radar observations, the variations of slopes of the radar reflectivity in the low troposphere are examined over the stratiform and convective precipitation regions. Radar reflectivity below the freezing level usually decreases toward the surface over land, but increases toward the surface over the ocean. Increasing reflectivity toward the surface is hypothesized to occur mainly when raindrops grow while falling through low clouds, which is favored by high humidity at low levels, and by updraft speeds lower than the fall speed of raindrops, both more likely over oceans. Other things being equal, proxy evidence is presented that the more intense the convection, the more likely reflectivity is to decrease toward the surface, and that this is at least as important as low-level relative humidity. Over monsoon regions with more moderate convection but higher humidity, such as southeast China and the Amazon, there are more profiles with reflectivity increasing toward the surface than over other continental regions such as Africa. Radar reflectivity tends to increase toward the surface in shallow warm rain systems in trade cumulus regions, but tends to decrease toward the surface when high reflectivity values are present at or above the freezing level. Key Points Reflectivity decreases/increases toward surface over land/ocean dBZ decreases when high reflectivity above freezing level Strength of updraft is important in dBZ slope. © 2012 American Geophysical Union. All Rights Reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/63973
Appears in Collections: 影响、适应和脆弱性 气候减缓与适应
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作者单位: Department of Atmospheric Sciences, University of Utah, 135S 1460E, Salt Lake City, UT 84112-0110, United States
Recommended Citation:
Liu C.,Zipser E.J.. Why does radar reflectivity tend to increase downward toward the ocean surface, but decrease downward toward the land surface?[J]. Journal of Geophysical Research Atmospheres,2013-01-01,118(1)