DOI: 10.1175/JCLI-D-14-00352.1
Scopus记录号: 2-s2.0-84961291041
论文题名: The convolution of dynamics and moisture with the presence of shortwave absorbing aerosols over the southeast Atlantic
作者: Adebiyi A.A. ; Zuidema P. ; Abel S.J.
刊名: Journal of Climate
ISSN: 8948755
出版年: 2015
卷: 28, 期: 5 起始页码: 1997
结束页码: 2024
语种: 英语
Scopus关键词: Aerosols
; Atmospheric aerosols
; Atmospheric humidity
; Atmospheric pressure
; Atmospheric radiation
; Clouds
; Convolution
; Dynamics
; Landforms
; Moisture
; Troposphere
; Aerosol optical depths
; Anticyclones
; Continental outflow
; Horizontal dynamics
; Humidity inversions
; Observational study
; Potential temperature
; Radiative forcings
; Absorption cooling
; aerosol
; anticyclone
; atmospheric moisture
; biomass burning
; cloud cover
; humidity
; optical depth
; radiative forcing
; Saint Helena
英文摘要: Biomass burning aerosols seasonally overlie the subtropical southeast Atlantic stratocumulus deck. Previous modeling and observational studies have postulated a semidirect effect whereby shortwave absorption by the aerosol warms and stabilizes the lower troposphere, thickening the low-level clouds. The focus herein is on the dynamical and moisture effects that may be convoluted with the semidirect effect. Almost-daily radiosonde data from remote St. Helena Island (15.9°S, 5.6°W), covering September-October 2000-11, are combined with daily spatial averages (encompassing the island) of the MODIS clear-sky fine-mode aerosol optical depth (τaf ). Increases in τaf are associated with increases in 750-500-hPa moisture content. The net maximum longwave cooling by moisture of almost 0.45Kday-1 reduces the aerosol layer warming from shortwave absorption. ERA-Interim spatial composites show that polluted conditions are associated with a strengthening of a deep land-based anticyclone over southern Africa, facilitating the westward offshore transport of both smoke and moisture at 600 hPa. The shallower surface-based South Atlantic anticyclone exhibits a less pronounced shift to the northeast, strengthening the low-level coastal jet exiting into the stratocumulus deck and cooling 1000-hPa potential temperatures. Warm continental outflow further increases the 800-hPa potential temperatures (θ800), reinforcing the lower tropospheric stability (θ800 - θ1000) over the stratocumulus deck. Enhanced southerly dry air advection also strengthens the cloud-top humidity inversion. The increased stability helps explain an observed decrease in cloud-top heights despite an anomalous reduction in subsidence. The changes to the horizontal dynamics enhance low-level cloudiness. These are separate but not necessarily distinct from an aerosol semidirect effect, encouraging care in attribution studies. © 2015 American Meteorological Society. 资助项目: AGS, National Oceanic and Atmospheric Administration
; NASA, National Oceanic and Atmospheric Administration
; NOAA, National Oceanic and Atmospheric Administration
; NSF, National Oceanic and Atmospheric Administration
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/50877
Appears in Collections: 气候变化事实与影响
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作者单位: Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Miami, FL, United States; Met Office, Exeter, United Kingdom
Recommended Citation:
Adebiyi A.A.,Zuidema P.,Abel S.J.. The convolution of dynamics and moisture with the presence of shortwave absorbing aerosols over the southeast Atlantic[J]. Journal of Climate,2015-01-01,28(5)