DOI: 10.1175/JCLI-D-17-0234.1
Scopus记录号: 2-s2.0-85040560863
论文题名: The role of nonlinear drying above the boundary layer in the Mid-Holocene African Monsoon
作者: Dixit V. ; Sherwood S. ; Geoffroy O. ; Mantsis D.
刊名: Journal of Climate
ISSN: 8948755
出版年: 2018
卷: 31, 期: 1 起始页码: 233
结束页码: 249
语种: 英语
英文关键词: Atmospheric circulation
; Convection
; Energy budget/balance
; Monsoons
Scopus关键词: Atmospheric thermodynamics
; Boundary layer flow
; Boundary layers
; Budget control
; Climate models
; Heat convection
; Heating
; Orbits
; Rain
; Atmospheric circulation
; Earth system model
; Energy budget/balance
; Monsoons
; Nonlinear mechanisms
; Northern Hemispheres
; Thermodynamic process
; Vertical advection
; Atmospheric boundary layer
; atmospheric circulation
; atmospheric convection
; boundary layer
; climate modeling
; energy balance
; energy budget
; Holocene
; monsoon
; nonlinearity
; paleoclimate
; proxy climate record
; Sahara
; Sahel [Sub-Saharan Africa]
英文摘要: Paleoclimatic proxies indicate that significant summertime rainfall reached the Sahara region during the mid-Holocene, presumably in response to stronger summertime heating in the Northern Hemisphere. Climate models generally do not replicate the enhanced precipitation. As a step toward understanding the response and possible role of model errors, a series of idealized experiments were conducted with the Community Earth System Model in which local atmospheric heat sources of increasing magnitude were applied in the boundary layer over the Sahel and Sahara. In response to this local heating, the cold and moist southwesterly monsoon inflow encroaches farther northward. A source strength of roughly 1 K day-1 produces responses similar to those in a simulation with mid-Holocene orbital forcing imposed globally, while that of 1.5 K day-1 produces a precipitation response similar to that from paleoproxies. The precipitation increases nonlinearly, with a jump at heating of around 1 K day-1, even though the low-level monsoon inflow increases linearly. Competition at low-to-middle levels between drying by a shallow return flow just above the boundary layer and moistening by vertical advection within the layer affects convection and determines the northward extension of precipitation. When the heating becomes 1.5 K day-1, the boundary layer flow encroaches sufficiently northward to weaken the shallow return flow, further aiding precipitation. This novel nonlinear mechanism operates without biogeophysical feedbacks, and suggests that poor representation of the local thermodynamic processes may hamper a model's ability to simulate dynamical feedbacks and hence the strength and poleward extension of monsoon rains under forcings like those during the mid-Holocene. © 2018 American Meteorological Society. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/111706
Appears in Collections: 气候减缓与适应
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作者单位: Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia
Recommended Citation:
Dixit V.,Sherwood S.,Geoffroy O.,et al. The role of nonlinear drying above the boundary layer in the Mid-Holocene African Monsoon[J]. Journal of Climate,2018-01-01,31(1)