1 Introduction The lowest few kilometers of the tropical marine atmosphere are frequently capped by an inversion layer Under this inversion lie several types of boundary layer clouds A ID: 240690
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The strength of the tropical inversion and its response to climate change in 18 CMIP5 models
1. Introduction The lowest few kilometers of the tropical marine atmosphere are frequently capped by an inversion layer. Under this inversion lie several types of boundary layer clouds. A key factor controlling the amount of the clouds is the strength of the inversion. A stronger inversion suppresses the mixing of boundary layer air with warmer and drier air in the free-troposphere, leading to a shallower, moister and cloudier boundary layer. In this study, we examine the realism of the tropical inversion and the response of inversion strength to anthropogenic forcing simulated in 18 CMIP5 models.
2. Present-day inversion While CMIP5 models generally capture the geographic distribution of observed inversion strength, they systematically underestimate it off the west coasts of continents, due to a warm bias in sea surface temperature.
Fig. 1: Geographic distribution of present-day estimated inversion strength (EIS) in both reanalysis and simulations. (a) The ERA-Interim reanalysis. (
b) The ensemble-mean of 18 coupled model simulations. (c) The ensemble-mean of 13 amip simulations. The thick curve in each diagram represents the zero contour line.
3. Changes in the inversion strength There are widespread EIS increases in a warming climate. The largest increase occurs primarily in the eastern parts of subtropical oceans, due to the small surface warming there.
Fig. 2: Geographic distribution of the ensemble-mean EIS change in the first 30 years of eight abrupt4xCO2 simulations.
Fig. 3: Changes in the tropical inversion and their four contributors (fast response, uniform oceanic warming,
nonuniform
oceanic warm and residual) in the first and last 30 years of eight abrupt4xCO2 simulations.
4. Summary
The inversion strength increases in fully-coupled ocean-atmosphere simulations, due to both fast and temperature-mediated changes.
Reference:
Qu, X., A. Hall, S. A. Klein and P. M. Caldwell, 2014: The strength of the tropical inversion and its response to climate change in 18 CMIP5 models.
Clim
.
Dyn
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doi
: 10.1007/s00382-014-2441-9.