[Eoas-seminar] **REMINDER***THIS AFTERNOON**** GFDI COLLOQUIUM ON MONDAY, MARCH 27, 2017 AT 1:00PM IN MELVIN STERN SEMINAR ROOM, #18 KEEN BLDG.

eoas-seminar at lists.fsu.edu eoas-seminar at lists.fsu.edu
Mon Mar 27 10:01:01 EDT 2017




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********REMINDER******THIS AFTERNOON AT 1:00 PM ******REMINDER******


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&                                                         GFDI COLLOQUIUM                                                                               &

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Title

“The Bizarre Antarctic: Why can the greenhouse effect be negative over Antarctic?”


Speaker

Dr. Ming Cai

 Florida State University

(on leave at NSF)

Time
Monday, March 27, 2017 at 1:00PM

Place
Melvin Stern Seminar Room
Room 18 Keen Bldg.

Refreshments will be served at 12:45PM

Abstract:
Greenhouse gases warm the climate system by reducing the energy loss to space through a process known as the greenhouse effect. Thus, a common way to measure the strength of the greenhouse effect is by taking the difference between the surface longwave (LW) emission and the outgoing LW radiation. Based on this definition, the existence of a paradoxical negative greenhouse effect is found over the Antarctic Plateau, as greenhouse gases cause an increase in energy loss to space. We find that the strongest negative greenhouse effect is found within water vapor and CO2 bands. A principle-based explanation is provided to show that the sign of the greenhouse effect is fundamentally dictated by the vertical absorptivity and temperature profiles, which are partly determined by non-greenhouse factors. The dependence on temperature and absorptivity (i.e., emissivity) implies the sign of the greenhouse effect will vary seasonally and with wavenumber. The atypical climatological conditions found over the Antarctic Plateau, such as a robust surface-based temperature inversion, severe scarcity of water vapor above the inversion layer, and warmer stratospheric than surface temperatures cause the negative greenhouse effect. We thus conclude that a negative greenhouse effect can occur, but only under very abnormal conditions.


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