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UID:20260409T043941EDT-8920bNuiB6@132.216.98.100
DTSTAMP:20260409T083941Z
DESCRIPTION: \n\nStudent Seminar Series\n\nDepartment of Atmospheric & Ocea
 nic Sciences\n\npresents\n\na talk by\n\nMatthew Henry\n	PhD candidate\n\nD
 ecomposing the Drivers of Polar Amplification with a Single Column Model\n
 \nThe Arctic amplification of surface temperature change is a common featu
 re of both models and observations. The lapse rate feedback dominates the 
 attribution to forcings and feedbacks of polar surface warming under incre
 ased CO2. The surface temperature change attribution method based on top-o
 f-atmosphere (TOA) energy budget changes assumes forcings and feedbacks le
 ad to vertically uniform temperature changes\, and accounts for the deviat
 ion from vertically uniform warming by assigning it to the lapse rate feed
 back. Here\, we decompose the temperature change while accounting for the 
 vertical structure of the temperature change contributions from each forci
 ng and feedback. An idealized moist atmospheric General Circulation Model 
 (GCM) with slab ocean boundary conditions\, no clouds or sea ice is forced
  with a quadrupling of CO2 concentrations with and without a polar surface
  heat source. It is shown to have a polar amplified pattern of surface tem
 perature change comparable to comprehensive GCM simulations. Then\, we use
  a single column model to decompose the tropical and polar temperature cha
 nge from the idealized GCM into contributions from forcings and feedbacks 
 excluding the temperature feedback\, by individually perturbing the CO2\, 
 water vapor and energy transport. The warming from increasing longwave abs
 orbers (CO2 and water vapor) is bottom-heavy and accounts for most of the 
 surface warming in the absence of a surface heat source\, whereas the warm
 ing from atmospheric heat transport preferentially warms the mid and upper
  atmosphere. The warming from CO2 alone is polar-amplified as tropical con
 vection moves the warming maximum to the upper troposphere. Adding the `lo
 cal' water vapor feedback preferentially warms the tropical surface temper
 ature\, which cancels polar amplification. And\, adding the atmospheric en
 ergy transport and its implied water vapor change contributes to further p
 olar amplification. The surface heat source\, which could represent oceani
 c heat transport convergence or the surface albedo feedback\, increases po
 lar surface warming and is only partially compensated by a decrease in dry
  atmospheric energy transport. While this decomposition is applied to an i
 dealized GCM\, we hope it can be generalized to a fully comprehensive GCM.
 \n\nWednesday Sep 25/ 2.30 PM/ Room 934 Burnside Hall\n\n \n\n \n\n \n
DTSTART:20190925T183000Z
DTEND:20190925T193000Z
LOCATION:Room 934\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue 
 Sherbrooke Ouest
SUMMARY:Decomposing the Drivers of Polar Amplification with a Single Column
  Model
URL:https://www.mcgill.ca/meteo/channels/event/decomposing-drivers-polar-am
 plification-single-column-model-300649
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