Radiation & Clouds WG

IASOA Radiation & Clouds 
Wed, Mar 7, 2018 9:00 AM - 10:30 AM MST 

Date: 
Wednesday, March 7, 2018 -
09:00 to 10:00
Agenda: 

Agenda

- Introductions - 10 min

- Presentation on ice-albedo feedbacks over snow vs sea-ice (Key) - 20 min

- Discussion - 20 min

Minutes: 

IASOA Radiation & Cloud Working Group

March 7, 2018

 

Attendees: Sara Morris, Chris Cox, Lei Liu, Allison McComiskey, Chuck Long, Jeff Key, Alessio Bozzo, Barbara Casati, Bob Stone, Matthew Shupe, Andreas Massling, Aaron Letterly, Yinghui Liu, Gabriela Schaepman-Strub, Elin McIlhattan, Von Walden

 

Role Call of group members

 

Presentation: Changes in Sea-Ice Extent Will Outweigh Changes in Snow Cover in Future Arctic Climate Change (Key):

  • Primary dataset: AVHRR Polar Pathfinder Extended (APP-x) 1982-2015, 25km, high-sun time
    • Surface radiation, surface temp, surface albedo, cloud properties, and more
  • Reanalysis: NASA MERRA2
  • Study area: land and ocean, 60-90 °N latitude (Summit ignored/not included)
  • Trends in absorbed solar radiation
    • The magnitude and rate were different over land and ocean
    • Look at average monthly (annual monthly average) SW absorption per year for combined land and ocean, land only, and ocean only
  • Spatial distribution of trends
    • Strong increase in absorption due to decreasing springtime snow cover is seen in May
    • June to October, the ocean area absorption rate increased faster than absorption over land
  • APP-x vs MERRA2
    • Show similar patterns
    • Larger magnitudes in APP-x
  • Cloud cover
    • Over land: an increase in highly reflective cloud cover is associated with a decrease (increase) in surface absorption
    • Over ocean: changes in cloud cover, but the effect on trends in absorption is less because most of the ocean is ice-covered and the reflectivities of ice and cloud are similar
  • Timing of the low albedo
    • Over ocean, movement of lower albedos to earlier in the year means that more sunlight was absorbed over the ocean in 2015 than in 1982
    • Over land, the regression of low albedo towards earlier in the year still results in an increase in absorbed energy, but it can only increase asymptotically due to decreasing sunlight
  • Albedo feedbacks
    • The magnitude of the ice-albedo feedback is four times that of the snow-albedo feedback in summer
  • Summary
    • The trend of solar absorption over the ocean is more than double that over land
    • The magnitude of the ice-albedo feedback is four times that of the snow-albedo feedback in summer
    • The low albedo period each year has been changing such that over ocean it is moving toward the summer solstice, while over land it is moving away from the solstice
      • Decreasing sea ice cover, not changes in terrestrial snow cover, may be the foremost radiative feedback mechanism affecting future Arctic climate change

 

Action Items:

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Research Group: