Wednesday, 9 January 2013
Exhibit Hall 3 (Austin Convention Center)
A feedback attribution analysis is conducted for the ENSO-related atmospheric and surface temperature anomalies in boreal winter. Local temperature anomaly is decomposed into partial temperature changes due to changes in oceanic dynamics/heat storage, water vapor, clouds, atmospheric dynamics, ozone, and surface albedo. It is shown that atmospheric dynamics plays distinctly different roles in establishing the tropical and extratropical temperature response to El Niño: it disperses out of the tropics excessive energy production due to oceanic dynamical forcing serving as a primary negative feedback to the tropical (tropospheric) warming, and in the northern extratropics, it is the main forcing of atmospheric temperature changes and meanwhile modulates surface temperatures via longwave radiative heating and cooling. This provides an alternative view of the atmospheric bridge mechanism from the perspective of local energetics and temperature feedback attribution. Substantial tropospheric cooling over the eastern North Pacific is found to be collectively contributed by water vapor, cloud and atmospheric dynamical feedback, driven at least partly by the equatorward shift of the Pacific storm track during El Niño. Polar stratospheric warming (cooling), largely due to atmospheric dynamics, is seen over the Eurasian-Pacific (Atlantic) sector with ozone feedback contributing significantly to the mid-stratospheric cooling over the Atlantic sector. Water vapor (atmospheric dynamical) feedback has an overall warming (cooling) effect throughout the tropical troposphere, and cloud feedback cools (warms) the tropical lower-mid (upper) troposphere. Atmospheric dynamics induces stratospheric warming over the entire northern extratropics and drives over northern mid-latitudes (high-latitudes) a tropospheric cooling (warming) that generally intensifies with altitude.
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