AIRS data in Giovanni provide a unique view of the occurrence of a Sudden Stratospheric Warming event commencing in mid-January 2009. The effects of this event are still being analyzed and evaluated by meteorologists and atmospheric scientists.
The wintertime Arctic polar stratosphere is usually characterized by a broad circumpolar jet stream (the polar vortex). Every few years, large-scale weather systems or waves move upward from the troposphere into the stratosphere and interact with the polar vortex. This wave-vortex interaction results in a sudden rise of stratospheric temperature by tens of Kelvin, the so-called Sudden Stratospheric Warming (SSW). This stratospheric warming is usually accompanied by a slowdown or even a reversal of the jet stream.
A major stratospheric warming occurred and persisted during the last week of January 2009. The Goddard Giovanni system, a visualization and analysis tool for many kinds of Earth science data, was utilized to capture the evolution of the stratospheric warming event over time using Atmospheric Infrared Sounder (AIRS) data. As can be seen from the time vs. pressure cross-sectional view of AIRS daily temperature data shown below, the warming started at the stratopause level (near 1 hPa or about 48 km altitude), and around the end of January 2009, penetrated down to the lower-stratosphere (200 hPa or 12 km). Long-range weather forecasters have been attempting to predict how this event will influence winter weather in the Northern Hemisphere during February 2009.
AIRS data is plotted below for the northern polar region in a latitude band between 79.5° N and 81.5° N. The warming event (reds and yellows indicating a temperature range between 250-280 kelvins) is observed commencing about January 18-19. [Click to view full-size image]
The time scale goes from left to right, with early January on the left side of the plot, and early February on the far right of the plot. The pressure range is from 500 to 1.0 hectoPascals (hPa). The approximate location of the boundary between the troposphere and the stratosphere, the tropopause, in hPA is 300-350 hPA in the polar regions; in km, the tropopause is found at an altitude of about 10 km over the poles. (900-1000 hPA is atmospheric pressure at sea level.)
To learn more about AIRS, visit: http://disc.gsfc.nasa.gov/airs/ or http://airs.jpl.nasa.gov/.
To learn more about Giovanni, visit: http://giovanni.gsfc.nasa.gov.
NASA's Earth Observatory also discusses this event:
Stratosphere Influences Winter Weather
* A Kelvin is the same increment of temperature as a degree on the Celsius scale. The kelvin is the official base unit of temperature in the International System of Units (SI).