Consequences of recent Southern Hemisphere winter variability on polar mesospheric clouds

Variations in the Southern Hemisphere (SH) winter of 2007, 2008 and 2009 had important consequences on polar mesospheric clouds (PMCs) observed in the corresponding Northern summers. Specifically, the stratospheric SH winter of 2007 was observed to be warmer than in 2008 and 2009. Using the high altitude analysis from the Navy Operational Global Atmospheric Prediction System-Advanced Level Physics High Altitude (NOGAPS-ALPHA) forecast/assimilation system we show that this warmth was linked to similar temperature increases in the high latitude summer mesosphere. These temperature changes led to a dramatic reduction in PMC occurrence (factor of 5–6) recorded by the SHIMMER instrument at sub-arctic latitudes and a factor of 2 decrease in total ice water content in PMCs seen by the SOFIE instrument on the NASA AIM satellite. Microphysical modeling confirms the overall effect of these temperature changes on PMCs at high latitudes; however, a detailed comparison of the cloud occurrence with the SHIMMER data for all three years shows that the clouds are associated with a surprisingly wide range (130–165 K) of temperatures.

► Northern summer mesopause region was warmer in 2007 than in 2008 and 2009.
► Warmth linked to temperature increases in the concurrent Southern winter.
► Polar mesospheric cloud occurrences at 50–58°N were five times rarer in 2007.
► Ice water content near 68°N was factor of 2 lower in 2007 than in 2008 or 2009.
► PMCs occur over wide range of temperatures including some greater than 150 K.