A short-duration cooling event around the tropical tropopause and its effect on water vapor

For the 2008/2009 winter, extremely low temperatures near the tropical tropopause (∼83 hPa) were observed at the beginning of February 2009 by COSMIC over the western Pacific and over eastern Pacific-South America in association with a wave response to the tropical heat source. At the same time, the water vapor field at 83 hPa detected from Aura MLS recorded a minimum, with a higher frequency of cirrus cloud observed by CALIOP. Although the temperature minima rapidly disappeared after the event, one possible interpretation is that the low water-vapor concentration remained at this level and spread gradually over the entire tropics, finally impacting on the cold phase of the atmospheric tape recorder. However, further study is required to establish a link between the large-scale reduction in water vapor and the dehydration that occurred during the cold event in early February.