Study of the stratospheric sudden warming impact on the water vapor and clouds in the tropical troposphere

The impact of the stratospheric circulation on the tropical troposphere during the stratospheric sudden warming event has been suggested by previous studies [Kodera and Yamada, 2004; Eguchi and Kodera, 2007; Eguchi and Kodera, 2010; Kodera et al, 2011]. A common feature of the tropical tropospheric impact of the sudden warmings event is an increase of the upwelling in the equatorial region. The response can differ according to the different characteristics of the convective active regions, which is especially apparent in the Tropical Tropopause Layer (TTL). Here, we focus a sudden change in the tropical circulation observed during a record breaking stratospheric sudden warming event in mid-January 2009. Tropical temperature decreased in the stratosphere in response to a strengthening of the mean meridional circulation associated with the stratospheric sudden warming. At the same time, drastic change is observed in the TTL: the cirrus occurred frequently at the south side of the equator where the temperature became low. The spatial distributions of water vapor exhibits smaller scale variation, suggesting that the convective process becomes important after the onset. Tropical convection was active over the maritime continent before the sudden warming. After the onset, the convection becomes active at the southern tropics particularly over Indian Ocean and the Africa and South America continents. The convections excited over the Indian Ocean then moved eastward as Madden-Julian Oscillation. Large-scale tropospheric circulation also changed drastically from an east-west to a north-south type or from Walker- to Hadley circulation type.