Trends in the temperature and water vapor content of the tropical lower stratosphere: Sea surface connection

Abstract

[1] The tropical lower stratosphere is an important region of the atmosphere, where strong convective activity in the underlying troposphere affects both its chemical and dynamical properties. Temperatures near the tropopause influence the input of water vapor from the troposphere and act as an indicator of the dynamical properties of the region. This paper addresses long-term trends in the temperature of the tropical lower stratosphere. Correlations with recent changes in tropical stratospheric water vapor are also noted. Special attention is given to the convectively active tropical western Pacific Ocean, where sea surface temperatures (SSTs) are among the highest in the world. The region contains several island radiosonde stations with records reliably extending over several decades. Results show only weak cooling trends occurred before the 1990s, but a strong and rapid cooling of 4°to 6°C took place in the mid-1990s and has persisted since that time. The properties of the temperature records during and following this cooling event are discussed, and a significant anticorrelation with SST anomalies in the underlying ocean is noted. The rate of ocean warming increased in the early 1990s, coinciding approximately with the mid-decade cooling event, while individual monthly anomalies in both time series are also anticorrelated. Past work has shown that cooling of the tropical lower stratosphere is a dynamical result of tropospheric convection, which in turn partially depends upon sea surface temperatures. Convection may therefore be the link between the ocean and the stratosphere, and the increased cooling may be an indication of strengthening tropical convection.Citation: Rosenlof, K. H., and G. C. Reid (2008), Trends in the temperature and water vapor content of the tropical lower stratosphere: Sea surface connection,

On the structural changes in the Brewer-Dobson circulation after 2000

“…They found a marked increase of upwelling near the tropopause level at the end of 2000 that is not evident at higher levels in the stratosphere. The cause of the increased vertical velocity in the tropics is not fully understood yet, but may be connected to a region of warmer than average tropical Pacific sea surface temperatures (Rosenlof and Reid, 2008).…”

“…They also noted that the actual temperature drop at the end of 2000 appears to be correlated with an intensified Brewer-Dobson circulation. Rosenlof and Reid (2008) estimated the anomalies in the 10 • S-10 • N zonal tropical upwelling. They calculated the anomalies by first estimating the radiative heating rates using as input constituent measurements from HALOE and temperatures from UARS/UKMO, and then calculating the residual circulation streamfunction as described by Rosenlof (1995).…”

CALIPSO, des cristaux dans le ciel

“…Corti et al, 2008) et humidifier la stratosphère en amenant très haut des cristaux de glace. Environ 50 fois plus sèche que la troposphère, la stratosphère voit son humidité diminuer depuis 1996 après avoir augmenté de près de 1 % par an pendant un demisiècle (Rosenlof et Reid, 2008). Ces variations inexpliquées ont de sérieuses implications climatiques.…”

Numerical Modeling of Climate-Chemistry Connections: Recent Developments and Future Challenges

“…So far, the reason for the residuary increase of water vapor mixing ratio for the period ending in 2000 is still unclear [54][55][56][57]. Since the end of 2000, an obvious reduction in the amount of water vapor entering the tropical stratosphere occurred [58,59], which was accompanied by a drop in tropical tropopause temperatures that occurred during a period without an increase of methane concentration [60]. The drop in tropical tropopause temperature and reduced entry of water vapor into the stratosphere at the end of 2000 appears to be connected to an enhanced rate of tropical upwelling [58,59] and associated changes in eddy wave driving [61].…”

“…Since the end of 2000, an obvious reduction in the amount of water vapor entering the tropical stratosphere occurred [58,59], which was accompanied by a drop in tropical tropopause temperatures that occurred during a period without an increase of methane concentration [60]. The drop in tropical tropopause temperature and reduced entry of water vapor into the stratosphere at the end of 2000 appears to be connected to an enhanced rate of tropical upwelling [58,59] and associated changes in eddy wave driving [61]. Moreover, there is still no agreement about the cause-effect-chain for the strengthening of tropical upwelling near the tropical tropopause; both tropical SST changes [62] and changes in high-latitude wave forcing [63] have been suggested.…”