Implication of tropical lower stratospheric cooling in recent trends in tropical circulation and deep convective activity

Kunihiko Kodera, Nawo Eguchi, Rei Ueyama, Yuhji Kuroda, Chiaki Kobayashi, Beatriz Funatsu, Chantal Claud

Research output: Contribution to journalArticle

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Abstract

Large changes in tropical circulation from the mid-to-late 1990s to the present, in particular changes related to the summer monsoon and cooling of the sea surface in the equatorial eastern Pacific, are noted. The cause of such recent decadal variations in the tropics was studied using a meteorological reanalysis dataset. Cooling of the equatorial southeastern Pacific Ocean occurred in association with enhanced cross-equatorial southerlies that were associated with a strengthening of the deep ascending branch of the boreal summer Hadley circulation over the continental sector connected to stratospheric circulation. From boreal summer to winter, the anomalous convective activity center moves southward following the seasonal march to the equatorial Indian Ocean-Maritime Continent region, which strengthens the surface easterlies over the equatorial central Pacific. Accordingly, ocean surface cooling extends over the equatorial central Pacific. We suggest that the fundamental cause of the recent decadal change in the tropical troposphere and the ocean is a poleward shift of convective activity that resulted from a strengthening of extreme deep convection penetrating into the tropical tropopause layer, particularly over the African and Asian continents and adjacent oceans. We conjecture that the increase in extreme deep convection is produced by a combination of land surface warming due to increased <span classCombining double low line"inline-formula">CO2</span> and a reduction of static stability in the tropical tropopause layer due to tropical stratospheric cooling.

Original languageEnglish
Pages (from-to)2655-2669
Number of pages15
JournalAtmospheric Chemistry and Physics
Volume19
Issue number4
DOIs
Publication statusPublished - Feb 28 2019

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cooling
tropopause
sea surface
ocean
summer
convection
decadal variation
land surface
troposphere
monsoon
warming
trend
winter
continent
Indian Ocean
tropics

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

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Implication of tropical lower stratospheric cooling in recent trends in tropical circulation and deep convective activity. / Kodera, Kunihiko; Eguchi, Nawo; Ueyama, Rei; Kuroda, Yuhji; Kobayashi, Chiaki; Funatsu, Beatriz; Claud, Chantal.

In: Atmospheric Chemistry and Physics, Vol. 19, No. 4, 28.02.2019, p. 2655-2669.

Research output: Contribution to journalArticle

Kodera, Kunihiko ; Eguchi, Nawo ; Ueyama, Rei ; Kuroda, Yuhji ; Kobayashi, Chiaki ; Funatsu, Beatriz ; Claud, Chantal. / Implication of tropical lower stratospheric cooling in recent trends in tropical circulation and deep convective activity. In: Atmospheric Chemistry and Physics. 2019 ; Vol. 19, No. 4. pp. 2655-2669.
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