Influences of boreal summer intraseasonal oscillation on heat waves in monsoon Asia

Influences of boreal summer intraseasonal oscillation on heat waves in monsoon Asia AbstractBy analyzing observation-based high-resolution surface air temperature (SAT) data over the Asian monsoon region for 1981-2007, modulation of boreal summer intraseasonal oscillation (BSISO) on heat waves (HW) occurrence is examined. Strong SAT variability and high probability of HW occurrence on intraseasonal timescale are found consistently in the densely-populated regions over central India (CI), Yangtze River valley (YR) in China, Japan (JP) and Korean Peninsula (KP). The two distinct BSISO modes (e.g., 30–60-day BSISO1 and 10–30-day BSISO2) show different contributions to HW occurrence in monsoon Asia. A significant increase in HW occurrence over CI (YR) is observed during phases 2–3 (8–1) of BSISO2 when the 10–30-day anticyclonic and descending anomaly induces enhanced upward thermal heating and sensible heat flux (warm advection) around the areas. On the other hand, the northeastward propagating BSISO1 is closely connected to the increased HW probability over JP and KP. During phases 7–8 of BSISO1, the 30–60-day subsidence along with the low-level anticyclonic anomaly moves into Northeast Asia, leading to enhanced diabatic (adiabatic) warming near surface in JP (KP). Analysis of a three-dimensional streamfunction tendency equation indicates that diabatic cooling induced by the BSISO-related suppressed convections is the main forcing term of anticyclonic anomaly although it is largely offset by the decreased static stability associated with adiabatic warming. The BSISO-related vorticity advection causes anticyclonic (cyclonic) tendency to the northwestern (southeastern) part of the center of anticyclonic anomaly, favoring northwestward development of the BSISO anomalous circulations that provide a favorable condition for HW occurrence over the western Pacific-East Asia sector. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Climate American Meteorological Society

Influences of boreal summer intraseasonal oscillation on heat waves in monsoon Asia

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1520-0442
D.O.I.
10.1175/JCLI-D-16-0505.1
Publisher site
See Article on Publisher Site

Abstract

AbstractBy analyzing observation-based high-resolution surface air temperature (SAT) data over the Asian monsoon region for 1981-2007, modulation of boreal summer intraseasonal oscillation (BSISO) on heat waves (HW) occurrence is examined. Strong SAT variability and high probability of HW occurrence on intraseasonal timescale are found consistently in the densely-populated regions over central India (CI), Yangtze River valley (YR) in China, Japan (JP) and Korean Peninsula (KP). The two distinct BSISO modes (e.g., 30–60-day BSISO1 and 10–30-day BSISO2) show different contributions to HW occurrence in monsoon Asia. A significant increase in HW occurrence over CI (YR) is observed during phases 2–3 (8–1) of BSISO2 when the 10–30-day anticyclonic and descending anomaly induces enhanced upward thermal heating and sensible heat flux (warm advection) around the areas. On the other hand, the northeastward propagating BSISO1 is closely connected to the increased HW probability over JP and KP. During phases 7–8 of BSISO1, the 30–60-day subsidence along with the low-level anticyclonic anomaly moves into Northeast Asia, leading to enhanced diabatic (adiabatic) warming near surface in JP (KP). Analysis of a three-dimensional streamfunction tendency equation indicates that diabatic cooling induced by the BSISO-related suppressed convections is the main forcing term of anticyclonic anomaly although it is largely offset by the decreased static stability associated with adiabatic warming. The BSISO-related vorticity advection causes anticyclonic (cyclonic) tendency to the northwestern (southeastern) part of the center of anticyclonic anomaly, favoring northwestward development of the BSISO anomalous circulations that provide a favorable condition for HW occurrence over the western Pacific-East Asia sector.

Journal

Journal of ClimateAmerican Meteorological Society

Published: Jun 26, 2017

References

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