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Impacts of MJO convection over the Maritime Continent on eastern
China cold temperatures
Lei Song and Renguang Wu
Email: [email protected]; [email protected]
Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
How can the tropical convection over the MaritimeContinent influence cold anomalies over eastern China?
What is the difference between the process of the influenceby the convection over the tropical Indian Ocean and theMaritime Continent on the happening of cold anomaliesover eastern China ?
Questions
Introduction
Previous studies have indicated that tropical convectionover the Indian Ocean can exert influence on theoccurrence of cold anomalies over eastern China.
It is not clear if the tropical heating over the MaritimeContinent can lead to robust cold anomalies over easternChina.
Data and methodology
Summary
The anomalous convection over the MaritimeContinent can work together with the negativeAO in the occurrence of MC convection relatedcold events over eastern China.
The IO convection related cold events overeastern China are caused by both thetropospheric Rossby wave train propagatingalong the polar front and the poleward wavetrain trigged by anomalous convective heatingover the tropical Indian Ocean.
Anomalous overturning circulations caused bythe MC and IO convections lead to thedevelopment of the Siberian high.
Daily NCEP-DOE Reanalysis 2 data (Kanamitsu et al. 2002)from 1979 to 2016 during boreal winter (December-January-February)
RMM index (Wheel and Hendon 2004)
Daily AO index
30-60-day band-pass filter
Selection of the tropical Indian Ocean (IO) convection and theMaritime Continent (MC) related cold events over easternChina
Features of the MC and IO convection related
cold events
Figure Composite surface air temperature anomalies (shading, °C) from
20°N to 70°N and longwave outgoing radiation (OLR) anomalies (shading,
W/m2) between 20°S and 20°N on days (a) -12, (b) -9, (c) -6, (d) -3, (e) 0,
(f) 3, (g) 6, (h) 9 of MC (left) and IO (right) convections related
intraseasonal cold events over eastern China. The upper color bar is for
the temperature anomalies and the lower color bar is for the OLR
anomalies. Black dots indicate anomalies significant at the 95%
confidence level.
The negative AO and the convection anomalies over theMaritime Continent work together in the occurrence of MCconvection related cold events over eastern China
Figure Time evolution of
regional mean surface air
temperature anomalies (°C)
(red curve) over the region of
20°N-40°N and 100°E-120°E,
OLR anomalies (W/m2) (black
curve) over the Maritime
Continent (15°S-15°N, 110°E-
160°E) (a) and the Indian
Ocean (15°S-15°N, 50°E-100°E)
(b), the Siberian high index
(hPa) (blue curve) and the AO
index (green curve) during the
life cycle of the MC (a) and IO
(b) convection related cold
events. Dots on the curves
indicate anomalies significant
at the 95% confidence level.
This study is supported by the National Natural Science Foundation of China grants (41705063, 41530425, 41775080, 41721004, and 41475081).
Figure Composite sea level pressure anomalies (shading, hPa) and
surface wind anomalies (vector, scale on right bottom) on days (a) -
12, (b) -9, (c) -6, (d) -3, (e) 0, (f) 3, (g) 6, (h) 9 of MC (left) and IO
(right) convections related intraseasonal cold events over eastern
China. Black vectors denote wind anomalies significant at the 95%
confidence level.
Figure Composite OLR anomalies (shading, W/m2) between 20°S
and 20°N, stream function anomalies (contour, blue and red
contours indicate negative and positive anomalies, respectively,
interval: -8, -6, -4, -3, -2, -1, 1, 2, 3, 4, 6, 8 × 106 m2/s2), and wave
activity fluxes (m2/s2) (vector, scale at the right-bottom) at 300-
hPa on days (a) -12, (b) -9, (c) -6, (d) -3, (e) 0, (f) 3, (g) 6, (h) 9 of
MC (left) and IO (right) convection related intraseasonal cold
events over eastern China.
Figure Composite anomalies of vertical
circulation consisting of divergent meridional
wind (m/s) and vertical p-velocity (0.01 Pa/s)
along 110°E-140°E of MC (left) and IO (left)
convection related intraseasonal cold events
over eastern China. Only the anomalies
significant at the 95% confidence level are
plotted.
Anomalous heating over both the Maritime Continent and the tropical Indian Ocean can induce anomalous upper-level convergence and anomalous descending motion over the mid-latitudes through anomalous meridional overturning circulation, which leads to enhancement of the Siberian high.
Song, L. and R. Wu, 2019: Impacts of MJO convection over the Maritime Continent on eastern China cold temperatures. J. Climate, https://doi.org/10.1175/JCLI-D-18-0545.1