Impact of tibetan plateau snow cover on tropical cyclogenesis via the Madden-Julian oscillation during the following boreal summer
Por:
Han, Xiang, Zhao, Haikun, Klotzbach, Philip J., Wu, Liguang, Raga, Graciela B.
Publicada:
1 may 2021
Ahead of Print:
1 ene 2021
Categoría:
Atmospheric science
Resumen:
This study investigates the role of the interannual variation of boreal
winter (December-February) snow cover over the Tibetan Plateau (TPSC) in
modulating the relationship between the Madden Julian Oscillation (MJO)
and tropical cyclogenesis over the western North Pacific (WNP) during
the following boreal summer (June-October). During the boreal summer
following a high snow cover anomaly (SCA), MJO-associated convection
tends to be confined to the west of 140 degrees E, coinciding with more
frequent tropical cyclone (TC) activity in this region. By contrast,
there tends to be stronger MJO-associated convection extending farther
east during years following low SCA. The MJO-associated convection
extends to similar to 160 degrees E over the WNP basin with a peak
around 140 degrees E. Thus, more TCs form farther east in the WNP in
these years. We use composite analyses of large-scale environmental
factors to demonstrate that low-level relative vorticity is one of the
most important factors in controlling TCs in response to the change of
MJO-associated convection between years with high SCA and low SCA.
Meanwhile, eddy kinetic energy variations associated with the MJO are
consistent with changes in tropical cyclogenesis over the WNP basin
between years with high and low SCA. The Asian summer monsoon plays an
important role in linking prior winter TPSC to MJO activity in the
following summer. During high-SCA years, increased snow cover results in
positive soil moisture anomalies and cooling over the Tibetan Plateau,
thus weakening the following summer Asian monsoon and weakening
associated water vapor advection, while the opposite chain of events
occurs in low-SCA years. These changes in high-SCA years are favorable
for MJO propagation and are unfavorable for MJO propagation in low-SCA
years. Meanwhile, the interannual variation of SCA exerts a significant
impact on the upper-tropospheric circulation and thus changes in
vertical wind shear. During high-SCA years, there are anomalous
upper-level easterlies in the Indian Ocean and upper-level westerlies in
the Pacific Ocean, which result in anomalous easterly wind shear in the
Indian Ocean and anomalous westerly shear in the Pacific Ocean. The
opposite shear pattern arises in low-SCA years. In addition to changes
in wind shear, the background vertical motion associated with changes in
TPSC may also be partly responsible for changes in MJO activity.
Filiaciones:
Han, Xiang:
Nanjing Univ Informat Sci & Technol, Collaborat Innovat Ctr Forecast & Evaluat Meteoro, Minist Educ, Key Lab Meteorol Disaster, Nanjing, Peoples R China
Chinese Acad Sci, South China Sea Inst Oceanol, State Key Lab Trop Oceanog, Guangzhou, Peoples R China
Zhao, Haikun:
Nanjing Univ Informat Sci & Technol, Joint Int Res Lab Climate & Environm Change ILCEC, Collaborat Innovat Ctr Forecast & Evaluat Meteoro, Key Lab Meteorol Disaster,Minist Educ KLME,Pacifi, Nanjing 210044, Peoples R China
Klotzbach, Philip J.:
Colorado State Univ, Dept Atmospher Sci, Ft Collins, CO 80523 USA
Wu, Liguang:
Fudan Univ, Dept Atmospher & Ocean Sci, Shanghai, Peoples R China
Fudan Univ, Inst Atmospher Sci, Shanghai, Peoples R China
Raga, Graciela B.:
Univ Nacl Autonoma Mexico, Ctr Ciencias Atmosfera, Mexico City, DF, Mexico
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