TY - JOUR
T1 - Northern Hemisphere Winter Blocking
T2 - Differing Onset Mechanisms across Regions
AU - Miller, Douglas E.
AU - Wang, Zhuo
N1 - Funding Information:
This work is supported by the National Oceanic and Atmospheric Administration (NOAA) Grant NA16OAR4310080 and NA18OAR4310271. We acknowledge the NCAR Computational and Information Systems Laboratory (CISL) for providing computing resources. We thank the three anonymous reviewers for enhancing the quality of this manuscript.
Funding Information:
Acknowledgments. This work is supported by the National Oceanic and Atmospheric Administration (NOAA) Grant NA16OAR4310080 and NA18OAR4310271. We acknowledge the NCAR Computational and Information Systems Laboratory (CISL) for providing computing resources. We thank the three anonymous reviewers for enhancing the quality of this manuscript.
Publisher Copyright:
© 2022 American Meteorological Society.
PY - 2022
Y1 - 2022
N2 - Atmospheric blocking is a prolific producer of extreme weather with significant socioeconomic impacts. Different physical mechanisms for blocking onset have been proposed and are generally focused on two sectors: the Eurasian and the North Pacific. Here, we objectively separate blocking into four regions and investigate how the blocking onset mechanisms vary from one region to another, focusing on three factors: scale interactions between three frequency bands, Rossby wave breaking (RWB), and diabatic heating. Atlantic blocks are dominated by the low-frequency flow evolution that resembles the negative phase of the North Atlantic Oscillation and are influenced by cyclonic RWB toward the western edge of the anticyclone. Europe blocks are influenced by high-frequency, traveling waves across the Atlantic Ocean and develop rapidly, mainly attributed to strong anticyclonic RWB and interaction between high- and intermediate-frequency flow components. Asian blocks are fixated within a stationary wave train that spans upstream to the western Atlantic Ocean and do not have strong potential vorticity or RWB features. The Pacific blocks are mainly influenced by an intermediate-frequency retrograding wave train, while a low-frequency component resembling the Pacific–North American pattern is evident. The Pacific blocks also contain precursor signals in the stratosphere. Backward trajectory analysis revealed that 35%–45% of parcels initialized within the Atlantic, Europe, and Pacific blocking anticyclones experience heating and ascent, while adiabatic processes dominate Asian blocking. Overall, our analysis demonstrates the importance of decomposing the flow into three frequency bands and illustrates different blocking onset mechanisms over four sectors.
AB - Atmospheric blocking is a prolific producer of extreme weather with significant socioeconomic impacts. Different physical mechanisms for blocking onset have been proposed and are generally focused on two sectors: the Eurasian and the North Pacific. Here, we objectively separate blocking into four regions and investigate how the blocking onset mechanisms vary from one region to another, focusing on three factors: scale interactions between three frequency bands, Rossby wave breaking (RWB), and diabatic heating. Atlantic blocks are dominated by the low-frequency flow evolution that resembles the negative phase of the North Atlantic Oscillation and are influenced by cyclonic RWB toward the western edge of the anticyclone. Europe blocks are influenced by high-frequency, traveling waves across the Atlantic Ocean and develop rapidly, mainly attributed to strong anticyclonic RWB and interaction between high- and intermediate-frequency flow components. Asian blocks are fixated within a stationary wave train that spans upstream to the western Atlantic Ocean and do not have strong potential vorticity or RWB features. The Pacific blocks are mainly influenced by an intermediate-frequency retrograding wave train, while a low-frequency component resembling the Pacific–North American pattern is evident. The Pacific blocks also contain precursor signals in the stratosphere. Backward trajectory analysis revealed that 35%–45% of parcels initialized within the Atlantic, Europe, and Pacific blocking anticyclones experience heating and ascent, while adiabatic processes dominate Asian blocking. Overall, our analysis demonstrates the importance of decomposing the flow into three frequency bands and illustrates different blocking onset mechanisms over four sectors.
KW - Anticyclones
KW - Blocking
KW - Dynamics
KW - Northern Hemisphere
KW - Winter/cool season
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U2 - 10.1175/JAS-D-21-0104.1
DO - 10.1175/JAS-D-21-0104.1
M3 - Article
AN - SCOPUS:85128668147
SN - 0022-4928
VL - 79
SP - 1291
EP - 1309
JO - Journal of the Atmospheric Sciences
JF - Journal of the Atmospheric Sciences
IS - 5
ER -