ming cai department of earth, ocean, and atmospheric science, florida state university
DESCRIPTION
Variability of Mass Transport into Polar Stratosphere and Winter Cold Air Outbreaks in Mid- latitudes. Ming Cai Department of Earth, Ocean, and Atmospheric Science, Florida State University. Acknowledgement: Huug M. van den Dool, Y-Y Yu, R-C Ren. Grant Support: NOAA CPO: NA10OAR4310168. - PowerPoint PPT PresentationTRANSCRIPT
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Variability of Mass Transport into Polar Stratosphere and Winter Cold Air
Outbreaks in Mid-latitudes
Variability of Mass Transport into Polar Stratosphere and Winter Cold Air
Outbreaks in Mid-latitudes
Ming CaiDepartment of Earth, Ocean, and Atmospheric Science,
Florida State University
Ming CaiDepartment of Earth, Ocean, and Atmospheric Science,
Florida State University
Acknowledgement: Huug M. van den Dool, Y-Y Yu, R-C Ren
Grant Support: NOAA CPO: NA10OAR4310168
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• Prognostic component: Dynamical prediction for (extratropic) stratospheric anomalies using CFS.
Status: Zhang et al. (2013): Evaluation of CFSv2 Predictions for the Stratospheric Circulation Anomalies (see the poster on Wednesday and Thursday).
• Diagnostic component: Statistical “instantaneous” relations between stratospheric and surface temperature anomalies (downscaling)
Status: This presentation (manuscript under preparation)
• Development of prototype forecast toolsStatus: waiting for availability of DAILY forecasts or
reforecasts with lead time > 2 weeks and new funding
• Prognostic component: Dynamical prediction for (extratropic) stratospheric anomalies using CFS.
Status: Zhang et al. (2013): Evaluation of CFSv2 Predictions for the Stratospheric Circulation Anomalies (see the poster on Wednesday and Thursday).
• Diagnostic component: Statistical “instantaneous” relations between stratospheric and surface temperature anomalies (downscaling)
Status: This presentation (manuscript under preparation)
• Development of prototype forecast toolsStatus: waiting for availability of DAILY forecasts or
reforecasts with lead time > 2 weeks and new funding 22
A hybrid forecasting strategy for intraseasonal cold season climate predictions (14 - 60? days)A hybrid forecasting strategy for intraseasonal cold season climate predictions (14 - 60? days)
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Mean meridional mass circulation in winter hemisphere (Cai and Shin 2014)
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Vertical and meridional couplings by baroclinically amplifying (westward tilting)
waves (Johnson 1989)
Vertical and meridional couplings by baroclinically amplifying (westward tilting)
waves (Johnson 1989)
• A net poleward (adiabatic) transport of warm air mass aloft and a net equatorward (adiabatic) transport of cold air mass transport below.
• A net poleward (adiabatic) transport of warm air mass aloft and a net equatorward (adiabatic) transport of cold air mass transport below.
• Stronger poleward air mass transport in the warm air branch aloft is coupled with stronger air mass transport in the cold air branch near the surface and vice versa.
• Stronger poleward air mass transport in the warm air branch aloft is coupled with stronger air mass transport in the cold air branch near the surface and vice versa.
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60N
25N
90NStronger Meridional Mass Circulation near surface
Mass circulation variability and cold air outbreaks in the mid-latitudes
Warmair
Cold air
60N
25N
90NWeaker Meridional Mass Circulation near surface
WarmairCold
air
Less cold air outbreaks in mid-latitudesColdness in high latitudes
More cold air outbreaks in mid-latitudesWarmness in high latitudes 55
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Indices of mass circulation crossing the polar circleIndices of mass circulation crossing the polar circle
The results with n = 0 are representative
• WB60N: the total air mass transported into the polar region
• CB60N: the total air mass out of the polar region
WB60N and CB60N are nearly perfectly positively correlated.
WB60N is representative mass circulation crossing 60N
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The constant of 0.3085 corresponds to the fractional area of a given domain occupied by SATA exceeding/below 0.5LSD. 7777
Indices of coldness and warmnessIndices of coldness and warmness
The results with n = 0 are representative
CH(t) and CM(t): Percentage of area occupied by negative temperature anomalies below 0.5*standard_deviation (local) in high latitude zone (60 N poleward) and mid-latitudes (between 25 and 60N).
WH(t) and WM(t): Percentage of area occupied by positive temperature anomalies exceeding 0.5*standard_deviation (local) in high latitude zone (60 N poleward) and mid-latitudes (between 25 and 60N).
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• ERA Interim Daily fields of T_surf, p_surf, 3D air temperature and winds in winters from 1979-2011 (33 winters): winter = Nov. 1 – Feb. 28 (120 days)
• Anomaly field = departure of the total field from the daily annual cycle.
• 6 WB60N threshold values: (1) WB60N’ < -1.0SD (weaker circulation), (2) WB60N’ < -0.5SD (weak circulation); (3) -0.5SD WB60N’ < 0 (Neutral-); (4) 0<WB60N’< 0.5SD (Neutral+); WB60N’> 0.5SD (strong); and WB60N’> 1.0SD (Stronger)
• Unless specified otherwise, all statistics of T_surf anomalies are obtained in the period of 1-10 days after WB50N reaches one of the threshold values.
• ERA Interim Daily fields of T_surf, p_surf, 3D air temperature and winds in winters from 1979-2011 (33 winters): winter = Nov. 1 – Feb. 28 (120 days)
• Anomaly field = departure of the total field from the daily annual cycle.
• 6 WB60N threshold values: (1) WB60N’ < -1.0SD (weaker circulation), (2) WB60N’ < -0.5SD (weak circulation); (3) -0.5SD WB60N’ < 0 (Neutral-); (4) 0<WB60N’< 0.5SD (Neutral+); WB60N’> 0.5SD (strong); and WB60N’> 1.0SD (Stronger)
• Unless specified otherwise, all statistics of T_surf anomalies are obtained in the period of 1-10 days after WB50N reaches one of the threshold values. 88
Data and Analysis ProceduresData and Analysis Procedures
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9999
Lead
/Lag
Cor
rela
tions
bet
wee
n W
B60
N a
nd
war
mne
ss/c
oldn
ess
Indi
ces
Amp.
Masscirculation
High latitudes
Mid-latitudes
Coldness Warmness
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Shift of PDFs of temperature indices with WB60N Shift of PDFs of temperature indices with WB60N
Coldness
Warmness
Weaker Stronger Weaker Stronger
Weaker Stronger Weaker Stronger
Whigh Wmid-lat
Coldness
Warmness
Chigh Cmid-lat
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Strong Circulation
Weak Circulation
Map
s of
Pro
babi
lity
of
T >
0.5
LS
D o
r T
< -
0.5L
SD
T > 0.5LSD T < -0.5LSD
T < -0.5LSDT > 0.5LSD
1111
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Strong Circulation
Neutral-
Com
posi
te M
ean
Sur
face
Tem
pera
ture
Ano
mal
ies
Neutral+
Stronger Circulation
Weak Circulation
Weaker Circulation
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EOF113.1%
EO
F m
odes
of
Sur
face
Tem
pera
ture
Ano
mal
ies
EOF38.4%
EOF55.4%
EOF211.3%
EOF47.6%
EOF64.8%
Sum=50.3% 1313
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Strong Circulation
Neutral-
Con
trib
utio
n to
the
mea
n co
mpo
site
pat
tern
Neutral+
Stronger Circulation
Weak Circulation
Weaker Circulation
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15151515
Com
posi
te M
eans
of
Tim
e S
erie
s of
EO
Fs
Amp.
Masscirculation
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16161616
Con
trib
utio
n to
Var
ianc
e of
EO
Fs
Amp.
Masscirculation
EOF1
EOF5
EOF2
EOF6
EOF3 EOF4_______Strong
Circulation
_______Climatology
________Weak
Circulation
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Survey of mass circulation crossing 60N in winter of 2013-14Survey of mass circulation crossing 60N in winter of 2013-14
Stratosphere
Warm Branch
Cold Branch
climatology
1SD
-1SD
12/9/13 1/1/14 1/18/14
1717
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18181818
Com
posi
te M
eans
of
Tsu
rf d
ay 1
-7 a
fter
Amp.
Masscirculation
Mean Ts 12/10-12/16 Mean Ts 1/2-1/7
Mean Ts 1/19-1/25 Mean of the three cases
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• Variability of mass flux warm air branch is synchronized with that of cold air branch.
• Lack of warm air into polar region is accompanied by weaker equatorward advancement of cold air near the surface. As a result, the cold air mass is largely imprisoned within polar circle, responsible for general warmness in mid-latitudes and below climatology temperature in high latitudes.
• Stronger warm air into polar stratosphere is accompanied by stronger equatorward advancement of cold air near the surface, resulting in massive cold air outbreaks in mid-latitudes and warmth in high latitudes.
• EOF1 and EOF4 of T_surf correspond to warm Arctic and cold over the two major continents after a stronger mass circulation (PDF shift in response to mass circulation).
• Positive phase of EOF2 represents warm Eurasian and cold N. America or vice versa. Amplitude of both positive and negative phases of EOF2 tends to increase after a stronger mass circulation (var. increase in response to mass circulation).
• Variability of mass flux warm air branch is synchronized with that of cold air branch.
• Lack of warm air into polar region is accompanied by weaker equatorward advancement of cold air near the surface. As a result, the cold air mass is largely imprisoned within polar circle, responsible for general warmness in mid-latitudes and below climatology temperature in high latitudes.
• Stronger warm air into polar stratosphere is accompanied by stronger equatorward advancement of cold air near the surface, resulting in massive cold air outbreaks in mid-latitudes and warmth in high latitudes.
• EOF1 and EOF4 of T_surf correspond to warm Arctic and cold over the two major continents after a stronger mass circulation (PDF shift in response to mass circulation).
• Positive phase of EOF2 represents warm Eurasian and cold N. America or vice versa. Amplitude of both positive and negative phases of EOF2 tends to increase after a stronger mass circulation (var. increase in response to mass circulation). 1919
SummarySummary