Mesoscale Convective Vortices

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Mesoscale Convective Vortices
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Outline

• Background and introduction
• Definitions
• Satellite and radar examples
• Structure
• Formation of MCVs
• Mature MCV structure
• Impacts of MCVs
• Tropical cyclogenesis
• Convection-vortex interactions
• Rainfall

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courtesy C. Davis, NCAR
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MCV example 6-7 May 1985
02 CST
00 CST
05 CST
07 CST
Brandes, MWR, 1990
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MCV example 6-7 May 1985
02 CST
00 CST
05 CST
07 CST
Brandes, MWR, 1990
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MCVs a common occurrence over the U.S.
2131 UTC 14 May 1984
1531 UTC 22 May 1982
1430 UTC 1 May 1987
Bartels and Maddox, MWR, 1991
1830 UTC 8 July 1982
Menard and Fritsch, MWR, 1989
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And elsewhere over the globe
Africa
India
South America
Velasco and Fritsch 1987
Laing and Fritsch 1993a
Laing and Fritsch 1993b
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Temporal distributions of MCCs
Monthly distributions of MCCs in U.S. and South
America
Life cycles of low-latitude MCCs from 1981-1983
Velasco and Fritsch 1987
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Typical tracks of MCVs
courtesy C. Davis, NCAR
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Outline

• Background and introduction
• Definitions
• Satellite examples
• Structure
• Formation of MCVs
• Mature MCV structure
• Impacts of MCVs
• Tropical cyclogenesis
• Convection-vortex interactions
• Rainfall

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MCV formation

• Derived from circulations that develop as a
  response to diabatic heating
• If you have heating, how do you know if that
  will result in warming?
• Rossby radius of deformation, LR, describes how
  the atmosphere restores geostrophic (or gradient)
  balance once a mass or momentum perturbation is
  imposed

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Rossby radius of deformation
Regardless of source of perturbation (e.g.,
diabatic heating, momentum forcing from
upper-level trough interactions)
Mass field adjusts to wind field
If L lt LR
Example isolated thunderstorm in environment of
low background rotation initiates gravity waves
that propagate energy away from mass perturbation
Wind field adjusts to mass field
If L gt LR
Example jet streaks on synoptic scale
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Importance of having a broad area of diabatic
heating
No stratiform region
Stratiform region
reflectivity
potential vorticity
27 June 1985 squall line
11 June 1985 squall line
Hertenstein and Schubert, MWR, 1991
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Semigeostrophic model runs
No stratiform region
Stratiform region
Diabatic heating profile
Potential vorticity
Geostrophic wind
Hertenstein and Schubert, MWR, 1991
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Factors that can alter Rossby radius

• increase of background vorticity

Transverse circulation streamfunction
Warming
Vor f
Vor 6f
Schubert and Hack, JAS, 1982
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Axisymmetric primitive-equation model of vortex
response to diabatic heating
Tangential wind
Dynamic efficiency
72 h
96 h
120 h
Hack and Schubert, JAS, 1986
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Factors that can alter Rossby radius

• reduction of static stability through saturation

Vortex-following parameters from MM5 simulation
of long-lived MCV
Rogers and Fritsch, MWR, 2001
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Mature MCV Structure
Schematic diagram from 6 May 1985 MCV
Brandes, MWR, 1990
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June 3-4 1985 MCV
00 UTC 4 June 1985 IR image
WSR-57 radar images
Smull and Augustine, MWR, 1993
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June 3-4 1985 MCV
Smull and Augustine, MWR, 1993
00 UTC 4 June
geopotential height
relative vorticity
divergence
550 mb
divergence
temperature
800 mb
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June 3-4 1985 MCV
Profiles of relative vorticity and divergence at
00 UTC 4 June
apex of convective lines
trailing stratiform region
Smull and Augustine, MWR, 1993
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June 3-4 1985 MCV
Schematic diagram from 4 June 1985 MCV
Smull and Augustine, MWR, 1993
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June 23-24 1985 MCV
Schematic diagram from 24 June 1985 MCV
Johnson and Bartels 1992
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Mesoscale downdraft signature
The onion sounding
Leary and Rappaport, MWR, 1987
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Some MCVs sampled during BAMEX in 2003
(courtesy C. Davis, NCAR)
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BAMEX MCV vertical structures
(courtesy C. Davis, NCAR)
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(courtesy C. Davis, NCAR)
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Doppler-derived winds from IOP 17 MCV
(courtesy C. Davis, NCAR)
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Vertical cross section of IOP 17 MCV
(courtesy C. Davis, NCAR)
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Surface reflection of MCVs
IR image
Surface mesoanalysis
06 UTC 7 July 1982
12 UTC 7 July 1982
Menard and Fritsch, MWR, 1989
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Outline

• Background and introduction
• Definitions
• Satellite examples
• Structure
• Formation of MCVs
• Mature MCV structure
• Impacts of MCVs
• Tropical cyclogenesis
• Convection-vortex interactions
• Rainfall

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Tropical cyclogenesis
The Johnstown, PA Flood of 1977 and subsequent
tropical cyclogenesis
Bosart and Sanders, JAS, 1981
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Tropical cyclogenesis
Bosart and Sanders, JAS, 1981
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Tropical cyclogenesis
Surface mesoanalyses
00 UTC 22 July
12 UTC 21 July
00 UTC 23 July
12 UTC 22 July
Bosart and Sanders, JAS, 1981
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MCC tracks over Africa
Laing and Fritsch, MWR, 1993a
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An example of tropical cyclogenesis off Africa
Laing and Fritsch, MWR, 1993a
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MCC tracks over North and South America
Velasco and Fritsch, JGR, 1987
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Structural similarities of MCVs and post-landfall
tropical cyclones
Potential temperature and potential vorticity
cross sections
Long-lived Great Plains MCV
Hurricane Andrew after landfall
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Relationship between convective activity and
tropical cyclogenesis
Zehr 1992
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Conceptual model of stages of tropical
cyclogenesis
Zehr 1992
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Role of MCVs in tropical cyclogenesis Theories
How does vorticity, maximized in mid-levels in
MCVs, become maximized near the surface?
Rossby-Prandtl-Burger Depth scales of the
vertical penetration of wind fields induced by PV
anomalies

• Diabatic heating within an existing vortex
• Vortex axisymmetrization and vortical hot towers
• Boundary-layer warming and moistening underneath
  vortex
• Vortex mergers

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Vortex-following parameters from MM5 simulation
of long-lived MCV
Rogers and Fritsch, MWR, 2001
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Vorticity budget in isobaric coordinates
horizontal advection
vertical advection
tilting
stretching
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Terms in vorticity budget
Vertical advection
Horizontal advection
Total tendency
Tilting
Stretching
all terms x 10-10 s-2
Rogers and Fritsch, MWR, 2001
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Observations of the genesis of Tropical Storm
Dolly
P-3 Doppler-derived winds and relative vorticity
Reasor et al., JAS, 2005
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Observations of the genesis of Tropical Storm
Dolly
P-3 Doppler-derived winds and relative vorticity
Reasor et al., JAS, 2005
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3-D isosurfaces of potential vorticity evolution
in Dolly
Reasor et al., JAS, 2005
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Primitive-equation model simulation of the
genesis of Dolly
Reasor et al., JAS, 2005
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Observations of the genesis of Tropical Storm
Guillermo
LF reflectivity and flight-level winds
Doppler winds at 2 km
Virtual pot temp. at 3 km
02 Aug
04 Aug
Bister and Emanuel, MWR, 1997
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Observations of the genesis of Tropical Storm
Guillermo
Virtual pot temp at 3 km
Flight-level winds at 3 km
05 Aug
Bister and Emanuel, MWR, 1997
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Conceptual model of the genesis of Tropical Storm
Guillermo
Bister and Emanuel, MWR, 1997
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Observations of the genesis of Typhoon Irving
00 UTC 1 Aug
12 UTC 1 Aug
06 UTC 1 Aug
18 UTC 1 Aug
00 UTC 2 Aug
Ritchie and Holland, MWR, 1997
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Primitive equation model simulation of vortex
merger
Azimuthal average of relative vorticity
0 h
72 h
Ritchie and Holland, MWR, 1997
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Observations of the genesis of Tropical Storm
Gert (2005)
23 July
P-3 LF radar and flight-level winds
Surface winds from dropsondes
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Observations of the genesis of Tropical Storm
Gert (2005)
24 July
P-3 LF radar and flight-level winds
Surface winds from dropsondes
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Convection-vortex interactions
Conceptual model of isentropic lifting within a
steady balanced vortex
Raymond and Jiang, JAS, 1990
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Two long-lived MCVs
July 1977 Johnstown flood
July 1982
Fritsch et al., JAS, 1994
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Vortex size increase over time
Composites of radar echo tracks
00 UTC 15 July
00 UTC 16 July
12 UTC 17 July
12 UTC 16 July
Fritsch et al., JAS, 1994
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Conceptual model of redevelopment mechanism of
convection within MCV
Dashed isentropes Solid PV contours
Fritsch et al., JAS, 1994
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Rainfall and MCVs
(courtesy C. Davis, NCAR)
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12-hr rainfall accumulations from Johnstown flood
case
Bosart and Sanders, JAS, 1981
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Rogers and Fritsch, MWR, 2001