mesoscale convective vortices (mcvs) chris davis (ncar essl/mmm and ral) stan trier (ncar essl/mmm)...
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Mesoscale Convective Vortices (MCVs)
Chris Davis (NCAR ESSL/MMM and RAL) Stan Trier (NCAR ESSL/MMM)
Boulder, Colorado
60-h Radar Composite Animation (00 UTC 11 June – 12 UTC 13 June, 2003)
500 km
Acknowledgements: Morris Weisman, EOL staff
Long-time Behavior of MCSs
• Convection develops (often in response to synoptic-scale of mesoscale features)
• Convection organizes (internally or externally)• Convection leads to modified or new balanced
features (vortices)• Balanced features produce new convection
Long-time Behavior of MCSs
(twice)
ˆ ( )g
dvfk u u
dt
L
H
HWarm
Cool
Cool
Diabatic Heating• Deep convection (heating)• Mesoscale updraft (heating)• Melting and evaporation (cooling)• Radiation (cooling)• Gradient along vorticity vector determines PV
generation rate
• Dependencies in models– Cumulus parameterization– Cloud physics (and radiative interaction)– Surface-atmosphere coupling (heating versus
moistening)
MCV Induced Lifting and Destabilization
Fritcsh et al. 1994, MWR
Raymond and Jiang (JAS 1990) Conceptual Model of Isentropic Lifting within a Steady Balanced Vortex (e.g., MCV)
Mature MCVs from the Bow Echo and MCV Experiment (BAMEX)
20 May – 6 July 2003
• May 24: remnant of severe bow echo• June 2: hybrid with cyclone wave• June 5: remnant of large MCS• June 11: Multi-day MCS/MCV system, late
became frontal cyclone• June 24: MCV from multi-MCS complex
• Data: dropsondes, MGLASS, profilers (storm relative and time-space corrected)
Precursor Conditions
500 hPa 850 hPa wind
IOP 1: 00 UTC 24 May
IOP 4: 00 UTC 2 June IOP 5: 00 UTC 5 June
IOP 8: 00 UTC 11 June
IOP 15: 00 UTC 29 June
MCS MCV
MCS Precursors to MCVs
IOP 1, 24 May
IOP 4, 2 June IOP 15, 29 June
1500 UTC
0600 UTC
IOP 5, 5 June1100 UTC
IOP 8, 11 June0600 UTC
0500 UTC
150 km
= Primary Vortex
IOP 1
IOP 5
IOP 8
IOP 15
Reflectivity, Temperature, and System-relative
Winds
IOP 4
= new convection triggered
No CAPE
No CAPE Localized CAPE Widespread CAPE
Widespread CAPE
Analysis Method• Dropsonde, profiler and MGLASS
• Composited to common reference time (const MCV motion assumed)
• Divergence and vorticity analyzed assuming linear variation along sides
• Restrictions on minimum angle, area; maximum side length and area
• Overlapping triangles used to assess “confidence” ()
•25-km analysis grid
MCV Vertical Structure
Shading=low confidence
Red line=vortex axis
Contour: 5x10-5 s-1
MCV Vertical Structure
v’
v’
Wind Profiles (averages of quadrant means)
Balance within MCVs
Procedure:
via nonlinear balance
Tv (hydrostatic)
Tv profile at sounding locations
Quadrant averages (r<Rmax; r≥Rmax)
Subtract mean outer profile from inner profile: T'v
Pre
ssu
re (
hP
a)
T'v (K)
Obs
Bal
IOPs 1 and 8 have best data coverage
00 UTC 6 July
12 UTC 6 JulyEta 500 mb , wind analysis
Airborne Doppler Domain
06 UTC 6 July
Radar Composite
Evolution of Mid-tropospheric Vortex
12 UTC 6 July
00 UTC 7 July
18 UTC 6 July
Diabatic Rossby Vortices
Conzemius et al (2007, JAS) – idealized MM5 simulations in weakly sheared flow: shown are relative vorticity and potential temperature
T=120 h (just prior to deep convection) T=173.6 h (after 2 days of convection)
Observed MCV centers
Summary4-8 km deep, centered between 500 and 600 mb
V~10 m/s
Nearly in gradient balance (Ro~1)
Tilts of vortices consistent with vertical shear
Temperature anomalies weak, even below MCV center
Deep vortices may require cyclonic precursor
Implications for rainfall organization, see S. Trier’s talk on Friday