composite analyses of tropical convective systems prior to tropical cyclogenesis
DESCRIPTION
Composite Analyses of Tropical Convective Systems Prior to Tropical Cyclogenesis. Chip Helms Jason Dunion Lance Bosart University at Albany Cyclone Research Group 4 November 2013. Funding through NSF AGS-0849491 and NASA HSRP #NNX12AK63G. Motivatio n. - PowerPoint PPT PresentationTRANSCRIPT
4 Nov. 2013Future WorkResultsMethodologyMotivation
Chip Helms Composite Analyses of Tropical Convective Systems 1
Composite Analyses of Tropical Convective Systems Prior to
Tropical Cyclogenesis
Chip HelmsJason DunionLance Bosart
University at Albany
Cyclone Research Group4 November 2013
Funding through NSF AGS-0849491 and NASA HSRP #NNX12AK63G
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Chip Helms Composite Analyses of Tropical Convective Systems 2
Motivation
Motivating Questions and Working Hypotheses
• Why do some marginal systems develop despite the presence of inhibiting factors?
• Why do viable systems fail to develop?
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Chip Helms Composite Analyses of Tropical Convective Systems 3
Relating Vorticity and Buoyancy
Goal: Include thermodynamics in vorticity tendency without invoking thermal wind balance.
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Motivation
Genesis Process Hypothesis
Tropopause
500 hPa
SurfaceWave Axis
Convergenceand ascentalong wave
Cooling (Melting, Evaporation, Radiation?)
Concentration of background vorticity produces low-level vortex
Deep convectionforms along
convergence line
Deep convection fuels formation of stratiform
sheild downshear
+PV, +
Latent Heat Release
Radiative Cooling/HeatingShear
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Motivation
Genesis Process Hypothesis
Tropopause
500 hPa
Surface
− 𝑫𝟐
𝑫𝒕𝟐Mid-Level Vortex
+/-
Low-Level Vortex
Shear
− 𝑫𝟐
𝑫𝒕𝟐-B +B− 𝑫
𝟐𝑫𝒕𝟐
− 𝑫𝟐
𝑫𝒕𝟐+B
+y+x
+𝑫𝟐𝑫𝒕𝟐
− 𝜕𝑣𝜕 𝑧𝜕𝐵𝜕 𝑥 +
𝜕𝑢𝜕 𝑧
𝜕𝐵𝜕 𝑦 +(+ 𝑓 ) 𝜕𝐵𝜕 𝑧
− 𝑫𝟐
𝑫𝒕𝟐
Night: -B / Day: +B
-/?− 𝑫
𝟐𝑫𝒕𝟐
− 𝑫𝟐
𝑫𝒕𝟐− 𝑫
𝟐𝑫𝒕𝟐
+/- +/-+/-
− 𝑫𝟐
𝑫𝒕𝟐
− 𝑫𝟐
𝑫𝒕𝟐
− 𝑫𝟐
𝑫𝒕𝟐− 𝑫𝟐𝑫𝒕𝟐
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Creating Subset Composites• Metrics represent system evolution
– System structure– Near-system environment
• Metrics define a phase space
Methodology
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Vortex Tracker• Based on NCEP vortex tracker (Marchok
2002)– Multiple fields to generate center fix– Link fixes using steering flow and previous
motion
• Currently using Climate Forecast System Reanalysis (CFSR)
Methodology
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Vortex Tracker - Variables
100% = non-divergent cyclonic0% = irrotational
-100% = non-divergent anticyclonic
Methodology
NCEP vortex tracker Pre-genesis vortex trackerVariable Levels Variable Levels
Vorticity 850, 700 hPa Tangential Velocity 850 hPa
Pressure Surface MSLP gradient Surface
Pressure gradient Surface Vortex Idealization 850, 700, 500 hPa
Geo. height 850, 700 hPa
Wind 850, 700 hPa
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Idealized ExampleMethodology
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Merging CirculationsNon-developing SystemCape Verde TCs ????
Track ExamplesMethodology
850 hPa Vortex Idealization
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Phase Space
2010 Atlantic Hurricane Season
Pre-genesis and Non-developing
Results
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Future Data Sources
• Reanalyses– ERA-Interim, NCEP/NCAR, MERRA
• Operational– GFS, ECMWF, CMC
• Observational– CIMSS satellite winds, dropsondes, satellites
Future Work
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Analysis Goals• Examine differences between dev/non-dev in variety
of composites– Kinematic, dynamic, and thermodynamic fields
• Examine how parameters vary with phase space location– SST, OHC, MPI (Emanuel 1988),
ventilation index (Tang and Emanuel 2012), genesis pathway (McTaggart-Cowan et al. 2008)
• Will allow us to explore why viable systems sometimes fail to develop and marginal systems sometimes succeed
Future Work
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