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Airborne Radar Observations of Atlantic Tropical Cyclones. Jennifer DeHart 09.21.11. Motivation. Andrew: $26.5 billion in damage Katrina: 1200 deaths, $108 billion in damage. Adam Willemssen. National Hurricane Center. Forecast error. National Hurricane Center.
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Airborne Radar Observations of Atlantic Tropical Cyclones Jennifer DeHart 09.21.11
Motivation Andrew: $26.5 billion in damage Katrina: 1200 deaths, $108 billion in damage Adam Willemssen National Hurricane Center
Forecast error National Hurricane Center
Basic Axisymmetric Eyewall Structure Willoughby 1998
Eyewall Asymmetries • Potential Causes • Gradient of f • Storm Track • Environmental Moisture Distribution • Vertical Shear Black et al., 2002 Braun et al., 2006 Chen et al., 2006
UL DL UR DR Black et al., 2002 modified by Houze 2009
Quantifying Vertical Structure • Deanna Hence studied satellite data from TRMM • Snapshots of radar reflectivity • 10+ years of data • Contoured by Frequency Altitude Diagrams (CFADs)
Height (km) Reflectivity (dBZ) Hence and Houze 2011
Statistics to Dynamics • Can we relate vertical structure of reflectivity to dynamics? • Aircraft Observations • 3-D reflectivity, thermodynamics, winds
GRIP • August 15th – September 30th, 2010 • Aircraft: DC-8, Global Hawk, WB-57 • Data collected: Radar, dropsondes • APR-2: Ka and Ku band
RAINEX • September – August 2005 • Hurricanes sampled • Katrina, Ophelia, Rita • P3 Tail and ELDORA Radars • X band
Hurricane Katrina – 8.28.05 • Data from 17-23Z • Rapidly Intensified to Category 5 by 12Z • Peak Intensity of 150 kt at 18Z • Weakened, made landfall as Category 3 at 11Z on 8.29.05 • Shear shifted from SE toESE with constant speedof 4 m/s. National Hurricane Center
Conclusions So Far: Katrina’s Structure vs. TRMM • Consistent with statistics • Eyewall echoes stronger and taller downshear • Low-level DL echoes have more variability than DR • Upshear quadrants dominated by weak echoes at high altitudes • Differences related to intensity/shear • Modal distributions upshear on high end
Future Plans • Extend shear analysis to other fields • Thermodynamics, vertical wind shear • Dropsondes • 3D Wind • Doppler analysis of radar data • Subdivide storm into eyewalls, concentric eyewalls, rainbands • Focus on Katrina (2005), Rita (2005) and Earl (2010)
Doppler Analysis NOAA HRD
Future Plans • Extend shear analysis to other fields • Subdivide storm into eyewalls, concentric eyewalls, rainbands • Focus on Katrina (2005), Rita (2005) and Earl (2010) • All major storms
Thank you! • Dr. Houze • Stacy Brodzik • Housemates/Grads10+Kirsten • Mesoscale Group Felipe
References • Black, M. L., J. F. Gamache, F. D. Marks, C. E. Samsury, and H. E. Willoughby, 2002: Eastern Pacific Hurricanes Jimenaof 1991 and Olivia of 1994: The effect of vertical shear on structure and intensity. Mon. Wea. Rev., 130, 2291–2312. • Braun, S. A., M. T. Montgomery, and Z. Pu, 2006: High-resolution simulation of Hurricane Bonnie (1998). Part I: The organization of eyewallvertical motion. J. Atmos. Sci., 63, 19–42. • Chen, S. Y. S., J. A. Knaff, and F. D. Marks, 2006: Effects of vertical wind shear and storm motion on tropical cyclone rainfall asymmetries deduced from TRMM. Mon. Wea. Rev., 134, 3190–3208. • Corbosiero, K. L., and J. Molinari, 2002: The effects of vertical wind shear on the distribution of convection in tropical cyclones. Mon. Wea. Rev., 130, 2110–2123. • Houze R. A., 2010: Clouds in tropical cyclones. Mon. Wea. Rev., 138, 293–344.
Effects of Shear • Azimuthal distribution of vertical motion, lightning, reflectivity and rainfall • Asymmetries maximized downshear • Inner core: left of shear • Outer bands: right of shear • Vortex tilted Braun et al., 2006 Chen et al., 2006 Corbosiero and Molinari 2002 Corbosiero and Molinari 2003
Mesovortices • Occur along inner edge of eyewall reflectivity • Instability of axisymmetric annulus of vorticity Braun et al., 2006