research on landfalling hurricanes utilizing ground- based mobile research platforms kevin knupp,...
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Research on Landfalling Hurricanes Utilizing Ground-
Based Mobile Research Platforms
Kevin Knupp, Dan Cecil, Walt Petersen, and Larry Carey
University of Alabama in Huntsville
Mobile facilities MIPS: Mobile Integrated Profiling System (UAH):
915 MHz wind profiler (915) X-band Profiling Radar (XPR)* 12-channel microwave profiling radiometer Ceilometer Parsivel laser disdrometer Surface instrumentation (electric field mill is an option)
MAX: Mobile Alabama X-Band dual polarization radar (UAH)* Portable Lightning Mapping Array (NASA)* Instrumented automobile (standard meteorological variables)
* under development, expected prior to hurricane season
MIPS Components
915 MHz profiler
Electric Field Mill
12-channel Microwave Profiling Radiometer
Ceilometer
2 kHz Doppler sodar
Surface instr.Satellite comm.
Not shown: 2 raingages and disdrometer
X
A vertically-pointing X-band radar (fabrication in progress) will replace the sodar
Mobile Alabma X-band (MAX) dual polarization radar
(Joint effort between UAH and Baron Services)
Initial tests conducted on 3/4/08 were successful! Now in the process of calibration.
Miscellaneous surface instruments
Parsivel disdrometerElec. Field Mill
Scientific topics• Kinematics, microphysics, and thermodynamics
of rain bands and stratiform rain areas– Mesoscale updrafts and downdrafts within stratiform– Convective transports
• Hurricane-spawned tornadoes:– Kinematics of intense rainbands– Mini-supercell kinematics
• Boundary layer characteristics– Mean wind profiles– TKE profiles– BL transition: water to land; land to water– Shear/convergence along the coast (differential drag)
• QPE• Miscellaneous targets of opportunity
Mesoscale motions within stratiform areas
• Example:– Hurricane Ivan (2004)– Relationship to cooling by evaporation
(mesoscale downdrafts) and associated intensity change around the time of landfall
• Stratiform precipitation is the majority within the TC
Vertical Velocity (contoured; e plotted below the figure)Outer stratiform and rainbands
core
2 km TREC analysis (KMOB) ground-relative winds: 2230 UTC
Microphysics of of an intense stratiform rainband
• Tropical Storm Gabrielle (2001)
• EVAD analysis of SMART-R
• Analysis of 915 vertical beam spectra– Bright-band physics (example follows)– DSD profiles and their variability
Detailed look at the bright bandAggregation occurs most of the time
Aggregation-dominant periods Breakup-dominant periods
rainrain
snowsnow
VZ
VZ=γ Breakup dominant
Reflectivity factor
€
γ=ZsnowVsnowZrainVrain
Boundary layer transition
• Tropical Storm Gabrielle (2001)
• Combined Doppler radar (SMART-R) and 915 analysis
• On-shore flow vs. off-shore flow
915 MHz profiler moments
Enhanced spectrum width (turbulence) marks the BL
Details of the wind profiles for onshore flow
a)Wind profiles have a similar shape.
b)A combination of spatial (mesoscale) and temporal variability may be present.
c) A side experiment: compare dropsonde wind profile with mean wind profiler profile and wind components within an RHI vertical plan
MAX sampling• VAD to high elevation
– Vertical motion– Hydrometeor fall speeds– Profiling of both mean
wind and TKE
• Sector scans
• RHIQuickTime™ and a
TIFF (Uncompressed) decompressorare needed to see this picture.
Doppler radars and serve as very powerful profiling systems
Generic experimental designs
• A specific design will satisfy more than one scientific objective
• Two types: – MIPS and MAX co-located– MIPS and MAX separated
a) XPR will provide high resolution vertical profiles of Doppler spectra
b) 915 will scan in normal profiling mode (wind profiles)
c) MAX: RHI scans over MIPS; VAD scans for dual Doppler and profiing
d) MIPS within dual Doppler lobee) P-3 Doppler support, in situ
microphysics, dropsondes
MIPS915
Disdrometer
XPR MAXVAD & RHI
Plan view88D
MIPS MAX
Rainband kinematics and microphysicsQPEBoundary layer (shear along the coast)
15 km
30-40 km
P-3
Dual Doppler lobe
Dual Doppler lobe
Locate within 30-40 km of 88D when possible
MIPS and MAX co-locateda) XPR will provide high resolution
turbulent fluctuationsb) 915 will scan in normal profiling
mode (wind profiles)c) MAX will conduct: (1) VAD scans to
high elevation to get W, DIV, Vh and TKE profiles; (2) RHI’s normal to the coast
MIPS915
Disdrometer
XPR MAX
EVAD
Plan view88D
MIPS MAX
Boundary layer experiment Stratiform kinematics and microphysicsQPE
P-3
Dual Doppler lobe
Dual Doppler lobe
MIPS and MAX separated by 5-10 kma) XPR will provide high resolution
vertical profiles of Doppler spectrab) 915 will scan in normal profiling
mode (wind profiles)c) MAX will run in profiling mode and
acquire RHI scans over MIPS and opposite MIPS
MIPS915
Disdrometer
XPR MAXRHI
Plan view88D
MIPSMAX
Boundary layer transitionRainband kinematicsQPE
30-40 km
P-3
Dual Doppler lobe
Dual Doppler lobe
Other considerations
• Coordination with other groups– Other radars (DOW, SMART-R)– Surface measurements (USA network, FMCP
and TTU deployments)
• Specific design depends on locations of good sites and intensity of the tropical cyclone.
Summary• Mobile ground-based instruments will provide additional
information on the physical processes associated with landfalling TC’s
• Perhaps the best targets are weaker hurricanes (<Cat 2) and tropical storms
• The measurements will also likely enhances understanding of TC physical processes over the ocean:– Microphysical processes– Mesoscale motions within the stratiform regions– Rainband kinematics– Eye/eyewall dynamics– Boundary layer characteristics