Houston-Induced Rainfall Anomalies

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• Houston-Induced Rainfall Anomalies
• Potential NASA Contributions to HEAT
• Dr. J. Marshall Shepherd
• Research Meteorologist and Deputy Project
  Scientist,
• Global Precipitation Measurement Mission
• NASA Goddard Space Flight Center
• Marshall.Shepherd_at_nasa.gov
• Contributions from B. Demoz, W.K. Tao, G.
  Schwemmer, B. Gentry,
• D. Whiteman, M. Manyin, A. Negri

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Mean Reference Wind Direction at 700 hPa is 230
(black arrow)

lt 1.7 mm/h




















1.7-2.2 mm/h












2.2-2.7 mm/h





















2.7-3.2 mm/h





















3.2-3.7 mm/h





















gt 3.7 mm/h











Houston Area with Coordinate System and Gauge
Locations
TRMM PR at 0.5 Degree with Coordinate System
Left Side TRMM Satellite-Indicated Anomaly in
Rainfall Rate over and downwind (NE and E) of
Houston (Shepherd et al. 2002, Shepherd and
Burian, 2003) Right Side Lightning Flash Rate
Anomaly over and downwind of Houston (Orville
et al. 2001)
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Urban-Induced Rainfall-Warm Season Phenomenon 14
Years of Data
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Average annual diurnal rainfall distributions at
gage 4311 (Urban Area) for the urbanized
(1984-1999) and pre-urban (1940-1958) time periods
Average warm season diurnal rainfall distribution
at gage 4311 (Urban Area) for the urbanized
(1984-1999) and pre-urban (1940-1958) time periods
The peak fraction of daily rainfall is more
pronounced for the 12-16 and 16-20 4-hr time
increments for the urbanized time period compared
to the pre-urban time period The warm season
experiences a greater diurnal modification
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Research Hypothesis

• The central Houston Urban District and regions to
  the Northeast through Southeast exhibit enhanced
  rainfall amounts relative to sectors west of the
  city, particularly during the warm season.
• Possible mechanisms include
• Enhanced convergence zone created by Houston
  UHI-Sea Breeze-Galveston Bay Interaction in
  subtropical environment
• Enhanced convergence due to increased surface
  roughness in urban area
• Destabilization due to UHI-thermal perturbation
  of the boundary layer.
• Enhanced aerosols in Houston urban environment
  (increase or decrease rainfall???)
• Urban Storm Splitting and Downstream merging

Urban Heat Island-Sea Breeze Convective
Generator? (Hinted at in Orville et al. 2001)
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Shepherd Work Plans HEAT

• Mesoscale modeling of Interaction of Houston
  UHI-Sea Breeze-Galveston Bay and the implications
  for rainfall modification Improve
  Representation of Model Urban Environment
  Parameters with MODIS, Airborne Lidar, and other
  Sources
• Continued Analysis of Satellite, Radar, and Rain
  Gauge Rain Fields ( Lake Charles)---Want Rates
  (e.g. tipping bucket) and Amounts
• Analysis of Hydro-meteorological response to
  Houston induced precipitation events
• Collaborations with other GSFC colleagues (Tao,
  Demoz, etc.--next slides)
• Translate Relevant Knowledge from 2004 SPRAWL
  Campaign in Atlanta (Shepherd et al. 2004, in
  press)

Urban No Urban
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What Role Do Urban Aerosols Play?
0.5 Degree Carbon Monoxide Measurements from
MOPPITT on Terra (Mean Summer)
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Conclusions (Work presented by D. Rosenfeld,
Hebrew University, at 2003 Fall AGU Urban Session)

• Hypothesize Urban Aerosol Impacts?
• Convective precipitation processes are delayed to
  greater heights in the clouds, respectively delay
  the downdraft and allowing the clouds to
  invigorate further. This causes
• In dry and unstable conditions Reduced
  precipitation due to very low precipitation
  efficiency.
• In tropical and moist subtropical conditions
  Enhanced storm vigor overcompensates the reduced
  precipitation efficiency.

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TOGACOARE High CCN produced more rainfall and
less stratifrom rain PRESTORMHigh CCN produced
slightly less rainfall and more stratiform
rain Low CCN produced rainfall at surface sooner
and more during the first 60-90 min
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PRESTORM High and Low CCN simulated very similar
cloud organization. Ice processes are more
important than TOGA COARE case - Rainfall
originates through melting of large ice species.
TOGACOARE High CCN - Simulated convection is
stronger and penetrated at higher altitude, More
small cloud ice and klarge snow/graupel.
Organization (multi-cellular - multi-cloud-updraft
s)
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NASA/GSFC - Scanning Raman Lidarhttp//ramanlidar
.gsfc.nasa.gov

• Ground-based, mobile laser remote sensing system
  that measures both Rayleigh Mie and Raman
  scattering
• Measurements
• Water vapor mixing ratio
• Aerosol backscatter, extinction, depolarization
• Boundary layer and cirrus cloud studies
• Cloud ice water content
• Particle size, number density
• Cloud liquid water content
• Droplet size and number density

On location for the International H2O Project
May-June, 2002 Oklahoma
Boundary layer water vapor (left) and aerosol
backscatter (right) evolution during the passage
of a dryline on May 22, 2002 during IHOP.
Convectively driven clouds can be seen to develop
above the water vapor updraft regions
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The Goddard Lidar Observatory for Winds (GLOW)
GLOW is a mobile direct detection Doppler lidar.
Radial wind speed is determined from the Doppler
shift of the laser signal backscattered from
molecules. Wind profiles from the ground to 20
km are possible with 100 m vertical resolution
and 1 minute sampling. An aerosol channel can be
added to provide high resolution (lt20 m), 1
minute winds in the planetary boundary layer.
GLOW mobile Doppler lidar
Tropospheric wind speed and direction can be
derived from multiple azimuth profiles
Radial wind speed measured from multiple
azimuths. IHOP experiment, May-June 2002
GLOW Products - Range resolved scans of radial
wind speed - Vertical Profiles of u,v,w
component winds wind speed and
direction Coverage 0.1 to 20 km Minimum range
resolution 40 m Accuracy 0.5 to 2
m/s Operating wavelength 355 nm
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Holographic Airborne Rotating Lidar Instrument
Experiment (HARLIE)

• 1µm Aerosol Backscatter,
• 45 elevation, azimuthal (PPI) scans
• 2-axis volume imaging scans
• 0-20km altitude, 24/7 all-weather operation
• Wide-angle visible and infrared video

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GSFC Lidar/Model Proposed Objective - 12

• Objective-1 Pollution effects
• Are CCN concentration related in any way to
  ambient aerosol loading (Via lidar backscatter,
  extinction, OD, etc)?(Ghan and Colins, 2003
  personal communication S. Ghan)
• Provide a semi-continuous vertical picture of the
  evolution of the PBL and the aerosol loading in
  pre-storm conditions.
• Compare airborne CCN measurements from HEAT to
  lidar derived aerosol parameters values

• Objective-2 UHI Dynamics
• What is the role of the Houston UHI in the
  vertical distribution of water vapor mixing
  ratio? (test Shepherd et al. It is this increase
  to Mid-trop that is important for T-Strm activity
  and trigger not a mere increase in the low level
  q).
• Do MM5-based sensitivity tests. Provide HEAT with
  Time-height profiles of wind and moisture
  profiles.
• Compare urban and non-urban moisture profiles,
  BL, Wind, and PPT.

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GSFC Lidar/Model Proposed Objective 3

• Sea breeze interaction with UHI
• Extension of Shepherd and Burian (2003).
  Specifically
• Sea/bay breeze-coastline interaction with UHI
  -induced circulations?
• enhanced convergence due to increased surface
  roughness in the urban environment
• Provide a semi-continuous picture of the
  evolution of the PBL and the aerosol in pre-storm
  conditions. Specifically,
• HARLIE Spatial evolution description of UHI-BL
  and surrounding-BL
• GLOW direct observation of the existence of
  convergence lines and the intensity (via wind
  shifts).
• SRL Any destabilization of the BL should be
  manifested in the moisture structure and lofting
  in the UHI.

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GSFC Lidar/Model Proposed Objective 4

• Objective 4 Aerosol loading and Thunderstorm
  activity
• Inflow and anvil regions are best sampled/defined
  using the water vapor mixing ratio profile
  measurements (see fig). And, the vertical
  transport of pollution (read aerosol) is best
  visualized and quantified using lidars.
• Provide wind, moisture and semi- 3D picture of
  the pollution distribution in the pre and
  post-thunderstorm environment.
• Quantify moisture flux in the inflow and
  outflow regions of the thunderstorm. Characterize
  the pre and post thunderstorm environment

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NASA Earth Science Spacecraft in OrbitRelevant
to HEAT
TRMM 11/27/97
Landsat 7 4/15/99
Aqua 5/4/02
Terra 12/18/99
Aura launching by 2005!

• TRMM
• Precipitation rates, browse imagery,
  instantaneous rainfall, monthly rainfall
• Terra Aqua (Aerosol Optical Depth, Land
  Classification, Cloud Products, Surface Albedo,
  NDVI, Carbon Monoxide, etc.)
• Landsat 4, 5, 7 ASTER
• Browse imagery, cloud cover, WBS, and shopping
  cart interface

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GSFC MODELING EFFORTS and HEAT (Led by W.K. Tap)

• Cloud-Scale Modeling
• The Goddard Cloud Ensemble (GCE) model has been
  developed and improved upon at the NASA Goddard
  Space Flight Center over the past two decades.
  It will be used here to 1) validate the proposed
  conceptual framework, 2) simulate cloud
  development with observational data sets as
  input, 3) separate and quantify the role of
  aerosols in cloud formation and development and
  4) understand and interpret observed
  relationships between aerosols and cloud
  microphysics.
• The GCE model has explicit spectral-bin
  microphysics that can be used to study
  cloud-aerosol interactions and nucleation
  scavenging of aerosols, as well as the impact of
  different concentrations and size distributions
  of aerosol particles upon cloud formation. The
  multi-component spectral bin model is based on an
  improved version of the model developed by Chen
  and Lamb (1994, 1999). A recent GCE study using a
  spectral-bin microphysical scheme on the
  evolution of the deep tropical clouds under
  "clean" (low CCN) and "dirty" (high CCN)
  conditions shows that the high CCN cloud system
  has smaller cloud droplet sizes, narrower size
  distributions, which is in general agreement with
  a finding based on TRMM satellite data
  (Rosenfeld, 2000). But the high CCN cloud
  system is more efficient in producing rainfall in
  a tropical case.

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GSFC MODELING EFFORTS and HEAT (Led by W.K. Tap)

• Mesoscale Modeling
• The Penn State/NCAR Mesoscale Model System (MM5)
  provides forcing data that better resolves the
  spatial and temporal variation of meteorological
  fields. The Goddard mesoscale modeling group has
  made several improvements to the MM5, including
  cloud microphysics, land-atmosphere-cloud
  exchange parameterization, conservation of water
  budget, mesoscale bogus vortices, precipitation,
  radiative transfer process and in-line tracer
  calculations (Tao et al, 2002 Pu et al. 2002).
• We will use the model outputs, plus a few more
  special experimental runs, to evaluate the method
  proposed. Various sensitivity tests and control
  runs will then be carried out to study how
  microphysical, thermodynamical and dynamical
  processes dictate cloud development and
  precipitation. For example, we can investigate
  the relative importance and contribution of the
  urban heat island effect and industry/urban
  elevated aerosol concentrations in the
  enhancement of precipitation observed downstream
  of Houston. To help understand the observed
  relationship between aerosol and cloud
  microphysics, we will compare results obtained in
  the coastal region where HEAT is conducted and
  the interior SGP where the ARM project is
  conducted.
• Shepherd et al. studies described in previous
  slide C. Peters-Lidar LIS work1

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The Impact of Aerosol on Cloud-Precipitation
Processes in Tropical-Oceanic and
Midlatitude-Continental Convective Systems

• TOGA COARE West Pacific Warm Pool Region (Feb
  22, 1992 - moist and less unstable) - Warm Rain
• PRESTORM Mid-USA Summer Squall Line (June 12,
  1985 - dry and unstable) - Ice and Melting