1. The Houston Environmental Aerosol Thunderstorm (HEAT) Project: 2005
Richard (Dick) Orville
with John Nielsen-Gammon, Renyi Zhang, Don Collins and Amy Stuart
Dept. of Atmospheric Sciences
Texas A&M University
College Station, TX
March 15, 2004
-Background picture taken by Stephen Phillips (TAMU). This CG lightning flash was over College Station (October 2000).

2. Introduction: Houston, the Lightning Capital of Texas
National Lightning Detection Network (NLDN) analyzed climatological data (Orville et al. 2001) have indicated a significant CG lightning enhancement (60%) over and near the city of Houston, Texas (pop. 5 million).
The hypothesized causes include:
The urban heat island effect enhancing convection
The petroleum refining operations (49% of the USA capacity)
The sea breeze circulation system and increased CCN/IN concentrations from the multitude of pollution sources in the Houston region.

3. Intracloud Lightning

4. Cloud-to-ground lightning

5. Data and Methods The National Lightning Detection Network (NLDN)
Detects only CG flashes
106 sensors (DF/TOA) across the U. S.
Since 1994, the resolution is 500 m, and detection efficiency is ~85%
Created and analyzed lightning flash density maps for different season and time periods
-NLDN sensor locations [Orville and Huffines, 2001].
-The DF system (lower left) uses the ratio of the signals induced in two orthogonal loops to determine lightning ground strike location. Three DF’s provide best accuracy.
-In the TOA system (lower right), the intersection of the time difference (of arrival of signal between stations) loci determines the strike location. Four stations are required for best accuracy.
-Spacing between sensors varies (Houston 250 km).

6. -All maps shown are at 5 km resolution.
-Texas CG lightning distribution shows a distinct southwest-northeast increase in values. This agrees well with the climatological rainfall distribution.
-Note relative maxima (> 5-7 flashes km-2) over SW OK, and the Houston & Lake Charles areas.

7. E=60%
-Most of the enhancement was over the city and industrial areas (3-3.5 flashes km-2 – highest max. values of any seasonal time period).

8. Sea – Heat Island Breeze
From MM5 simulations [Orville et al., 2001], enhanced low-level convergence does not occur without the city.
The main effect is increased thunderstorm initiation directly over the city.
Greater warm season daytime enhancement gives support for this.
-This figure shows the result of a numerical simulation which included the effects of the city and bay/gulf waters. The temperature is contoured; black arrows = sea breeze; red arrows = urban breeze.
-Stronger lightning enhancement during the warm season afternoons (warm season, afternoons – stronger circulations and convergence) gives some support for these factors.
-Easterly wind shown on the east side of Houston also concentrates more pollutants over the city.

9. Pollution
Houston atmosphere is polluted due to the oil refineries and automobiles
Hypothesis: Effect of CCN concentrations on lightning
Higher CCN
Mean drop radius decreased
More small supercooled droplets above 0o C level
Greater volume of mixed phase (ice and supercooled water)
More charge separation
More lightning!
-Dependence on CCN distributions:
-if have many CCN, means that the available liquid water in the environment must be shared among many particles and will result in smaller droplets. These small droplets do not coalesce and fall as rain very easily, and hence can be carried above the freezing height (below 0ºC) in a cloud’s updraft. This acts to increase the amount of supercooled liquid water available in the cloud. Supercooled water is one of the key ingredients needed for the charge separation process. Hence, if a storm ingests many CCN, it may become more electrically active! This was named the Rosenfeld hypothesis, after the scientist who recently proposed it.
-Need to measure CCN, droplet distributions over Houston to test this hypothesis!
-Also, greater summer enhancement and winter enhancement location is supportive of this hypothesis (pollution concentrations higher in summer).

10. Proposed Research
Houston has a significant lightning enhancement during all seasons, but highest in the summer.
Field experiments (CCN/IN, cloud droplet size distributions over Houston), and modeling (separate effects from city, bay, and pollution) should help in determining the relative importance of each factor.
HEAT Project is needed with measurements of total lightning (both cloud-to-ground and intracloud lightning), polarimetric radars, and aircraft sampling of clouds.
-Causes = urban heat island/sea breeze system, pollution, thermodynamic energy, and frictional effects The latter two were not discussed here as no evidence was found to support them. Thermodynamic energy may be more/less over a city compared to background areas.

11. Houston Environmental Aerosol Thunderstorm (HEAT) Project 2005
Houston Environmental Aerosol Thunderstorm Project (HEAT)
                    DRAFT                   
Scientific Overview & Operational Plan for HEAT-2004/2005
Table of Contents:     [ Download PDF ]
Abstract 1. Introduction     1.1 Primary Goals of HEAT           Pollution Effects           Urban Heat Island Dynamics           The Effect of a Complex Coastline           Atmospheric Chemistry           Lightning 2. Project Overview 3. Scientific Objectives     3.1 Pollution Effects     3.2 Urban Heat Island Dynamics     3.3 The Effect of a Complex Coastline     3.4 Atmospheric Chemistry     3.5 Lightning 4. Operation Plan: Daily Schedule and Conduct of Operations     4.1 Briefings     4.2 Conduct of Field Operations and the Operations Center           Operations Center Team           Chief Coordinators and Representatives for the                    Major Components and Observing Systems     4.3 Operations Center Layout   

12. Primary Goals of the HEAT Project
Evaluate the pollution effects (small aerosols) and precipitation suppression
Evaluate the urban heat island (UHI) dynamics (e.g. Huff and Changnon 1972)
Evaluate the effect of a complex coastline
Low level convergence
Interaction of sea breeze with UHI
Effect of sea breeze on convection intensity

13. Atmospheric Chemistry:
Thunderstorms are efficient in transporting planetary boundary air to higher levels. Flux of certain atmospheric constituents (CO, CO2, O3, HC, NOx and aerosols) will be measured by aircraft observations into and out of storms.
Lightning: Total lightning (IC and CG) will be measured. Why a 58% enhancement (CG) over urban area?

14. Scientific objectives
Lightning
Measure the total lightning over Houston
Determine the lightning polarity over Houston
Obtain thunderstorm electric field profiles over Houston and over non-urban environments.

15. Cloud microphysics Objective M1: Mixed-phase region
(cont)
Cloud microphysics
Objective M1: Mixed-phase region
Objective M2: Cloud droplet spectra
Objective M3: Precipitation drop-size distributions
Objective M4: Pollution effects in the early-storm stages

16. Urban heat island dynamics
(cont)
Urban heat island dynamics
Objective U1: Urban heat island thermodynamics
Objective U2: Urban wind modification
Objective U3: Urban updraft enhancement
Objective U4: Urban effects on convective storm mergers and lightning production

17. The effect of a complex coastline
(cont)
The effect of a complex coastline
Objective C1: Sea breeze modification: low level convergence field associated with a complex coastline and its effects on convective initiation
Objective C2: Sea breeze interaction with the Houston heat island
Objective C3: Intensity of sea breeze convection

18. Atmospheric chemistry
(cont)
Atmospheric chemistry
Objective A1: NOx production by lightning
Objective A2: Transport and fate of pollutants in thunderstorms
Objective A3: Effect of urban thunderstorms on upper tropospheric chemistry

19. Project Overview: Approximate locations of CSU-CHILL polarimetric radar, S-Pol polarimetric radar, NWS WSR-88D radar, upper air sites, TAOS sites, and wind profiler sites. The Houston metro area is outlined in red.

20. Total (CG plus IC) Lightning and Polarimetric Radar Measurements

21. Note that the sensor spacing is closer in the middle of the network and farther apart on the outside of Houston.
Green stars = airports with the exception of the green star in the center of Houston.

22. Radar Systems NCAR S-Pol radar CSU-CHILL Research radar
NWS WSR-88D Operational weather radar
Texas A&M, NSSL, OU, Texas Tech mobile C- band radars (2)

23. Aircraft Systems University of Wyoming King Air WMI Lear Jet
North Dakota Citation
Airborne chemistry instrumentation (Baylor)
HIAPER

24. Balloon Sounding Units
MGLASS Units (2)
Mobile electrical sounding units (2)
TAOS units
Upper air sounding station

25. Lightning Detection
National Lightning Detection Network (NLDN) for CG lightning (in place since 1989)
Lightning Detection and Ranging (LDAR II) network (Funded September 2003; NSF) to detect total lightning (IC and CG)

26. Conclusions Field observing systems in HEAT (2005) will include
Radar systems
Surface mesonet systems
Aircraft
Balloon sounding units
Lightning detection and mapping arrays
All lightning discharges are detected
Cloud-to-ground
Intracloud
Up to several thousand locations for an individual flash
Location accuracy of 50 to 100 meters
Charge layers can be identified
Flash type can be identified

27. The Beginning!

28. Time of Arrival Lightning Mapping System (LDAR II)
Radiation occurs at time t, at location (x, y, z)
Measure time RF pulse arrives at multiple stations
Determine position and time of source
Locate hundreds to thousands of sources per flash
Radiation arrives at station i at time ti, location (xi, yi, zi)

29. Layout of LDAR II Plots Altitude vs. Time (Color Coded)
Number of LDAR II Points vs. Height
Altitude vs. x
Plan View
(x vs. y)
Altitude vs. y

30. LDAR II Image of an airplane avoiding
thunderstorms
20 Minutes of Data
Plane Flying
400 MPH at
30,000 ft

31. Intra-Cloud Lightning

32. Cloud-to-Ground
Lightning

35. LDAR-II Antenna – FAA Facility in Texas
Ground Mount

37. LDAR-II Antenna -Roof of DFWAirport

39. Note that the sensor spacing is closer in the middle of the network and farther apart on the outside of Houston.
Green stars = airports with the exception of the green star in the center of Houston.

40. 3D/2D Lightning Mapping - LDAR II
Most advanced lightning detection capability in the world
In 1997, GAI and NASA entered into a technology transfer agreement (NASA had been using VHF lightning detection for many years)
In 1999, GAI and NMT began a collaboration that lead to the future commercialization of LDAR II (NMT had developed a similar VHF lightning detection sensor with slightly different technology)
3-Dimensional mapping within network perimeter
meter or better location accuracy
Greater than 95% expected flash detection efficiency
Reduces to 2-dimensional mapping well outside of the network (~150 km)
2 km or better location accuracy
Greater than 90% expected flash detection efficiency

41. Conclusions Field observing systems in HEAT (2005) will include
Radar systems
Surface mesonet systems
Aircraft
Balloon sounding units
Lightning detection and mapping arrays
All lightning discharges are detected
Cloud-to-ground
Intracloud
Up to several thousand locations for an individual flash
Location accuracy of 50 to 100 meters
Charge layers can be identified
Flash type can be identified

42. The Beginning!

44. Lightning sensor for cloud-to-ground lightning
Installation for experimental use at Texas A&M

45. Option I: No Storm/Before Storm Initiation/Before Storm Enters Domain (including Sea Breeze)
Goals: Document ambient pollution levels, vertical atmospheric thermodynamic structure and E-fields
Instruments: King air, T-28, MGLASS, mobile electrical sounding units
Harris
County
Sea Breeze
Front

46. Option II: Isolated Urban Storm
Goals: Document storm cloud droplet spectra, ice nuclei content, and amount of supercooled water; E-field measurements inside/outside of storm
Instruments: T-28, mobile electrical sounding units

47. Option III: Isolated Environmental and Urban Storms in Coexistence
Goals: Document cloud droplet spectra, ice nuclei content, amount of supercooled water, and E-fields in/near convective cores for an urban and one environmental storm.
Instruments: T-28, mobile electrical sounding units
Galveston
Bay
Harris
County N

48. Option IV: Storm System Transgressing Study Area (i.e., squall line)
Goals: Document cloud droplet spectra, ice nuclei content, amount of supercooled water, and E-fields in/near convective cores for urban and environmental portions of the system. Sample before, during, and after propagating through Houston.
Instruments: T-28, mobile electrical sounding units

49. Title: “The Houston Environmental Aerosol Thunderstorm (HEAT) Project”
Principal Investigators: Richard Orville, John Nielsen-Gammon, Renyi Zhang, and Don Collins (Texas A&M University)
Proposed Co-investigators: Danny Rosenfeld (Hebrew University), William Woodley (Woodley, Inc.), Earle Williams (MIT), John Helsdon and Andy Detwiler (South Dakota Tech), Steve Rutledge (Colorado State), Paul Krehbiel (New Mexico Tech), Maribeth Stolzenburg and Tom Marshall (U. of Mississippi), Walt Lyons (FMA, Inc.), Ron Holle, Ken Cummins, and Nick Demetriades (Global Atmospherics, Inc.), David Rust and Don MacGorman (National Severe Storms Laboratory), Bill Read and Steve Allen (National Weather Service, Houston), Daewon Byun (University of Houston), J. G. Hudson (Desert Research Institute, Nevada), J. Marshall Shepherd (NASA-Goddard), Gary Huffines (U.S. Air Force), NCAR-MMM personnel to be determined,
Lead Institutions: Texas A&M University and the National Center for Atmospheric Research (NCAR)
Project Period: Four years ( ); field program (summer 2005)