The Houston Environmental Aerosol Thunderstorm (HEAT) Project: 2005 http://www.met.tamu.edu/ciams/heat/index.html 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 Email: rorville@tamu.edu March 15, 2004 -Background picture taken by Stephen Phillips (TAMU). This CG lightning flash was over College Station (October 2000).

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.

Intracloud Lightning

Cloud-to-ground lightning

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).

-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.

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).

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.

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).

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.

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           4.2.1 Operations Center Team           4.2.2 Chief Coordinators and Representatives for the                    Major Components and Observing Systems     4.3 Operations Center Layout    http://www.met.tamu.edu/ciams/heat/index.html

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

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?

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.

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

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

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

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

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.

Total (CG plus IC) Lightning and Polarimetric Radar Measurements

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.

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)

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

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

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)

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

The Beginning!

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)

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

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

Intra-Cloud Lightning

Cloud-to-Ground Lightning

LDAR-II Antenna – FAA Facility in Texas Ground Mount

LDAR-II Antenna -Roof of DFWAirport

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.

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 100-200 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

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

The Beginning!

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

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

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

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

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

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 (2003-2007); field program (summer 2005)