NASA GHRC Collaboration between NASA MSFC and The University of Alabama in Huntsville
  • Access Data
    • Dataset List (HyDRO)
      • View a list of all GHRC dataset holdings using our custom search tool, HyDRO.
    • Search (HyDRO)
      • HyDRO is GHRC's custom dataset search and order tool.

        With HyDRO, you can search, discover, and filter GHRC's dataset holdings.

        HyDRO will also help you find information about browse imagery, access restrictions, and dataset guide documents.
    • Coincidence Search
      • The GHRC Coincidence Search Engine (CSE) may be used to search for times when up to four satellites were over or within the same geographic area simultaneously.

        Searches may be constrained by time, geographic area, and/or distance between the satellites.
    • THREDDS
      • This is our current OPeNDAP server.

        You can access, download, and subset selected datasets with THREDDS. You can also obtain WMS links and applicable documentation and browse images for some datasets.
    • Storm Tracks DB
      • The Tropical Storm Tracks database is derived from the storm data published by the National Hurricane Center (NHC).

        This web page provides a convenient user interface for casually browsing storm information, including location, category, and wind speed.
    • AMSU Temp Trends
      • Daily averaged temperatures of the Earth are measured by the Advanced Microwave Sounding Unit (AMSU) on NASA's Aqua satellite.
    • NASA Earthdata Search
      • Earthdata is NASA's next generation metadata and service discovery tool, providing search and access capabilities for dataset holdings at all of the Distributed Active Archive Centers (DAACs) including the GHRC.
    • Latest Data (HyDRO)
      • View the latest additions to our data holdings using HyDRO.
  • Measurements
  • Field Campaigns
    • Hurricane Science
      • GHRC has worked with NASA's Hurricane Science Research Program (HSRP) since the 1990's. We are the archive and distribution center for data collected during HSRP field campaigns, as well as the recent Hurricane Science and Severe Storm Sentinel (HS3) Earth Venture mission. Field campaigns provide for intensive observation of specific phenomena using a variety of instruments on aircraft, satellites and surface networks.

        GHRC also hosts a database of Atlantic and Pacific tropical storm tracks derived from the storm data published by the National Hurricane Center (NHC).
    • HS3 (2012-14)
      • Hurricane and Severe Storm Sentinel (HS3) is an Earth Ventures – Suborbital 1 mission aimed at better understanding the physical processes that control hurricane intensity change, addressing questions related to the roles of environmental conditions and internal storm structures to storm intensification.

        A variety of in-situ, satellite observations, airborne data, meteorological analyses, and simulation data were collected with missions over the Atlantic in August and September of three observation years (2012, 2013, 2014). These data are available at GHRC beginning in 2015.
    • GRIP (2010)
      • The Genesis and Rapid Intensification Processes (GRIP) experiment was a NASA Earth science field experiment in 2010 that was conducted to better understand how tropical storms form and develop into major hurricanes.

        The GRIP deployment was 15 August – 30 September 2010 with bases in Ft. Lauderdale, FL for the DC-8, at Houston, TX for the WB-57, and at NASA Dryden Flight Research Facility, CA for the Global Hawk.
    • TC4 (2007)
      • The NASA TC4 (Tropical Composition, Cloud and Climate Coupling) mission investigated the structure and properties of the chemical, dynamic, and physical processes in atmosphere of the tropical Eastern Pacific.

        TC4 was based in San Jose, Costa Rica during July 2007.

        The Real Time Mission Monitor provided simultaneous aircraft status for three aircraft during the TC4 experiment. During TC4, the NASA ER-2, WB-57 and DC-8 aircraft flew missions at various times. The science flights were scheduled between 17 July and 8 August 2007.
    • NAMMA (2006)
      • The NASA African Monsoon Multidisciplinary Analyses (NAMMA) campaign was a field research investigation based in the Cape Verde Islands, 350 miles off the coast of Senegal in west Africa.

        Commenced in August 2006, NASA scientists employed surface observation networks and aircraft to characterize the evolution and structure of African Easterly Waves (AEWs) and Mesoscale Convective Systems over continental western Africa, and their associated impacts on regional water and energy budgets.
    • TCSP (2005)
      • The Tropical Cloud Systems and Processes (TCSP) mission was an Earth science field research investigation focused on the study of the dynamics and thermodynamics of precipitating cloud systems and tropical cyclones. TCSP was conducted during the period July 1-27, 2005 out of the Juan Santamaria Airfield in San Jose, Costa Rica.

        The TCSP field experiment flew 12 NASA ER-2 science flights, including missions to Hurricanes Dennis and Emily, Tropical Storm Gert and an eastern Pacific mesoscale complex that may possibly have further developed into Tropical Storm Eugene.
    • ACES (2002)
      • The Altus Cumulus Electrification Study (ACES) was aimed at better understanding the causes and effects of electrical storms.

        Based at the Naval Air Station Key West in Florida, researchers in August 2002 chased down thunderstorms using an uninhabited aerial vehicle, or "UAV", allowing them to achieve dual goals of gathering weather data safely and testing new aircraft technology. This marked the first time a UAV was used to conduct lightning research.
    • CAMEX-4 (2001)
      • The Convection And Moisture EXperiment (CAMEX) was a series of NASA-sponsored hurricane science field research investigations. The fourth field campaign in the CAMEX series (CAMEX-4) was held in 16 August - 24 September, 2001 and was based out of Jacksonville Naval Air Station, Florida.

        CAMEX-4 was focused on the study of tropical cyclone (hurricane) development, tracking, intensification, and landfalling impacts using NASA-funded aircraft and surface remote sensing instrumentation.
    • CAMEX-3 (1998)
      • The Convection And Moisture EXperiment (CAMEX) is a series of hurricane science field research investigations sponsored by NASA. The third field campaign in the CAMEX series (CAMEX-3) was based at Patrick Air Force Base, Florida from 6 August - 23 September, 1998.

        CAMEX-3 successfully studied Hurricanes Bonnie, Danielle, Earl and Georges, yielding data on hurricane structure, dynamics, and motion. CAMEX-3 collected data for research in tropical cyclone development, tracking, intensification, and landfalling impacts using NASA-funded aircraft and surface remote sensing instrumentation.
    • GPM Ground Validation
      • The NASA Global Precipitation Measurement Mission (GPM) Ground Validation (GV) program includes the following field campaigns:

        a) LPVEx, Gulf of Finland in autumn 2010, to study rainfall in high latitude environments

        b) MC3E, cental Oklahoma spring and early summer 2011, to develop a complete characterization of convective cloud systems, precipitation and the environment

        c) GCPEx, Ontario, Canada winter of 2011-2012, direct and remove sensing observations, and coordinated model simulations of precipitating snow.

        d) IFloodS, Iowa, spring and early summer 2013, to study the relative roles of rainfall quantities and other factors in flood genesis.

        e) IPHEx, N. Carolina Appalachians/Piedmont region May-June 2014, for hydrologic validation over varied topography.

        f) OLYMPEx, Washington's Olympic Peninsula scheduled November 2015-February 2016, for hydrologic validation in extreme coastal and topographic gradients
    • OLYMPEX (Upcoming)
      • The OLYMPEX field campaign is scheduled to take place between November, 2015, and February, 2016, on the Olympic Peninsula in the Pacific Northwest of the United States.

        This field campaign will provide ground-based validation support of the Global Precipitation Measurement (GPM) satellite program that is a joint effort between NASA and JAXA.

        As for all GPM-GV campaigns, the GHRC will provide a collaboration portal to help investigators exchange planning information and to support collection of real-time data as well as mission science, project and instrument status reports during the campaign.
    • IPHEx (2014)
      • The Integrated Precipitation and Hydrology Experiment (IPHEx) was conducted in North Carolina during the months of April-June, 2014.

        IPHEx sought to characterize warm season orographic precipitation regimes, and the relationship between precipitation regimes and hydrologic processes in regions of complex terrain.
    • IFLOODs (2013)
      • The Iowa Flood Studies (IFloodS) experiment was conducted in the central to northeastern part of Iowa in Midwestern United States during the months of April-June, 2013.

        IFloodS' primary goal was to discern the relative roles of rainfall quantities such as rate and accumulation as compared to other factors (e.g. transport of water in the drainage network) in flood genesis.
    • GCPEX (2011-2012)
      • The GPM Cold-season Precipitation Experiment (GCPEx) occurred in Ontario, Canada during the winter season (Jan 15- Feb 26) of 2011-2012.

        GCPEx addressed shortcomings in GPM snowfall retrieval algorithm by collecting microphysical properties, associated remote sensing observations, and coordinated model simulations of precipitating snow. Collectively the GCPEx data set provides a high quality, physically-consistent and coherent data set suited to the development and testing of GPM snowfall retrieval algorithm physics.
    • MC3E (2011)
      • The Mid-latitude Continental Convective Clouds Experiment (MC3E) took place in central Oklahoma during the April–June 2011 period.

        The overarching goal was to provide the most complete characterization of convective cloud systems, precipitation, and the environment that has ever been obtained, providing constraints for model cumulus parameterizations and space-based rainfall retrieval algorithms over land that had never before been available.
    • LPVEx (2010)
      • The Light Precipitation Evaluation Experiment (LPVEx) took place in the Gulf of Finland in September and October, 2010 and collected microphysical properties, associated remote sensing observations, and coordinated model simulations of high latitude precipitation systems to drive the evaluation and development of precipitation algorithms for current and future satellite platforms.

        In doing so, LPVEx sought to address the general lack of dedicated ground-validation datasets from the ongoing development of new or improved algorithms for detecting and quantifying high latitude rainfall
  • Projects
    • HS3 Suborbital Mission
      • Hurricane and Severe Storm Sentinel (HS3) is an Earth Ventures – Suborbital 1 mission aimed at better understanding the physical processes that control hurricane intensity change, addressing questions related to the roles of environmental conditions and internal storm structures to storm intensification.
    • DISCOVER - MEaSUREs
      • DISCOVER was funded by NASA’s MEaSUREs program to provide highly accurate, multi-decadal geophysical products derived from satellite microwave sensors.
    • LIS Mission
      • Lightning observations from the Lightning Imaging Sensors (LIS) aboard the NASA’s TRMM satellite and International Space Station, as well as airborne observations and ground validation data.
    • SANDS
      • The SANDS project addressed Gulf of Mexico Alliance priority issues by generating enhanced imagery from MODIS and Landsat data to identify suspended sediment resulting from tropical cyclones. These tropical cyclones have significantly altered normal coastal processes and characteristics in the Gulf region through sediment disturbance.
    • LANCE AMSR2
      • The Land, Atmosphere Near real-time Capability for EOS (LANCE) system provides access to near real-time data (less than 3 hours from observation) from AIRS, AMSR2, MLS, MODIS, and OMI instruments. LANCE AMSR2 products are generated by the AMSR Science Investigator-led Processing System at the GHRC.
  • Resources
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      • A collection of tools & technologies developed and/or used by GHRC.
    • Publications
      • View GHRC & ITSC publications on the ITSC website
    • Innovations Lab
      • The GHRC Innovations Lab is a showcase for emerging geoinformatics technologies resulting from NASA-sponsored research at the University of Alabama in Huntsville.
    • Educational Resources
      • A list of resources from NASA, MSFC, and other sources for teachers and students focused on global change, hydrology, and science education.
    • Data Citations and Acknowledgements
      • GHRC dataset citation help and examples
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Lightning & Atmospheric Electricity Research

Lightning Home

The Lightning Team

A Lightning Primer

File Cabinet and Bookshelf

 

Global Lightning Image
Global Lightning Image
Global lightning strikes from January 1998 to present day from the NASA/MSFC Lightning Imaging Sensor

A Lightning Primer

Characteristics of a Storm

LIGHTNING
Lightning As the ice particles within a cloud (called hydrometeors) grow and interact, they collide, fracture and break apart. It is thought that the smaller particles tend to acquire positive charge, while the larger particles acquire more negative charge. These particles tend to separate under the influences of updrafts and gravity until the upper portion of the cloud acquires a net positive charge and the lower portion of the cloud becomes negatively charged. This separation of charge produces enormous electrical potential both within the cloud and between the cloud and ground. This can amount to millions of volts, and eventually the electrical resistance in the air breaks down and a flash begins. Lightning, then, is an electrical discharge between positive and negative regions of a thunderstorm.

A lightning flash is composed of a series of strokes with an average of about four. The length and duration of each lightning stroke vary, but typically average about 30 microseconds. (The average peak power per stroke is about 1012 watts.)

THUNDER

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Sound is generated along the length of the lightning channel as the atmosphere is heated by the electrical discharge to the order of 20,000 degrees C (3 times the temperature of the surface of the sun). This compresses the surrounding clear air producing a shock wave, which then decays to an acoustic wave as it propagates away from the lightning channel.

Although the flash and resulting thunder occur at essentially the same time, light travels at 186,000 miles in a second, almost a million times the speed of sound. Sound travels at the relatively snail pace of one-fifth of a mile in the same time. Thus the flash, if not obscured by clouds, is seen before the thunder is heard. By counting the seconds between the flash and the thunder and dividing by 5, an estimate of the distance to the strike (in miles) can be made.

CLOUDS AND RAIN
Cloud and Rain When moisture-laden warm air is heated, it begins to rise. As these currents or bubbles of warm moist air rise higher in the atmosphere, both the surrounding air pressure and temperature decrease. The air bubbles expand, causing cooling of the moisture which eventually condenses to form clouds. As the cloud cools further, more moisture condenses and the water droplets making up the cloud grow and merge until some become so large and heavy that the air currents within the cloud can no longer support them. These water droplets begin to fall as rain.

 

HAIL
Hail Air currents in cumulonimbus clouds can be very violent. Even when lightning is not produced, pellets of ice may grow by the accumulation of liquid droplets. When the updrafts are very strong, the growing ice pellets can be suspended for long periods, allowing them to grow larger. Eventually some may become too large for a given updraft and begin to fall as hail. Diameters are typically 5 to 10 mm, although a l40 mm hailstone has been recorded.

 

Types of Lightning Discharges

THE MOST COMMON TYPES OF LIGHTNING
LightningCloud-to-ground lightning is the most damaging and dangerous form of lightning. Although not the most common type, it is the one which is best understood. Most flashes originate near the lower-negative charge center and deliver negative charge to Earth. However, an appreciable minority of flashes carry positive charge to Earth. These positive flashes often occur during the dissipating stage of a thunderstorm's life. Positive flashes are also more common as a percentage of total ground strikes during the winter months.

Intra-cloud lightning is the most common type of discharge. Intra_cloud Lightning This occurs between oppositely charged centers within the same cloud. Usually the process takes place within the cloud and looks from the outside of the cloud like a diffuse brightening which flickers. However, the flash may exit the boundary of the cloud and a bright channel, similar to a cloud-to-ground flash, can be visible for many miles.

The ratio of cloud-to-ground and intra-cloud lightning can vary significantly from storm to storm. Storms with the greatest vertical development may produce intra-cloud lightning almost exclusively. Some suggest that the variations are latitude-dependent, with a greater percentage of cloud-to-ground strikes occurring at higher latitudes. Others suggest that cloud-top height is a more important variable than latitude.

Details of why a discharge stays within a cloud or comes to ground are not understood. Perhaps a flash propagates toward the Earth when the electric field gradient in the lower regions of the cloud is stronger in the downward direction.

Depending upon cloud height above ground and changes in electric field strength between cloud and Earth, the discharge stays within the cloud or makes direct contact with the Earth. If the field strength is highest in the lower regions of the cloud a downward flash may occur from cloud to Earth.

Inter-cloud lightning, as the name implies, occurs between charge centers in two different clouds with the discharge bridging a gap of clear air between them.

OTHER TYPES OF LIGHTNING
There are numerous names and descriptions of various types and forms of lightning. Some identify subcategories, and others may arise from optical illusions, appearances, or myths. Some popular terms include: ball lightning, heat lightning, bead lightning, sheet lightning, silent lightning, black lightning, ribbon lightning, colored lightning, tubular lightning, meandering lightning, cloud-to-air lightning, stratospheric lightning, red sprites, blue jets, and elves.

DESCRIPTION OF LIGHTNING DISCHARGE PROCESSES
With the initial breakdown of the air in a region of strong electric fields, a streamer may begin to propagate downward toward the Earth. It moves in discrete steps of about 50 meters each and is called a stepped leader. As it grows, it creates an ionized path depositing charge along the channel, and as the stepped leader nears the Earth, a large potential difference is generated between the end of the leader and the Earth. Typically, a streamer is launched from the Earth and intercepts the descending stepped leader just before it reaches the ground. Once a connecting path is achieved, a return stroke flies up the already ionized path at close to the speed of light. This return stroke releases tremendous energy, bright light and thunder. Occasionally, where a thunderstorm grows over a tall Earth grounded object, such as a radio antenna, an upward leader may propagate from the object toward the cloud. This "ground-to-cloud" flash generally transfers a net positive charge to Earth and is characterized by upward pointing branches.

 

Description of lightning discharge processes
The lower part of a thundercloud is usually negatively charged. The upward area is usually positively charged. Lightning from the negatively charged area of the cloud generally carries a negative charge to Earth and is called a negative flash. A discharge from a positively-charged area to Earth produces a positive flash.

The initial breakdown and propagation are similar for intra-cloud lightning, but the discharge generally occurs between regions of opposite charge. Without the benefit of air conducting Earth, intra-cloud lightning does not produce a return-stroke-like feature. Rather, it is characterized by slower propagating "recoil streamers" and "K" changes. Nevertheless, tremendous energy, bright light, and thunder are still produced by intra-cloud lightning.

 

 

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