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      • 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
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      • 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.
      • 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.
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Guide Documents

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Dataset Software

Vaisala US NLDN Lightning Flash Data

These data are restricted to collaborators that have a working relationship with the NASA Marshall Space Flight Center (MSFC) Lightning Group.

About Vaisala
Data Collection
Spatial Coverage
Temporal Coverage
Flash Data File Format
File Naming Convention
Citing NLDN Lightning Flash Data
Contact Information


A lightning flash is the result of a transfer of significant charge between two charged objects. Lightning discharges can occur inter-cloud, cloud-to-cloud, cloud-to-air and cloud-to-ground. Generally, cloud-to-ground (CG) lightning has the greatest immediate impact on our lives. A CG stroke can kill, destroy equipment, start fires and disturb power delivery systems. Lightning detection in real-time is used to track, record and anticipate the occurrence of lightning. With adequate lead time, preventative measures can be taken which can help to minimize its destructive potential.

A CG flash is typically composed of a sequence of individual cloud-to-ground return strokes which transfer significant charge from the cloud to ground, each stroke exhibiting peak currents in the range of 5 kA to 300 kA. These strokes have a nominal duration of 20-50 microseconds, and are typically separated in time by 20 to 100 msec. A flash will typically be comprised of 2-3 strokes, but may contain as few as one and as many as twenty strokes. The number of strokes in a flash is frequently referred to as multiplicity. For most flashes, the subsequent strokes (strokes which occur after the first stroke of a flash) will contact the Earth at the same strike point as the first stroke because they travel through the ionized channel of air established by the first stroke. However, approximately one third of all flashes can contain strokes with different ground strike points, separated by a few hundred meters to several kilometers. For practical purposes, researchers have typically defined a flash as consisting of all CG discharges which occur within 10 km of each other within a one second interval.

IMPACT sensors that determine the ground point of the CG lightning flash make use of both direction finding (DF) and time-of-arrival (TOA) methods of location. Direction finding provides azimuth information to the ground point, and any two df antennas can be used to locate that point. The more antennas, the better the location. TOA antennas record the precise (based upon GPS timing) time that they 'hear" the characteristic CG electromagnetic signal. Using the signal from two TOA antennas produces an infinite number of possible ground point solutions. These solutions produce a locus of points on the ground in the shape of an hyperbola. If another antenna is employed with either of the original two, a second hyperbola is generated, with the ground point at the intersection of the two curves. Occasionally, a third hyperbola is required to create a unique ground point solution.

Since the IMPACT sensors make use of both types of locating methods, their accuracy has been shown to out perform either method by itself. This is true for both CG location accuracy and probability of detection because each method provides for an independent solution.  The only constraint for a location solution is that there are more independent observations of angle and/or time than there are variables to estimate (latitude, longitude, and stroke time). The NLDN is designed to have an average of 6-8 sensors contributing to the detection and location of a stroke.

When only two stations detect a flash, there is redundant information for an optimized estimate of location. In that case there are four measured parameters (two azimuths and two arrival times), while only three parameters are calculated (latitude, longitude, and time). Location and time are determined by interactively adjusting initial estimates of the parameters so that differences between observed and calculated azimuths and propagation times are minimized. Although IMPACT systems detect and analyze individual return strokes from each flash, they group all strokes that belong to the same flash and provide only one data record per flash. This record contains time, location, and peak signal amplitude of only the first return stroke, but provides multiplicity or number of strokes that made up the flash.

About Vaisala

Vaisala Thunderstorm is the lightning-specialty business unit within the Vaisala Group. Vaisala's US NLDN® is the most reliable lightning information system monitoring cloud-to-ground lightning activity across the continental United States, 24 hours a day, 365 days a year. The NLDN consists of more than 100 remote, ground-based Vaisala IMPACT ESP Lightning Sensors. These sensors instantly detect the electromagnetic signals given off when lightning strikes the Earth's surface. Within seconds of each strike the NCC's central analyzers process information on location, time, polarity, and amplitude of each stroke, and this information is sent to customers across the country. NLDN sensors use both magnetic direction finding and time-of-arrival recording methods to provide multiple identifiers for each lightning event. Highly refined algorithms, the result of over twenty years of lightning research, are used to process sensor information and calculate accurate lightning solutions. Since 1989, the NLDN has reported more than 20 million cloud-to-ground lightning flashes that occur every year. The development and maturity of the data product can be followed via the following timeline:

NLDN Timeline

1984-1989: Three separate regional lightning networks develop and operate at various locations. These networks used early direction finding methods for lightning detection
1989: Regional networks share data to establish a national network, the NLDN. This cooperative project is funded by the Electric Power Research Institute (EPRI) and operated by the State University of New York (SUNY) at Albany. For the first time, real-time data is available to users across the country.
1991: Real-time and historic lightning data becomes commercially available.
1993: NLDN Network Control Center is moved to its current location in Tucson, Arizona.
1994: Comprehensive customer research leads to the development of new, more powerful lightning display and lightning analysis software.
1995: First major system-wide upgrade completed with project partner EPRI. This upgrade added new lightning sensors that combined magnetic direction finding and time-of-arrival detection methods in a single sensor, the original IMPACT Lightning Sensor. NLDN began reporting flashes and individual return strokes within a flash. Flash detection efficiency increased to 80-90% with median stroke location accuracy of 500 meters.
1996-1999: Commercial applications of historic lightning data proliferate in electric power, insurance, and other industries as a result of improved location accuracy and application-specific software developments.
1998: The Canadian Lightning Detection Network, owned by Environment Canada, is completed. Operations for the CLDN are combined with NLDN operations in Tucson. The lightning data from the NLDN and CLDN sensors – close to 200 sensors – are processed on a single processing platform.
2000: NLDN real-time and historic lightning data is available on the Internet in several application-specific formats.
2003: Second major system-wide upgrade completed with replacement of aging sensors and earlier sensing technology with new, more advanced, third generation Vaisala IMPACT ESP Lightning Sensors throughout the network. Preliminary evaluations indicate overall minimum 90% flash detection efficiency and 60-80% stroke detection efficiency.

Data Collection

Vaisala's US NLDN Lightning Flash Data consists of more than 100 remote, ground-based lightning sensors. Sensors send raw data via satellite to the Network Control Center (NCC) in Tucson, Arizona. Sensors instantly detect the electromagnetic signals created when lightning strikes the Earth's surface. Within seconds, the NCC's central analyzers process information on location, time, polarity, and amplitude of each stroke. Quality checks are performed for each location, and the lightning solutions are then archived and sent to the real time subscribers. Monthly quality controlled data are subsequently sent to subscribers on CD. These QC 'ed data files received monthly via CD-ROM are then archived at the GHRC.

Spatial Coverage

The spatial coverage of the Vaisala US NLDN Lightning Flash Data includes continental United States and extends 200-300 km off the coastline. The detection accuracy decreases with distance from the antenna networks.

Temporal Coverage

The temporal coverage of the Vaisala US NLDN Lightning Flash Data, in the Version 2 (v2) and Version 3 (v3) millisecond format, is from January 1, 1995 to the present. However, flash data in a one second format goes back to January 3, 1988. This is the "GAI Lightning Ground Strikes" dataset (gdslightn). More information on this dataset can be found here: Data for dates prior to 1 Jan 1994 were collected with either a direction finding system (Lightning Location and Protection, Inc. sensors) or time of arrival system (Lightning Position and Tracking System, LPATS sensors) or a combination of both.

Flash Data File Format

All GHRC lightning file names that include a "v2" will be in the following standard format (first 12 fields). On March 1, 2008, we promoted to "v3", which added a Cloud-to-Ground / In-Cloud Discriminator (G, C) as the 13th field (2008.061 - current). The entire Vaisala US Lightning Flash dataset is in this expanded format, as well as our long range flash data after June 10, 2007.

Sample data line:

06/27/07 16:18:21.898 18.739 -88.184 0.0 kA 0 1.0 0.4 2.5 8 1.2 13 G

Column Number
Field name
Date of strike (mm/dd/yy GMT)

Time of strike (to milliseconds) in GMT of flash event
Latitude (Deg)
Longitude (Deg)
Polarity and strength of strike (kA)
0.0 kA
Multiplicity of flash
Semimajor Axis in Kilometers, 50% probability ellipse for each flash
Semiminor Axis in Kilometers,50% probability ellipse for each flash
Ratio, Semimajor to Semiminor
Angle of 50% probability ellipse from North
Chi-squared value of statistical calculation
Number of sensors reporting the flash
Cloud-to-Ground / In-Cloud Discriminator (G, C)

File Naming Convention

A raw data file is produced for each day. The naming convention for the Vaisala US NLDN Lightning Flash raw data file is:



yyyy = Year
ddd = Day Of Year
vx =  version number, where:
v2= Long millisecond format (12 fields) (1995.001 - 2008.060)
v3=Added Cloud-to-Ground / In-Cloud Discriminator (G, C) as 13th field (2008.061 - current)

As an example, the raw data file containing the cloud-to-ground lightning flashes detected on 22 July 2007 from 00:00:000 to 23:59:599 UTC would be contained in the file named "Nflash2007.203_daily_v2_lit.raw".

Citing NLDN Lightning Flash Data

Our data sets are provided through the NASA Earth Science Data and Information System (ESDIS) Project and the Global Hydrology Resource Center (GHRC) Distributed Active Archive Center (DAAC). GHRC DAAC is one of NASA's Earth Observing System Data and Information System (EOSDIS) data centers that are part of the ESDIS project. ESDIS data are not copyrighted; however, in the event that you publish our data or results derived by using our data, we request that you include an acknowledgment within the text of the article and a citation on your reference list. Examples for general acknowledgments, data set citation in a reference listing, and crediting online web images and information can be found at:


Cummins, K.L., R.O. Burnett, W.L. Hiscox, and A.E. Pifer, 1993: Line reliability and fault analysis using the National lightning detection network. Preprints, Precise Measurements in Power Conference, Arlington, VA, Oct. 27-29, 1993.

Cummins, K.L., W.L. Hiscox, A.E. Pifer, and M.W. Maier, 1992: Performance Analysis of the U.S. National Lightning Detection Network. Proceedings, 9th International Conference on Atmospheric Electricity. St. Petersburg, Russia. A.I. Voeilkov Main Geophysical Observatory, Karbysheva 7, 194018, St. Petersburg, Russia.

Maier, M. W., et al., 1983: Locating Cloud-To-Ground Lightning With Wideband Magnetic Direction Finders. Presented at 5th Symposium on Meteorological Observations and Instrumentation. Toronto, Ontario, Canada, April 11-15, 1983.

Orville, R.E., 1994: Cloud-to-ground Lightning Flash Characteristics in the Contiguous United States: 1989-1991. Journal of Geophys. Res., Vol. 5., 10833-10841.

Reap, R.M., D.R. MacGorman, 1989: Cloud-to-Ground Lightning: Climatological Characteristics and Relationships to Model Fields, Radar Observations, and Severe Local Storms. Monthly Wea. Review, 117, 518-535.

Contact Information

To order this data or for further information, please contact:

Global Hydrology Resource Center
User Services
320 Sparkman Drive
Huntsville, AL 35805
Phone: 256-961-7932




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