NASA GHRC Collaboration between NASA MSFC and The University of Alabama in Huntsville
  • Find Data
    • Find Data (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.
      • 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.
  • 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 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.
  • Resources
    • Tools & Technologies
      • 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.
    • Referencing our data
      • GHRC dataset citation help and examples.
    • Documents
      • Documentation related to GHRC datasets, software, and other offerings.
    • Featured items
      • The latest tools from GHRC.
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      • Local resources, lodging information, and weather to help you plan your visit to GHRC.
    • GHRC Personnel
      • A list to help you keep in touch with our personnel
    • FAQ
      • Frequently Asked Questions about GHRC data and services, and their answers.
    • Glossary
      • Terms and their definitions
    • Referencing our data
      • GHRC dataset citation help and examples
  • Cite Us
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Lightning & Atmospheric Electricity Research

Lightning Home

A Lightning Primer

Lightning Micro Articles and Data Recipes


Global Lightning Image
Global Lightning Image
Global lightning strikes from January 1998 to present day from the NASA/MSFC Lightning Imaging Sensor on the Tropical Rainfall Measuring Mission satellite

Space Research and Observations

Optical Transient Detector

OTDThe Optical Transient Detector (OTD) is a highly compact combination of optical and electronic elements. It was developed as an in-house project at NASA's Marshall Space Flight Center in Huntsville, Alabama. The name, Optical Transient Detector, refers to its capability to detect the  momentary changes in an optical scene which indicate the occurrence of lightning. The OTD instrument is a major advance over previous technology in that it can gather lightning data under daytime conditions as well as at night. In addition, it provides much higher detection efficiency and spatial resolution than has been attained by earlier lightning sensors.

OTD microlabAt the heart of the system is a solid-state optical sensor similar in some ways to a TV camera. However, in overall design and many specific features, OTD had to be uniquely designed for the job of observing and measuring lightning from space. Like a TV camera, the OTD has a lens system, a detector array (serving a function somewhat analogous to the retina in the human eye), and circuitry to convert the electronic output of the system's detector array into useful data.

The sensor system (camera) is approximately 8 inches in diameter and 15 inches high, while the supporting electronics package is about the size of a standard typewriter. Together, the two modules weigh approximately 18 kilograms (40 pounds). The total weight of the satellite placed on orbit is 75 kilograms (165 pounds). Operations Under an agreement between NASA and the Orbital Sciences Corporation, the Optical Transient Detector was carried as a secondary payload on a Pegasus, an Orbital Sciences Corporation air-launched rocket. The Pegasus launch on April 3, 1995, delivered the OTD into an Earth orbit of approximately 710 kilometers (446 miles) altitude, with an inclination of 70 degrees. With that orbit, and OTD's wide 100-degree field of view, it surveys virtually all areas of the globe where lightning normally occurs. The combination of the wide field-of-view lens and the altitude of the orbit allows OTD to observe an area of the earth equivalent to 1300x1300 sq km (about 1/300 of the total surface area of the earth) as it orbits the globe.

OTD was expected to be in operation for only two years, but has continued recording the occurrence and worldwide distribution of lightning beyond the expected mission lifetime. The data are transmitted on a daily basis from OTD to a ground station in Fairmont, West Virginia. From there, the data are sent to the Global Hydrology and Climate Center in Huntsville, Alabama, for processing, analysis, and distribution to the scientific community.

The OTD data and associated scientific research has confirmed its importance in contributing to the understanding of atmospheric and precipitation processes. This contribution has reinforced the need for similar observations from geosynchronous orbit, where storm morphology can be monitored continuously.

In recent years, scientists have become increasingly aware of the key role played by lightning in the dynamic interplay of forces occurring in the Earth's atmosphere. Research has indicated that lightning may be a very good indicator of the strength of convective storm systems. The OTD has contributed to the discovery of potential lightning indicators for application to more timely hazardous weather and tornado warnings, and for improved forest fire and wild-land fire management; to the use of lightning as a proxy for detecting intense atmospheric convection; to the production of the most complete and detailed maps of the global lightning distribution; and to the discovery that the global flash rate is approximately 40 flashes per second, less than half of the widely accepted estimates dating back to 1925. One of Many Results Between September 1, 1995 and August 31, 1996, the OTD observed nearly 1 million lightning flashes worldwide. The lightning flash densities (flashes per square kilometer per year) shown on the image have been calculated statistically using OTD data from more than 400 separate 3 minute observations of each location on the earth. From this information, it is now estimated that over 1.2 billion lightning flashes (intracloud plus cloud-to-ground) occur around the world every year. Most of the lightning is in the InterTropical Convergence Zone (ITCZ) over the continents, and there is far more lightning over the land masses than over the oceans. This results from the stronger vertical motions in continental clouds than in oceanic clouds. Lightning Observations Data Information OTD was launched on April 3, 1995 aboard the MicroLab-1 satellite into a near polar orbit at an inclination of 70 degrees with respect to the equator. The satellite orbits the Earth once every 100 minutes at an altitude of 740km, and at any given instant views a 1300km x 1300km region of the Earth at 128 x 128 pixels. The instrument has a spatial resolution of 10km and a temporal resolution of 2ms.

"Flashes" are determined by comparing the luminance of adjoining frames of OTD optical data. If the difference is more than a specified threshold value, an "event" is recorded. One or more adjacent events in the same 2ms time frame is recorded as a "group". One or more groups within a sufficiently small time period are classified as a "flash". These are grouped into "areas" if there are one or more sufficiently separated from existing areas.

The OTD detects lightning flashes during both daytime and nighttime conditions with a detection efficiency ranging from 40% to 65%, depending upon external conditions such as glint and radiation. The LIS instrument, for which OTD is the engineering prototype, will have a detection efficiency of approximately 90%. The reason for the discrepancy is that the OTD was built under rush conditions and was the best that could be constructed in the mere nine months the team spent on design, fabrication, space qualification, calibration, and delivery.

Because the OTD never observes a given location for more than a few minutes each day its data may be unsuitable for studying localized weather. What it is suitable for is studying global lightning patterns and how they change with time. It can also prove a valuable comparison item if the OTD happens to be in the right spot at the right time to gather data on a given storm. In these cases, the data can be compared against data from other sources to get an estimate of the total flash rate of the storm.

OTD Browse Data is available to provide a quick, graphical overview of the OTD data. Each day of OTD data has been totaled into a single image. Using these images, it is easy to tell from a glance on which days there was a particularly high or low amount of lightning activity over a given area. At the end of each month, OTD Browse Data is quality checked and archived.

A QuickTime movie of example OTD data is also available. This movie consists of a series of browse images played as a sequence to give a feel of the lightning dispersion over the Earth.


1. The Optical Transient Detector (OTD), Christian, H. J., K. T. Driscoll, S. J. Goodman, R. J. Blakeslee, D. A. Mach, and D. E. Buechler; Proceedings of the 10th International Conference on Atmospheric Electricity; Osaka, Japan; June 10-14, 1996; pp 368-371.

2. Christian, H. J., "Optical Detection of Lightning from Space," Proceedings of the 11th International Conference on Atmospheric Electricity, Guntersville, Alabama, June 7-11, 1999, pp. 715-718.

3. Blakeslee, R. J., K. T. Driscoll, D. E. Buechler, D. J. Boccippio, W. J. Boeck, H. J. Christian, S. J. Goodman, J. M. Hall, W. J. Koshak, D. A. Mach, and M. F. Stewart, "Diurnal Lightning Distribution as Observed by the Optical Transient Detector (OTD)," Proceedings of the 11th International Conference on Atmospheric Electricity, Guntersville, Alabama, June 7-11, 1999, pp. 742-745.

4. Christian, H. J., R. J. Blakeslee, D. J. Boccippio, W. L. Boeck, D. E. Buechler, Kevin T. Driscoll, Steven J. Goodman, J. M. Hall, D. A. Mach, and M. F. Stewart "Global Frequency and Distribution of Lightning as Observed by the Optical Transient Dector (OTD)," Proceedings of the 11th International Conference on Atmospheric Electricity, Guntersville, Alabama, June 7-11, 1999, pp. 726-729.

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