NASA’s Lightning Imaging Sensor (LIS)

Lightning has long been a source of intrigue and debate. Despite what we have learned about lightning over the centuries, there is still more to learn. Scientists are exploring the role lightning plays in the dynamic forces of the Earth’s atmosphere. To better understand how lightning affects climate change, lightning has been added to the Global Climate Observing System’s list of Essential Climate Variables (ECVs). ECVs provide the empirical evidence needed to understand and predict the evolution of climate as well as to guide mitigation and adaptation measures in support of scientists, governments, agencies, and international climate policy.

The primary objectives of lightning studies include determining the relationship between the electrical characteristics of storms and precipitation, convection, and severe weather. Lightning data can be used to protect people, assets, and operations from the risks of direct and indirect lightning strikes. Knowing when and where lightning may strike can help determine risk factors for forest fires, damages to electrical infrastructure, when to issue related air traffic advisories, and weather services can generate severe storm and heavy precipitation warnings.

Images 1 & 2 are of the TRMM satellite. Image 3 shows the location of the LIS sensor aboard the ISS.

While there are numerous ground-based instruments providing lightning data, they all use triangulation to determine the flash location. In addition, cloud-to-cloud lightning is often rejected because only two of the three required locations are detected for triangulation. Thus, cloud-to-cloud lightning is often underestimated. In addition, ground sensors can only detect activity over land. On the other hand, space-based lightning detection systems use direct observation and can detect cloud-to-ground, cloud-to-cloud, and intracloud lightning. A space-based sensor can also provide calibration and validation to ground-based lightning networks. Its only drawback is that the data is not available in real-time.

The Lightning Imaging Sensor (LIS) is an example of a space-based sensor. It was first launched November 1997 aboard NASA’s Tropical Rainfall Measuring Mission (TRMM) satellite and operated until April 2015 when its mission ended. The 17-year mission was so successful that the spare LIS module, which was in storage, was sent to the International Space Station (ISS) in 2017 to take advantage of the laboratory’s high inclination. From this vantage point, the sensor will be able to look farther towards Earth’s poles than the original LIS aboard the TRMM.

LIS measures the amount, rate, and radiant energy of global lightning, providing storm-scale resolution, millisecond timing, and high, uniform-detection efficiency; and, it does this without land-ocean bias. While on the TRMM observatory it travelled 7 kilometers every second, or 16,000 miles per hour, and was able to view a point or cloud on Earth for almost 90 seconds. Despite the brief duration, it was long enough to estimate the flashing rate of most storms. The TRMM LIS detection efficiency ranged from 69% near noon to 88% at night. The sensor provides valuable information on data-sparse regions, such as oceans.

“Only LIS globally detects all in-cloud and cloud-to-ground lightning — what we call total lightning — during both day and night,” said Richard Blakeslee, LIS project scientist at Marshall. “As previously demonstrated by the TRMM mission, better understanding lightning and its connections to weather and related phenomena can provide unique and affordable gap-filling information to a variety of science disciplines including weather, climate, atmospheric chemistry and lightning physics.”

The TRMM satellite was designed to improve our understanding of the distribution and variability of precipitation within the tropics as part of the water cycle in the current climate system. Its orbit was circular, at an inclination of 35 degrees to the equator, and at an altitude of 350 km. Its low altitude provided high resolution images, thus, more accurate rainfall measurements. (Video by Nasa).

This visualization tallies up all the lightning strikes detected by the Lightning Imaging Sensor (LIS) onboard the now defunct Tropical Rainfall Measuring Mission (TRMM) from April 1998 to January 2015—more than 16 years’ worth of lightning data. The visualization starts out showing how the LIS sensor (green square) sweeps out an orbit path from approximately 35 degrees north to south latitude (blue), detecting lightning flashes as it passes overhead. As the sensor completes more orbits, a long-term count of the number of flashes observed at each location can be accumulated. Adjusting the total number of counts by the number of times the location has been observed gives the average flash rate, also known as a climatology (shown in the last frame of the visualization). — Content and related video by NASA

This link will take you to an interactive globe consisting of five lightning climatologies: the full climatological mean (VHRFC), monthly (VHRMC), diurnal (VHRDC), annual cycle (VHRAC), and seasonal (VHRSC). These gridded climatologies include annual mean flash rate density, mean diurnal cycle of flash rate density, and the mean annual cycle of flash rate density with daily, monthly, or seasonal resolution.

Peterson, M., W. Deierling, C. Liu, D. Mach, and C. Kalb (2016), The Properties of Optical Lightning Flashes and the Clouds They Illuminate, J. Geophys. Res. Atmos., 121, doi:10.1002/2016JD025312.

Albrecht, R., S. Goodman, D. Buechler, R. Blakeslee, and H. Christian, 2016: Where Are the Lightning Hotspots on Earth?. Bull. Amer. Meteor. Soc., 97, 2051–2068, doi: 10.1175/BAMS-D-14-00193.1.