GLM is coming: The origin of the GLM

The Geostationary Lightning Mapper (GLM) successfully launched aboard GOES-R (now GOES-16) on November 19, 2016.  Now we are a week away from the initial preliminary, beta data observations being made available.  This is an exciting time, especially with some of the early public release imager from the GLM available on the GOES-R multimedia page (http://www.goes-r.gov/multimedia/goes-16DataAndImagery.html).  In advance of next week’s milestone here is some of the history that has led to the development of the GLM.

One of the earliest satellite-based instruments specifically designed for lightning observations was the Optical Transient Detector (OTD).  Figure 1 (below) shows the annual flash frequency for 1995 to 2000. This was developed by NASA’s Marshall Space Flight Center in Huntsville, Alabama.  Amazingly, the OTD was built in nine months.  Launched on April 3, 1995 the OTD was placed in a near polar orbit allowing it to monitor lightning over much of the Earth during both the day and night.  However, the OTD only provides a few minutes a day for any given location.  This prevented the OTD from studying local weather activities, but allowed the OTD to study global lightning patterns and their evolution.  The OTD also launched at a time when the awareness of the important role lightning played in the Earth’s atmosphere was becoming better understood and that lightning was likely an indicator of the strength of convective storms.  OTD efforts would contribute to the discovery of lightning as an indicator of potential severe weather, what we now call lightning jumps.  Additionally, OTD discovered that the global flash rate is approximately 40 flashes per second.  Ultimately, the OTD’s contributions reinforced the need for lightning observations from geosynchronous orbit, which would ultimately lead to the development and launch of the GLM.

OTD_images

Figure 1:  Annual flash frequency from 1995 to 2000 from Christian et al. (2003).

Given its short production time, the OTD served as a production prototype for a more robust, low-Earth orbiting lightning sensor.  This new instrument was the Lightning Imaging Sensor (LIS) aboard the Tropical Rainfall Measuring Mission (TRMM).  The LIS was designed by scientists at the University of Alabama in Huntsville as well as NASA’s Marshall Space Flight Center.  Launched in 1997, LIS, and the TRMM satellite as a whole, far exceeded their projected service life and provided 17 years of continuous observations.  Unlike the OTD, the LIS was on an orbit that focused on the tropical regions of Earth.  However, LIS had superior detection abilities for both day and night.  Figure 2 (below) shows the lightning activity in the LIS field of view for 2012.  Once operational, the LIS has provided significant contributions to investigating convective and precipitation processes.  The long operational life of LIS has also helped identify most lightning active regions on Earth, such as Lake Maracaibo, Venezuela with 232 flashes per square kilometer per year!  Like the OTD, LIS reinforced the importance of a geostationary platform where storm morphology can be monitored continuously.  Many concepts in the design of the LIS have been used in the GLM instrument.

lis_example

Figure 2:  Lightning Imaging Sensor observations of lightning across the instrument’s field of view for 2012.  Image courtesy of NASA’s Marshall Space Flight Center.

Stay tuned for the next “GLM is coming” blog post that will focus on the efforts to prepare for the Geostationary Lightning Mapper.

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