Geostationary Lightning Mapper (GLM) over New Mexico

An interesting case using the GLM occurred over New Mexico from July 2.  The time period spans 00Z to 03Z for that day.  You can access an animation of the entire period at the following link.  (NOTE:  The animation is ~76 megabytes.  Several still images highlighting key points are shown below.)  This shows the GLM 8 km, 1 minute group density (upper left), ABI 11.2 micron IR (upper right), and the composite radar reflectivities from the Albuquerque, El Paso, and Cannon AFB radars.  (Apologies to the ABI as only the full disk imagery was archived and therefore only updates every 15 minutes.)  No NLDN or Earth Networks data are shown at this time as the data have not been added to the archive as of this writing.  A still image from the animation is shown in Figure 1.

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Figure 1:  A still image from the 00-03Z animation of the GLM 8 km, 1-minute group density (upper left), ABI full disk, 15-minute 11.2 micron IR (upper right), and composite radar reflectivity from Albuquerque, El Paso, and Cannon AFB (lower right) at 0133 UTC on July 2, 2017.

 

[76 MB] GLM over New Mexico (00-03Z, July 2, 2017)

 

The main emphasis is using the GLM in data sparse locations.  NOAA has a great graphic showing the available WSR-88D coverage across the United States (Figure 2). This example focus on New Mexico and the availability of four radars: Albuquerque (KABX), El Pasa (KEPZ), Holloman AFB (KHDX), and Cannon AFB (KFDX).  On this day, it is important to note that the Holloman radar was unavailable.

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Figure 2:  NOAA graphic showing the NEXRAD coverage in the continental United States below 10,000 Feet above ground level.

Several interesting features stand out during these three hours of data.  The first is in northwestern New Mexico and south of the Four Corners region.  At 0022 UTC, the GLM detected a small flash.  Five flashes occurred between 0022-0041 UTC and with a final flash at 0112 UTC.  Figure 3 shows a snap shot at 0036 UTC.  Figure 1 shows that this region of New Mexico has no radar coverage below 10,000 feet above ground level.  The composite reflectivity from the Albuquerque radar (ABX) hints at some activity at the limit of its range and the ABI observes a small region of cooler cloud tops.  Although very little lightning was observed, this can alert forecasters that convectively driven precipitation is occurring where it is otherwise difficult to observe via radar.  Also, a small amount of lightning can be observed in the storms in east-central New Mexico as well.

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Figure 3:  This is the same as Figure 1, but for 0036 UTC.  The yellow circles highlight the area of interest.

A similar case occurred at 0116 UTC (Figure 4) through 0136 UTC.  Again, a very weak, isolated cell as observed by the ABI and the El Paso (KEPZ) radar had an initial GLM lightning observation at 0116.  The storm never intensified beyond two dozen flashes, but persisted for 20 minutes before dissipating.  Also, while the GLM values are quite low, the brighter locations in the group density display highlight some of the stronger cells in the line of storms.

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Figure 4:  Same as Figure 1, but for 0116 UTC.  The yellow circles highlight the area of interest.

We also begin to see the areal extent of the lightning changing by 0152 UTC (Figure 5).  Now, the GLM group density observations are beginning to show lightning that is extending behind the main region of convection.  This is highlighting that even in a low flash rate environment, lightning can still extent tens of miles away from the convective core.

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Figure 5:  The same as Figure 1, but for 0152 UTC.  The small yellow and black circles highlight the location of the long flash.

The final example showing lightning initiation versus radar observations occurs at 0204 UTC (Figure 6) in central New Mexico.  As in Figures 2 and 3, a small lightning flash is observed in a region of weak radar composite reflectivity and cool, but not cold ABI cloud tops.  This highlights the initiation of the lightning threat that the radar composite reflectivity may not emphasize in relation to the active lightning associated with the stronger reflectivity regions.  The animation shows that this preceded the storm intensifying on radar and overall lightning activity through the end of the animation at ~0300 UTC.

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Figure 6:  Same as Figure 1, but at 0204 UTC.  The small yellow and black circles highlight the region of interest.

NOTE:  NOAA’s GOES-16 satellite has not been declared operational and its data are preliminary and undergoing testing. Users receiving these data through any dissemination means  (including, but not limited to, PDA and GRB) assume all risk related to their use of GOES-16 data and NOAA disclaims any and all warranties, whether express or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose.

 

GLM and Spatial Extent

One of the key advantages of the Geostationary Lightning Mapper (GLM) is the ability to observe the spatial extent of lightning.  The example here shows a 1 minute accumulation of the GLM event density over Louisianna and the Gulf of Mexico.  As an aside, a GLM event is any light detected by the GLM in a 2 ms time frame.  The GLM event density is compared with the corresponding radar reflectivity and the corresponding National Lightning Detection Network (NLDN) cloud-to-ground flash density, also at 8 km.  Unlike the GLM, the NLDN identifies the location that a flash goes to ground.  (For this example, the data were accumulated into an 8 km grid that masks this NLDN capability.)  The GLM in this example shows that the total lightning is extending well beyond the locations where flashes are coming to ground into the stratiform region.  Additionally, in the southwestern portion of this example, the GLM is showing intra-cloud lightning over the Gulf of Mexico where there are no cloud-to-ground observations.

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GLM 8 km, 1 minute event density accumulation (left) with the corresponding radar reflectivity and 8 km, 1 minute NLDN cloud-to-ground density (right).

NOTE:  NOAA’s GOES-16 satellite has not been declared operational and its data are preliminary and undergoing testing. Users receiving these data through any dissemination means  (including, but not limited to, PDA and GRB) assume all risk related to their use of GOES-16 data and NOAA disclaims any and all warranties, whether express or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose.

GLM observes a long flash in Minnesota

One of the unique, new features of the Geostationary Lightning Mapper, or GLM, is the instrument’s ability to observe the spatial extent of lightning flashes.  This capability had been previously demonstrated with the ground-based lightning mapping arrays (LMAs).  The LMAs, however, only have a range of 200 km versus the GLM’s near hemispheric field of view.

The figure below shows the 1 min, 8 km GLM group density plot in AWIPS.  The GLM data have been intentionally made all yellow to highlight spatial extent only.  The GLM data are overlaid on the Advanced Baseline Imager (ABI) daytime convection red-green-blue (RGB) composite.  Here, the brighter, more yellow cloud tops indicate newer, more vigorous convection give large numbers of small, ice particles.  The redder cloud types are more mature/dissipating convection due to warmer cloud tops and amount of larger ice particles.  The GLM observes a flash that extends well behind the main convection (observed by the radar mosaic) and spans over 100 miles.  The extent is roughly between Duluth, Minnesota and International Falls, Minnesota.  This example shows the importance that the spatial extent of GLM observations can play in lightning safety as the threat of lightning is non-zero, even after the main convective line has passed.  This case will be analyzed further to compare with the National Lightning Detection Network and Earth Networks observations.

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Figure:  AWIPS screen capture of 1 min, 8 km GLM group densities (yellow, filled) overlaid on the ABI daytime convection RGB, along with the corresponding radar mosaic from NOAA (inset).  Annotations highlight the main features, particularly a long flash observed by the GLM (black dashed oval) that extended around 100 miles in the stratiform region across Minnesota on June 13, 2017.

NOTE:  NOAA’s GOES-16 satellite has not been declared operational and its data are preliminary and undergoing testing. Users receiving these data through any dissemination means  (including, but not limited to, PDA and GRB) assume all risk related to their use of GOES-16 data and NOAA disclaims any and all warranties, whether express or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose. 

A Simple GLM Animation

The achievement of GLM reaching beta status is a big hurdle for the instrument as it prepares to become operational later this year.  SPoRT has been testing the GLM data feed since it started yesterday.  Part of the process has been to put together quick look imagery and animations to test out display and color curve options.  A simple animation was assembled from 8:15-9:45 PM (Central) as storms moved across Tennessee.  The animation highlights the strongest storm cores with the most lightning (darkest colors) along with several long flashes that can be seen on the northern and western edges of the storm.  Several severe wind reports were recorded in this region.

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Animation:  8 km GLM group density centered on Tennessee from 8:15-9:45 PM (Central) on July 5, 2017.  Animation courtesy of Paul Meyer.

NOTE:  NOAA’s GOES-16 satellite has not been declared operational and its data are preliminary and undergoing testing. Users receiving these data through any dissemination means  (including, but not limited to, PDA and GRB) assume all risk related to their use of GOES-16 data and NOAA disclaims any and all warranties, whether express or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose. 

GLM is here! First beta-release imagery

The Geostationary Lightning Mapper (GLM) has completed a product validation review and has been cleared for distribution through the GOES-R Re-broadcast system.  The GLM data are currently in a “beta-status”.  This means that additional updates will occur with the data processing before GOES-R (now GOES-16) moves to the east position in November.  However, this is a great opportunity to get an initial look at the GLM data in real-time.  The two examples below show the first data to be received at 1454 UTC today (5 July 2017) over the eastern United States and for the GLM field of view.  The data have been manually ingested into the National Weather Service’s AWIPS display for demonstration purposes.  Stay tuned for more examples as convection becomes more active!

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Figure 1:  The first GLM-beta status observations (in this example 1 minute GLM group density) from the GOES rebroadcast zoomed in over the eastern United States at 1454 UTC on 5 July 2017.

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Figure 2:  This is from the same time as Figure 1, but is now showing the 1-minute beta-GLM group density over the entire field of view.

NOTE:  NOAA’s GOES-16 satellite has not been declared operational and its data are preliminary and undergoing testing. Users receiving these data through any dissemination means  (including, but not limited to, PDA and GRB) assume all risk related to their use of GOES-16 data and NOAA disclaims any and all warranties, whether express or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose. 

GLM is coming: The instrument

The first beta-release data of the Geostationary Lightning Mapper (GLM) instrument will be out this week. (Update as of 12 June 2017:  GLM beta release has been delayed until July.)  As we get closer to having real-time GLM observations, here is a quick post about the GLM instrument itself.

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Figure 1:  An artist’s image of the GOES-16 satellite with the Geostationary Lightning Mapper (GLM) shown as the zoom out in the upper right.

In the post describing the origin of the GLM (here), it was discussed how the GLM is not the first space-based instrument to observe lightning.  However, it is the first lightning sensor available in geostationary orbit.  Conceptually, the GLM can be thought of as a very large digital camera.  Each pixel of the camera is identifying optical brightness difference from cloud top.  Each pixel is monitoring if any light is observed and if the light observed exceeds a background threshold.  This check is occurring every 2 ms and these observations become the basic GLM “event” observations.  The background field and threshold criteria are designed to reduce false alarms.  The placement of the charge couple device, or CCD pixels, on the instrument designed to help with the instrument’s spatial resolution.  The instrument’s CCD pixels vary in size to help account for the increasing parallax the closer to the edge of the field of view the observations get.  This allows the resolution of the GLM to go from 8 km directly beneath the satellite to only 14 km at the edge of the field of view.

The actual field of view for GLM is shown in Figure 2 for both the GOES-East (eventual location of GOES-16) and -West (future position of GOES-17) positions.  The underlying, normalized annual lightning flash rate comes from observations made by the Optical Transient Detector and Lightning Imaging Sensor from 1995-2005.  Currently, the GLM is in the GOES-16 check-out location (Figure 3).  The total field of view will range from 52 degrees north and south.  Additionally, the GLM does observe total lightning, or the combination of intra-cloud and cloud-to-ground observations.  However, the GLM will not distinguish between the two.  Still, observing total lightning, particularly over such a large domain will aid in warning decision support, lightning safety, as well as situational awareness in data sparse regions.  This will be helpful for detecting flash flooding (noting where is convection) in the inter-mountain west, convection monitoring for aviation, as well as opening up new avenues of research for tropical cyclone forecasting.  Lastly, the GLM was designed to be able to detect 70% of total flashes over the entire field of view over 24 hours.  The false alarm rate was designed to be less than 5%.  Recently, a calibration and validation field campaign had been underway to investigate the GOES-16 instruments.  Early indications are that the GLM will likely exceed the design specifications.  Exact values will be provided later after the field data has been analyzed.

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Figure 2:  The field of view for GLM in the GOES-East and -West position.  The normalized, annual lightning flash rate shown is derived from 10 years of Optical Transient Detector and Lightning Imaging Sensor, low-Earth orbiting instrument observations.

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Figure 3:  Same as Figure 2, but showing the current GLM field of view through November 2017.

Subsequent posts will start to focus on actual GLM observations once they are made available.

GLM is coming: Preparations

Creating demonstration data and products to train forecasters for GLM has presented unique challenges.  Aside from the Optical Transient Detector (OTD) and the Lightning Imaging Sensor (LIS), no other space-based platform had similar capabilities to the GLM.  Furthermore, the OTD and LIS were low-Earth orbiting instruments and would only view a small portion of the Earth for no more than a couple minutes at a time.  This prevented their use as a demonstration data set as forecasters would need to see how total lightning (the combination of intra-cloud and cloud-to-ground) evolved with time.  That put the focus on ground networks, which could observe the entire life cycle of a storm.  The ground networks, unfortunately, lacked the ability to observe total lightning (or the capability was not yet available).  The exception was the ground-based lightning mapping array.

The lightning mapping array (LMA) was developed by New Mexico Tech and evolved out of earlier systems, some of which were tested at Kennedy Space Center.  By operating in the very high frequency end of the electromagnetic spectrum (~80 GHz), the LMAs could observe the entire lightning channel within a cloud.  Primarily designed for lightning research, these would become instrumental in the training activities for the GOES-R Proving Ground and the GLM.  This is because the LMAs were capable of observing total lightning.  Their accuracy was extremely good and they have been used for ground verification for OTD and LIS and will do so again for GLM.  Their primary disadvantage is a very short range; generally no more than 200 km from the center of the network.  Figure 1 shows the physical relationship of total lightning to a storm updraft as well as the lightning jump concept.

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Figure 1:  The top two panels show the total lightning density (left) and radar reflectivity at ~20 thousand feet (right) and 1442 UTC.  The radar elevation corresponds to the mixed phase region.  Total lightning is produced by a strong, voluminous updraft extending into the mixed phase region.  This is a non-linear relationship so the strongest updrafts will produce the most lightning.  This physical connection can be harnessed by forecasters as shown in the lower left (total lightning density at 1450 UTC) and right (radar reflectivity at 20 thousand feet at 1452 UTC).  The total lightning shows a “bull’s eye” feature indicating rapid intensification, or lightning jump.  This preceded the radar update at 1452 UTC showing the updraft now extending into the mixed phase region.  This allowed the total lightning to provide additional information on the intensification of this storm and the rapid increase indicates that severe weather is imminent.  Also, the total lightning information shows the spatial extent of the lightning that can be used for safety applications.

The Melbourne, Florida forecast office was the first office to use total lightning data from a local lightning detection and ranging network (very similar to an LMA) in the late 1990s.  This was a combined effort by the forecast office, Massachusetts Institute of Technology (MIT), MIT Lincoln Lab, and NASA Marshall Space Flight Center.  The data became extremely popular with the office and the Lightning Imaging Sensor Demonstration and Display (LISDAD) system was instrumental in investigating the uses of total lightning in real-time.

In 2002, NASA’s Marshall Space Flight Center had installed the research oriented North Alabama Lightning Mapping Array (NALMA).  By March 2003, the NASA SPoRT team, in collaboration with the Huntsville weather forecast office, had made NALMA data available in the National Weather Service display system; AWIPS.  The Huntsville forecast office would then go on to issue its first warning using total lightning data that May.  NASA SPoRT would extend collaborations with a handful of other forecast offices using NALMA as well as the NASA owned Washington D.C. LMA in the late 2000s.

By 2008, the GOES-R Proving Ground was accelerating its efforts with training and hands-on activities, such as the Hazardous Weather Testbed in Norman, Oklahoma.  This required a demonstration product for GLM that could be used in real-time.  The Marshall Space Flight Center had developed the GLM proxy that was derived from NALMA to test data processing algorithms for the GLM.  The drawback was that it could not be run in real-time.  However, in 2009 NASA SPoRT produced the pseudo-GLM (PGLM) product (Figure 2).  It was not an exact replica of future GLM observations, but it represented a reasonable facsimile that allowed for hands-on training that let forecasters better learn about total lightning and its relation to storms intensity and severe weather.

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Figure 2:  An example of the pseudo-GLM flash extent density product derived from the Washington D.C. lightning mapping array during the derecho event of 2012.  The radar reflectivity (right) shows a strong line of storms approaching Washington D.C.  The greatest reflectivities (and likely strongest storms) are towards the northeast.  The pseudo-GLM (left) shows that it has update sooner than the radar, but also emphasizes the northeastern end of the line.  In fact, over 110 flashes are observed in two minutes at one location, highlighting the strongest overall storm.  The convection to the southwest is weaker as evidenced by the lack of pseudo-GLM observations.

NASA SPoRT, thanks to funding via the GOES-R visiting scientist program, was able to reach out to each of the other LMAs that were in operation across the country (and one in Canada!).  By 2014, almost a dozen LMAs were collaborating.  This allowed for the PGLM to be produced for numerous locations as well as expand partnerships to over a dozen forecast offices, three center weather service units, and the Aviation Weather Center.  Figure 3 shows the approximate domain and collaborating organization for each available LMA.  Combined, the collaborations between the forecasters, LMA owners, and the testbeds allowed for a wide variety of feedback discussing operational uses and visualization concepts.  Much of this has directly supported my own efforts as the GLM satellite liaison for the ongoing work in the Satellite Foundational Course for GOES-R, preparing for operational applications training, and the 2017 summer assessment.

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Figure 3:  The approximate domain of the 11 collaborating lightning mapping arrays that have been used as part of the GLM preparations for the GOES-R Proving Ground.  The numbers correspond to the list at top showing the owners of the collaborative network.

Next up in the “GLM is coming” series is a post describing the GLM instrument itself as we await in initial release of GLM data.