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.

glm_instrument

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.

glm_fov_E_and_W

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.

goes16_central

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: 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.

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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.

It’s Dust (RGB) Season!

It’s Dust (RGB) Season!

A large dust plume occurred over the southwest CONUS on 23 March 2017 as high winds lofted surface materials from the Mexican plateau across the border toward Texas and New Mexico.  Blowing dust events are common in the Spring in this region given the frequency of strong cyclones passing over dry land with sparse vegetation at this time.  For this event the dust plume could be detected during the day in visible imagery and even infrared single channel imagery from the newly launched GOES-16 satellite; however, the high resolution visible imagery traditionally used to monitor dust is not valid after sunset and through the overnight period.  The nighttime impacts of the dust plume eventually extended to locations downstream in Colorado, Oklahoma, and Kansas. Fortunately, a combination of infrared channels from GOES-16 can be used within an red, green, and blue (i.e. RGB) imagery product to highlight the dust location (bright magenta coloring) both day and night.

DustRGB_west-20170324_025722

Dust RGB Imagery from GOES-16 at 0257 UTC (~9:57 PM Central) on 23 March 2017 centered on northwestern Texas of the U.S.  Dust plume is identified by magenta coloring while thick cloud features are mostly in tans to reds with other thin clouds in dark shades ranging from purples and blues to black.

 

For the above and subsequent images/animations: 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.

loopDustRGB_west00to04Z

Dust RGB Imagery from 0002 to 0357 UTC, 23 March 2017 centered over western Texas of the U.S.  Blowing dust is colored in magenta.

This “Dust RGB” was originally created by EUMETSAT nearly a decade ago during initial use of the MSG/SEVIRI instrument in order to more efficiently utilize the 3-fold increase of infrared channels available to forecasters. NASA/SPoRT transitioned this Dust RGB to U.S. forecasters via MODIS and VIIRS starting in 2011 in preparation for GOES-16, and this is the first look at geostationary Dust RGB imagery of a major blowing dust event over the southwest CONUS. This event continued into the night when visible imagery was no longer useful.  For this post note the Dust RGB and visible animations below and how the initial development of dust plumes in Mexico are more easily noticed in the Dust RGB around 1700 UTC in magenta while the plume is not readily evident in the visible imagery even at the end of the animation at 1842 UTC.  In addition, the visible imagery shows the thin clouds (orographically-induced) in northern Mexico as very similar in nature to the dust plumes themselves.  However, the Dust RGB shows the thin clouds in blue to black coloring and easily differentiates the dust from the clouds as well as land surface features.

loopDustRGB_SENM_16to19Z

 

loopVis064_SENM_16to19Z

Dust RGB and visible 0.64 micron imagery from 1617 to 1842 UTC on 23 March 2017 centered over western Texas near the U.S./Mexico border (click on animation to enlarge)

Nighttime Microphysics RGB: Stratus and Fog Cover much of the Great Plains and South, March 2017

Nighttime Microphysics RGB: Stratus and Fog Cover much of the Great Plains and South, March 2017

The development of low clouds and fog over wide areas of the Gulf Coast states and the Great Plains began in the early morning around 0600 UTC on 22 March 2017.  Expansion of these features by 1200 UTC stretched from Texas to Florida in the South and from Oklahoma into the Dakotas along the Great Plains.  These features are easily distinguished in the Nighttime Microphysics (NtMicro) RGB imagery (Fig. 1) from the newly launched GOES-16 imager.  The low cloud/fog range from aqua coloring in the south and become more lime colored toward the colder portions of the Great Plains.  The Pueblo Colorado NWS Weather Forecast Office (PUB) commented on the use of GOES-16 to monitor these low cloud and fog features when considering possible impacts to the public and aviation users.

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Figure 1. Nighttime Microphysics RGB imagery from GOES-16 at 1207 UTC, 22 March 2017 over the CONUS.

For the above image and subsequent animations: 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.

The forecast discussion from PUB included this paragraph in the aviation portion:

“GOES-R fog loop shows stratus deck expanding over the plains as of 10z, and expect at least patchy MVFR stratus along and east of I-25 until midday. Western fringe of the cloud deck will likely produce some IFR cigs/vis near the mountains and Palmer divide as clouds push up against higher terrain.”

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Figure 2. GOES-16 “Fog” product (i.e. 3.9 – 11 micron difference) and ceiling/visibility observations.   A default color enhancement is applied to the “Fog” product.  The animated GIF is from 0812 – 1207 UTC, 22 March 2017

The “fog” loop product mentioned above is the channel difference of 3.9-11 microns , and it is shown in the default AWIPS color curve (Fig 2.) where one can see the pink to nearly white features representing negative differences that correspond to low clouds and/or fog.  As anticipated, some MVFR conditions did occur due to ceilings below 3000 ft, and many parts of the Palmer Divide and the Raton Ridge became surrounded by these features.

While the “fog” product shows the various low cloud and fog features, this same capability is found in the “green” component of the Nighttime Microphysics RGB.  This event of low clouds and fog can also be seen in the NtMicro RGB below (Fig. 3) where the land surface and various mid/high clouds are more easily distinguished from the low clouds and fog. This differentiation of features occurs due to additional infrared channels/differences that help to classify cloud thickness and height.  While the event mostly involved low stratus, fog can be seen developing in the low lying areas of southeast Colorado and northeast New Mexico.  Given the improved resolution of GOES-16 in space and time and the availability of more channels compared to legacy GOES imagers, monitoring the fog between in situ observations becomes easier with the NtMicro RGB, and thus allows forecasters to better anticipate impacts to aviation sites and public roadways.

 

output_NtMicroRGB_CO_lowCloud_20170322

Figure 3. Nighttime Microphysics RGB imagery from GOES-16 from 0812 – 1207 UTC, 22 March 2017 centered on west Kansas.

For more information regarding the Nighttime Microphysics RGB, including interpretation guides for the color features in the imagery:

SPoRT Quick Guide: Nighttime Microphysics RGB in the SPoRT Training Site

SPoRT Nighttime Microphysics RGB Fundamentals (Module) ~20 minutes

 

 

A GOES-16 Multispectral View of the Late Season Nor’easter

A high impact late season Nor’easter is unfolding across the Mid-Atlantic and New England today.  An enhanced view of the impressive storm is possible with multispectral (i.e. RGB) imagery since GOES-16 ABI has 16 bands available compared to legacy GOES sensors. Both the Day Land Cloud RGB (Fig. 1) and Air Mass RGB (Fig. 2) were developed by EUMETSAT and provided to European forecasters with the launch of Meteosat-8 SEVIRI in the early 2000s. These RGBs are part of the set of EUMETSAT RGB best practices that was later adopted by the WMO and today are widely used by other countries such as Japan and Australia who have access to Himawari-8 AHI derived RGB products.  NASA SPoRT has worked closely with the GOES-R/JPSS Proving Grounds to provide RGB products derived from MODIS, VIIRS, AVHRR, and AHI to NWS offices, National Centers, and the Operations Proving Ground to prepare forecasters for multispectral capabilities with GOES-16.  More recently, NASA SPoRT has been working with the Total Operational Weather Readiness – Satellites (TOWR-S) and the Satellite Enhancement Team to provide client-side RGB imagery to the National Weather Service for use in operations.  These are just two examples of GOES-16 ABI RGB imagery that will be available to NWS forecasters in the near future.  A brief explanation of each product is found in the caption and links to training resources are below.

GOES16_Storm_DLCe-20170314_155251

Fig. 1 Day Land Cloud RGB 14 March 2017 15:52 UTC.  Provides the ability to distinguish snow from clouds.  Snow appears cyan, low water clouds appear gray to dull white, and high ice clouds appear cyan.  Although snow and high ice clouds both appear cyan, snow can be distinguished since it remains stationary.

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.

GOES16_Storm_AM-20170314_155251

Fig. 2 Air Mass RGB 14 March 2017 15:52 UTC.  The Air Mass RGB was designed to anticipate rapid cyclogenesis by enhancing regions of anomalous potential vorticity near the jet stream in orange/red tones.  These regions indicate where warm, dry, ozone-rich stratospheric air is being pull downward by the jet stream, which can be in indication of rapid cyclogenesis.  Low-, mid-, and high-clouds can also be identified in the RGB. Low clouds appear blue/green, mid clouds appear tan, and high clouds appear bright white.  Compare the clouds in the Air Mass RGB with the clouds in the Day Land Cloud RGB above to identify cloud height.

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.

For more information on the Day Land Cloud and Air Mass RGBs, including interpretation please see:

NASA SPoRT Natural Color RGB Quick Guide (PDF and Interactive)

EUMETSAT Natural Color RGB Interpretation Guide

NASA SPoRT Air Mass RGB Quick Guide (PDF and Interactive)

EUMETSAT Air Mass RGB Interpretation Guide

Dust RGB Imagery GOES Beyond Visible

The Dust RGB imagery product was originally developed by EUMETSAT for the MeteoSat Second Generation (MSG) SEVIRI imager and later applied to the JMA Himawari-8 (H8) imager (same as GOES-16). Now the same capabilities are seen with the GOES-16 Advanced Baseline Imager (ABI).  NASA/SPoRT has transitioned this product to operational users since 2011 as part of the NOAA Satellite Proving Ground efforts to prepare users for this new geostationary era in the U.S.  SPoRT has co-authored an NWA/JOM article about the impacts this Dust RGB Imagery has already had in operation procedures via use with MODIS and VIIRS instruments. The value of the Dust RGB is the ability the user has to analyze dust plumes when single channel imagery, such as visible channels, do not adequately depict the dust feature.  In addition, true color imagery will often “miss” seeing dust because the underlying surface has a similar color to the dust itself.  And lastly, the Dust RGB allows one to continue monitoring the dust event in both day and night scenes.  Below is an example from a blowing dust event today (March 6, 2017) in the Nebraska and Colorado areas.  Note in the comparison image that the dust (shown in magenta coloring) is readily apparent compared to using single channel visible (0.64 micron, channel 2) imagery alone.  Further below are loops of the imagery for comparison.  Also, note that dry vs. moist air is apparent and another utility of the imagery will be the analysis of drylines in the deep south of the U.S.

DustRGBcompare_Vis_20170306

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.

While the Dust RGB Imagery is not intuitive at first, one only has to look at the area over southern Nebraska  (see below) to see a streak of magenta that represents a dust plume.  The Dust RGB uses several infrared-based channels to differentiate various cloud characteristics and dust.  Particularly useful is the difference between channels 15 and 13 (i.e. 12.3 – 10.4 micron difference) that takes advantage of the low absorption by dust in channel 15, which results in a relatively large positive differnce.  This is the red component of the Dust RGB and it causes dust to have a greater amount of red compared to other cloud features.  The magenta color in the RGB results because the dust is relatively warm and the blue component of the RGB is the 10.4 micron channel which is sensitive to the thermal properties of the object.  In addition to the streak across Nebraska, the region of eastern Colorado also has a dust signature in the RGB.  At the time of this imagery, there were 40 kt wind gust and haze reported over this area, but the dewpoint temperatures were below zero degrees Celcius. While no dust was reported in the METAR observations at the time, it’s likely some type of blowing dust was causing the “haze” and some reduced visibility reports.

GOES16DustRGBExample

GOES16-VIS-Example

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.

Resources for the Dust RGB:

NASA/SPoRT Quick Guide: Dust RGB

SPoRT Application Library: Dust RGB Identifies Aviation Ceiling Hazard at KFMN (micro-lesson)

The Nighttime Microphysics RGB from GOES-16 ABI

The Nighttime Microphysics (NtMicro) RGB imagery provides multiple cloud characteristics of thickness, particle phase/size, and height within a single image in order to analyze cloud features. Below is an example of the NtMicro RGB from the full disk scans taken every 15 minutes.

fd_every15min

Nighttime Microphysics RGB from GOES-16 from 0610 UTC to 1225 UTC on 3 March 2017.

 

Please note, the GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.

The NtMicro RGB imagery (below) over Florida in the early morning of 3 March 2017 show a variety of clouds in the scene.  In southern Florida, various shades of aqua represent low, water clouds where surface observations indicated ceilings of 1000-1500 ft (MVFR conditions).  Slightly further north in central Florida, cloud tops are represented by more tan/yellowish coloring with the RGB representing thicker, colder clouds with larger particles.  This suggests clouds that are a bit higher above the ground.  Continuing northward the cloud features are seen streaming to the east, northeast.  These clouds have mostly dark coloring suggesting little contribution from all the color components (red, green, blue).  The purple clouds are thin, mid-level clouds with ice.  One can tell that the clouds are thin because the underlying surface (land vs water) influences the resulting shade of color as the cloud passes over.  The dark blue is very thin, cold cirrus clouds while the dark red represents similar cirrus clouds but with slightly thicker characteristics.  Also note that some bright red clouds appear over the Gulf Stream (right side of image) representing very thick, cold ice tops of convection.   Overall, quite a number of cloud features can be seen in this IR-based RGB in a very efficient product.

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Nighttime Microphysics RGB over Florida from GOES-16 0701 UTC to 1156 UTC on 3 March 2017. Aqua colored clouds depicting impacts to TAF sites experiencing MVFR ceilings.

 

Please note, the GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.

For more information regarding the Nighttime Microphysics RGB, including interpretation guides for the color features in the imagery:

SPoRT Quick Guide: Nighttime Microphysics RGB in the SPoRT Training Site

SPoRT Nighttime Microphysics RGB Fundamentals (Module) ~20 minutes

AGU EOS Project Update: Transforming Satellite Data to Weather Forecasts