Level 2 - Events, Groups, Flashes

The base Level 2 product produced by the GOES Ground System (GS) includes GLM events, groups, and flashes.

  • GLM Event: occurrence of a single pixel exceeding the detection threshold during a single ~2 ms frame
  • GLM Group: one or more simultaneous GLM Events observed in adjacent (neighboring/diagonal) pixels
  • GLM Flash: 1+ sequential GLM Groups separated by less than 330 ms and 16.5 km

GLM Flash rates are most closely tied to updraft and storm evolution, Event locations best depict the spatial extent, and Groups are most similar to ground-based network strokes/pulses.

The radiance is recorded for each illuminated pixel (Event), and the Group/Flash locations represent radiance-weighted centroids that consider all constituent Events/Groups. 

The L2 GLM data will not be available in AWIPS for the foreseeable future, rather gridded products will be distributed.

 

 

Gridded GLM Products

Description of GLM gridded products can be found here.

The GLM captures images 500 times per second, producing imagery rather than point observations.  The size and shape of the GLM pixels vary throughout the field of view, so a novel gridding procedure was developed to resample the GLM observations to the 2 x 2 km ABI fixed grid.  Polygon clipping techniques are employed to properly report the GLM observations on the finer resolution fixed grid.  The image below illustrates the gridding process.  

The initial product is a flash extent density (FED) grid that reports the number of flashes occurring over each grid cell during the specified time interval (see animation below).  Additional gridded products are planned for deployment later this year, including average flash area and total optical energy grids.

 

 

AWIPS Implementation

Tools have been developed for real-time processing of the new gridded GLM products.  An integration activity tailored them to the requirements of the NWS operational environment. NWS machines host the initial real-time implementation while developers transition the processing to a permanent home.