A new tool tracking lightning across the northern hemisphere is helping to change our understanding of the phenomenon called "thundersnow." Technically defined as, "a compound of the words ‘thunder’ and ‘snow’ used informally to describe an observation of snow at the surface that occurs with lightning and thunder" by the AMS Glossary of Meteorology, thundersnow occurs rarely and has been difficult to record. But data from the recently launched Geostationary Lightning Mapper promises to change all that.
According to NOAA and NASA, the GLM is the first operational lightning mapper flown in geostationary orbit. It measures lightning activity continuously over the Americas and adjacent ocean regions with a spatial resolution of approximately 10 km. And when the GLM says lightning, it means total lightning: in-cloud, cloud-to-cloud and cloud-to-ground.
Data capture from the GLM combined with upgrades to the National Lightning Detection Network means that there are new opportunities to examine the secrets of thundersnow and to unlock forecasting possibilities. The NLDN looks at lightning from the ground, providing supplementary data to help verify and define what the GLM's data means. Sebastian Harkema and Phillip Bitzer of the University of Alabama, Huntsville, along with NASA scientists Christopher Schultz and Emily Berndt, found that the flashes of lightning associated with thundersnow lasted longer than lightning during rain-fall events; and that during snowfall, the areas with lightning had less snow accumulation than those without a thundersnow event overhead.
The GLM is not limited to thundersnow. Its data assists with everything from severe storm identification to lightning-sparked wildfires; and contributes both to further research and the accuracy and coverage of forecasts. We look forward to all the new lightning information to come.