Rain Patterns During the Alaska Wildfires

NASA's satellite-based estimate of global precipitation can provide valuable information to officials monitoring the many wildfires in Alaska this summer.  Wildfires occur in Alaska each summer, but July 2019 is shaping up to be a particularly active month.  Few rain gauges exist in the large tracts of Alaskan wilderness, but wildfires unchecked can spread to populated areas within the state.  Satellite-based precipitation estimates are particularly valuable here because of precipitation's relationship to wildfire hazard.

The movie shows NASA's IMERG precipitation estimates for May 1 through July 18, 2019.  The total accumulation since May 1 is shown in millimeters (inches) on the left half, while the accumulation during a 3-hour period is shown on the right half.  The locations of likely fires are shown in red, based on thermal anomalies observed by the VIIRS instrument on the Suomi NPP polar-orbiting satellite.  The VIIRS "hot spot" data has a resolution of approximately 0.25 square kilometers and is based on infrared brightness temperature.  Locations of lightning strikes are shown in yellow, as detected by the network of ground sensors that make up the World Wide Lightning Location Network.  A flash is detected when five or more WWLLN stations around the world detect a radio-frequency atmospheric signal from the same lightning flash. A gray circle along the southern coast or center of Alaska represents the cities of Anchorage or Fairbanks, respectively.

The first part of the movie covers May 2019, and it is a period of little precipitation, little lightning, and few wildfires. June 2019 shows an increasing amount of lightning but still few fires.  During June, the storms that do pass through central Alaska deliver only about half of the climatological normal amount of precipitation according to NOAA's Climate Prediction Center.

At end of June and into July, things start to heat up.  Numerous wildfires are present in Alaska even though regional storms put out some of the fires.  One such storm passes through Alaska's west coast on June 27 and another on July 1 near Fairbanks. During the first half of July, many wildfires burn.  There is an absence of large storms coupled with significant lightning activity, which together contribute both to a dry fuel supply and lightning to ignite it.

References: 

For IMERG data, visit NASA's Precipitation Measurement Missions  Data Access webpage: https://pmm.nasa.gov/data-access/downloads

The Visible Infrared Imaging Radiometer Suite (VIIRS) hot-spot data was downloaded from NASA's Fire Information for Resource Management System: https://firms.modaps.eosdis.nasa.gov  

Lightning data provided by University of Washington: https://www.wwlln.net

Climatological data provided by NOAA's Climate Prediction Center: https://www.cpc.ncep.noaa.gov/product

Visualization by Owen Kelley at NASA's Precipitation Processing System and Jacob Reed (Telophase / NASA GSFC)

Text by Owen Kelley (NASA GSFC)