By John Abatzoglou.
What do you get when you have an exceptionally dry and warm summer that follows in the heels of a wet winter across British Columbia and the northwestern US? If you answered wildfire, you might be on the right track. Climate Engine illustrates measures of fuel dryness using Land Surface Temperature from MODIS during the 2017 summer fire season out West. Fuel dryness is one measure of the propensity of vegetation to be able to ignite and carry a wildfire.
Interactive View on Climate Engine: (Click Here)
We previously reported on the exceptionally wet winter across the western US, leading to unusually prolonged persistence of snow at high elevations and unusually lush vegetation in arid portions of the Great Basin and Northwest. Then things changed. Since May, most of the northwestern US and British Columbia has been unusually dry and warmer than normal. Places from Seattle, Washington, Victoria, British Columbia, to Missoula, Montana all set records for the number of consecutive dry days this summer. Also clearly evident is the ongoing drought over the northern Great Plains.
The additional moisture last winter and spring has given way to an ample crop of fine fuels that helped enable wildfire potential in arid regions. The combination of pitiful precipitation totals and well above normal temperatures for the past several months have collectively allowed fuel moistures to be below normal throughout the fire season. Toss in some ignitions from lightning and human causes and you have an active fire season across the Northwestern US and a historically record setting (as long as records go back) in British Columbia. Widespread wildfire activity across the western US forced fire management to increase resources committed to wildfire suppression to a preparedness level of 5 on August 10 2017. Through August 16, approximately 2.7 million acres have burned so far in 2017 across the northwestern portion of the US (including portions of the Great Basin, Northern Rockies and Northern California). Over 2.2 million acres have burned so far in British Columbia, already surpassing the largest fire year in modern record keeping set in 1958. These fires have resulted in numerous hazards to infrastructure and emitted tremendous volumes of smoke to share with other parts of the globe.
How is it measured?
One measure of moisture stress and atmospheric dryness that can be assessed globally using remotely sensed observations is land surface temperature. Land surface temperatures (LST) acquired from satellites like MODIS reflect the partitioning of energy going into heating the surface versus that used to evaporate water. When surface moisture conditions becoming limiting, more energy is used to heat up the land surface. Some studies have also shown that LST is a good proxy for atmospheric dryness and the dryness of fine fuels ~ both of which have been implicated in wildfire danger. LST varies substantially across land-cover types, however the use of LST anomalies may be more adept at examining broad scale patterns.
About Climate Engine
Climate Engine provides the ability to map climate and remotely sensed datasets globally for several datasets archived and regularly updated through Google’s Earth Engine. Users can select from datasets and variables, as well as choose to view the raw data or data expressed as a deviation from some baseline or expected value (e.g., long term averages). Users can choose from a set of variables and time periods, examine percentiles or anomalies, and customize the maps to their liking.
Users can also add features to the maps. For example, we added a KML of the Active Fire Product from MODIS that covers Canada from
in the map shown here. This can be done by copying the address of the KML layer and adding it to the custom KML layer option.