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Santa Ana winds and power line failures found to be behind autumn and winter fires in Southern Cali

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rangerrebew:

Santa Ana winds and power line failures found to be behind autumn and winter fires in Southern California
Posted: July 26, 2021 by oldbrew in data, flames, research, Temperature, trees, wind   
 
Will this be the end of climate alarmists feeding their confirmation biases over these events, resulting in the usual hysteria against atmospheric gases generated by humans? Almost certainly not, as they can still cling to the notion that the summer fires aren’t mostly due to lightning, arson or faulty power lines. Another report says: ‘Further analyses suggested that large fires were not associated with higher temperatures’.
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A team of researchers affiliated with multiple institutions in the U.S. and one in Canada has found that the increasing number of large fires in Southern California during the autumn and winter months is mostly due to the Santa Ana winds and power line failures, rather than rising temperatures, reports Phys.org.

In their paper published in the journal Science Advances, the group describes their study of fires in Southern California going back to 1948.

https://tallbloke.wordpress.com/2021/07/26/santa-ana-winds-and-power-line-failures-found-to-be-behind-autumn-and-winter-fires-in-southern-california/

roamer_1:
No... Santa Anna winds and power lines have been there a long, long time. Why is it that there were not such conflagrations in the past?

Failure to manage brush and ladder fuels will be the culprit. Not allowing folks to cut in fire breaks will be to blame... And all of that is nothing but poor governance.

thackney:
Ignitions explain more than temperature or precipitation in driving Santa Ana wind fires
https://advances.sciencemag.org/content/7/30/eabh2262

...From 1948 to 2018, there were 3258 days with SAWs, and contiguous days of these winds were considered a SAW event. There were 643 SAW events that lasted from 1 to 36 days each (90% between 1 and 10 days) averaging 5.2 days per event. SAW days were concentrated between October and January, with shifts in the past 35 years in peak month, average wind speed per event, and duration of events (Fig. 1). Some of the most notable changes were a substantial drop in SAW events in September during the past 35 years and increased wind speeds in October through January.

...During the 71 years (1948–2018), a total of 3,269,611 ha burned in the region with 45.3% from fires ignited during SAW events. Although there were many more summer fires than autumn and winter SAW fires, the largest fires were during SAW events; 42 events had very large areas burned, ranging from 5000 ha to several over 100,000 ha (Fig. 2A). There was marked temporal variation. In recent years (1984–2018), October had the peak of SAW-associated wildfire numbers and hectares burned, and September and November had a drop in both numbers and hectares burned (Fig. 2, B and C) over the first 36 years of our record. In brief, over the past 35 years, the SAW fire season no longer includes September as an important month, and of greater importance are winter months December and January....

...The number and type of ignitions played a substantial role in determining area burned in Southern California wildfires. Of the 643 SAW events, >75% had no fires (Fig. 5A), showing that ignitions were a limiting factor in SAW area burned. Even during extreme winds (Fig. 5B), there was >50% chance of no burning. During SAW events, 100% of the fires were caused by humans, either intentionally or accidentally. From 1948 to 1983, campfires were the leading cause, whereas from 1984 to 2018 arson and powerline failures dominated (Fig. 5C), and in the past decade, arson fires played a minor role compared to powerline failures (fig. S1)....

...In summary, SAW speed is an important factor determining area burned, but SAW events by themselves do not predict large fire events; over 75% of all wind events result in no fires. Even extreme winds do not always result in large fires, e.g., events with two and three extreme SAW days had little or no area burned. Thus, a major limiting factor to large fires is whether or not there is an ignition that escapes initial attack during the wind event, and the probability of this increases with the number of fires ignited. The importance of this factor cannot be underestimated, as in all months the effect of number of ignitions during a wind event is a major factor determining area burned. In the southern California region, 100% of all SAW fires are the result of human ignitions, either intentionally or accidentally. Over the past 71 years, the sources have changed markedly, with arson, and especially powerline failures, becoming more frequent in the latter part of the 20th century (27, 28)....

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