Observed variations in U.S. frost timing linked to atmospheric circulation patterns

The primary drivers of US frost timing variations over the past century are atmospheric circulation patterns originating over the Pacific Ocean. Hemispheric warming appears to have amplified some of these patterns, contributing in particular to later fall frost timing over the North and West regions.

- Court Strong, Associate Professor Department of Atmospheric Sciences University of Utah[1]

• States that several studies document lengthening of the frost-free season within the conterminous United States (U.S.) over the past century, and report trends in spring and fall frost timing that could stem from hemispheric warming
• Partitions the U.S. into four regions and uncovers atmospheric circulations that account for 25–48% of spring and fall-frost timing
• Finds that these circulations appear responsive to historical warming, and they consistently account for more frost timing variability than hemispheric or regional temperature indices