Friday, May 26, 2017

Here's a Fascinating New Way to Define the Seasons

Brian Donegan
Published: May 25,2017

While most people think of the seasons astronomically, when summer begins about June 21 and winter begins about Dec. 22 in the Northern Hemisphere, meteorologists define them climatologically, when summer runs from June through August and winter spans December through February.
But what if there were a third way to classify the beginning and end of each season?
Climatologist Dr. Brian Brettschneider of the University of Alaska-Fairbanks and the Western Regional Climate Center created the maps below using a new method.
Brettschneider defined summer as the days within the warmest quarter of the annual temperature range, and winter as the days within the coldest quarter. Spring is defined as the time between those ranges before summer, and fall is the time between those ranges after summer.
(MORE: Why Seasons Aren't the Same to Meteorologists as the Rest of Us)
This is the length of summer if defined as the days within the warmest quarter of the annual temperature range.
(Dr. Brian Brettschneider)
Based on Brettschneider's definition, summer lasts four months or longer in much of the East, but closer to the coast, the season is 10 to 20 days shorter due to sea breezes keeping temperatures cooler at times.
The length of summer in the West is highly variable, ranging from 85 to 100 days in the highest elevations of the mountain West to over four months in parts of the San Francisco Bay Area.
Along the Gulf Coast and into the Florida Peninsula, summer actually lasts almost five months.
(MORE: Here's When You Can Expect Your First 80- and 90-Degree Temperatures)
In this definition, parts of the upper Midwest, Adirondacks of northern New York and a large swath of Canada actually have long summers.

This is the length of winter if defined as the days within the coldest quarter of the annual temperature range.
(Dr. Brian Brettschneider)
Using the above definition of winter, this season lasts 100 to 120 days in the East, so it's slightly shorter than summer when looking at the annual temperature distribution.
Once again, the length of the winter season is highly variable in the West, where it's as long as four and a half to five and a half months in the Sierra, Cascades and Olympics, but as short as 100 to 110 days in portions of the Bay Area.
Much of the Mississippi Valley, Ohio Valley, Gulf Coast and Florida Peninsula experience winter 100 to 110 days of the year.
(MORE: The Winter Storms of 2016-17)
By this definition, portions of the Desert Southwest have a rather long winter, which spans four months or longer in much of Arizona and into western New Mexico.

This is the length of spring if defined as the time between the coldest quarter and warmest quarter of the annual temperature range.
(Dr. Brian Brettschneider)
If we assume spring is the time between winter and summer, the season ranges from 55 to 70 days in the Northeast and 70 to 75 days in the Southeast, except in Florida, where spring lasts 65 to 70 days.
Spring persists longest in much of the West, with many locations experiencing this season for approximately three months before summer finally arrives.
Portions of Missouri, Oklahoma, north Texas, southwest Missouri and Arkansas also have a fairly long spring which spans 75 to 80 days.
(MORE: When the Last Freeze of the Season Typically Occurs)

This is the length of fall if defined as the time between the warmest quarter and coldest quarter of the annual temperature range.
(Dr. Brian Brettschneider)
If fall is the time between summer and winter, this season lasts just over two months for much of the Northeast, though portions of Maine experience autumn for 70 to 83 days. The Northeast region has the longest fall in comparison with the rest of the U.S. – good news for those who aren't ready for winter's chill.
The West Coast has the shortest fall, ranging from 36 to 50 days from western Washington through western Oregon, most of California, southern Arizona and southwestern New Mexico.
The Rockies, Plains and Southeast have an autumn which lasts just under two months in many locations. The Sunshine State is different than the rest of the Southeast, as south Florida only experiences fall for 36 to 50 days, while the rest of the state has an autumn which lasts 50 to 55 days.
(MORE: A Handy Guide to When Your First Freeze Typically Arrives)
Brettschneider selected a few cities to show the exact breakdown of how long each season runs, based on his methodology defined above.

Annual Temperature Curve for New York City
(Dr. Brian Brettschneider)
In New York City, for example, summer and winter are nearly the same length, as are spring and fall.
Summer kicks off around Memorial Day in the Big Apple and persists for 118 days, while winter is 113 days long. The transition seasons, spring and fall, are 68 days and 66 days, respectively.
Annual Temperature Curve for Denver
(Dr. Brian Brettschneider)
Looking at the Mile High City, winter is about one month longer than summer. Summer is a measly 99 days in Denver – beginning in early June and ending in mid-September – and winter persists for a long 131 days as it begins in mid-November and doesn't end until mid-March.
Since winter is so long, it takes longer to get rid of the cold air that's been locked in for several months. Therefore, spring is about three weeks longer than fall.
Annual Temperature Curve for Minneapolis/St. Paul
(Dr. Brian Brettschneider)
Taking a closer look at a northern city, the Minneapolis/St. Paul metro area may be the opposite of what you'd expect.
By this definition, summer in the Twin Cities actually starts in mid-May rather than late June. Summer lasts 129 days – 20 days longer than winter's span of 109 days.
Spring and fall are relatively close in length, however. Spring is 67 days in Minneapolis/St. Paul, while fall is only a week shorter with 60 days.
Brian Donegan is a digital meteorologist at Follow him on Facebook and Twitter.
MORE: Summer in Winter

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