Most March Snow Coverage in 26 Years


The latest data from the Rutgers Snow Lab is available so it is time to look at how the Earth’s climate behaves as the Northern Hemisphere starts spring each year and what spring means to the snow coverage.  The NH is on average 1.5 °C warmer in the month of March than it is in February.  That is not a lot, but it is enough to really drop off the snow coverage.  This is the start of the huge drop in snow coverage that happens each year.

The Inconvenient Skeptic

(Brown) 2011 NH Snow Extent, (Green) 2010 NH Snow Extent, (Blue) Average Snow Extent

I like this chart because it shows the context of the changes.  Each week has a different average snow coverage and this type of chart shows this clearly.  In this way it makes it easier to understand the context of anomaly data.

With that in mind here is the year so far at the weekly anomaly level.

The Inconvenient Skeptic

2011 Weekly Snow Coverage Anomaly

Weather plays a big role as the snow storms in the last week of February had the 2nd highest weekly total coverage of the year.  Only the week of Jan 22nd managed to have higher total snow.

For the year the snow coverage is above average.  Since every week in March was above average, so was the month as a whole.  Statistically the year has been well within the normal distribution for snow coverage around the hemisphere as a whole.  The anomaly is only about 3% of the total snow coverage.

To put that into context requires looking back at how March has behaved in the past.  Here is the March anomaly from 1972-2011.

The Inconvenient Skeptic

March snow extent anomaly since 1972.

In this regard March of 2011 does stand out by a fair margin.  It has the highest anomaly since 1985.  Even though it has the highest anomaly in 25 years, it isn’t a top 5 year.  The period from 1978-1985 had six years that were higher than 2011.  So March of 2011 is impressive for the level of snow that remained through the beginning of spring.  It has been 25 years since so much snow remained this late in the year.

This requires one more chart to find out where the extra snow is this year.

The Inconvenient Skeptic

(Brown) Eurasia Snow extent anomaly, (Green) North America snow extent anomaly for the month of March

This chart is very useful.  It tells the story of the extra snow in a way that the simple anomaly chart could not.  Eurasia is the key contributor to the overall snow anomaly.  When that region has little snow or snow that melts early, the overall anomaly is low.  This year it had one of the top 4 years since 1985, but it happened to coincide with a positive anomaly for North America.  There is extra snow around, but it all over the place instead of only one region.

All of this does lead to an interesting observation.  In 1985 there was lots of snow in March, then for 25 years there was less snow.  For the first time since 1984-1985, Eurasia has a positive anomaly in March for two years in a row.  Since such behavior was common before and it has now happened again it might be an indicator that some climate situation that existed back then is now switching back.

This matches well with the separate observation that the rate of warming has stopped of in the past few years.   This might be a leading indicator that the Earth is headed into another period of cooling.  Since that fits in with the normal climate pattern of the Earth, I do not find it surprising.

Posted in Anomaly and Climate by inconvenientskeptic on April 5th, 2011 at 1:37 pm.

1 comment

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  1. Bruce Apr 6th 2011

    The PDO switched recently. It drives most of the climate.

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