2011 Northern Hemisphere: Snow Coverage Part 2


Part 2 is going provide some seasonal and regional detail that was not covered in Part 1 in the discussion of the NH snow coverage.  One of the things I am trying to show in these articles is how normal it is for certain parts of the world to experience a mild (low snow) winter while others are experiencing a harsh (more snow) winter.  This year has made headlines by being unusually mild in the United States, but that is one of the only regions that is experiencing a mild winter this year, but the discussion of 2012 remains an article for the future.

The regional discussion of the snow coverage in the NH is centered on North America and the Eurasian continent.  2011 as a whole was slightly below average, but the different regions had different results from each other.  That is also normal, but not always the case.

North America:  +0.03 million km2

Eurasia:             -0.23 million km2

Here is the time series of the two regions over the course of the year.

The Inconvenient Skeptic

(Browns) Eurasia average monthly snow and 2011 snow extent. (Greens) North American average monthly snow and 2011 snow extent.

The periods with less than average snow were mostly in the late spring and summer while the rest of the year had a positive anomaly.  Interestingly enough,  that has been the ongoing trend over the past 40 years, but the trend is basically insignificant.  I am not going to use the technical seasons, but 3 month divisions that are Dec-Feb, Mar-May, June-Aug and Sep-Nov.

The Inconvenient Skeptic

(Green) Winter, Dec-Feb (Brown) Spring, Mar-May (Purple) Fall, Sep-Nov (Black) Summer, June-Aug

The inconvenient Skeptic

(Green) Winter, Dec-Feb (Brown) Spring, Mar-May (Purple) Fall, Sep-Nov (Black) Summer, June-Aug

For both regions the trend is slightly positive from Sep-Feb and slightly negative from Mar-August.

Here is where a persons individual perceptions tend to cause problems.  We remember mostly the abnormal events (like a major blizzard from our youth) and that forms our perceptions of what the climate was like in the past.  Then when there is an unusually mild year, we are comparing the two extremes to each other.  Only people living in places that have late spring and summer snow extent are seeing a negative trend.  The actual winter snow extent is not decreasing in either region.

Local variations do occur.  To show this I am going to show the daily snow anomaly maps of the past 13 years.  This will show that for the most part, different regions experience different winters, every year.

The Inconvenient Skeptic

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 1999

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2000

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2001

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2002

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2003

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2004

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2005

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2006

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2007

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2008

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2009

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2010

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2011

(Red) Negative Snow Coverage, (Blue) Positive Snow Coverage for Feb 5, 2012

So while the USA is currently experiencing less snow than average, the northern part of Africa is experiencing the most snow of the entire period of time.  A person experiencing snow for the first time in Africa will have a very different perspective of what the climate is doing than someone in the United States.

Posted in Snow / Snowpack by inconvenientskeptic on February 6th, 2012 at 2:59 pm.

4 comments

This post has 4 comments

  1. Richard Feb 8th 2012

    Surely there must be something wrong with this data. I cannot see how the Eurasian coverage figure can go down nearly to zero in 2011 when it contains the highest elevation land in the world (Tibet et al) whilst the North American figure never gets so low, ~3.0 in 2011.

    That seems to be counter intuitive.

  2. inconvenientskeptic Feb 8th 2012

    Richard,

    The reason is that Greenland is part of North America. That dwarfs the mountain tops.

    In fact few glaciers are large enough to matter. This is a very low resolution picture of snow coverage. Pixel size is enormous and a small glacier would not register at all.

  3. Richard Feb 9th 2012

    That seems reasonable. Sorry. It just struck me as odd at first glance.

    What also strikes me is that this looks like a case of phase modulation on a base (historic) signal (or so it would be in an analogue signal world).

    I have been trying to think of ways to visually realise these types of data sets that may allow underlying, natural patterns to show. Some method that shows both magnitude and phase changes in the data set would seem best.

    A posible solution is to plot the data on a year long circle (such as a 365 day radar plot in Excel) with the inner/central value being some absolute minimum and the outer being some absolute maximum.

    The resultant elipses should demonstrate both magnitude and phase changes over time.

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