Posted by: mynaturaldiary | January 6, 2012

First Song 2012

First birdsong of the year on 06/01/2012 at 09:00.  Welcome again,  Song Thrushes!

This is about one month earlier than last year…

The weather in the early part of winter 2011-2012 has been warm, wet and very windy. This is because we are in a strong positive phase of the North Atlantic Oscillation, when high pressure in the Azores coincides with low pressure over Iceland, causing westerly winds and Atlantic lows to run into the UK, bringing mild and wet conditions.

There is an opposite condition, the negative phase of the North Atlantic Oscillation, when low pressure in the Azores coincides with high pressure over Iceland, causing Atlantic lows to run into Iberia, and cold, dry easterly winds over the UK.

The NAO is a modulation in the strength and position of the surface westerlies over the Atlantic. It exerts a dominant influence on temperatures, precipitation and storms, of the Atlantic sector and surrounding continents

The time series of the NAO for 2010 and 2011 is below.

So 2010 and January 2011 showed a strong negative phase of the North Atlantic Oscillation, corresponding to cold conditions, especially the winters.

The positive phase of the AO reappeared in the spring of 2011 (warm conditions). The North Atlantic Oscillation went negative in the summer (cold conditions) and back to positive from September 2011 until now, corresponding to the warm, wet and very windy conditions we’re experiencing. The winds are so extreme this year, it’s apparently affecting transatlantic flights.

Right now the NAO is trending down again.

Let’s hope the birds aren’t about to experience a snap cold spell.


Responses

  1. […] in turn has seen the leading indicator for cold times in the north, the arctic oscillation, to […]

  2. […] North Atlantic Oscillation, which is […]


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