These are our Northern Hemisphere atmospheric anomalies. Can we discover teleconnection linkages between any/all of them?
Phases refer to strong (+) or weak (-) pressure differences between pairs of high and low pressure atmospheric systems. The upper scale denotes strong, or positive phase and the lower scale indicates weaker, negative phase. We consider the Earth as a system with the atmosphere as a fluid, because air and water both respond in similar ways to pressure. If we were to take a water balloon, and pinch out or push in on one side, the other side would have some degree of response…..these world wide systems may be communicating with one another…somehow.
Here is an example of teleconnection linkages, using a specific hour, on a specific day, to examine the well known North Atlantic Oscillation. In this example, the clockwise rotation of the Azores (or Bermuda) high pressure area, is shown in orange. The counterclockwise rotation of the Icelandic low pressure area is shown in yellow. Note that they do not seem to actually touch.
Note that the two resident systems, in this particular time frame, seem to act almost as a set of gears, which, as can be seen below, in the same time space envelope, contribute to characteristics of the jet stream over the North Atlantic Ocean.
So why is this even relevant and what does it really mean? In a word, Storm tracks. Check out the tropical system below, in the Caribbean, at the same time on the same day.
Now take a look at how the forecast storm track has been modeled by computer.
In this example, the storm is modeled to move north and be steered north east, between the two NAO pressure systems, by the jet stream winds. The Jet Stream is also referred to as the “Storm Track”, because it controls the pathway storms will follow.
The NAO may also be responsible for surface current distribution of nutrients, larval fish and thermal energy.
NAO transitions between + and – PHASES, each with consequences for our weather:
While we are studying potential teleconnections between Northern Hemisphere, positive and negative phases (strong or weak) of atmospheric oscillations, we are still aware that there may be world wide links, with other oscillations.
World wide teleconnection linkages?
World wide teleconnection linkages can be challenging to comprehend but let’s take a look at one of the oscillating anomalies in the Pacific and then see how it may contribute to severe winter weather which impacted Cape Cod.
Referred to as El Nino Southern Oscillation (ENSO) this is a world class, Pacific Ocean oscillating system, which shifts phases from La Nino to El Nino. Each phase has weather consequences, many of them in distant parts of the world, where they may influence insurance rates for crops and affect the frequency of Atlantic Basin hurricanes. All of our oscillating atmospheric systems seem to be driven by ocean atmosphere temperature differences. Thermal masses at different temperatures drive all of the world’s weather systems but not on the scale of El Nino.
El Nino “begins” (although remember it is actually a cycle) when a 8-10 centimeter bulge of very warm water in the western Pacific, incorporating thousands and thousands of square miles, begins moving as a Kelvin Wave, in an easterly direction. This central Pacific, basin wide transfer of warm water, creates a powerful atmospheric body of warm moist air above the Kelvin Wave. These ocean/atmosphere interactions become more powerful as the Kelvin Wave of warm water concentrates in the eastern Pacific. These interactions influence the Jet Stream, drawing it down to a more southerly latitude. Any alteration in the jet Stream alters the dividing line between warm/cold air masses and changes storm tracks for North America. In this instance, during the winter of 2009-2010, the Gulf states were slammed with unexpected snow and the east coast, including Washington DC, were shut down by blizzards.
For Cape Cod, this change moved the Jet Stream west of us. Ocean low pressure storms that would normally go outside of us, as nor’easters, now came into Cape Cod Bay as sou’westers. These storms tore the inside shoreline of the Bay apart. Some shore front home owners attempted to respond to the unprecedented erosion with an unprecedented scale of nourishment.
