Posted on Tuesday, January 28, 2014
As the Northeast recovers from another blast of snow and frigid air on the heels of the "polar vortex," Assistant Professor of Geoscience Nick Metz talks winter weather, climate change and the progress of the National Science Foundation-funded meteorological study undertaken by HWS science faculty and students in coordination with eight other institutions. Metz, who joined the faculty in 2011, has expertise in the effects of high-impact weather on climate and polar cold surges in the Southern Hemisphere, not unlike those sweeping across North America.
What are the major meteorological features of the "polar vortex"? What's unique about the cold snaps we've seen this winter?
The polar vortex is a large area of low pressure in the upper atmosphere; it's a continuous feature of the poles, as the term "polar" implies, but what happens from time to time is that a piece of the vortex breaks off, and that's when we have our coldest outbreaks. Undoubtedly the weather we had was the coldest in many places in two decades, but in some respects, the "polar vortex" is the latest product of the media. It's a term that has been used in meteorology for decades; as meteorologists we talk about this quite often, but it's been stretched a little, sensationalized. A few years ago, Europe and Russia experienced this type of weather. Sometimes, a piece of the vortex breaks off from the poles and affects us as atypical.
To what extent is this "polar vortex" related to climate change?
The polar vortex exists irrespective of the changing climate. It's important to understand the difference between weather (day to day) and climate (long term, over many years). Even in a world where the globe is slowly warming, we'll still experience colder outbreaks. I like to give my students an analogy that relates to a six-sided die. If the world were not warming, three sides of this die would be red (representing the chance for above normal temperatures) and three would be blue (below normal). If you rolled the die, you would have equal chances of above and below normal temperatures. In a warming climate the "die" has been altered so that maybe four sides are red and two are blue. Thus, a roll of the die can still bring up colder than average temperatures but the chances are not as great.
How have these colder outbreaks affected the field research on lake-effect?
It's been great for our field project. This year we've already had an abnormally large number of days with lake-effect snow, which happens when you have cold air moving over warm lakes. And when you plan a year in advance, there's no way of know if a winter is going to be like last winter, with a large warm spell, or like this year, when we've really struck gold with number of days we can study lake-effect snow. The atmosphere has really helped us out.
During the project there have been multiple periods of repeated very intense snow, where we were deploying every day. One day during the first week of January, we deployed at SUNY Oswego for almost 20 hours, it was negative four or five degrees Fahrenheit, with windchills around negative 30. A couple of our weather balloons nearly hit trees because the winds were so strong. It's really exhausting work. You're dealing with time constrains, the process of setting up, blowing up balloons, calibrating instruments, all while you feel like your fingers are about to fall off from the cold. In this setting, you don't want anything to go wrong.
With lake-effect snow, one city can get hammered, while one 10 miles south will be sunny, so it's important to be precise in our forecasts of these many different events. Because this is a multi-institution project, we have multiple teams involved in the forecasting process. Once every three days HWS students take what they've learned in our courses and make a forecast, which is shared with all 100 participants and is used to help determine where our instruments are placed. The students provide the forecasts, and based on their forecasts, decisions are made. Do we deploy, or have a down day? What strategies do we use? How often do we sample the atmosphere? What are the start times and end times?
At the end of this two-month project, we'll have more than 20, rich data sets collected. Actually collecting that data can be challenging, but the forecasting, data analysis, field research projects-it's all very valuable experience. Very few undergrads have this opportunity.