Today you could walk on the Root River all the way to the Mississippi without getting your feet wet. The 2018 stream trout fishery opened this week with clear skies and sub-zero lows. While it’s still too early for lots of trout talk, the weather is a failsafe topic in any midwestern winter. And, as we shall see later, the weather is vitally important to fish at all scales, from creeks and ponds to seas and oceans.
With the onset of the New Year, the east coast is enduring a “bomb cyclone” while most of us are wondering where the term came from. Heark back to the subliminal mutterings of professional meteorologists Frederick Sanders and John Gyakum at MIT in the late 1970s. They defined an atmospheric surface cyclonic circulation as a “bomb” if its central atmospheric pressure falls at an “explosive” rate of at least 1 millibar per hour over a 24-hour period. Such storms were known to be primarily maritime cold-season events at mid-temperate latitudes. This is daunting language to describe what New Englanders might more readily characterize as a nor’easter.
In the last few decades, we have become accustomed to broadcast media images showing well-structured weather systems moving across oceans and continents. To see how this bomb cyclone looks from outer space we can examine the images transmitted from the East CONUS satellite and published on the internet by the National Oceanic and Atmospheric Administration. Note that if you hit the link in the previous sentence, the view that you get will be the current view from the satellite. The video below (Upwelling1 link) is from January 4, 2018, recording the infra-red frequencies observed by the satellite cameras over a period of about 4 hours (and repeated here in a playback loop). In the gray-scale depiction, lighter is colder, whereas darker is warmer. Wind direction is revealed by the movement of the lightest streaks in the video. These are actually streams of ice crystals in the uppermost atmosphere. The bomb cyclone is starkly defined by the anti-clockwise circulation of a “comma” figure crawling in a northeasterly direction along the mid-Atlantic to New England coast of North America.
In addition to the bomb cyclone, the video reveals the large-scale effects of wind-stress on water on the surface of the planet. Replay the video and observe the dark band of water along the Texas to Florida Gulf coast, and along the Florida to North Carolina east coast. The dark band is the result of warmer water rising to the surface of the ocean as the upper layer of water (cooler) is pushed eastward by the prevailing northwest or westerly wind.
This phenomenon is upwelling, a hydraulic process critical to biological production through photosynthesis. This circulation process brings nutrient-laden (deep) waters up to the surface where sunlight drives photosynthesis in microscopic plants.
Play the video one more time and observe the Great Lakes coastlines. Note that the northwest coast of Lake Superior (Minnesota coast) and the west coast of Lake Michigan (Wisconsin coast) show upwelling of warmer bottom water to replace surface waters blown to the east by the prevailing winds.
Who knew that our curiosity about naming winter storms would lead to a greater understanding of biological production in the Great Lakes?