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Posts Tagged ‘Summer’

Summer daylight and heat cycle by USA Today

 

 

by Erik Baard

 

A kid waiting to kayak at the Clearwater Festival last Solstice weekend asked me, “If this is the longest day of the year, then why isn’t it the hottest?” It’s a logical question, and I guess a common one. The incomparable Joe Rao addressed it in his New York Times astronomy blurb last week, and USA Today explored the question as well. The graphic above comes from USA Today.

 

In short, if Earth lacked an atmosphere, then surface temperature, apart from heat retained by rocks, would correlate with sun exposure. But our relatively stable atmosphere slowly and steadily receives energy from sunlight over the course of the spring and summer, as days lengthen. That energy, which we feel as heat, builds higher and higher until reaching its peak in July and early August.

 

I suppose an economist might call day length a leading indicator of summer, whereas as temperature is a lagging indicator. Swimmers and boaters (who are perpetually potential swimmers) know that this phenomenon of delay is even more pronounced with water temperatures.

 

Of course both air and water move around, so there’s a good bit of chaos and complexity to the fluid dynamics that make for summer weather and those late night skinny dips in open water that feel as warm as a bathtub. But the principle of heat retention is a far more powerful truth than its exceptions.

 

I’m also reminded of my good friend, David Grinspoon (with whom, for the record, I’ve never skinny-dipped), who joined us with comments about the Orion Nebula for the very first essay on Nature Calendar. He’s an astrobiologist (with an Earthly incarnation as a rhythm guitarist) with prestigious Mars and Venus robotic probe science assignments from both NASA and the European Space Agency, and serves as the curator of astrobiology at the Denver Museum of Science and Nature. He’s devoted much of his career to the planet Venus. He notes that if there was intelligent groundling life on Venus, it won’t see dominant temperature zones as we see them, corresponding to latitude, but instead look skyward to temperate altitudes. This is because Venus has an atmosphere that’s so dense, and therefore conductive, that heat overloads long ago seeped across all geographic areas. The surface is now isothermic, meaning that temperatures at the poles and the equator are the same. It’s gotten so hot there, due to a greenhouse effect gone into overdrive, that David postulates Venusian life would prefer a cloud habitat

 

Of course, our cities perversely punish themselves, with air conditioners dumping extra heat into the dense local ecosystem through their exhaust, building electrical wires, regional transmission lines, and the power plants required to power them. Makes you wonder if there’s intelligent life on Earth.

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When Transportation Alternative’s absolutely wonderful Tour de Queens (enjoy the Street Films video above) rolled into Maspeth on Sunday under the blaze of a record-setting June heat wave, we were subjected to a brutal lesson in urban planning and natural history.

 

The Newtown Creek is infamous for being home to the largest oil spill in U.S. history, and to heavy metals and other industrial pollutants. Increasingly, lay greens are becoming aware of the combined sewer overflows that plague the waterway with pathogens after rainstorms. What’s less known is that, apart from airport landing strips, you won’t find hotter a hotter place in New York City than the banks of the Newtown Creek. The area’s sewage and swelter share the same origin: a concrete and asphalt “hardscape” instead of a landscape. In the absence of trees, grass, and other plants, water rolls off the impermeable surfaces and floods the sewage system while sunlight beats down on unshaded streets that reradiate heat.

 

NASA used Landsat to map our “urban heat island,” where temperatures are over seven degrees Fahrenheit hotter than surrounding region. Maspeth was of particular interest to the NASA researchers because it was both particularly afflicted and a prime candidate for mitigation, with low, flat-topped, strong buildings that could bear the weight of green roofs.

 

 NASA thermal image of New York City.

 

The natural history element I alluded to above is of greater concern to bikers than NASA: Oh, the hills! Maspeth sits on the western end of the Harbor Hill Moraine (as you can see in the U.S. Geological Survey map below) that was plowed up by glaciers over 10,000 years ago.

 

 

USGS Harbor Hill Moraine.

 

The image below is Helen Ho’s photograph of the Queens Museum’s celebrated New York City panaroma model, with pink tape showing our route over the hills and through the mini-torrid zone. 

 

 

Tour de Queens route in the panorama. Photo by Helen Ho.

 

I wrote for the Village Voice about the Urban Heat Island phenomenon (including diet, lifestyle, and city planning tips to survive it) and various animal heat adaptations last year. One part that didn’t get published is the fascinating possibility that migrating birds are leaving New York City plumper than they arrived because they needn’t burn as many calories to stay warm at night. I spent a morning in the woods of Bronx Park observing Chad Seewagen, a Wildlife Conservation Society ornithologist, investigating this hunch. My friends Robin Lloyd and David Berreby later wrote up items about Chad and his work for Live Science and the New Yorker, respectively.

 

 

 

These days, however, most species are working hard to shed heat. Humans are particularly lucky in that we sweat copiously, a gift from our tropical heritage that remains with people of all ancestries. Bear in mind, however, that parents can undo in their own kids’ resilience by raising them with air conditioning; sweat glands that aren’t activated in infancy remain dormant for life. Dogs are among the species that have wet noses, long tongues, and very wrinkled nasal passages to allow for heat exchanges with the air.

 

My favorite evolutionary solution is the carotid rete, a fine web where arteries dump heat into veins and the upper respiratory system so that blood rising to the brain is significantly cooler than the rest of the body. Gazelles have an extraordinarily well-developed carotid rete, but humans are much less impressive in that regard. It’s usually brain temperature that dictates when an animal must stop or pass out, so you can imagine how useful such a tool is for hunters and especially fleeing prey.

 

And so I might have been the only volunteer marshal ready to scream, “A carotid rete! My kingdom for a carotid rete!”

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