Happy September equinox, everyone.

One of the cool things about this day is that it has a fairly high profile on the common, demi-Gregorian calendar, the equinoxes perhaps figuring even larger than solstices in my casual surveys. Another one is that it is only the autumnal equinox if you live north of the equator: otherwise, it is the vernal kind.

Read the rest of this entry »

Advertisements

Wayfinding and waves

27 April 2009

I once had a brief discussion with a much smarter fellow than myself wherein he argued that four was an arbitrary number for cardinal geographic directions. While I concede (now, as I didn’t then) that he is correct from a geometric point of view, there seems to be at least one evident physical reason for the choice: one direction each for sunrise, sunset, and halfway from each to the other.

While Guy Ottewell gives a potential (if esoteric) thesis for why A is the first letter of a couple of different alphabets, I have nothing like the speculative erudition to say whether my guess holds any water. I do know, though, that while useful direction finding tools can be simple, they can also be arbitrary. Polynesian navigators use celestial coordinate systems shaped from the rising and setting of the Sun and other stars, and these coordinate systems are sometimes symmetrical and even, but not always. Navigators also shape their course based upon other information including clouds, wind, sea critters, birds, and other factors.

One of these other factors was brought into sharper focus for me as I flew from Minneapolis to Cleveland last week, passing over Lakes Michigan and Erie on the way. As far as I’ve been able to figure, this trip was at a similar altitude to those from Hilo to Honolulu, flying at approximately 30,000 feet. What struck me as different, though, was that while I was used to seeing the Pacific Ocean with increasing complexity as more and different sets of waves gradually revealed themselves crossing and rolling on its slightly rough skin, I didn’t see any texture of swells on the two Great Lakes.

Having grown up about six blocks from the edge of Lake Superior, and spent time tagging along on boats with my father from a tender age, I can attest that the Great Lakes do possess waves of sufficient size as to be seen from the air. Those waves might not be the sixty-foot seas of the northern Pacific that cause the weather announcers to doubt their script in the middle of reading it, or even the massive rollers that create the fantastic offshore breaks at Peahi near Maui or Mavericks off California, but Great Lakes waves have sunk ships and otherwise imposed their presence in plenty of ways. In short, I was surprised that I couldn’t see anything from the air, even on a relatively calm day.

My guess as to the cause is something called fetch. In this case a noun, fetch refers to the distance across the water that a wind blowing in that direction has to build up waves. While modeling the problem quantitatively is by nature more complicated, fetch can have an effect equal to that of the speed of the wind. It is the biggest reason why small lakes don’t have big waves. Wind speed and fetch can also affect the rate at which waves come in, their period, a characteristic well known and scrutinized by surfers everywhere.

I’ll do some checking with other resources, but I would guess that the tapestry of overlaid swells that help Polynesian navigators orient themselves on the Pacific was also present on Lake Michigan a week ago, and that the chief difference in appearance wasn’t caused by a difference in height of the waves, but rather in their frequency. Lake Michigan is long and thin, perhaps 85 miles wide from Milwaukee, WI on the west side to Grand Haven, MI on the east, but 280 miles north to south from rural Summer Island on the UP to industrial Gary, Indiana. Thus, when the wind is blowing most directions, there is fairly little water to build up long distances between waves. Only if the wind blows due north or due south (winds being named for the direction they are blowing _from_, in most cases) is their enough fetch to produce swells wide enough to be seen from the air.

Any kindly contributors with more knowledge are invited to comment, particularly if you have done some calculations. I am halfway through building a KML file for the trip, and will post it to the comments when it’s finished.

Well, if I can say something without jinxing it, it appears as though our two weeks of winter may be over. Not but what it won’t be grey and rainy for a while yet, but the incipient buds are swelling more greenly on their socially networked branches. The leaves cluttering the sidewalks are from the sweetgums, and most of them only just fell within the last month. We’ve had some sunny warmth here and there, and while I haven’t seen any hummingbirds yet, the Steller’s Jays have been joined by squads of robins.

But the thing that really brought a sense of seasonal change for me was at the end of the cold snap we had in December. Hardly seems fair of me to use that term, when Fairbanks has been pretty chilly by comparison, but people take notice when we get a weeks worth of heavy frosts in Corvallis. At any rate, on about 29 December, I woke to find cirrus clouds covering most of the sky, and causing a strong, beautiful 22 1/2 degree halo around the Sun. I’ve long since given up any pretensions to being able to photograph such phenomena, so I contented myself with staring upward for several blocks on the way to work.

Read the rest of this entry »

Once again, I find that when I settle in to my life, finding few things worth blogging about, I am unsuited to change pace when I do bump into something blogworthy. Also, since I haven’t had an iPhone implanted directly into my brain yet, I still need to be near a computer with internet access for long enough to type a post. Tricky.

Anyway, on Wednesday I got to see both the Atlantic Ocean and the Pacific in a single day. While transcontinental flights are now so common that almost no one bothers to call them transcontinental anymore, I still think it is pretty cool. At the end of our trip to New York we took off from JFK which, like most other infrastructure in New York City, seems to be much too big, old, and held together by a combination of rust and duct tape to actually survive the traffic it handles. The flight landed at Long Beach, CA, and its airport provided a stark contrast in that regard.

Read the rest of this entry »

Well, no tsunami yesterday, completing the trifecta of non-disasters. The potential here was anulled rather quickly, but it took a while longer to clear things in Chile. We did, however, have another earthquake last night. This one was centered, as nearly as I can tell, just a few miles northwest of our house. Also, again last night the clouds were at just the right elevation to be spectactularly illuminated by the 21 July fissure.

And another thing. . .

15 August 2007

Oddly enough, while I was writing the last post about earthquakes, a m7.5 occurred off the coast of Peru, prompting a potential tsunami message. Then two more near-m6 earthquakes in Peru.

Here we go again.

In the spirit of recommending planetarium software in the last post, I’d like to solicit input on good bird books. I browsed for a while today, but couldn’t figure out whether Corvallis was ‘grassland,’ or ‘woodland,’ according to their classifications.

At any rate, I saw five nene flying over the Mauna Kea access road yesterday on my way down from the summit. I’ve seen a few in the same spot (between the runaway truck ramp and the reservoir) before, but never airborne. Cool.