Why So Hot, So Soon?

It happens every spring. Early in the season, before the trees have grown leaves and the flowers in bloom, there is always a hot dry day. Temperatures push 90 in the New York Metro region, perhaps a week or two after a cool, damp day where the temperatures don’t get out of the 40’s. For us this year, it was yesterday Wednesday April 7. The map below shows temperatures at 4pm yesterday:



Newark and Hartford have exceeded 90 and unofficial reports from Orange County suggested temperatures of 94! But why and how? Well it has to do with trees, or in this case a lack there of.

Trees do two things that tend to reduce surface temperatures, first they reflect radiation and shade the surface and secondly they are a driver in evapo-transpiration. Let me explain.

Trees, when they have leaves and are photosynthesizing, draw moisture out of the soil and release it to the atmosphere when their stomata are open and they are pulling in CO2 (go-go introduction to biology!). In effect they act to moisten atmosphere when the sun is up. In much of the solar radiation (sunlight) that would go into heating the surface instead heats the water in the atmosphere. This is the same reason that the deserts in northern Africa are hotter than the rainforests at the equator, even though the rainforests receive more sunlight. Overall trees keep temperatures down, and increase the humidity.

So if we had had Tuesday’s weather, sometime in May when the trees were fully deployed – temperatures would have been much milder, perhaps with highs in the lower 80’s - even the sun being higher and stronger in the sky!

Another interesting effect to note on the above temperature map is the influence of the cold ocean on air temperatures. With water temperatures still below 50 in many places, when the wind blows off the ocean it acts to cool costal locations. That is why Long Island showed temperatures in the 60’s and 70’s while Newark burned up in the 90’s.

Interesting weather day in the New York Metro Region.

Sensationalizing Earthquakes in New York

It was just a few years back that some folks forking for the NASA Earth Observatory got in touch with my advisor Nicole Riemer and I. Nicole and I had submitted an abstract for a talk at the AGU meeting in Acapulco, Mexico. This fellow from NASA had read the abstract and decided that our research was interesting enough to write about on the Earth Observatory website. Needless to say, we were pretty excited, any sort of publicity for science research really helps get future grants looked at in a favorable light. After playing e-mail tag, it was decided that we’d talk on the phone. He called me. We started talking. It seemed like he found the research interesting. We talked more about the project, the findings and the impacts on society. Then he asked about how NASA funded the research. I was surprised, and noted that we received no funding from NASA. Shortly after that the interview was over, and it was decided there would be no article, as it was not NASA sponsored research. I was surprised because the research included lots of data generated by NASA satellites, one would think that would be enough?

Since then, I’ve been skeptical about the NASA Earth Observatory’s news branch. Are they science reporters or public relations experts? I am think it’s the later.

None the less, I will put my skepticism on hold to discuss a recent post at the Earth Observatory on earthquake activity in the New York Metro area. (Here is the link to the article and here is the link to the research paper for the brave souls out there). The study finds that earthquake activity in the New York region is higher than what was previously thought, primarily along a narrow fault line known as the Mesozoic Rampapo Fault. In so far as my pathetic knowledge of geology goes, I think Mesozoic refers to a period in time, which would correspond to a depth under the Earth, so the name implies the location and the depth of the fault.

The authors look back at the long term history of earthquakes in the region (since 1677), and again at an instrumental record since the 1970’s to asses the frequency of earthquakes. Their finding is that there are indeed more earthquakes in the region than previously thought, and that the majority of these earthquakes are category 3.0 or less on the Richter Scale. Based on the figure shown here to the right, since the year 1677 it looks like there have been about 25 earthquakes between category 3 and 4, two earthquakes between category 4 and 5, and three earthquakes of category 5 or higher. Based on the figure shown just below, it looks like there have been no earthquakes larger than category 3 since 1974.

For reference, Category 3 earthquakes are described as “minor: Often felt, but rarely causes damage.” Category 4 earthquakes are described as “light: Noticeable shaking of indoor items, rattling noises. Significant damage unlikely.” And Category 5 is described as “moderate: Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings.”

A bit of math tells us that that the study has a period of 329 years. It also tells us once every 13.16 years there is a minor earthquake, once every 65.8 years there is a light or moderate earthquake in the study region. I would conclude from this study that earthquakes occur more often than previously thought but not frequently, and that when they do they are quite minor.

How does NASA’s Earth Observatory interpret the findings?

A study by a group of prominent seismologists suggests that a pattern of subtle but active faults makes the risk of earthquakes to the New York City area substantially greater than formerly believed. Among other things, they say that the controversial Indian Point nuclear power plants, 24 miles north of the city, sit astride the previously unidentified intersection of two active seismic zones.

The authors compiled a catalog of all 383 known earthquakes from 1677 to 2007 in a 15,000-square-mile area around New York City. Coauthor John Armbruster estimated sizes and locations of dozens of events before 1930 by combing newspaper accounts and other records. The researchers say magnitude 5 quakes – strong enough to cause damage--occurred in 1737, 1783 and 1884. There was little settlement around to be hurt by the first two quakes, whose locations are vague due to a lack of good accounts; but the last, thought to be centered under the seabed somewhere between Brooklyn and Sandy Hook, toppled chimneys across the city and New Jersey, and panicked bathers at Coney Island. Based on this, the researchers say such quakes should be routinely expected, on average, about every 100 years. "Today, with so many more buildings and people, a magnitude 5 centered below the city would be extremely attention-getting," said Armbruster. "We'd see billions in damage, with some brick buildings falling. People would probably be killed."

I’ll keep my opinion about sensationalizing science to myself here, but my point is that everyone should be sure to go and look through findings for themselves, and not just take the word of a journalist, a public relations person or worse yet a blogger.