Ground-truth, the eyewitness verification of atmospheric conditions, is an important part of weather reporting. It supplements the data received from remote-sensing equipment like radar and satellites.
On a recent trip to Bermuda, an island that gets its fair share of severe weather, I came across the Early Bermuda Weather Stone in a park near Fort Scaur. At first glance I thought this was a bit of local humor, but then it hit me. This hanging rock is exactly what it claims to be, “…the perfect weather indication.” In essence, it is a ground-truth indicator. The instructions on its sign sum up how to verify the current local atmospheric conditions. It states:
- A dry stone means… it is not raining.
- A wet stone means… it is raining.
- A shadow under the stone means… the sun is shining.
- If the stone is swinging it means… there is a strong wind blowing.
- If the stone jumps up and down it means… there is an earthquake.
- If ever it is white on top… believe it or not… it is snowing.
The stone may be low tech, but its pretty accurate.
Photo Credit: MF at The Weather Gamut
Snapple Real Fact #237, listed under the bottle cap, states, “The number of times a cricket chirps in 15 seconds, plus 37, will give you the current air temperature.”
Intuitively, this makes sense as all living things react to the weather in some way. Crickets are cold-blooded insects and the ambient temperature directly affects their metabolic rate. As the temperature goes up, their energy level increases and they can produce more chirps. As the temperature drops, the rate of chirping declines.
I have seen a few versions of the cricket-thermometer equation. Most differ according to the species of cricket. Others vary in time duration. The first person to study the correlation between air temperature and cricket chirps was Amos Dolbear, a physics professor at Tufts University in the late 1800’s. His equation measures the number of snowy-tree cricket chirps heard in one minute.
It states: T= 50 + [(N-40)/4] …where T= temperature and N= number of chirps per minute. This is now known as Dolbear’s Law.
A simplified version, more akin to the Snapple fact, is: T= N14 + 40 … where T= temperature and N14= number of chirps heard in 14 seconds.
These equations are for temperature readings in degrees Fahrenheit.
- Snowy Tree Cricket
Photo credit: Wikipedia
It’s raining satellites! Well, at least parts of satellites. Over the weekend, an out-of-service NASA weather satellite broke apart and rained down on the Earth. Experts believe the space junk touched down in the Pacific Ocean, but cannot say where exactly. Luckily, no injures have been reported.
The source of this metallic precipitation was an Upper Atmosphere Research Satellite (UARS) that was launched in 1991 to study the chemical composition of the atmosphere and the amount of UV light coming from the sun. It was decommissioned in 2005.
It is rather poetically ironic that experts had a difficult time forecasting exactly when and where the weather satellite would fall. The best estimate was somewhere between 57 degrees north latitude and 57 degrees south latitude… a huge section of the planet … with a debris field some 500 miles long. The behavior of the falling satellite was uncontrolled and unpredictable. A fitting final tribute, I think, to the chaos inherent to the weather that the satellite monitored.
Image Credit: NASA
This summer was not the hottest on record for New York City, that honor goes to the summer of 2010 with 32 days of temperatures at or above 90 degrees Fahrenheit. The summer of 2011, however, was still pretty hot here with 20 days of temperatures at or above 90 degrees. We hit 104 degrees on July 22, the hottest day of the season.
I have to admit that in the early part of the summer, I was concerned about the lack of rain and the possibility of a drought. We received less than average amounts of rain in both June and July. Then came August. We had 18.95 inches of rain in the month of August. That is 14.52 inches more than normal. Most of it came down during Hurricane Irene.
Summer 2011 will be remembered as the wettest summer on record in NYC with 25.23 inches of rain in a three month period. It shattered the old record of 20.40 inches of rain from 1975. And the rain keeps coming.
Autumn arrived a bit soggy this year with 2.61 inches of rainfall on its first day. To add to the drama of the new season’s arrival, the New York metro area was put under a flood watch. We have already seen more than our monthly average of rain for September on top of the record rainfall in August. The ground is saturated.
Based on NWS 30 year averages, we expect about 4.28 inches of rain in September, but as of today we have already received 8.16 inches for the month. With more showers in the forecast this week, keep your rain gear handy!
Today is the September Equinox…the first day of autumn in the northern hemisphere and the first day of spring in the southern hemisphere. It is also the first day of my new blog about all things weather.
Autumn officially began at 9:04 UTC this morning, that is 5:04 AM here in New York.
Seasons are the result of the tilt of the Earth’s axis, a 23.5 degree angle. If we did not have a tilt, we would not have seasons. Today, as autumn begins, the Earth’s axis of rotation is neither tilted toward nor away from the sun. Our equator and the sun are more or less perpendicular. This position gives us approximately equal hours of day and night. This is where the term equinox comes from. It is Latin for “equal night”.
As the days get shorter and the temperatures get cooler, we should see the leaves changing color soon.
Photo Credit: NASA