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Davis Instruments Weather Club
April 2008
In This Issue:
WEATHER STATIONS IN ACTION:
Vantage Pro2 Runs (Well, Rides) Boston Marathon
Runners of the 112th Boston Marathon might see a familiar (to us) profile if they happen to look up as they pass the finish line. A brand new Davis Vantage Pro2 will be there on an overpass reporting on the exact weather conditions as the runners come in. And another Vantage Pro2 will be there too - mounted atop a vehicle. The vehicle-mounted station will set out over the course about an hour before the race, stopping at several spots to record wind speed and temperature. The Boston Marathon, the oldest annual marathon in the world, is also the one of the most prestigious. It's only fitting that a Davis weather station will be part of it.
Ed Jacobs, the Boston Marathon Technical Producer, says his company, Interstate Rentals, has been collecting weather data for the marathon using Davis stations for ten years.
Recently, that historical information has become an invaluable resource for race planners. Ed explained that as more marathons are set up, "most tend to be circular - they start and end at the same place. But the Boston marathon is 26 miles (42 kilometers) in a straight line. Questions came up about the effect of headwinds. If a course is circular, it was assumed that any headwinds runners hit would be balanced by tailwinds on the return part of the course. But with our data, we've shown that the course is a series of microclimates and there is no wind disadvantage or advantage over the straight course."
Ed, who has been the Technical Producer of the race for over 30 years, is adding a second console and a repeater to his set up. The station at the finish line will send data to a console on the timers' tables, as well as to one in Ed's trailer about 800 feet (244 meters) and around the corner away.
Marathon runners aren't the only ones who will benefit by the weather data Ed's Vantage Pro2 will provide this year. It will also be at the US Olympic trials which will be held in Boston, on the Mass. Avenue Bridge (sometimes known to non-locals as the Harvard or M.I.T. Bridge).
We didn't sign up to run the race this year. But if we'd known there was a Vantage Pro2 involved, well, we still wouldn't have. (Hey, it's only 26 miles, and you have a whole six hours to finish.)
Want to run the marathon route, or another one in Boston, or anywhere in the US? Check out WalkJogRun
- it'll help you run a route anywhere, with speed and distance calculator. Cool!
Weather Check Quiz Question 1: If a runner has a tailwind on the way back that is exactly equal to the headwind he faced on the way out, will the two equalize each other as far as the runner's speed?
Extra Credit 1: The Mass Ave Bridge is the only bridge in the world measured in:
A. Seriometers
B. Inches
C. Smoots
D. Cubits
E. Mickeys
(Click here for answers.)
Dan and His Kids Use a Vantage Pro2 to Teach UV Danger and Water Conservation Down Under 
Dan Levin told us about his “UV & Me Project” to teach kids about staying safe in the Australian sun. Data is reported from this Vantage Pro2 Plus, mounted at his son, Elliott’s, school.
Dan Levin of Melbourne, Australia, wrote to tell us the story (“so far”) of his Caulfield South Weather Station.
“Caulfield South Weather Station features a Vantage Pro2 Plus,” Dan wrote, “(with a leaf/soil moisture station soon to come). It is the only Australian weather station we know of that is devoted entirely to the benefit of kids. Saying this, it is seen and used by a great number of adults as well. I set it up as a project for all kids to interpret the weather in a simple and somewhat visual format that enhances their ability to understand and question. Through this was born the ‘UV & Me Project,’ a project that actively engages kids to be aware of the dangers of UV and communicate this to others. The project was launched at a local primary school and it was deemed to be of such importance and is so successful that it has been written into the school’s rights and responsibilities to do every year. (The Australian sun is a harsh sun.) The project has spread now to a second school and can be seen
online.
“Not only has Caulfield South Weather Station provided a great source of enjoyment personally to me and my two kids, Elliot (10), and Rachel (7), but our work has been published and featured in the media. A major cover story was done on Caulfield South Weather Station by a local, but very influential newspaper,
The Australian Jewish News . They gave us the full cover and and a couple of pages of the paper! CSIRO, Australia’s peak science body, also featured Caulfield South Weather Station in their science magazine ECOS with a half page article and inclusion in the main magazine index. (
‘Local weather station for 'slip slop slap' alert’).
“We are the current ‘Sunsmart Champions’ of Sunsmart in Victoria, Australia for the work we do on the ‘UV & Me’ project and are also the only private family entry on the Bureau of Meteorology website throughout Australia for Electronic Weather Monitoring.
“Caulfield South Weather Station (at last look at its online stats) is taking between 300,000 and 600,000 hits per month – whatever that means – but it is huge for me!” “I recently purchased a leaf /soil station, three temperature probes, a leaf wetness sensor and two soil moisture sensors, and I am programming up a water conservation system to encourage water conservation. We are experiencing a severe drought that has been ongoing for many years. I hope to develop sustainable gardens encouraging the use of native Australian plants and measurements of soil moisture to indicate when (and how much) water to be used in gardens all around my community and local schools.
“So with this all being said and done, I also want to acknowledge the services of
Ecowatch in Melbourne for guiding me and helping me with Davis equipment when I need it to keep us being the leader in what we are doing.”
Dan, Elliot and Rachel, good job! You’re on our Planet Earth Heroes list!
Weather Check Quiz Question 2: What are folks like Dan hoping kids will think of when they hear: “slip, slop, slap?”
A. “Slip up, let your homework get sloppy, get slapped with detention”
B. The sound of water running wastefully down a drain
C. A dance craze that keeps young backs limber and strong
D. “Slip on a shirt, slop on the sunscreen, slap on a hat”
E. “Slip on ice, slop through mud, slap on goggles: get out in the weather!”
(Click here for answers.)
WEATHER 101:
Dew You Understand Your Dew Point?
Let’s say you’ve just won a spa vacation for your essay, “So Dry I Can’t Even Cry: Living Water Free,” awarded by the American Legion of Loathers of Water in Every Terrain (ALL WET), an association of aquaphobics. You tell the travel agent you’ll go anywhere as long as there is no water – no ocean, lake, river, pond, or puddle, and the driest possible air. But the agent, some kind of water-loving activist, will only tell you the humidity (meaning relative humidity or RH) of two spas: one is 21%, the other is 80%. You choose the first one and end up at the Desert Flower Spa, which is nice and dry. But had you chosen the second, you’d be breathing the “dryer” air at the Polar Bear Spa!
If the weatherman also told you the air temperature (Desert Flower Spa: 110ºF [43ºC], Polar Bear Spa: 24ºF [-4ºC]) and you understood what RH means, you’d know that the warm desert air was actually holding more moisture! But had he just given you ONLY the two dew points (choice one, Desert Flower Spa: 69ºF [21ºC], choice two, Polar Bear Spa: 20ºF [-7ºC]), you would have the short version: there is actually less moisture in the air at the Polar Bear Spa!
RH gives you moisture as a percent of how much total moisture the air could hold, if it was saturated. It is like comparing the amount of water in a container that is 25% full with the amount of water in another that is 75% full – without telling you how big the containers are. (Example: Which has more water, a jug that is 25% full or one that is 75% full? The 75% full one. A 25%-full one-gallon jug has 946 milliliters [3785 milliliters X 25%], while a 75%-full one-quart jug has 709 milliliters [946 milliliters X 75%].) RH is good for describing how humid the air feels.
Dew point, as it turns out, is actually a better measure of the “absolute” amount of moisture in the air.
Dew point is a temperature. It is the temperature to which the air would have to cool, with no changes in pressure or moisture content, to make the air saturated. While it is a faulty example in many ways, thinking of a sponge can make it a bit clearer. A large sponge (warmer air) can hold more water than a small (cooler air) one before it becomes saturated. Imagine pouring a cup of water over a large sponge (it soaks it all up) and then over a small sponge (the sponge holds some, the rest forms a puddle). Cooling air is like making a sponge smaller – it will get closer and closer to its “holding” capacity, until finally, it is saturated and a puddle begins to form. But air is not a sponge, so the analogy ends here. The capacity of air in our environment to “hold” moisture is complicated, but in the end, warmer air “holds” more moisture than cooler air.
Assuming air pressure doesn’t change (if you squeeze the denser sponge, you can make a puddle!) and no moisture is added, as air cools it will eventually reach a point where evaporation and condensation will equalize (relative humidity = 100%) – that’s the dew point. Fog, rain, dew, frost, and/or clouds begin to form depending on the conditions.
Generally, if the dew point is over 70ºF (21ºC), you are going to be very uncomfortable. Dew points near 55ºF (13ºC) are needed for most severe weather.
To see the dew point on your Vantage Pro2 console, press “2nd” and “DEW.”
Weather Check Quiz Question 3: Which one is “less true” than the others? Dew point can be used to:
A. determine the height of a cumulus cloud.
B. predict rain.
C. predict minimum temperature.
(Click here for answers.)
Meet Your New Weatherman: Finn “Smiley” Toothman
Researcher Lauren Smith has discovered something: sharks know when the weather is changing. As storms approach, they dive deep. Ms. (almost “Dr.”; she’s doing the research as part of her Ph.D) Smith is completing a study of how they know – with the hopes of using their ability to help predict weather. Apparently, the sharks are able to accurately sense changes in pressure using hair cells in their balance system. For more about this research, check out the story by Jonathan Heffer in
The Scotsman .
While you are in a sharkish mood, click
Tagging of Pacific Pelagics (TOPP) (and
here) where you can watch the movements of tagged sharks, whales, turtles, pinipeds, and sea birds.
TECH TIPS :
Is Her Original Vantage Pro Compatible with a Vantage Pro2 Console?
Donald and Noelene Mitts, our hot and dry readers from Laughlin, Nevada, checked in with the “How-Hot-Is-It-In-Laughlin Weather Report.”
“When you live here, during the summer the main topic of conversation when greeting friends and strangers is ‘how about this heat?’ or ‘how hot was it?’ Last summer, we had a couple days of 122ºF (50ºC). Most people out here have the little ‘cheapo’ weather stations under their carports where the heat is held in thus making the readings 5 -10 degrees higher than it actually is. But we have an original Vantage Pro, so our readings are right on.”
This led to a good tech question: “Some of our neighbors have asked if they would be able to pick up the signal from our Vantage Pro. It is my understanding that if they were to buy a receiver today that it would not be compatible with the data from our old Vantage Pro. Is this a correct statement and if so is there anything that can be done short of us buying a new Vantage Pro2?”
You’re right, Noelene, about both the actual temperature and about the incompatibility of original Vantage Pro with Vantage Pro2. When we created the Vantage Pro2, we gave it a fancy new, very far reaching radio that hops over a range of frequencies to provide uninterrupted data flow. It was a major improvement, but it did mean that older Vantage Pros, with the original radio, would not be compatible with it. We stopped making the Vantage Pro line, although we still service them. So your neighbors would not be able to share your data.
Noelene, maybe your neighbors would like to share the cost of a new Vantage Pro2? Extra Vantage Pro2 Console/Receivers are available – so one ISS could report to several consoles (up to about 1000 feet [300 meters] away from the ISS.)
(BTW, George Gridley, of Fayetteville, NY, wrote to tell us he finally got a Vantage Pro2, after trying several of our competitors’ products. “I can tell you they are junk when compared to yours,” asserts George, who also likes that our stations are American-made. He goes on to say he’s just waiting for his dad’s non-Davis station to fail (“and it will”). When it does, George is going to get a second console so Dad can share his Vantage Pro2 data.)
Weather Check Quiz Question 4: Reno, Nevada is known as the Diurnal Destination. Well, actually, we made up that moniker, but why?
(Click here for answers.)
MAILBAG:
Weather Monitor II, Age 11, Still Going Strong In North Carolina
We thought you might like to see Rosie and her tall friend, watching over things in Whittier, North Carolina.
Rob Hawk of Whittier, North Carolina, sent us some pretty photos of his oldie-but-goodie Weather Monitor II, a Christmas, 1996, gift.
“It is one of my greatest joys, since I love recording daily weather records at my home in Whittier near the Great Smoky Mountains National Park in extreme western North Carolina, elevation 2,086' (635 meters). The Weather Monitor II has been just awesome through the last 11 years. The pictures attached include the instruments at my home during a heavy snow shower during the winter of 2007 with my cattle dog Rosie in the foreground.”
Thanks, Rob and Rosie!
Weather Check Quiz Question 5: On an aircraft, ice is ice, right?
(Click here for answers.)
YOU'RE BRILLIANT!:
Answers to Quiz Questions
Question 1: No, according to Cool Running, a headwind slows you down more than a tailwind speeds you up.
Extra Credit 1: C. A smoot is 5'7" (1.7 meters) long, the exact height of MIT freshman George Smoot (class of 1966), who was used as a measuring device by his frat brothers who rolled him, end over end, across the bridge. The Mass Ave Bridge is 364.4 smoots, plus a smoot-ear, long.
(FYI: A seriometer is an astronomical measurement equaling one million times the average distance between the Earth and the Sun, about 15.8 light years. A cubit is about 6 palms, the distance between thumb and forefinger on an "average" person, equaling about 18 inches (45 cm). A Mickey is the length of the "smallest detectable movement" of a computer mouse, approximately equal to 0.1 mm, depending on the equipment used. [Wikipedia]) (Back to stories.)
Question 2: D. “Slip, slop, slap” is the motto of an Australian health program to combat sunburn and skin cancer. The program’s mascot is a seagull named Sid (see Sid singin’ the S-S-S song on UTube), but in New Zealand, it’s a lobster. (Back to stories.)
Question 3: B. Rain is formed higher up in the atmosphere; dew point is a surface measurement. Dew point is the starting point for rain prediction, but whether rain will form or not is much more complicated. (Dew point, along with surface temperature can determine the height of a cumulus cloud because we know the rate at which rising air cools and the rate at which the dew point of rising air falls. The cloud will form at the height where the air temperature equals the dew point. Dew point is a good indicator of minimum temperature, as long as the afternoon relative humidity is above 50%. You can use your weather station to verify this: today’s dew point will usually be tonight’s lowest temperature.) (Back to stories.)
Question 4: Diurnal range of temperature refers to the difference in daily maximum and minimum temperatures. Reno is known for its huge diurnal range change! In July, the average daytime maximum is 92ºF (33ºC), but because of chilly nights, the average daily minimum is 47ºF (8ºC). That’s a 45-degree difference. (Back to stories.)
Question 5 :Wrong. Aircraft ice falls into two categories: clear ice and rime ice. Clear ice forms when the plane flies through an area of large supercooled droplets in a cumuliform cloud. It is transparent, builds quickly and is hard to remove. Rime ice forms when the plan flies through a cloud composed of tiny, supercooled droplets. It is lighter and easier to remove. Usually, what forms on wings is a mixture of both. Neither is good for flight. (Source: Meteorology Today, by C. Donald Ehrens) (Back to stories.)
WHO YOU GONNA CALL?
Davis!
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Well, that’s it for this edition. You’ll be hearing from us again next month!
The Davis Weather Club E-Newsletter is published by Davis Instruments.
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