Davis
Instruments Weather Club
July 2003
In This Issue:
WeatherLink
5.4 Ready to Go!
Yippee and hooray!
Brand new boxes of our WeatherLink 5.4 software and data loggers
are lining up on our shelves, ready for shipment.
Now owners of Monitor, Wizard and Perception stations can enjoy
the same software features as Vantage Pro owners. For example, the
new software provides a weather forecast feature, with "quick-view"
icons and text messages of expanded details. You'll also get the
moon phase; automatic Daylight Saving Time adjustment for North
America, Europe and Australia; updated Wind Chill formula; improved
Heat Index; and new Temperature-Humidity-Wind Index. Possibly the
most exciting development is the software's support for sharing
data with Weather Underground and CWOP (see below), but there is
lots more to enjoy. Click here
to see all the details.
WeatherLink users who own Monitor, Wizard, and Perception stations
should call Davis Customer Service (800) 678-3669 to order the upgrade
for $49.00. (But if you call soon, you can take advantage of the
Early Bird Special of just $39.00!)
Max Riseman of South Portland, ME, reminded us that we ought to
be tooting our own horn more when it comes to the APRS (Automatic
Position Reporting System) capabilities of WeatherLink.
"It would make a good story," Max wrote. "It could
maybe even save your life [by improving forecasts]."
He's right. You can use WeatherLink's APRS features to participate
in the National Oceanic and Atmospheric Administration (NOAA) Citizen
Weather Observation Program (CWOP) and add your data to the NOAA
mesonet data set. Your real-time weather data will be used to help
the NOAA improve prediction models.
Real time observations from your home weather station can be of
great interest to the many people across the country who share your
interest in the weather. Your data is also valuable to NOAA in their
ongoing weather research. Weather data from stations participating
in the APRSWXNET appear on the NOAA Mesonet Map Display.
You can also use WeatherLink to share your data via Weather Underground,
a personal weather station data exchange. Weather Underground, unlike
APRS, does not require your WeatherLink to be running continuously.
The new software archives data and can fill in the gaps when WeatherLink
was not running.
WeatherLink also provides the necessary protocols for participation
in GLOBE, an international weather-related science
program for elementary and high school students.
And of course, there's Davis' own Weather World 'Round,
which provides links to loads of Davis weather station websites.
If you would
like to participate in any of these programs, you need an Internet
connection and WeatherLink software. Instructions on how to participate
are in the WeatherLink software Help files.
Attention Davis Shoppers: The Clearance Center is Now Open!
We don't want
to say this too loudly, as there is a danger of inciting an e-stampede
of weather bugs. So, come closer, we're going to whisper: There
are major bargains to be had at our new Clearance Center. Like,
half off…. Now, now, no e-pushing. There's room for everybody
at the Clearance Center!
Programmers,
Listen Up
(Note: Those
of you who don't speak computese may skip this section.) The new
Vantage
Pro Serial Protocol Docs are now available for download. With
it, programmers can create their own applications that communicate
with their Vantage
Pro weather systems (including Weather Envoy
) and Vantage Pro WeatherLink data logger, regardless of their OS
platform. It describes the low level communications protocol and
commands necessary to communicate between the Vantage Pro WeatherLink
and a computer. (Note: Vantage Pro WeatherLink data logger [product
no. #6510C ] required.)
Summertime,
and the Livin' is Easy If you Wear a Hat and Sunscreen
Don and Noelene
Mitts, of Laughlin, NV enjoyed reading about humidity's role in
the Heat Index, especially in those places where the high humidity
made the index skyrocket. Out there in dryyyyy Laughlin, they wrote,
"the humidity is so low that the Heat Index is always lower than
the outside temps." So we guess Don and Nolene felt just as cool
as a couple of cucumbers the other day when their weather station
was reporting 115ºF and 8% humidity (HI = 109.9ºF) … right.
We do love the
Heat Index (on the Mitts' Vantage Pro console, push "2nd," then
"TEMP/HEAT"), which tells you how hot you'll feel standing out there
in their backyard. But even more useful is the Temperature-Humidity-Wind
index, which takes into account that nice little breeze bumping
the tumbleweeds across the desert out there. (You can get this index
in your software.) But best yet is what all you Vantage Pro Plus
owners can see: the Temperature-Humidity-Solar-Wind index, which
tells you how much hotter you'd suddenly feel in the Mitts' backyard,
watching the tumbleweeds, and the patio umbrella you were just standing
under, bounce off across hot sand. You need a solar radiation sensor
for that one. It predicts how much that lovely sun on the old body
affects your sense of how hot it is. (To see this index on your
Vantage Pro Plus console, push "2nd," "TEMP/HEAT," and then "2nd,"
"TEMP/HEAT," again.)
While we're
on that summertime subject of sunshine, let us take this opportunity
to offer yet another warning about UV radiation. A recent tropical
vacation that included sea kayaking and snorkeling left us rosily
wondering why we didn't heed our own warning, but we'll try to save
you from a similar fate.
Our friend,
Mr. Sol, sends us light in all kinds of wavelengths in which we
can grow our wheat and paddle our kayaks. A portion of that radiation
is of shorter wavelength, or ultraviolet, and beyond our range of
vision. Scientists have divided UV radiation into three groups:
UV-A, UV-B, and UV-C, with each group containing progressively shorter
wavelengths.
It wouldn't take a long stay in the January UV-rich sunshine pouring
down on the airstrip at Patriot Hills, Antarctica, to do damage
to anybody's skin. Because of the unique weather conditions in Antarctica
the stratospheric ozone level above Antarctica has been dropping
each spring for the past decade. Although the level rebounds each
winter, the so-called "ozone hole" has been known to last well into
December. Since stratospheric ozone absorbs UV radiation, it is
no surprise that the Davis weather station there at Patriot Hills
shows very high UV radiation levels all summer long. You can find
out more about ozone depletion, and why it is more severe at the
poles, on the EPA's
site. This photograph was taken near the Davis weather station
set up by our Stanford research friends.
UV-C's very
short wavelengths (100 to 280 nm) are deadly, but luckily for us,
the stratospheric ozone (concentrated between 6 to 30 miles above
the Earth's surface) does an excellent job of absorbing all of it.
The ozone does a pretty good job as well on most of the UV-B radiation
(280 - 320 nm), especially on the shortest wavelengths in this group,
but is a bit less effective stopping those closer to the 320 nm
limit. However, we all know what's happening to that ozone: it's
disappearing, thanks to environmental pollution. Although changes
in use of CFCs has led to improvement, the EPA predicts ozone depletion
to continue for a few more years before it finally stabilizes.
UV-A (320 -
400 nm) has no trouble escaping the ozone and bouncing merrily off
the unprotected skin of humans. Both UV-A and UV-B damage the skin,
with UV-B in the short term causing the red shoulders we brought
back to work from our vacation. In the long run, it also causes
skin cancer, cataracts, and suppression of the immune system. UV-A
is not quite so evil, in fact, we need some of it to synthesize
Vitamin D. (Don't worry, unless you live in a cave and only come
out at dusk, you probably get all the UV-A you need without needing
to bake on a beach…) But in the long term, UV-A ages your skin,
suppresses the immune system, and also contributes to reddening
the skin and to cataracts. The biggest danger of UV exposure is
melanoma, a form of skin cancer that can be deadly and that is much
more likely to occur on the skin of people who have had several
intense overexposures resulting in sunburn.
How likely the
UV radiation hitting those shoulders is to cause a burn depends
on many factors. Latitude, season, and time of day are obvious ones.
There's not much you can do about the latitude and the season, but
you can avoid exposure during the peak midday hours. You are much
more likely to burn at noon than at 7 a.m. because the sun's rays
coming in at an angle in the morning take a longer path through
the stratospheric ozone, which allows the ozone layer to absorb
more of the dangerous radiation. (Six times more than when the sun
is directly overhead!) And don't be fooled by temperature: while
it might actually be hotter later in the afternoon than at noon,
UV radiation decreases in the afternoon. Elevation is another factor
that affects the amount of UV radiation that hits you, as are clouds,
reflection from water or snow, and even surface pollution.
If you are an
outdoorsy type, UV radiation control boils down to this: stay out
of the sun during peak hours; cover up when you can't get into shade.
You should, of course, wear a hat and use sunscreen -- and reapply
it often -- when you are out in the sun. But you should know that
while sunscreen, properly used, is a good sunburn preventative,
there is no evidence that it protects from malignant melanoma.
If you have
a solar radiation sensor, check out the UV Index on your weather
station the day before venturing out. This number can range from
0 (at night) to up to 16 (if you live in the tropics, at high elevation,
and the skies are clear). Moderate risk begins at a UV Index of
about 5, depending on your skin type. Once that number hits 10,
the danger becomes very high.
The UV index
was designed to give a more user-friendly number than the standard
scientific measurement of Watts per square meter. (For you very
mathematical types out there -- and we know you are there -- the
UV Index is equal to the EAS-weighted irradiance, in Watts/m2, X
40. An Index of 10 is equal to an EAS-weighted irradiance of 0.25W/m2.)
The UV index
can also be expressed as Dose-rate, or MEDs per hour. (Minimum Erythemal
Dose is the amount of exposure that causes a barely perceptible
sunburn redness within 24 hours in previously unexposed skin; base
MED = 21mJ/cm2 of EAS-weighted UV energy.) This expression allows
for more accurate predictions of how long of an exposure will result
in burning a particular skin type. A Dose-rate of 4.3 MEDs per hour
is equivalent to a UV Index of 10. The Vantage Pro Plus calculates
the dose by using a real-time integration of the EAS-weighted intensity.
One last warning:
your UV radiation sensor may not be a position to measure any reflected
radiation you may be exposed to. Most weather stations are not placed
right next to the swimming pool, but many sunbathers are! We do
love hiking, kayaks, beaches -- and all of it bathed in our glorious
California sunshine. But when the VP+ says 11.1 (as it does today),
we'll opt for a snooze in the shade.
Weather
Check Quiz Question 1: (This question thanks to reader Dave Corder, owner of a Weather Monitor II.) What is the formula for calculating the Heat Index?
Chicken,
Anyone?
Ev Wittig, of
Bisbee, AZ, could relate to our comments about roadrunners and rattlers
in our last issue.
"Here in Arizona,"
Ev wrote, "roadrunners just love to eat rattlesnake! If a poor hapless
rattlesnake sees a roadrunner nearby, he knows the 'jig' is probably
up and his life is history. The roadrunners say it tastes a lot
like chicken!"
Uh, what was
the UV Index when you talked to that roadrunner, Ev?
Weather
Check Quiz Question 2: Roadrunners aren't the only ones who like to munch rattlers. If we were invited to a barbecue in say, Texas, we might find chicken and rattlesnake sizzling on the grill side-by-side. We try to choose high protein, low fat, low calorie foods. Upon which hunk of meat should we chow down?
UK
Kids Need Your Weather Data
Trevor Atkins,
the headmaster of Eccles Primary School in Norfolk, UK, has a fun
request of our readers. His 50 students, about half of whom have
special education needs, are studying weather and need data from
continuously monitored weather to compare and contrast different
localities and different regional locations. (Sounds like a great
idea!)
However, what
they haven't got is data and where better to turn than the Davis
Weather Club E-News? The students are PC based (using PCLink) and
have Trevor's own Weather Monitor II running at their school, but
would like to study 2002 weather data from anywhere in the world.
Trevor himself has already provided records from his station when
it was set up in Malyasia, so they are off to a good start. If you
can help, send a PC disk with your 2002 weather data to Eccles Primary
School, Wilby Road, Eccles, Attleborough, Norfolk. NR16 2PF, United
Kingdom.
Exploratorium's
Weather Website Up
In our last issue, we mentioned San Francisco's own Exploratorium with its Vantage Pro and web cam on the roof. They've set up their weather website, so you can check it out and see why everybody loves a San Francisco summer.
Weather
Check Quiz Question 3: The Exploratorium's website has a lovely picture of the Earth's albedo. What does albedo refer to? Whose albedo is stronger, the moon's, Mars', or Earths'?
E-Readers
E-Comment on the E-News
We're very disappointed
in you, our faithful Nit-Pick Club. Only one of you found the goof
in our June issue. Smart guy Robert Sant Fournier of Beverly, MA,
knows that unless Chile recently moved in with Guatemala, it does
not extend to 15º North latitude. 15º South latitude is more
like it. Good eye, Robert.
Then there's
Paul Grace, who re-opened the discussion on the final demise of
poor Apatosaurus: "Since the Chicxulub crater in the Yucatan Peninsula
is some 2600 kilometers from the nearest point in Utah, and the
speed of sound is about 350km/hr, it would have taken about 450
minutes for the Apatosaurus to be engulfed in flaming death. Your
'within minutes' might be technically correct, but 'within hours'
might be a little better."
In a fun email
exchange, we asserted that heat and radiation would travel at the
speed of light rather than sound, but Paul shook that argument too,
claiming that heat and radiation still would "not travel around
the curve of the Earth so the Apatosaurus probably wouldn't be cooked
until the burning hot shock wave hit him/her."
Paul may be
right, but the "within minutes" quote came from the Paleobiology
Department at the Smithsonian's National Museum of Natural History,
and we are in no position to challenge those guys/gals! Wonder if
any of those paleobiologists would like to take on Paul's argument?
And, after a
few months of not hearing a word from H. David Thayer, our Oregonian-atmospheric-scientist-genius
friend, we finally got a bit of good information about wind velocity
at ground surface from him:
"As your newsletter
stated, steady winds decrease to a velocity of zero at the surface
of the ground. Turbulent winds are, however, another story entirely.
Ask anyone who suffered through the horrible dust storms of the
1930s Dust Bowl era whether wind can pick up small particles from
the surface of the ground. Dust storms, complete with blowing dirt,
are a nasty feature of the climate in parts of Colorado and New
Mexico (and no doubt other places) to this day. Sand dunes are eloquent
testimony to the power of turbulent winds to carry small particles
of sand in great quantities. The dunes in Colorado's Great Sand
Dunes area of the San Luis Valley reach heights of 60 feet (or more)."
David has a
letter penned by his great-grandmother in June 1876 in Pueblo, Colorado,
in which she sighs, "The only drawbacks are the poor water from
the Arkansas River and the frequent sand storms. After one of these
dust storms you can almost shovel the dust that has come into the
house."
We asked David
if the dust was carried due to turbulence, or to the cumulative
effect of particles being bounced up or piling up (as in a dune)
into the wind flow. He said that bouncing particles can lead to
lots of dust being lifted.
"However," he
wrote, "our studies at Gunbarrel Hill (near Boulder) showed that
turbulence in the wind flow was effective at directing blasts of
wind at the surface of the ground, where they pick up lots of dust
and dirt. In fact, after some of the more infamous Boulder wind
storms, the ground looked as though it had been sand-blasted in
certain areas. The trick here is that the turbulence creates wind
vectors that are not parallel to the ground, allowing jets of air
to be directed at the surface of the ground.
"I'd say both
processes are important in creating dust and sand storms," David
concludes, and we know better than to disagree!
Weather
Check Quiz Question 4: Back in the 1680's, astronomer Edmund
Halley correctly suggested that the trade winds were created by
warm air rising near the equator, bringing a steady stream of surface
winds in toward the equator. Although Halley's belief that the winds
followed the sun, and were hence easterly, missed the mark a bit,
this explanation of the trade winds was the first to replace Aristotle's
assertion that winds were expelled from the earth itself. How does
Halley's explanation also explain the fact that many of the most
arid deserts are situated at around 30º N and S?
Extra
Credit: Why, according to legend, did sailors call the latitudes
around the 30's, the "horse latitudes?"
Extra
Extra Credit: So, if they are not following the sun,
why are the Trade Winds easterly?
You're
Brilliant! Answers to Quiz Questions
Question
1:
Trick question!! If you are looking for a nice clean formula, you'll find, as Dave did, that there is none. In the case of Heat Index, physics and mathematics can only go so far because what we seek is to express how the heat and humidity make a person feel. Math and physics just don't deal so well with the "person" part and the "feel" part of the equation. Instead, the Heat Index is determined by use of a table of temperatures and relative humidities. The short story of how this table came about goes back to the late 70's, when a meteorologist by the name of Steadman, using real people, in real clothing, assessed how hot a person feels at specific heats and humidities. From there, it was matter of "filling in the gaps" in the table. While math and physics are all over the place in the creation of that table, there is no simple formula one can use to determine the Heat Index. Your console uses an extended version of Steadman's table to do a pretty good job of indicating just how hot you'll feel out there today.
Question
2: Did we say we preferred high protein, low fat, and low calorie?
Perhaps we've changed our mind and are henceforce, for all Texas
barbecues, going high fat and high calorie; in fact, we think we
might be leaning toward vegetarianism. A nice three-ounce chunk
of rattlesnake has only 79 calories and two grams of fat, compared
to a three-ounce chicken thigh, which has 129 calories and four
grams of fat. The chicken does come out a bit ahead on protein,
with 23 grams, versus the snake's measly 15. (Source: PalateWorks
and EatChicken.com) The Humane Society however, warns
that rattlesnake meat can carry many varieties of salmonella and
parasites. (As if you really needed that information to say, "No,
thank you, ma'am," to the rattlesnake barbecue-lady.)
Question
3: Albedo refers to a surface's reflectivity. Clouds have high
albedo (up to 90%), and are largely why the earth appears bright
from outer space. Our home planet is the Albedo Champ in the Earth-Moon-Mars
competition. Earth: 30%, Mars: 17%, Moon: 7%. (Source: The Complete
Idiot's Guide to Weather, by Dr. Mel Goldstein.)
Question
4: What goes up, comes down, at least some of it. While some
of the warm air continues toward the poles, some of it begins to
descend, drying out and warming up as it sinks. This happens right
around 30º N and S, making for high pressure, sunny skies,
dry air, much evaporation, and …
Extra Credit:
. . . listless winds. Not great for filling sails and moving a ship.
Sailors often jettisoned cargo, and alas, horses, to try to get
the ship moving.
Extra Extra
Credut: The Coriolis Effect causes the northern hemisphere's
trade winds to come from the northeast, and the southern hemisphere's
trade winds from the southeast.
Who You Gonna Call?
Each month after the E-News goes out, we receive messages back.
Sometimes the messages are in response to a story we shared; other
times they are a request for help of some kind. We read all the
emails, answer those we can, and pass the rest on to the appropriate
departments.
We think you
should know, though, that if you're interested in the fastest possible
reply, news@davisnet.com
may not be the best place to send your message. Questions about
how things work should be addressed to tech support directly at
support@davisnet.com.
For general information about the products, such as how much cable
comes with a station contact sales@davisnet.com.
To request a catalog, you’ll find links for catalog requests
on our web site at http://www.davisnet.com/contact/catalog.asp
Please continue
to send your comments, weather URLs, and story suggestions to news@davisnet.com.
We look forward to getting your comments and any responses you have
to the E-News. Member participation is what keeps the E-News alive
and kicking.
Well, that’s
it for this edition. You’ll be hearing from us again next month!
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