||Why is the sun becoming so much
"brighter" than it was in the past?
First of all, there are many measurements
taken of the solar intensity. The earth's orbit is not precisely circular
so there is a time of year when we are closest to the sun and a time when
we are farther away. My recollection is we are closest during northern
hemisphere's winter season. We are closest to the sun in early January.
Our period between Equinoxes is one week shorter (Sept-March) than during
the other part of the year as a result of our orbital location.
Also, the output of the sun does vary, but imperceptably as far as you
or I being able to feel a difference. Only the precisest instrumentation
can detect tiny changes.
There are 3 factors that definitely do apply. It is true that brightness
and glare become a much great problem for us as we get older. I'm really
noticing that reality right now as I never have worn sun glasses in the
past (although I probably should have).
Secondly, fall is an excellent time to notice the sun. Our many east-west
streets have "sun in the eye" problems at this time of year
(early Sept into mid Oct or so) because the sun is often right in line
with the streets during morning and evening rush hour. We routinely see
an increase in traffic accidents at this time of year on clear days. This
is also a time of year, climatologically, when there is a greater likelihood
for perfectly clear skies both morning and evening. So sunshine is particularly
persistent. Also, the atmosphere is much drier now than it was a few weeks
ago which means there is greater penetration of certain energy wavelenghts.
Thirdly, the angle of the sun is a big factor now. It is relatively
low in the sky even at noon which means more sunlight reaches our faces
and bodies instead of just the top of our head and shoulders. I was just
outside a few minutes ago and was amazed at how "intense" the
sunlight seemed. We will reach a comparable sun angle again at the end
of February, and while the sun's energy will be the same it will not feel
as intense because air temperatures at that time will be quite a bit cooler.
So while I agree with your observation, the scientific data we have point
to the fact that 1) we are getting older and noticing it more and 2) the
fall -- particularly mid Sept to Mid Oct. is when it is most noticeable,
but that in reality the sun's intensity has not changed. If, however,
you now live in a different area than you did when you were younger, then
you might be perfectly correctly. I grew up in Illinois, much closer to
sea level than my current home in Colorado. Much more of the sunlight
is "attenuated" at low sun angles when you are closer to sea
level than when you are here a mile or more above sea level. That does
make a measurable difference. --Answered by Nolan
||How much sunshine do we get in Colorado?
On average for a year, how many days does the sun shine in Colorado?
This is a question that
comes up several times per year. You will find in many Chamber of Commerce
publications from all areas of Colorado that we get at least 300 days
of sunshine each year. The only problem is, there is no official definition
of "days of sunshine" so there is no data set that you can easily
Have you ever wondered if anyone actually keeps track of stuff like this?
It turns out that for many years, three locations in Colorado have operated
an instrument called a "sunshine switch" -- Pueblo, Denver and
Colorado Springs. If this instrument is cleaned and perfectly calibrated
(which it rarely is), it can tell you minute by minute each day when the
sun was shining. We did a study over 10 years ago based on these three
stations and found that for Denver if you count every day when the sun
came out for at least one hour, that then you could come up with an average
of around 300 "days of sunshine" each year.
But my assumption is that most people, if they heard "day of sunshine"
would assume that meant it was a sunny day. The National Weather Service
did establish a criterion for determining clear, cloudy and partly cloudy
days based on sky cover. Any day, with an average skycover of 30% or less
was considered a clear day, while if the sky cover was 80% or more, (averaged
from hourly sky condition reports between sunrise and sunset), it was considered a cloudy day. Anything
in between counts as "partly cloudy". Based on this definition,
there are 115 clear days, 130 partly cloudy ones and 120 cloudy days,
on average, each year. Over in Grand Junction the number of clear days
is great (137) but the number of cloudy days is almost the same (121).
But the fact is, here in Colorado and much of the Rocky Mountain region,
there are relatively few totally clear days but a whole lot of days when
the sun peeks out at least a little. Therefore, we tend to brag about
our sunshine -- but mislead folks along the way.
I am circling around your questions. Of course the answer will differ
from one location to another in Colorado with the most sunshine occurring
down around Alamosa with the least around Boulder and in the northern
mountains of the state. -- In the Denver area there are probably only
30-40 totally overcast days per year, and some of them are even fairly
bright -- about 300 days would have at least one hour of sunshine sometime
during the day, but only about 115 days per year fit the classic definition
of "clear". -- Answered by Nolan
country gets the most snow and why? We've searched and come up with no
This is a harder question than it seems. The problem is that there
are snow places in many countries, but the whole country may not be
very snowy. The US. for example, is less snowy than Canada, on average
-- by a lot. But there are places in the U.S. that receive more snow
than most places in Canada. So the question is, are you looking for
snowy countries, or just snowy places in countries. The U.S. has a long
history of measuring "inches of snowfall" while that has not
been a standard meteorological measurement in many other countries.
That being said, where are the snowy places. Basically, the best combination
is the northern mid latitudes to southern high latitudes (north of perhaps
40 deg N latitude but not all the way up to the Arctic and close to
a rich source of moisture (like an ocean). Throw in some mountains to
help squeeze out the moisture, and then you're in business. There are
snowy places in high mountains in other parts of the world (Asia, for
example) but snowfall generally falls short of those areas that are
closer to relatively warm oceans. So some of the possibilities become
the U.S. Pacific NW, British Columbia in Canada. The areas of SE Alaska
where mountain ranges are close to the Pacific. Then head over to Europe
-- the Alps harvest a lot of Atlantic and Mediterranean Sea moisture.
The mountains of Norway get tons of snow. And so on and so on. In the
southern Hemisphere there are fewer candidates, but the best is the
southern Andes mountains, and the mountain ranges of New Zealand.
You can pretty much narrow down the possibilities like this. Then,
perhaps, you may be able to find some specific data from those locations.
-- Answered by Nolan
Why is it so windy
in Huerfano County?
Episodic strong winds
are a part of life for all areas in the immediate lee (just east of) the
high Rocky Mountain chain. Most of these strong winds are relatively brief
but severe associated with rapidly descending air cascading over the crest
of the Rockies and racing out to the plains. These "Down Slope Wind
storms" are most common from late autumn into spring and accompany
upper level disturbances in the strong winter-teim jet stream.
Fort Collins, Boulder, Denver, Colorado Springs and Pueblo are all
prone to these windstorm events.
There are a few "preferred" areas that see strong winds much
more commonly. Particular topographic features along the Front Range
of the Rockies make certain areas more prone to strong winds than others.
You are in one of those wind zones. There are three topographic features
of your area that work together to produce a "wind tunnel".
A clue to this tunnel is the location of the Great Sand Dunes. The long,
relatively straight and broad valley of the Huerfano River happens to
run parallel to the strongest upper level winds that blow over the Rockies
in the winter. The bend in the Sangre De Cristo Mountains (and the protruding
Blanca Peak massive) channels the winds toward Mosca Pass. Mosca Pass
provides a low pass for the concentrated winds to blow through. Then,
on the eastern side is a long, broad and straight valley headed straight
for the open plains. And thar' she blows!
This is not a year-round wind tunnel. From late spring through mid
autumn when upper level winds are light, the Huerfano County winds are
not strong. But as long as the upper-level "Westerlies" are
blowing, your wind tunnel will often be working. One of the benefits
of these winds are markedly warmer winter temperatures. Compare temperatures
at Westcliffe to those of Gardner on a breezy winter morning. The difference
can be huge -- as long as you don't consider the wind chill effect.
Under certain circumstances winds can reverse and blow up the valley.
When easterly "upslope" winds blow, the Huerfano valley becomes
a preferred lcoation for heavy snows. In the summer, upvalley winds
create preferred locations for thunderstorm development. The wettest
areas in Colorado in July and August are often found in the Wet and
Sangre de Cristo Mountains where these upslope easterly daytime winds
converge with monsoonal winds blowing up from the south or southwest
at mountain top level. -- Answered by Nolan
What exactly is a
A 100-year "***"
refers to any event that has a one-percent chance of occurrence in any
year at a given point. Probabilities like this are normally determined
based on past historic data. 100-year events have usually been reserved
for heavy rain amounts for a specified duration (at a specified point
or small local area) or peak or annual stream flow volumes at a particular
point along a river or stream. Flood plains are often designated based
on estimated 100-year flood flow volumes. The values of a 100-year event
are area and duration dependent and cannot easily be generalized.
Based on statistical studies, you would like to have 200-400 years
of data in order to make a reasonable stab at estimating the magnitude
of a 100-year "***" In otherwords, there is quite a bit of
uncertainty in many estimates of 100-year events. We only have about
100 years of historic observations of precipitation and streamflow,
so we can estimate 25-year events reasonably well, but our estimates
of 100-year events are much less certain. For example, for Loveland
the 100-year rain storm for a duration of 24 hours is currently estimated
to be about 5.0 inches and for a 6-hour duration about 3.6 inches.
One could do the same sort of analysis for drought. It is fairly easy
to do for annual streamflow volumes, assuming the flow on the stream
has been undisturbed for the past 100+ years (not the case on the Big
THompson). For precipitation it's a bit more difficult as there are
infinite possibilities on how to define drought based on quantities,
durations and aras. But once you arrive at an acceptable definition,
you go through the historic data and determine what the probablity of
occurrence of any precipitation shortage over a prescribed period of
time and a defined area might be. There would be a whole myriad of "100-year
drought" numbers you could come up with based on your assumptions.
The Colorado Water Conservation Board has examined Colorado streamflow
records and can assign probabilities to annual and peak streamflow volumes.
From this, you could estimate a 100-year drought based on single-year
streamflow statistics. Likewise, the paleoclimatologists studying tree
rings could do the same. We have not tried to do the same with precipitation
at this time simply because of the large number of potential combinations
and the fact that no definition satisfies all users. -- Answered by
What is a river basin?
simply the land area that could contribute water to a river simply by
natural gravity. There must be a clearer and simpler definition than that,
but I can't think of it. The South Platte River Basin consists of all
the areas from the crest of the mountains (continental divide) where local
water if allowed to flow naturally by gravity without evaporating would
end up in the South Platte River. Thus Castle Rock is in the South Platte
River Basin as is Cheyenne, Wyoming and Estes Park -- as well as the cities
of Denver, Greeley, Fort Morgan, etc. that are immediately along the river.
-- Answered by Nolan Doesken
What is snow pack?
What is an average snow pack for this time of year?
here in Colorado refers to the accumulation of snow that graduallly adds
up over the course of the winter, mostly in our mountains. The water content
of that snowpack is what water officials monitor so closely since that
relates closely to the amount of water that will end up in our rivers
and stream, reservoirs and irrigation canals during the late spring and
summer. The water content in our mountain snowpack normally reaches its
greatest value in mid April and sometimes doesn't peak until late April
or even early May. Based on an average of over 70 monitoring locations
in high and moderately high snow accumulation areas of our mountains,
the average snowpack water content is about 18 inches at its peak. This
year the snow pack water content reached its maximum in late March at
about 10 inches (again, remember this is just an average of about 70 or
more individual monitoring points in Colorado -- depending on where you
measure, you get a different answer -- but as long as you measure at the
same places every year then you can compare one year to another). Snow
has been melting steadily since then and as of today the statewide average
snow water equivalent remaining in the mountain snowpack was 5 inches
compared to an average on this date of about 17 inches. This infomration
is provided by the USDA Natural Resouces Conservation Service who administers
this snowpack monitoring program. -- Answered by Nolan
What is stream flow
and what does it measure?
is the volume of water (typically measured in units of cubic feet per
second to define instantaneous flow rates or in acre-feet to define the
total volume of water over longer periods of time).passing a specified
point along a river or stream. In our state's system of water law, accurate
measurements of streamflow are critical for determining how much water
is available to each water owner. Hydrologists and engineers also track
streamflows carefully in order to know how large to build structures (bridges,
culverts, canals, dams, spillways, etc.) to safely convey water from snowmelt
and from heavy rains. Scientists have long established useful relationships
between measured snowpack levels and ensuing streamflow volumes so that
winter and spring snowpack measurements result in reasonably accurate
predictions of spring and summer streamflow from our mountain rivers and
streams. -- Answered by Nolan
What is the annual
average temp and annual average precipitation for Colorado?
actually a pair of numbers that we don't pay much attention to -- since
there is no place in Colorado that receives the average temperature and
average precipitation. That being said, 17" of precipitation per
year (rain and melted snow) is a reasonable estimate. If you include the
mountains (which in Colorado, you must), the statewide average annual
temperature is somewhere between 45 and 49 degrees F -- you could use
47. But, again, there is no place in Colorado that I know of where the
average precip. is 17" and the average temperature is 47 F, so this
is just an exercise in research. -- Answered by Nolan
||How deep is the frostline in the winter
in various parts of Colorado?
||A good question for which little
quantitative data are available. It is a function both of temperature (related
in a general sense to elevation but not strictly) and snow cover. Where
snow accumulates deeply, little frost penetration occurs. Here in Fort Collins
where we measure soil temperatures, there was one winter back around 1930
with extreme persisting cold and very little snow when frost penetrated
to more than 30 inches. In most years, the max frost penetration on level,
non-shaded ground is only 10-14" (much more in shaded). The greatest
penetration in the past 20 years has been 18" at our site. We have
had many mild winters recently, and we've had some with only a few inches
(3-8") penetration. The ground is most likely frozen from just after
Thanksgiving until sometime in early March at our station. This year, the
ground remained unfrozen all January except in the top 2 inches at night
and in the morning. This was very unusual.
A location known for deep frost penetration is the San Luis Valley since
they have little winter snow but prolonged cold temperatures. Penetrations
as great as 5-6 feet have been noted, although 3 feet is more common.
In snowier locations, frost penetration is not a big deal -- only a foot
or two -- except for where roads, driveways, sidewalks, etc are kept clear
of snow. There the frost penetration is much greater. We always recommend
contacting county building officials in each individual county, since
they are much more familiar based on regular contacts with experienced
excavators -- they don't have data, but they do have experience, and that
has usually been place into county building codes. -- Answered by Nolan
Please check back often as we add more questions &
answers to this section.