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No, it’s
not relativists’ plot against true humidity!
Relative humidity (RH) is a way to measure the
moisture content in the air around us.
"It is the ratio of the amount of water
vapor actually in the air compared to the
amount of water vapor the air can hold at that
particular temperature and pressure. The ratio
of the air's actual vapor pressure to its
saturation vapor pressure."-Essentials
of Meteorology by C. Donald Ahrens.
The
part about air "holding" water vapor
leads to some confusion, and will be addressed
shortly.
| RH = |
(e)
--------------------------
(es) |
|
X 100 |
The equation used to find RH is given
above;
Where “e” represents the vapor pressure in
the given parcel, and “es”
represents the saturation vapor pressure
(pressure water vapor would have on a given
parcel of air if that parcel of air’s
evaporation rate no longer exceeds its
condensation rate, or as some people say,
cannot “hold” any more vapor, or maximum
amount of water vapor that given parcel can
“carry”, or think of it as “e” when RH
is 100%.) RH of course is relative humidity,
and the 100 is used so that the product can be
represented as a percentage rather than in
decimal form. If you remove 100, then you will
end up with a decimal value. For example, 0.53
would be 53% if multiplied by 100, 0.76 would
be 76%, 0.10 would be 10% etc… So if the
relative humidity is at 100%, then we know the
equation must equal 1.00 or 100% if multiplied
by 100. Remember I said you can think of “es”
as “e” when RH is 100%? If both
“e” and “es” are the same,
then the quotient must be 1.00 or 100%!
Relative
humidity can change if the air temperature
changes or if more water vapor is added or
subtracted to a given parcel of air (check out
Dalton's Law of Partial Pressures in a
new window).
Obviously, if you remove water vapor from the
given air parcel, the RH will drop, if you add
water vapor RH will increase. Likewise, if you
raise the temperature of the air, the RH will
drop, if you chill the air RH will increase.
To summarize: If temperature goes up, RH goes
down. If temperature goes down, RH goes up (an
inverse relationship). If you add water vapor,
RH goes up, if you subtract water vapor, RH
goes down (a direct relationship).
This
is a good point to clarify a common
misunderstanding about relative humidity that
I see Bif Sundance, Snowy Sunshine, Windy Calm
Day, and other weather dudes and dudettes on
TV convey; "The air (mainly nitrogen and
oxygen) no more has a holding capacity for
water vapor, than, say, water vapor has for
nitrogen. The atmosphere is a mixture of
gases. While saturation (which involves bonds
between different molecules) is a real
phenomenon in liquids it does not describe the
interaction of atmospheric constituents. It is in regard to the inverse
relationship of relative humidity and
temperature."-Alistair B. Fraser. In other faq questions I address
the concept of temperature being a measure of
energy (it is a measure of molecular motion;
faster = higher temps, slower = lower temps).
Thermal energy increases then temperature
increases and vice versa.
We
can never directly see energy, but we know it
is there by the things it does, so we classify
it according to what it does; Electric energy,
Electromagnetic energy, Nuclear energy,
Mechanical energy, Chemical energy etc…
Additionally, different masses have
different Heat Capacities (sometimes called
Specific Heat).
The
higher a substance’s Heat Capacity, the
higher its potential to hold more energy is. If
a substance can hold more energy, then it can do more
work. Heat Capacity or Specific Heat (I only
capitalize these words to emphasize them.
They're not pronouns!) is the
ratio of the change in heat energy in a unit
mass of a substance (like water vapor) to the
change in that substance’s temperature. Heat
Capacity is a characteristic of all
substances. When you measure the heat capacity
of a substance you are partaking in calorimetry. We express a substance’s heat
capacity using the metric system’s unit
called calorie(s). Or, if you can’t get
enough of that efficient and wonderful English
system I promote in faq question #14, you can
use British Thermal Units (BTU).
The
more energy in a given air parcel, the more
evaporative work can be done in that air
parcel. I can measure its temperature, and that temperature tells me how
much work can be done in that air parcel
because it tells me the amount of energy in
that air parcel! And as we know, it requires
energy to do the work of evaporation.
Consider
two air parcels, one has a
temperature of 40°C and a second has a temperature of 20°C, I know that the net evaporation rate in the
warmer parcel is higher than the net
evaporation rate in the cooler parcel. In
other words, more work is being done in the
warmer air parcel because it has relatively
more energy than the cooler parcel. How do I
know this? Because it's warmer! Temperature and
energy are directly related. When higher
temperatures indicate higher energy levels. What does this mean? Well,
it doesn’t mean the warmer parcel can
somehow mysteriously “hold” more water
vapor, but what it does mean is that the
warmer parcel evaporates at a rate much higher
than the condensation rate and therefore has
more energy available to evaporate more
“free” liquid water molecules should they
become available, while the cooler air parcel
(with less energy) cannot supply as much
energy to evaporation because it… well, has
LESS energy, and therefore will exhaust its
energy supply to evaporation work sooner than
a warmer air parcel. Kinetic energy
is needed to break the hydrogen bonds holding
water molecules to each other. With enough
kinetic energy (energy of MOTION, thermal
energy, speed, momentum…) these hydrogen
bonds can be broken and a tiny little water
molecule is “liberated” = water vapor.
Think of it this way:
If evaporation rate is higher than
condensation rate, then there is energy
available to do work should more “free” water
molecules come into a given air parcel; RH
will be less than 100% if this is the case.
If condensation rate is higher than
evaporation rate, then there is no energy
available to continue evaporating more “free”
water molecules, all the energy in that air
parcel is being used and the condensation rate
will exceed the evaporation rate…. and a
cloud will form. "If more molecules are
leaving a liquid surface than arriving, there is
a net evaporation; if more arrive than leave, a
net condensation. It is these relative flows of
molecules which determine whether a cloud forms
or evaporates, not some imaginary holding
capacity that nitrogen or oxygen have for water
vapor."-Alistair B. Fraser
From what we’ve read
so far, we know that warmer air has more
kinetic energy available to do more
evaporation work than cooler air… with this
in mind:
Let
E = 1 unit of energy
Warm Air Parcel =
EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
Cold Air Parcel =
EEEEEEEEEE
30% of the warm air
parcel’s energy = EEEEEEEEEEEE
whereas, 30% of the
cool air parcel’s energy = EEE
So even though both
have a RH of 30%, that 30% doesn’t represent
the same number of energy units (calories or
BTUs).
Another way to put it:
If a WARM AIR PARCEL =
100 calories of energy
And if a COOL AIR PARCEL = 20 calories of
energy
Then, 30% of the warm air parcel’s energy =
30 calories of energy
And, 30% of the cool air parcel’s energy = 6
calories of energy
The latter doesn’t
leave much energy available to do a lot of
evaporation as compared to the warmer air
parcel! You can see there are 24 more units of
energy available in the warm parcel of air
even though it has a Relative Humidity equal
to that of the cooler parcel!
As
you can see, it is not a matter of warm air
somehow “holding” more water vapor than
cool air, or conversely, cool air somehow
being unable to “hold” as much water vapor
as warmer air. It is ONLY a matter of ENERGY.
In fact, everything boils down to energy. So
don't be tricked into believing the analogy of air being a
sponge, or having a “temperature-dependent
holding capacity”. Think in terms of
energy! Now you'll know that when Bif
Sundance the weather dude says it's a hot dry
day with only 20% RH, remember that that 20%
represents a lot more energy than it would on
a colder day.
To find
relative humidity (RH), weather observers use a psychrometer. This device
uses two mercurial thermometers side-by-side
in tandem, connected to a hinge and a handle.
The thermometers are identical, the only
difference being that one thermometer has a
wick on its bulb the other does not.
The wickless thermometer simply measures air
temperature; it is called the DRY BULB. The thermometer with the
wick is called the "WET BULB".
The wick on the wet bulb thermometer is soaked in
distilled water. Once the wick is saturated,
the psychrometer is swung about through the
air manually by the observer (on electric
psychrometers, an aspirating motor is used to
draw air over the wet bulb). As air passes over the wet bulb
thermometer, evaporation occurs. The rates of
evaporation vary depending on atmospheric
conditions (see faq #1). Evaporation
requires energy. This energy is acquired from the surrounding environment.
Energy is removed from the surrounding environment to
energize the evaporation process. The distilled water
in the wick evaporates away removing heat
energy from the air around it in the process
causing the temperature to change around the
wet bulb. The temperature becomes relatively
cooler immediately around the wet bulb
thermometer than it is for the dry bulb
thermometer. This is exactly what happens when
we sweat, which is why you feel cooler when
you sweat ( evaporating smelly
sweat removes thermal heat just above your
skin thus cooling you down). The result is a
cooler temperature recording for the wet bulb
than for the dry bulb*. The difference between
these temperatures is called the
DEPRESSION OF THE WET BULB (or simply,
"depression").
Dry
Bulb Temperature - Wet Bulb Temperature =
Depression.
Don't
worry, the psychrometer doesn't need Prozac or
lithium to feel better, the depression we are
talking about here is simply a the difference
between the dry and wet bulbs! The depression and the
dry bulb temperatures
are plugged into a special chart called the
Psychometric Chart which is a numbers chart
with an X and a Y axis. Across the
X-axis are Depression values, across the
Y-axis are the Dry Bulb Temperature values.
The weather observer locates the dry bulb temperature on the Y-axis
the depression value on the
X-axis. The point of intersection for these
two "points" on the chart will be a number. That number is the RH
value for the given temperature and
depression. Dew point temperature is
found the same way (using dry bulb temperature
and depression) only with a different chart
with different pre-calculated values on it.
*The
wet bulb will NEVER be warmer than the dry
bulb under natural conditions. The only time the wet bulb won't be
cooler than the dry bulb is when it is EQUAL
to the dry bulb. If this is the case, it means
that the air temperature is equal to the Dew
Point temperature and therefore air is at 100% RH.
The dew point temperature is the temperature air has to be cooled to reach saturation.
This is
why humidity levels rise dramatically
at night when temperatures drop, which
explains why dew
forms in the early morning
hours. At night, terrestrial thermal radiation
is lost (radiational cooling) which chills the
air above the ground thus bringing it closer
to dew point.
Moisture levels change constantly, so
there are actually two ways to reach
saturation (100% RH). One way is if air
temperature drops (assuming humidity stays
constant). The other way is if ambient
temperature is constant, then added moisture
to an air mass can cause that mass to reach
its
saturation point.
Generally, just before sunrise. During
the night, long-wave terrestrial radiation is
lost to space, and the longer it depletes the
colder it will become. Radiational cooling
occurs during the night and is particularly
effective on clear nights during winter when
nights are longest and radiational cooling is
allowed to continue for a longer period of
time (more time for heat loss).
In general, about 2-3 hours after noontime.
Incoming shortwave solar radiation is absorbed
by Earth. This energy is then radiated at
longer terrestrial wavelengths
between 1-30 micrometers (Infrared) which
heats the air. Maximum solar radiation input
occurs at noon. Given
time, convection, emission, and absorption of
radiation results in the day's extreme maximum
temperature.
First, a basic understanding
of the electromagnetic spectrum: What is it? It is a
classification of all wavelengths
according to their "size". Energy and wavelength are
inversely
proportional to each other. Longer
wavelengths are less energetic than shorter
wavelengths and
vice versa.
From longest to shortest you have the
following: Radio waves, Microwaves, Infrared,
Visible light
(Red, Orange, Yellow, Green,
Blue, Indigo, Violet), Ultraviolet, X-Ray, and
Gamma Ray.
Ultraviolet to Gamma are considered
to be ionizing radiation, which is another way
of saying BIOHAZARDOUS WAVELENGTHS! Some folks
may lump microwaves in with radio waves,
or
they'll lump indigo and violet together as
just violet. The wavelengths are the same,
just the names include more of the spectrum.
So if your friend says her favorite color is blue,
then you'll know she really likes a
high-frequency green.
Water vapor and
carbon dioxide absorb IR (Infrared)
wavelengths, and an abundance of these two
gases are found right here in the
troposphere. IR wavelengths are what we associate with
heat -- heat is actually
mechanical energy at
the molecular level (motion) -- the atmosphere is
consequently heated
from the ground up. If there is more water vapor and
carbon dioxide present, then
more IR can be
absorbed resulting in Earth being heated from
the lower troposphere. A large portion of
Earth's heating occurs from our own atmosphere
rather than directly from the Sun.
The more solar radiation received, the more Earth
has to convert to IR. And the more IR and
greenhouse gases present, the more
potential for heat we have.
Much of the
UV radiation from the Sun is absorbed by ozone
molecules in the
stratosphere. The rest of the solar radiation
(some UV included but mostly visible light)
continues into the troposphere where
approximately 20% is reflected and scattered
by clouds, 6% is reflected and scattered by
atmospheric molecules, and 4% is reflected and
scattered by Earth's surface (mainly
oceans,
and snow covered areas), and
.00000000000000000000001% is reflected by bald guys with
shiny domes
(just kidding about the bald guy part). Another 19% is
absorbed by the atmosphere and clouds, and the
remaining 51% is absorbed by Earth's
surface. **These percentages are averages**
Key Point: The energy
absorbed by Earth is NOT re-radiated,
or trapped by
greenhouse gases that act as "blankets" causing Earth to overheat!
When our
atmosphere emits radiation, it is not the same
radiation -- which ceased to exist upon being
absorbed by our atmosphere -- as it received. The radiation
absorbed and the radiation emitted do not have
the same spectrum, nor do they have the same photons.
The radiation absorbed
ceases to exist by definition, thus making the
term reradiate a nonsense term that some
dictionaries don't bother to define for
obvious reasons, and
those that do are, I
believe, at fault. Ignore Bif Sundance the
weather dude on TV when he tries to mystify
you with the "blanket" in the sky that "rereradiates"
heat energy causing global warming... His
physics are rusty at best!
The greenhouse effect is
actually energy being absorbed by "greenhouse"
gases, converted,
emitted at longer wavelengths (IR which we
associate with heat) and being absorbed again.
This natural process keeps
our planet from freezing over and putting
the penguins back in power.
With each conversion, energy is lost. If
it weren't we'd have a perfectly
efficient
system; an impossibility as demonstrated by my
car. It would defy the
laws of thermodynamics, and if possible would
probably be termed re-radiation or something
ridiculous like that! The temperature we feel
is the
result of a combination of emitted
radiation, absorption, conversion, and emitted
radiation at
longer IR wavelengths. It is NOT the result of trapped and reradiated heat
energy.
Furthermore, the comparison of our
atmosphere to a greenhouse is misleading too.
Once you've
shut the door on an actual
greenhouse it becomes a closed system that
ultimately suppresses
convection. Warm air just stagnates. Good for
whatever you've got growing in there, but bad
if you decided to live in there.
On the other hand, our atmosphere
facilitates convection, and in fact, we
wouldn't enjoy much
weather if it lacked the
ability to be convective. Without convection
life would hate life. Convection
allows for cooler air
to come in, and warmer air to move out so that
Earth doesn't get stagnant systems
and overheat. Precipitation would no longer occur, clouds would
not
form, and meteorologists would be unemployed without convection!
There is no correlation
between a greenhouse and our planet. The
processes involved in each do not parallel
each other. For simplicity the greenhouse
effect is explained with terms like
"trap", "reradiate",
"blanket", and... well,
"greenhouse". A point gets across
but it misses its target. So when you hear
analogous terms and descriptions trying to
explain something in weather, get suspicious
immediately! :)
"It is like trying to reduce the
fraction, 19 / 95, by imagining that you can
cancel the 9s. The right
answer ensues, but
for the wrong reason."
-Alistair B. Fraser
To open a new window to a great website
dedicated to meteorological-related
intellectual disasters see
Alistair's Bad Meteorology Website.
It's the weather we have during an
earthquake... BUT it has nothing to do with Earthquake!
Literary metaphors and
foreshadowing in books and on TV often use
weather to depict bad things
to come (that
have nothing to do with the weather.) Such
things have nothing to do with real life
situations like earthquakes, and shouldn't be
correlated to earthquakes. Floods, storm
surges,
tornadoes, etc. can foreshadow bad
things to come, but an earthquake isn't one of
them. On a
geological scale, the atmosphere is
a super-thin eggshell compared to Earth,
and doesn't have
the energy needed to induce
earthquakes. Contrary to popular belief,
exfoliating rocks aren't
enough to cause an
earthquake either! Earthquake weather is a
myth!
The human body heats the air
immediately above the skin. On windy days, the
heated air immediately above the skin is blown
away and replaced with cooler air, thus making
one feel cooler. On colder days, this becomes
more evident and can make one feel downright
cold!
The wind
chill factor is not an actual temperature, but
a "feels like" temperature developed
by Paul Siple, a polar scientist of the
1940s. Wind chill, or WET (Windchill Equivalent
Temperature) indicates that any
exposed skin will lose heat at a rate equal to
the rate that occurs when the temperature is
lower during calm air. The faster the wind
blows, the more intense WET becomes because
heat is being removed from above your skin
faster than your poor shivering body can replace
it! Here's a
partial example of the conversion chart developed by Siple and modified recently by
the folks at the National Weather Service (NWS).
Though, I find charts and
equations odd for windchill because it IS A FEELS
LIKE TEMPERATURE. My friend thinks it feels
like it's 40 degrees F outside, while I think
it feels closer to a 80... in fact,
sometimes my ears feel colder than my nose! Go figure. Anyway,
here's the chart:
As of November 1, 2001, the NWS
implemented the use of a new wind chill
temperature index. Here it is...
(Source: www.noaa.gov)
They also have a wind chill calculator on
their site. Check it out!
Yes! As humidity increases, so does the
length of your terrific hair! In fact, human
hair is used in
humidity measuring devices
called hair hygrometers. As the humidity
increases, the hair lengthens.
The hair is
attached to a lever, and the lever is attached
to a pen arm (the pen is attached to the pen
arm). As the hair lengthens or shortens, it moves the pen arm on the
hygrometer, and the pen arm draws an ink line
indicating this movement. The ink mark occurs
on a chart that indicates the relative
humidity. Our weather station
uses a hair
hygrometer along with a motorized psychrometer.
This is a result of another one of those
"feels like" temperatures. Here's
how it works: The human
body keeps itself from
overheating by sweating. This sweat is
evaporated. Evaporation removes
heat which
makes one feel cooler. High humidity decreases
the atmosphere's ability to evaporate
(it just
can't hold all that water vapor), so your
sweat doesn't evaporate as readily on really
humid
days, and you don't cool off as
efficiently. The result is. . . you feel
hotter. The temperature may be
80°, but you may feel like it's 90°. The "deep
south" tends to have higher humidity on
average during
the day than here in L.A. That
is why the days seem so much hotter back
there! There just so
happens to be a handy
little chart for figuring out humidity and
human discomfort : (The source for
this chart
is from Frederick K. Lutgens & Edward J.
Tarbuck's, "The Atmosphere 7th
Edition)
Again, these are "feels
like" temperature values, and should be
used as a guide, but not as a literal
reference.
|
Temperature
|
10%
|
20%
|
30%
|
40%
|
50%
|
60%
|
70%
|
80%
|
90%
|
100%
|
|
80°F
|
75°F
|
77°F
|
78°F
|
79°F
|
81°F
|
82°F
|
85°F
|
86°F
|
88°F
|
91°F
|
|
85°F
|
80°F
|
82°F
|
84°F
|
86°F
|
88°F
|
90°F
|
93°F
|
97°F
|
102°F
|
108°F
|
|
90°F
|
85°F
|
87°F
|
90°F
|
93°F
|
96°F
|
100°F
|
106°F
|
113°F
|
122°F
|
*
|
|
95°F
|
90°F
|
93°F
|
96°F
|
101°F
|
107°F
|
114°F
|
124°F
|
136°F
|
*
|
*
|
|
100°F
|
95°F
|
99°F
|
104°F
|
110°F
|
120°F
|
132°F
|
144°F
|
*
|
*
|
*
|
|
105°F
|
100°F
|
105°F
|
113°F
|
123°F
|
135°F
|
149°F
|
*
|
*
|
*
|
*
|
|
110°F
|
105°F
|
112°F
|
123°F
|
137°F
|
150°F
|
*
|
*
|
*
|
*
|
*
|
|
115°F
|
111°F
|
120°F
|
135°F
|
151°F
|
*
|
*
|
*
|
*
|
*
|
*
|
Storks.
(Source: Some cartoon I saw on
TV.)
The World Meteorological Organization
established a standard for what is normal. It
uses a
30-year span from which to calculate
normals. Precipitation and extreme
temperatures are most
commonly derived when
expressing normals. Every decade, the 30-year
span is updated. Up until December 31, 2000
normals were calculated from January 1, 1961
to January 1, 1991. Now in
2001 the normals
are derived from January 1, 1971 to January 1,
2001. To see the pattern used to determine
normals, see below:
1960s = Jan 01, 1931 - Jan
01, 1961
1970s = Jan 01, 1941 - Jan 01, 1971
1980s = Jan 01, 1951 - Jan 01, 1981
1990s = Jan 01, 1961 - Jan 01, 1991
2000s = Jan 01, 1971 - Jan 01, 2001
We currently use the
Jan-1971 to Jan-2001 span to calculate normals.
Be aware that comparing a
long-term average with daily absolute totals
can be like comparing apples and oranges. The
two will almost invariably be different. It is
misleading to hear your local weather wo/man
tell you that we are "above" or "below what is
normal for today" because s/he is comparing a
long-term average with absolute data collected
for a single day. Let's say today's normal
maximum temperature is 75 degrees F. Your
local weather wo/man tells you that today we
reached a high of 82 degrees which is 7
degrees above what is normal for this day.
However, next year this same date may record a
max temperature that is below normal, and the
year after that it will invariably be above or
below normal again... and again, and again....
until 30 years from now the max temperatures
recorded for this date -- whether they are
individually "above" or "below" normal -- may
simply average out to be 75 degrees, plus or
minus a degree. So in the larger scheme of
things today's temperature, be it above or
below normal, may very well average out to in
fact be just another normal day! It's just
another one of those misleading things many TV
weather wo/men tell you... the other being
percent chance of rain.
Good question! I think it's some sort of
tradition or something. Come to think of it...
why don't
we use the metric system?
Well, because everyone knows distance
conversions using the U.S. Customary System!
It's really,
really easy... 12 inches
makes a foot, 3 feet to a yard, which is the
distance from King Henry I's
nose tip to the
end of his fat thumb, 5.5 yards to a rod, and
320 rods to a mile, unless of course it's
a
nautical mile in which case there are 368.32
rods which isn't the same as a statute mile.
If we
know this, then we also know that volume
is just as easy to remember! You know, 12
cubic inches
to a cubic foot, 27 cubic feet to
a cubic yard, blah, blah, blah... But wait!
That was too easy, so we
have more for our
learning pleasure! There is a half quart in a
pint, 2 pints in a quart, 8 quarts in a
peck,
and 4 pecks in a bushel. And as we know, we
can only use pecks and bushels when
measuring
a non-liquid volume. And since we know that,
we probably know that a half quart or a
pint
of sand is 33.6 cubic inches, but a half quart
or pint of water is 28.875 cubic inches. To
keep
things simple, we'll just apply gallons
and barrels to liquid volumes only, in which
case there are 4
quarts in a gallon, and 31
gallons to a barrel. Of course (as we know) a
barrel could be anywhere between 31 and 42
gallons depending on usage and local laws. And
this is why we leave gallons
and barrels to
liquid volume measures only, because a
37-gallon barrel of flour would be 398.6
cubic
inches more volume than a 37-gallon barrel of
lemonade... duh! Don't forget that there are 3
teaspoons in a tablespoon, and 16 tablespoons
to a cup, and 2 cups to a pint. Well, 2 cups
in a pint
of vinegar, but 2.33 cups in a pint
of sugar, not to be confused with a cup used
in football, but that's
all common knowledge.
Converting volumes in the U.S. Customary
System is a cinch, so we have
a bunch of cool,
efficient, easy to remember units for weight
too! We all know that there are 16
ounces in a
pound and 2,000 pound to a ton. Well, unless
your talking about a long ton in which
case
there are 2,240 pounds which isn't the same as
a short ton. And come to think of it, there
are
only 16 ounces in a pound as long as that
pound isn't a weight value of a medicine,
because if it is,
then there are actually only
13.168 ounces in a pound. But it's easier to
simply remember that there
are 5,760 grains in
a an apothecary pound, and a smooth 7,000
grains in an avoirdupois pound.
And everyone
knows there are 60 grains in a dram, unless of
course its an avoirdupois dram in
which case
it would have only 27.344 grains. Now
remember, this isn't much more than a scruple,
which, as we know, is 20 grains in apothecary
weight! And then there is acre-feet, not to be
confused with an acre, which is 43,560 square
feet. And since we're on the subject of area,
we
might as well note that there are 320
square rods in 1 square mile which means that
there are 2
acres for every square rod. But we
knew that. And don't forget the temperature
scale! Remember,
212 degrees Fahrenheit is
boiling point of fresh water at sea level, and
32 degrees Fahrenheit is
freezing point. Nice
even numbers that are easy to remember. This
efficient system has withstood
the test of
time. So the next time someone mentions the
number, 368.32, the first thing that will
come
to your mind is, "hey, that's how many
rods are in a nautical mile!"... What a
coincidence eh?
Here's
the MUCH MORE DIFFICULT to learn metric system: Use
meters for
distance, liters for volume, and
grams for weight. Add the following prefixes
to the unit your using accordingly:
Yotta- (1024)
Zetta- (1021)
Exa- (1018)
Peta- (1015)
Tera- (1012)
Giga- (109)
Mega- (106),
kilo- (103)
hecto- (102)
deca- (101)
- - UNIT (1) - - (meter, liter, gram)
deci- (10-1)
centi- (10-2)
milli- (10-3)
micro- (10-6)
nano- (10-9)
pico- (10-12)
femto- (10-15)
atto- (10-18)
zepto- (10-21)
yocto- (10-24)
I would say its 1:1! Lightning almost
always strikes twice or more in the same spot!
In fact, what
appears to us as being as single
flash of lightning, is in fact several very
rapid strokes between the
cloud and the
ground. There is roughly 50 milliseconds
between each stroke, so several strokes can occur within a few tenths of a second! You may
not see it, but it happens! So the next time
someone says, "The chances of you getting
skin cancer from sitting nekid' in that tannin'
bed er like the chances of lightning striking
twice in the same spot!"...You should
probably stay out of the tanning bed, and KEEP
YOUR CLOTHES ON!
Spelling.
(Source: A dictionary)
Centigrade is actually an older term used, now
supposedly supplanted by Celsius. I still
prefer Centigrade because it sounds so cool.
I don't think they even know what they mean, but here's the gist of
it:
Precipitation probability forecasts were developed by the National
Weather Service in 1965. It
works on a scale of 0 to 1. 0 means there's no chance of precipitation (ppt)
occurring, and 1 means it's
inevitably going to precipitate.
However, when we see this scale used on the news, it has been
converted to percentages. 0.6 is
the same as 60%, 0.45 is 45% and so on. . . So what exactly does it
mean when they say there is
a 60% chance of rain? First of all, it must be understood that this
percentage refers to a specific
forecast area. i.e.) San Fernando Valley. Second, this percentage is
valid only within a specific time
frame; usually within a 12-hour time frame. Third, it is a percentage
that says that AT LEAST 0.01"
of ppt. will fall at ANY POINT within the specific area within
the next 12 hours (or whatever the
time frame is.) Anything less than .01" of ppt is considered trace
ppt, and does not fall into the
measurable ppt category.
Now, let's say Bif Sundance the weather dude says there is a 60%
chance of rain for Malibu tonight. This means there is a 6 in 10
chance that at least 0.01" of ppt. will fall at any point
within Malibu city limits. This doesn't mean 60% of Malibu's
surface area will receive ppt. It simply means that there is a 6
in 10 chance that measurable ppt will fall somewhere in Malibu within
the next 12 hours. It also means that there is a 4 in 10 chance that no
ppt. will fall anywhere within Malibu, in which case Bif could say
there is a 40% of no rain! (It's one of those half full/half empty cup
things). A problem here is that some TV weather forecasters don't fully
understand this concept and provide their audience with
percentages without area and time consideration. So if your in Reseda
and Bif Sundance says there is a 75% chance of rain, but the probability
forecast is for Ventura county, then you may not need that umbrella
after all.
(Source: Frederick K. Lutgens &
Edward J. Tarbuck's, "The Atmosphere 7th Edition)
Again, this is one of those "you gotta enroll in a Pierce
Meteorology course to get the answer"
questions due to its complexity. But here's the gist of the processes
behind it... El Niño is simple
physics with complex outcomes. Energy goes from where it is to where it
isn't in the direction of
least resistance. With that said, let's look at the mechanics of the
system. First, let's understand that
ocean currents are only little sections of a single ocean gyre. A gyre
is mainly fueled by the Coriolis
Effect (it's not actually a force). In simple terms, it is a clockwise circulation of water (in
the Pacific in this case) in the northern hemisphere, and a counterclockwise circulation of water in the
southern hemisphere.
These two circulations meet at the equator where they both go in the
same direction from east to
west. This section of the two gyres is commonly called the Equatorial
Current. At the equator,
the sun strikes Earth at a right angle twice a year. At that angle the
solar radiation needs only to
pass through one atmosphere, so there's a lot of energy input at the
equator. Water is heated and is carried along eastward
and is slowed against massive continental shelves of Australia and
Asia's Malaysia, Papua New Guinea,
Philippines, etc.)
The warm water continues to collect in the western Pacific because
those big chunks of
granite keep the warm waters from outflowing into the Indian Ocean
with any efficiency (it's really just one ocean with several names). Warm water
collects over there holding more energy in it relative to the eastern
Pacific. It's like a spring being recoiled. Water
in the western Pacific actually ends up becoming 20-50 cm higher than
the eastern Pacific which is a sure sign of an energy imbalance.
E=mc2 so we know that anything with mass has energy and
with conditions outlined above, there is definitely more mass building up in the western Pacific (near
Australia) than there is in the eastern Pacific (near here.) In other
words, there is more energy over there than here. That energy continues to
build as the equatorial current continues to provide more warm water
into the western Pacific. "Energy goes from where it is to where it
isn't"; Eventually the energy account in the western Pacific
overpowers the energy in the Equatorial
Current and the net result is an equatorial counter current. The energy (warm water) goes the other way! This affects
winds, semi-permanent pressure systems (Southern Oscillation -- ENSO), jet streams, and overall weather
patterns all over the planet due to the interconnectivity of energy.
Eventually the energy disperses to the point that the Equatorial
Current resumes its normal east-to-west flow along the meeting point of
the two massive ocean gyres in the northern and southern sections of the
Pacific. Then the process starts all over again.
That's basically how it works; minus a ton of details. The important
thing is that the process can now be conceptualized in simple terms. It
all boils down to energy inevitably going from
where it is to where it
isn't in the direction of least resistance! Yes, this means your
Splitfire sparkplugs only send a spark
across only one of those two forks!
September 13, 1922 the maximum temperature in Al
Aziziya, Libya was 136°F. Though this is the hottest temperature ever
recorded, the hottest place in the world is arguably California's Death
Valley. Here's an excerpt from pg. 18 in Christopher C. Burt's book,
"EXTREME WEATHER":
-----------------
Temperatures in Death Valley, located 282 feet below sea level in
interior California, have been maintained since 1911 at the Greenland
Ranch near Furnace Creek. With an average daily high of 115° (sic) and
low of 87° (sic) during the month of July, Death Valley is far and away
the hottest location in North America and perhaps the hottest place in
the world.
[Death Valley's] absolute maximum temperature of 134°
(sic), recorded on July 10, 1913, stands as the hottest ever observed in
the Western Hemisphere and has been surpassed globally only by a reading
of 136° (sic) measured in Al Aziziyah, Libya, located 20 miles south of
Tripoli (not in the Sahara Desert, by the way). A 135° (sic) reading
claimed by Tindoug, Algeria is of questionable veracity. The Greenland
Ranch figure of 134° (sic) has been the center of a small controversy
itself because there is no documentation of the accuracy of the
thermometer and condition of its shelter, and no other official reading
has ever since come close to this reading. A sandstorm was raging at the
time of the observation, and some speculate hot sand or dust was driven
into the thermometer casing, inflating the actual temperature.
A 130° (sic) temperature recorded at Amos (Mammoth
Tank) in the Mohave Desert in 1887 is also suspect for the same reasons.
So, Death Valley's second hottest readings of 129° (sic) recorded in
July 1960, and July 1998 may, in fact, be the highest true maximum
temperatures ever recorded in the United States. As weather historian
David Ludlum once put it, "Apparently, what this country needs is a good
135° (sic) reading made under standard conditions, so that the figure,
like Caesar's wife, may be beyond question."
The hottest summer of record in [Death Valley] was
that of 1917, when 43 consecutive days above 120° (sic) were recorded
between July 6 and August 17. The average temperature for the entire
month of July that year was 107.2° (sic), just shy of yet another
questionable national record of 107.4° (sic) recorded at Salton,
California, in August 1897.
In July of 2002, Death Valley averaged 106.0° (sic),
its hottest month in modern records. On July 13 of 2002, the temperature
ranged from a low of 100° (sic) to a high of 127° (sic), a daily average
of 113.5° (sic) and perhaps the hottest day ([in terms of] average
temperature) ever recorded anywhere in the world.
Overnight lows above 100° (sic) seem to be unique to
Death Valley (although the airport at Muscat, Oman, registered a low of
100° (sic) on the night of July 30, 1989). On the night of July 31,
2003, the temperature failed to drop below 104° (sic).
The longest stretch of consecutive days with a maximum
of 100° (sic) degrees (sic) or longer was 154 days in 2001. This
compares favorably to the world record of such days recorded at Marble
Bar, West Australia, with 161 straight days registering highs of 100°
(sic) or more.
-----------------
The coldest temperature ever recorded to date was -128.6°F in Vostok, Antarctica on
July 21, 1983. Vostok holds the global record. The coldest temperature
ever recorded here in North America was -81.4°F in Snag, Yukon, Canada.
Prospect Creek, Alaska came in a close second with a low of -79.8°F.
The most rainfall recorded in a 12-month period was
1041.78" in Cherrapungi, Assam, India from August 1860 to July 1861. The
most rainfall to fall in a single minute: 1.50" in Barot, Guadeloupe,
West Indies on November 26, 1970. The most rainfall to fall in a single
day (24 hour period): 73.62" in Cilaos, Reunion Island March 15-16,
1952. The most rainfall to fall in a week (7 days): 183.19" in Commerson,
Reunion Island during the week of January 20-27, 1980. The most rainfall
to fall in a single month: 366.14" in Cherrapungi, Assam, India in July
1861. Imagine the deluge from these storms!
Rainfall refers to the liquid water that falls in
droplets between the sizes of .5mm to 5mm in diameter. Precipitation
refers to water falling in both solid and liquid states. Precipitation
includes rain,
but is not restricted to it. Here is a list of what precipitation could
be referring to:
(The source for this chart is from
Frederick K. Lutgens & Edward J. Tarbuck's, "The Atmosphere 7th
Edition)
|
Ppt.
Type
|
Approx.
Size
|
State of
H2O
|
|
