Download Station #1 - Satellite Maps

Station #1 - Satellite Maps
Satellites orbiting high above the earth enable meteorologists to observe clouds at all
levels of the atmosphere over both land and the oceans. Satellites are crucial to
detecting and tracking intense storms over the oceans such as hurricanes, allowing
more advanced warnings to be issued before storms hit. In addition to taking photos
of clouds, satellites used radiometers to measure infrared radiation emitted by clouds.
Lower clouds are warmer and thus emit more radiation than higher clouds, which are
much colder. Low clouds appear gray on an infrared satellite picture while high
clouds appear white. By closely analyzing satellite images, meteorologists determine
cloud heights and thickness. Computer enhancement of an infrared satellite picture
increases the contrast between the different cloud features and the background, which
makes more detailed analysis possible.
A weather satellite is a type of satellite that is primarily used to monitor the weather and climate of the Earth.
These meteorological satellites, however, see more than clouds and cloud systems. City lights, fires, effects of
pollution, auroras, sand and dust storms, snow cover, ice mapping, boundaries of ocean currents, energy flows,
etc., are other types of environmental information collected using weather satellites.
Weather satellite images helped in monitoring the volcanic ash cloud from Mount St. Helens and activity from
other volcanoes such as Mount Etna. Smoke from fires in the western United States such as Colorado and Utah
have also been monitored.
El Niño and its effects on weather are monitored daily from satellite images. The Antarctic ozone hole is
mapped from weather satellite data. Collectively, weather satellites flown by the U.S., Europe, India, China,
Russia, and Japan provide nearly continuous observations for a global weather watch, used via visible light and
infrared rays of the electromagnetic spectrum.
Station #2 - Radar Maps
Radar displays show where precipitation is they also show the winds within thunderstorms which help them see
rotation in a thunderstorm to pick out where a tornado is possibly forming.
Weather radar images are generally a map view of reflected particles for a specified area surrounding the radar.
Depending on the intensity of the precipitation, different colors will appear on the map. Each color on the radar
display will correspond to a different level of energy pulse reflected from precipitation.
The Japanese squadron that bombed Pearl harbour was detected by a prototype Hawaiian Radar before the air
raid but no alert was sent out, as nobody believed the inexperienced radar operators!
Bats have a Doppler radar, of sorts. Their noses are able to send out a short 'cry' which reflects off objects in the
distance and sends back an echo received by their ears. From this the bat is able to tell if an animal is in its
vicinity and if that animal is moving towards or away from it.
Some wind changes can be seen on the radar as very thin slow moving lines. This is because insects usually
congregate around wind changes and if there are enough of them, the radar beam will be reflected. Similarly
when a swarm of bats take off at dusk they can sometimes be tracked on the radar.
The strength of the pulse returned to the radar depends on the size of the particles, how many particles there are,
what state they are in (solid-hail, liquid-rain) and what shape they are. After making many assumptions about
these factors and others, the approximate rain rate at the ground can be estimated. In fact, the most reflective
precipitation particles in the atmosphere are large and usually have a liquid surface (water-coated hailstones).
Radar works by sending out a beam of energy then measuring how much of that beam is reflected back and the
time needed for the beam to return. Objects that reflect the beam back to the radar include rain, snow, sleet and
even insects. If more of the beam is sent back, the object is said to have a high reflectivity and is indicated by a
bright color. Objects which return a small part of the beam have a low reflectivity and are indicated by darker
colors.
Television stations usually describe their radars as "Doppler," but the images you see are almost always
"reflectivity" images.
While the NWS radars and some radars operated by television stations have Doppler capability to show wind
direction and speed, the images are extremely complex and are much more difficult to understand than
reflectivity images.
Intensity levels
Radar images are color-coded to indicate precipitation intensity. The light blue color is the lightest precipitation
and the purple and white are the heaviest. Reflectivity not only depends on precipitation intensity, but also the
type of precipitation. ​Hail​ and ​sleet​ are made of ice and their surfaces easily reflect radio energy. This can
cause light sleet to appear heavy. Snow, on the other hand, can scatter the beam, causing moderate to heavy
snow to appear light.
Beam blockage
This is caused when objects such as trees, buildings and mountains prevent the radar beam from reading the
precipitation on the other side of them. As a result, the radar image may show no precipitation over an area
where it may actually be raining or snowing.
Station #3 - Precipitation Maps
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that is deposited on
the earth's surface. It occurs when the atmosphere becomes saturated with water vapour and the water
condenses and falls out of solution (i.e., precipitates). Air becomes saturated by two processes: cooling and
adding moisture. Precipitation that reaches the surface of the earth can occur in many different forms, including
rain, freezing rain, snow, ice pellets, and hail. Precipitation is a major component of the water cycle, and is
responsible for depositing most of the fresh water on the planet.
A precipitation map shows the total amount of precipitation received in a given area within a given period of
time. Precipitation is any product of condensation of the atmospheric water vapor that is deposited on the earth's
surface. It can be in form of rain, freezing rain, snow, ice pellets or hail.
The Weekly Precipitation map shows the amount of precipitation that has accumulated within the last 7 days.
The precipitation imagery displays precipitation estimates in colorized contoured bands by interpreting the
intensity levels of NOWrad mosaic radar into rainfall estimates each hour. These daily summaries provide a
cumulative precipitation estimate from 1200GMT yesterday to 1200 GMT (daily) or 1200 GMT 7 days ago to
1200 GMT today (weekly).
Rainfall is typically measured using a rain gauge. It is expressed as the depth of water that collects on a flat
surface, and is routinely measured with an accuracy up to 0.1 mm or 0.01 in. Rain gauges are usually placed at a
uniform height above the ground, which may vary depending on the country. There are two types of gauges.
Storage rain gauges are used to make daily or monthly measurements. Recording rain gauges measure the
intensity of rainfall using a tipping bucket which will only tip when a certain volume of water is in it. An
electrical switch can be used to record the tips.
Station #4 - Temperature Maps
The temperature chart shows the forecast minimum and maximum temperatures for all the major cities along
with a forecast icon. The contour lines relate to maximum temperatures expected.
Air temperature is one of those things that everyone is familiar with, which turns out to be more complicated
than it might seem at first.
A thermometer actually measures the average kinetic energy of the
various molecules that make up the air around it - let's call them "air
molecules."
As you can see in the graphic above, air molecules in colder air move
slowly compared to those in warmer air. The kinetic energy of an air
molecule is directly proportional to the velocity of the molecule.
This means that colder air has less kinetic energy than warmer air.
When air molecules collide with a thermometer, kinetic energy is
transferred from the air molecules to the glass and then to the mercury
molecules inside the thermometer.
As the mercury molecules begin moving faster they move farther apart, pushing the
mercury up in the thermometer.
In colder air, the energy from the air molecules colliding with the thermometer
transferring to the mercury molecules is less than the energy from warmer air. As a result,
the mercury molecules move slower in the colder air and the mercury inside the
thermometer does not expand as far up the tube as it does in the warmer air.
Station #5 - Wind Speed Maps
Winds begin with differences in air pressures. Pressure that's higher at one place than another sets up a force
pushing from the high toward the low pressure. Air always wants to become balanced so molecules will move
from high pressure to low pressure to achieve this.
The greater the difference in pressures, the stronger the force. The distance between the area of high pressure
and the area of low pressure also determines how fast the moving air is accelerated.
Meteorologists refer to the force that starts the wind flowing as the "pressure gradient force."
High and low pressure are relative. There's no set number that divides high and low pressure.
The graphic above ignores the effects of friction and other forces on the wind to concentrate on the force that
puts air into motion as wind.
Once the wind begins blowing the Earth's rotation changes its direction. This is known as the ​Coriolis effect​.
Friction of the wind against the Earth's surface also helps determine how fast it blows and from which direction
it blows.
Station #6 - Front Maps
What is a High Pressure System?
A high pressure system is a whirling mass of cool, dry air that generally
brings fair weather and light winds. When viewed from above, winds spiral
out of a high-pressure center in a clockwise rotation in the Northern
Hemisphere. These bring sunny skies. A high pressure system is represented
as a big, blue H.
What is a Low Pressure System?
A low pressure system is a whirling mass of warm, moist air that generally
brings stormy weather with strong winds. When viewed from above, winds
spiral into a low-pressure center in a counterclockwise rotation in the
Northern Hemisphere. A low pressure system is represented as a big, red L.
Cold Front
A cold front represents a boundary between cold air and warm air. The blue arrows
denote the direction the cold front is moving, typically from west to east. Most cold
fronts will have a noticeable change in temperature following the front's passage,
although not always. Cold fronts normally create storms because the warm air is pushed
up quickly causing it to condense. Dewpoints will typically drop as well following the
front's passage.
Warm Front
The opposite of a cold front. In this case, warmer, more humid air is overtaking colder
air. The red circles face in the direction of the front's movement, which is typically from
southwest to northeast. You will still have rain in a warm front but it will be hours of
steady rain instead of heavy storms.
Stationary Front
A stationary front is a boundary between cold air and warm air that is not moving. The
blue triangles point in the direction of the warmer air, while the red semicircles point in
the direction of the colder air. Once the front begins to move, it will become a warm
front or a cold front. There is typically heavy precipitation along the line representing a
stationary front.
Occluded Front
When a cold front overtakes a warm front, the point where the two meet becomes an occluded front. This
typically occurs near a low pressure system. An occluded front is represented with purple alternating
semicircles and triangles pointing in the direction of movement of the front.
Trough
A trough (sometimes called a trof) is a line of low pressure in the atmosphere. While troughs can exist in both
the upper atmosphere and the lower atmosphere, the troughs on this map, which are represented by dotted black
lines, are in the lower atmosphere. Troughs are often associated with short waves, which can cause
thunderstorms, depending on atmospheric conditions.
Station #7 - Weather Station Plots
Data for question 1
Map for question 2