There are 5 basic types of maps:1.Pressure2.Aviation3.Temperature4.Streamline5.Station Model

►Tells the air pressure

►Gives the locations of high-pressure areas and low-pressure areas

Low Pressure and Bad Weather Air warmed by the sun on the earth's surface can hold more moisture than cool air. As the warm moist air rises, it begins to cool. Eventually, the air reaches a level where it is too cool to continue to hold its moisture. At this point the moisture condenses out to become clouds. The clouds release their water as precipitation.

High Pressure and Clear Weather High pressure areas are produced by cooler, heavier, sinking air. This air contains less moisture and is more stable. In the summer, high pressure usually means sustained sunshine, few clouds, low winds, high temperatures, and dry weather.   In winter, the lack of cloud cover can cause the temperatures to be very cold, since the lack of clouds allows heat from the earth to travel away from the earth.

Tells information necessary for safe flight of aircraft:►Wind speed and direction►Dew point►Cold and warm fronts►Icing areas►Flight restriction information

Shows temperature either in color-coded format or with the actual numbers.

Shows wind patterns

Shows the weather conditions at a particular weather station (a place where weather is measured and recorded)

Several conditions are measured:►Temperature►Humidity►Air pressure►Cloud cover►Wind speed►Wind direction

Symbols are used

What information is this station model giving?

Temp - 81°

Dew Point – 59°

Air Pressure - 221

Cloud Cover – 75%

Winds 15 mph from the NE

How fast is this wind blowing..AND in what direction?

65 mph from the Northwest

Using the Symbol Key from the next slide…fill in this chart at your seat.

Humidity refers to the amount of moisture (water vapor) in the surrounding air.

RATIO of the amount of moisture in the air compared with the amount of moisture the air can hold at that temperature and pressure. Expressed as a percentage.

If the air is at 90% relative humidity, sweat will not evaporate into the air. As a result, we feel

much hotter than the actual temperature.

If the relative humidity is low, we can feel much cooler than the actual temperature. because our sweat

evaporates easily, cooling the body.

The length of a strand of human hair changes with different relative humidities.

As the relative humidity increases, hair becomes longer, and as the humidity drops it becomes shorter. On very humid days, your hair actually becomes longer and this extra length causes the frizziness that gives us bad hair days.

Sling Psychrometer

It consists of two identical mercury thermometers: Evaporating water

from the wick absorbs heat from the thermometer bulb, causing the thermometer reading to drop.

Find the difference between the DRY bulb and the WET bulb on the two thermometers

Use the Relative Humidity Table

Where the DRY bulb temperature and the DIFFERENCE between the two thermometers intersects…is your relative humidity.

Example – If the DRY bulb temperature reading is 22°C and the DIFFERENCE between the two thermometers is 6°…the relative humidity is 53%

1. Dry bulb = 12°Wet bulb = 7°

2. Dry bulb = 22°Wet bulb = 20°

3. Dry bulb = -10°Wet bulb = -7°

48%

83%

0%

Why Care about Relative Humidity?

If we can’t sweat…we could overheat and DIE!!

The temperature that air would need to cool to condense the water vapor into liquid water.

Dew Point is determined the SAME EXACT WAY that Relative Humidity is calculated…a Sling Psychrometer.

You just use a DIFFERENT chart… the DEWPOINT chart..DUH!!

1. Dry bulb = 12°Wet bulb = 7°

2. Dry bulb = 22°Wet bulb = 19°

1°

17°