1 / 14

# Weather An Introduction to Air Masses - PowerPoint PPT Presentation

Weather An Introduction to Air Masses. What We Measure. 1. Temperature Thermometer - device for measuring heat Mean Temp. - average temp., Diurnal (daily) Temp. = max + min / 2 = mean daily temp. Mean Monthly = mean daily temp / # of days in month

Related searches for Weather An Introduction to Air Masses

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'Weather An Introduction to Air Masses' - ostinmannual

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### WeatherAn Introduction to Air Masses

1. Temperature

• Thermometer - device for measuring heat

• Mean Temp. - average temp.,

• Diurnal (daily) Temp. = max + min / 2 = mean daily temp.

• Mean Monthly = mean daily temp / # of days in month

• Mean Annual = sum of all mean monthlies / 12

• Isotherm

• “equal heat”

• line drawn to join places of the same temp. - Temp. Map

• Barometer - device for measuring the weight exerted by a column of air

• Isobar - on a weather map, lines joining regions of equal P

• generally drawn at 4 mb (0.4 kPa) intervals

• Air Pressure

• Sea level [= 1 atm] = 1013 hPa (hecto Pascals) =101.3 kPa (kilo Pascals)

• 1000 mb (millibars) (10 mb = 1kPa)

• Weather map convention is to use only the last 3 figures in a measurement, e.g.,

• 1004.6 mb reads as 046 mb on a weather map

• 994.7 mb reads as 947 mb

• 99.47 kPa reads as 947 kPa

• Low Pressure

• Weather: cloudy, wet, moderate (warm/cool) e.g., by degrees of intensity: Depressions, Cyclones, Tropical Cyclones (hurricanes/typhoons), Mid-latitude Cyclones (Tornadoes)

• with air spiraling counter-clockwise about the central low

• High Pressure

• Weather: clear, sunny, dry, extreme (hot/cold)

• e.g., Anticyclone

• with air spirally clockwise about the central high

• Anemometer - device for measuring wind speed

• air flows from high P to low P = wind

• the steeper the gradient, the greater the wind speed

• Wind Speeds

• Beaufort scale

• a numerical wind-force scale ranging from:

• 0 (calm, winds less than 1.6 km/h) to

• 12 (hurricane, winds in excess of 120 km/h)

• [actually modified to 17- rare and catastrophic winds up to 220 km/h]

• Airmass - a large volume of air whose temp and humidity are relatively uniform, and covers an extensive area

• Types:

• Continental (c) - dry (extremes of temp.)

• Maritime (m) - humid (moderate temp.)

• Arctic (A) – cold

• Polar (P) - cool

• Tropical (T) - warm

m = over water = humid (maritime)

c = over land = dry (continental)

A = arctic (cold, dry) / [P = polar (cold, moist)]

T = tropical (warm)

• a zone of transition between two airmasses

• life cycle: embryo, maturity, and decay…

Cold Front

2. Forces warm up along

3. Cumulo-nimbus clouds

4. Heavy rain of short

duration

5. Cold Wind

6. Low Temp.

Warm Sector

1. aka Col (=saddle)

2. Warmer air

3. Thin cloud or clear

4. “Good” weather

Warm Front

2. Warm air rises

3. Nimbo-stratus (ppt)

4. Long duration of fog, mist or drizzle

5. Cirrus clouds precede

Warm Front

• wind from SE

• overcast and foggy

• long drizzle (expected)

• gradual drop in P

• air temp. rising, and humid

• P continues to drop

• wind shifts to SW (wind direction always described FROM)

• cloud thins and sunny breaks

Cold Front

• rapid change in weather

• sudden drop in temp.

• wind from NW (therefore = cold), and strong because of P gradient

• clouds: cumulo-nimbus common

• short, heavy rainfall, possible thunderstorms (summer)

• sky soon clears, but it is cold for the next few days

• P begins to rise

Eventually an Occluded Front forms

• a cold air mass overtakes the slower warm air mass, and completely undercuts it

1. Anticyclone

• a region of descending (clockwise [counter-clockwise in Southern hemisphere]) air forming a high P system

• Weather: clear, sunny, dry, cold

2. Cyclone

• a region of ascending (counter-clockwise [clockwise in Southern hemisphere]) air forming a low P system

• Weather: cloudy, wet, warm