Weather an introduction to air masses
This presentation is the property of its rightful owner.
Sponsored Links
1 / 14

Weather An Introduction to Air Masses PowerPoint PPT Presentation


  • 188 Views
  • Uploaded on
  • Presentation posted in: General

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

Download Presentation

Weather An Introduction to Air Masses

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


Weather an introduction to air masses

WeatherAn Introduction to Air Masses


What we measure

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

  • Mean Annual = sum of all mean monthlies / 12

  • Isotherm

    • “equal heat”

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


Weather an introduction to air masses

2. Pressure

  • 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


Weather an introduction to air masses

  • 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


Weather an introduction to air masses

3. Wind (& Pressure)

  • 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]


Airmasses

Airmasses

  • 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)


Front

Front

  • a zone of transition between two airmasses

    • life cycle: embryo, maturity, and decay…

Cold Front

1. Steep gradient

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

1. Gentler gradient

2. Warm air rises

3. Nimbo-stratus (ppt)

4. Long duration of fog, mist or drizzle

5. Cirrus clouds precede


Associated weather

Associated Weather

Warm Front

  • wind from SE

  • overcast and foggy

  • long drizzle (expected)

  • gradual drop in P


Weather an introduction to air masses

Warm Sector / Col

  • 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


Weather an introduction to air masses

Eventually an Occluded Front forms

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


Anticyclones cyclones

Anticyclones & Cyclones

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


  • Login