Understanding Weather and the Weather...

Understanding Weather

and the Weather Forecast

Week 10 – Upper Air

2021

10 am Monday

10 am Tuesday

10 am Wednesday

7.44 pm

Sunday

Areas of fog around Melbourne this morning

https://www.abc.net.au/news/science/2021-05-01/indonesian-sunken-

submarine-internal-waves-what-do-we-know/100107196

https://mlml.sjsu.edu/physoce/wp-

content/uploads/sites/18/2019/12/internal_waves.jpg

U3A Geology Field Trip

November 2019

Adriatic Sea - Wave clouds triggered by winds across the mountain range

https://theconversation.com/what-are-internal-waves-that-possibly-sank-the-

indonesian-sub-if-youve-ever-suffered-plane-turbulence-youve-been-inside-one-

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ation%20for%20May%204%202021%20-

%201937318962&utm_content=Latest%20from%20The%20Conversation%20for%

20May%204%202021%20-

%201937318962+CID_cb9dd009e4d548ae4e89b6cd89b20894&utm_source=cam

paign_monitor&utm_term=What%20are%20internal%20waves%20that%20possibly

%20sank%20the%20Indonesian%20sub%20If%20youve%20ever%20suffered%20

plane%20turbulence%20youve%20been%20inside%20one

Phase changes in water

Water vapour is a powerful fuel for the atmosphere

It can make a big difference once condensation starts, particularly in thunderstorms and tropical cyclones.

Moisture in the atmosphere

Several quantities are used to report the amount of water vapour in the air:

(a) Wet bulb depression:• Air flow over wet muslin over the bulb of the

thermometer leads to a lower temperature • from the wet bulb depression other measures of

water vapour content can be calculated

(b) Dew point • the temperature to which air would need for it to

become saturated, and dew to start forming

(c) Relative humidity• the ratio of the water vapour in the air to the amount

of water vapour if the air were saturated.

Humidity measurement - hygrometers

Based on the changes in the length

of (human) hair with relative

humidity

Propeller anemometer

Cup anemometer

Measurement of wind speed and direction• Surface wind speeds and directions are measured by an anemometer

(propeller, cup, ultrasonic, pressure tube).

• a continuous record of wind speed and direction is recorded on

an anemograph

Ultrasonic

Cup and pressure tube (Dines) anemometer

https://drive.google.com/drive/folders/0B_V-fcpNMrJjOTlPSi11dVdzMlk

https://www.youtube.com/watch?v=TXYklp3CuOQ

What is wind?

“Some say that what is called air, when it is in motion and flows, is wind, and that this same air when it condenses again becomes cloud and water, implying that the nature of wind and water is the same. So they define wind as a motion of the air.

“It is absurd that this air that surrounds us should become wind when in motion, whatever be the source of its motion.”

Aristotle, Meteorologica, (about 350 BC)

Quoted in “And soon I heard a roaring wind – a natural history of moving air”, Bill Streever (2016)

Even during the eighteenth century there was no successful scientific

explanation of wind. It was a rushing stream of vapour, each wind

distinct from the next. All that could be done was to note its

characteristics, often in colourful prose such as:

• A dashing breeze

• A galloping gale

• A Shakespearean tempest.

1806 Francis Beaufort – captain of HMS Woolwich started a

systematic approach in his ship’s log: 0 calm

1 Faint Breeze just not a calm .

6 Fresh breeze 7 Gentle steady gale.

1838 – Beaufort scale adopted officially for naval use.

Peter Moore: The Weather Experiment.

Measurement of wind speed and direction

Measurement of wind speed and direction

Measurement of wind speed and direction

For marine users wind is usually expressed in knots

(1 knot = 1.85 kilometer/hour)

Wind speed and direction –Fawkner Beacon Tuesday 4 May 2021

Measuring rainfall

PluviographRain gauge

• Daily rainfall totals measured using a rain gauge

• a continuous record of rainfall (allowing for the measurement

of rainfall rates) is recorded on a pluviograph.

Extreme weather station maintenance

Twitter post:

#ArmchairAntarctica ...it's winter in 2019: travel in convoy from

Australia's Casey research station to one of the snowiest places on

Earth...to defrost a remote weather station. Not all heroes wear capes.

Some maintain.”

https://twitter.com/AusAntarctic/status/1257777358708207616?s=09

Vertical structure of the atmosphere

Vertical structure of the atmosphere

How do you measure the temperature, humidity and winds in the air above the ground?

1. Take instruments up mountains

2. Take instruments in a crewed balloon

1783 – first crewed balloon flight near Paris (Rozier and the marquis d’Alandes) ascended to about 75 metres. Beforehand a small balloon was released to measure the upper winds

1804 – Gay-Lussac (French physicist) – carried barometers, thermometers, hydroscopes, compasses (to test magnetic field) and flasks (to collect samples of air) up to 8 km. He proposed that the temperature decreased by about 0.6 degrees C for every 100 metres of altitude.

1850s – John Welsh (Kew Observatory) and pilot Charles Green ascended to around 6 km with some instruments.

How do you measure the temperature, humidity and winds in the air above the ground?

1862 – British Association for the Advancement of Science (with some of the greatest scientists of the time) established a Balloon Committee to make some systematic studies – temperatures, winds, composition, atmospheric electricity.

James Glaisher and Henry Coxwell (pilot) made several flights. The third (5 September 1862) was very dramatic. They inadvertently discovered the effects of loss of oxygen at very high altitudes. Later flights stayed below 8 km (26,000 ft)

Leon Teisserinc de Bort – French meteorologist1896 – found that temperature above about 11 km remained relatively constant and proposed the terms “troposphere” (sphere of change) and “stratosphere” (stable sphere).

3. Once the technology had been developed use balloons with some telemetering capability

Paradox of the air being colder although

closer to the sun.

“Had Coxwell and Glaisher known the

dangers of subjecting the human body to

such fluctuations in pressure they would

have realised they were still in grave

danger. But Glaisher was oblivious. After

his brief spell of “insensibility” he had

resumed his observations as before. It

was as if they had suffered nothing more

than an inconvenience.

At 2.40 pm they touched down in a field

in the Shropshire countryside. Having

tidied away their balloon and belongings

they set out for the nearest village. They

walked for 7 or 8 miles until they found a

country inn in the village of Cold Weston,

near Ludlow, where they promptly drank

a pint of beer.”

(Peter Moore, The Weather

Experiment. 2015)

https://www.directexpose.com/paraglider-ewa-wisnierska-storm/