Understanding Weather and the Weather...
Transcript of 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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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/