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Troposphere height

Links , pictures, research, information.

troposphere rheemoclineatmosphere temperature layers with,height

In no specific order.

Theory. Height of the troposphere

http://www-das.uwyo.edu/~geerts/cwx/notes/chap01/tropo.html

extract

‘The height of the tropopause depends on the location, notably the latitude, as shown in the figure on the right (which shows annual mean conditions). It also depends on the season (1, 2). Thus, it is about 16 km high over Australia at year-end, and between 12 – 16 km at midyear, being lower at the higher latitudes. At latitudes above 60� , the tropopause is less than 9 -10 km above sea level; the lowest is less than 8 km high, above Antarctica and above Siberia and northern Canada in winter. The highest average tropopause is over the oceanic warm pool of the western equatorial Pacific, about 17.5 km high, and over Southeast Asia, during the summer monsoon, the tropopause occasionally peaks above 18 km. In other words, cold conditions lead to a lower tropopause, obviously because of less convection.

Deep convection (thunderstorms) in the Intertropical Convergence Zone, or over mid-latitude continents in summer, continuously push the tropopause upwards and as such deepen the troposphere. This is because thunderstorms mix the tropospheric air at a moist adiabatic lapse rate. In the upper troposphere, this lapse rate is essentially the same as the dry adiabatic rate of 10K/km. So a deepening by 1 km reduces the tropopause temperature by 10K. Therefore, in areas where (or at times when) the tropopause is exceptionally high, the tropopause temperature is also very low, sometimes below -80� C. Such low temperatures are not found anywhere else in the Earth’s atmosphere, at any level, except in the winter stratosphere over Antarctica.

On the other hand, colder regions have a lower tropopause, obviously because convective overturning is limited there, due to the negative radiation balance at the surface. In fact, convection is very rare in polar regions; most of the tropospheric mixing at middle and high latitudes is forced by frontal systems in which uplift is forced rather than spontaneous (convective). This explains the paradox that tropopause temperatures are lowest where the surface temperatures are highest.

The tropopause height does not gradually drop from low to high latitudes. Rather, it drops rapidly in the area of the subtropical and polar front jets (STJ and PFJ respectively in the Figure on the left), as shown in the Palmen-Newton model of the general circulation (Fig 12.16 or Fig on left). Especially when the jet is strong and the associated front at low levels intense, then the tropopause height drops suddenly across the jet stream. Sometimes the tropopause actually folds down to 500 hPa (5.5 km) and even lower, just behind a well-defined cold front. The subsided stratospheric air within such a tropopause fold (or in the less pronounced tropopause dip) is much warmer than the tropospheric air it replaces, at the same level, and this warm advection aloft (around 300 hPa) largely explains the movement of the frontal low (at the surface) into the cold airmass, a process called occlusion (Section 13.3) (4).

 

 

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Google search.. ‘pictures tropopause height’

https://www.google.com/search?q=picture+tropopause+height&tbm=isch&source=univ&client=firefox-b-d&sa=X&ved=2ahUKEwjlnsDf-bDjAhVDfX0KHcEUAu0QsAR6BAgEEAE&biw=1025&bih=491

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A study of cold fronts in Australia

I will collect information and observations

2019

Forecast for 532 thickness for Tasmania 6 days into Autumn. which can bring low level snow

low level snow tasmania 6th march 2019

dynamic jetstream AAO negative 4_3_2019

ABOVE

Nothing like a wavy sub polar jet associated with a negative dip in the AAO/ SAM since —early February 2019, to produce dynamic wavy jetstreams at the 200hpa stratosphere.

and satellite picture BELOW ……………………….

is the cold pool in the Bight 5th March 2019. The day before it travails over Tasmania.

The cold pool sits within the bulge of the sub polar jet but at the surface layer

The cold air is transported north into NSW  by the southern  and eastern flank of the

Mid -latitude High

5_3_2019. cold pool ijn the bight

SOURCE. BOM

http://www.bom.gov.au/australia/charts/viewer/index.shtml?type=mslp-thick&tz=AEDT&area=Au&model=CG&chartSubmit=Refresh+View

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Temperatures got down to 9.8 deg in Hobart and light splatter of snow on Mount Wellington

Mount Baw baw in Gippsland Victoria also had a light dusting of snow with temps down to 0 deg c for most of the day

NEWS article

Mount Mawson 6th March 2019

quote from Ben ” 6th March 2019

Today’s taste of wintry weather comes less than a week after the state endured a day of record-breaking March heat.

Dover’s 40.1 degrees on Sunday was the first time on record any location in Tasmania has exceeded 40 degrees during March.

Eight other weather stations, including Hobart (39.1C), also beat Tasmania’s previous March maximum temperature record of 38.0 degrees on Sunday.

Impressively, Hobart’s 39.1 degrees on Sunday was also hotter than any day in the city during summer. Last season’s highest temperature was 37.9 degrees.

Sunday’s heat now seems like a distant memory, as much colder southwesterly winds flow over the state today.

Hobart was only sitting on 13 degrees at 10am, although wind chill was making it feel more like eight degrees.”

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Thickness… Its meaning?

Click on the title of this post to load all further entries below

Reading a discussion on
http://forum.weatherzone.com.au/ubbthreads.php/topics/1270374/4

and thanks to contributor ‘inversion’ here is a start to answering this question
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I’d like to know what the thickness lines mean/represent?

thickness diagram
source
http://www.bom.gov.au/australia/charts/viewer/index.shtml?type=mslp-thick&tz=AEDT&area=Au&model=CG&chartSubmit=Refresh+View
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‘Inversion’ says
“‘Thickness’ is a measure of how warm or cold a layer of the atmosphere is, usually a layer in the lowest 5 km of the troposphere; high values mean warm air, and low values mean cold air. Some approximate reference levels for freezing level are:
5240 – 300m (snow to sea level in parts of Vic (10 Aug 2005)
5280 – 600m
5340 – 1000m
5400 – 1400m

Last night neared 5280, with Melbourne sounding showing freezing level at around 800-900m)

Doesn’t have to be zero for it to snow. Snow flakes may fall through sub-zero temps all the way to the last few hundred metres, when a warm layer melts them. The temp and height of this melting layer is the key. Yesterday (last night) this layer was 5 deg up to 300m, 3 deg at 500 and freezing near 800-900m. This was enough to allow snow to fall in places around 500-600m, but generally melted lower than this.

The other key factor is down-drafts from heavy showers/storms which can locally bring freezing air right down to the surface, allowing snow. I’ve witnessed this at Creswick in 2000 with an intense down-draft rapidly plummeting the temp from 7 deg to zero in a matter of minutes, allowing snow, then it went back up to 7deg 20 minutes later.”
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