## Useful Chart for earth.nullschool

I’ve played with the earth.nullschool thing for a few years now. It gives you atmosphere level choices measured in hPa of pressure. Kind of cryptic, IMHO. I’ve frequently wanted a way to figure out which hPa was the top of the troposphere (where convection turns into a high speed wind to the cold poles). Well, I finally found it, Or more accurately: I finally got motivated enough to go looking ;-)

http://weatherfaqs.org.uk/book/export/html/174

International Standard Atmosphere (ISA) and Pressure Settings

Based on the International Standard Atmosphere for dry air (ICAO 1964), which is defined as under:-

1. At mean sea level (msl), the pressure = 1013.25 hPa and temperature = 15.0 degC
2. From msl to 11 km, a decrease in temperature (or lapse rate) of 6.5 degC/km
3. From 11 km to 20 km, the temperature is held to be isothermal (not changing) at a value of – 56.5 degC
4. From 20 km to 32 km, an increase in temperature of about 1 degC/km

```hPa (mbar) ......... height (metres) ......... height (feet) ......... temperature (degC)
»...... 10 ................... 31 055 ................ 101 885 ................. -45.4
»...... 20 ................... 26 481 .................. 86 881 ................. -50.0
»...... 30 ................... 23 849 .................. 78 244 ................. -52.7
»...... 40 ................... 22 000 .................. 72 177 ................. -54.5
»...... 50 ................... 20 576 .................. 67 507 ................. -55.9
»...... 70 ................... 18 442 .................. 60 504 ................. -56.5
».... 100 ................... 16 180 .................. 53 083 ................. -56.5
».... 150 ................... 13 608 .................. 44 647 ................. -56.5
».... 200 ................... 11 784 .................. 38 662 ................. -56.5
»... (226/ISA TROP.. 11 000 .................. 36 091 ................. -56.5)
».... 250 ................... 10 363 .................. 33 999 ................. -52.3
».... 300 ..................... 9 164 .................. 30 065 ................. -44.5
».... 400 ..................... 7 185 .................. 23 574 ................. -31.7
».... 500 ..................... 5 574 .................. 18 289 ................. -21.2
».... 600 ..................... 4 206 .................. 13 801 ................. -12.3
».... 700 ..................... 3 012 .................... 9 882 ................... -4.6
».... 800 ..................... 1 949 .................... 6 394 ..................... 2.3
».... 850 ..................... 1 457 .................... 4 781 ..................... 5.5
».... 900 ........................ 988 .................... 3 243 ..................... 8.6
».... 950 ........................ 540 .................... 1 773 ................... 11.5
».. 1000 ........................ 111 ....................... 364 ................... 14.3
». (1013.25/ISA MSL ....... 0 ........................... 0 ................... 15.0)
».. 1050 ...................... - 302 .................... - 989 ................... 17.0
```

You can quickly see that the tropopause sets in about 225 hPa and transitions to the stratosphere at about 70 hPa.

So things below 225 are convective (generally, it will be lower at the poles as low as 700 hPa) while things 70 and above are well out of the convective reach and indicate high altitude global circulation.

At earth.nullschool, you can now pick hPa levels and have a clue what regime of atmosphere you are inspecting.

https://earth.nullschool.net/

Click on the “Earth” word down in the lower left to get the controls:

earth

Date | 2017-10-12 17:00 Local ⇄ UTC
Data | Wind @ Surface
Scale |
Source | GFS / NCEP / US National Weather Service
Control | Now
⊕Grid▷HD
Mode | Air – Ocean – Chem – Particulates
Height | Sfc – 1000 – 850 – 700 – 500 – 250 – 70 – 10 hPa
Overlay | Wind – Temp – RH – WPD – 3HPA – CAPE
| TPW – TCW – MSLP – MI – None
Projection | A – AE – CE – E – O – P – S – WB – W3

Note that “Height:” is in hPa

https://en.wikipedia.org/wiki/Troposphere

The troposphere is the lowest portion of Earth’s atmosphere, and is also where nearly all weather conditions take place. It contains approximately 75% of the atmosphere’s mass and 99% of the total mass of water vapor and aerosols. The average depths of the troposphere are 20 km (12 mi) in the tropics, 17 km (11 mi) in the mid latitudes, and 7 km (4.3 mi) in the polar regions in winter. The lowest part of the troposphere, where friction with the Earth’s surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred meters to 2 km (1.2 mi) deep depending on the landform and time of day. Atop the troposphere is the tropopause, which is the border between the troposphere and stratosphere. The tropopause is an inversion layer, where the air temperature ceases to decrease with height and remains constant through its thickness.

The word troposphere derives from the Greek: tropos for “turn, turn toward, trope” and “-sphere” (as in, the Earth), reflecting the fact that rotational turbulent mixing plays an important role in the troposphere’s structure and behaviour. Most of the phenomena associated with day-to-day weather occur in the troposphere.

So at the tropics, we’re looking for 20 km or 12 miles that our chart says is about 50 hPa while at the poles it is down to 7 km or 4.3 miles that works out to about 400 hPa.

Since earth.nullschool is not giving use that granularity, we can roughly use the 70 hPa for equatorial stratosphere and below that for troposphere – 250 hPa. While at the poles, we can drop down to 500 hPa for the tropopause.

Hopefully that will make it easier to interpret their nice visuals…

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
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### 3 Responses to Useful Chart for earth.nullschool

1. Larry Ledwick says:

The same sort of selectivity of view is available on windy.com
It has a slider on the lower right side of the window that allows you to pick the elevation it will display.

On the upper right is a slider where you can select the type of data it will display and the bottom lets you choose what time (current or future) so you can see how the models expect the wind fields to change with time.

I find windy.com to be a bit more intuitive but they appear to basically do the same thing.

2. tom0mason says:

Also of note is that wind,temperature, and pressure developments at 500 (mid tropo) is useful for seeing how the tropopause turbulence and the jet-stream is interacting the movement of air mass below. Before these modern days of numerical computerized predictions meteorologists often would look there for a ‘first look’ as indications of probable wind direction, temperature, and atmospheric pressure changes when compiling the up-coming short term weather forecast. Sometimes they now use 800hPa and sometimes, to see specific of a particular change, the vertical variation from 500hPa to 800hPa.

Surface pressure is about 1000 hPa (1000 mb), this is the total force (weight) of the atmosphere. The height at which the pressure is 500 hPa roughly divides in half the atmosphere vertically, half the mass of air being above and half below that height. In terms of height, 500 hPa is about 5,500 metres (18,000 feet) above the ground. The top of that part of the atmosphere in which our weather is formed is known as the tropopause and is at about 11,000 metres (35,000 feet). The 500 hPa level is, thus, effectively half way up the atmosphere as we know it.

http://weather.mailasail.com/Franks-Weather/Are-500-Hpa-Charts-Useful

3. Hans Erren says:

On this very useful polar tropopause map you’ll see that tropopause pressure is not a constant.
https://www.atmos.washington.edu/~hakim/tropo/?page=trop_pres&hem=