Subject: Re: Noctilucent Clouds - cumulonimbus clouds
From: Alex Kemp
Date: Wednesday, 09 July 2014 23:00:45 +0100
To: Micaela Kemp

On 09/07/2014 20:18, Micaela Addison Kemp wrote:
no, dont worry. its has not made me uninterested. we are learning about colinumbus clouds (or something like that) xxx

‘Cumulus’ clouds (the fluffy ones)?:

Cumulus clouds

They are also the ones that you learnt to ‘bust’ with me a year ago.

Or do you mean ‘cumulonimbus’ (those are the thunder-heads):

Cumulonimbus clouds

(you can clearly see the ‘anvil’ on that one!) (that is where the rising air hits the Tropopause)

Also, just to show that I did not make all this up, here is an excellent annotated photo from a Welsh weather site:


The chap was trying out his new digital camera in Winter 2008 when he shot the photo above. Being a weatherman he was able to look at some records and get some very specific information. This is what he wrote (I’ve not copied the graph from the weather-balloon readings, but it is on that page if you want to look at it):
Telephoto shot. Classic overshooting top - the ‘bulge’ of cloud rising from the middle of the flat top of the anvil. Thunderstorm anvils form at the Tropopause - the boundary between the Troposphere (where virtually all weather goes on) and the Stratosphere above. Here, there is a monster temperature inversion - it gets warmer into the Stratosphere, so the buoyant warm air rising through the cold Troposphere meets its match at the Tropopause, loses its buoyancy and spreads out beneath it, to make the familiar anvil-shape. Overshooting tops occur when particularly powerful updraughts push through the Tropopause by dint of their momentum, although the air cannot convect any further upwards. Imagine a fountain - this is simply a cloud version!

Valentia, in S Ireland, is ‘upstream’ of mid-Wales in a SW wind, so this atmospheric sounding, taken from the ascent of a weather-balloon two hours before the storm was photographed, gives a good picture of the atmosphere over Wales at the time. On the left-hand side we have air pressure (L) and altitude (R). We can thus see that the Tropopause was, at this time, situated at about 8300m (Everest is 8848m high), where the air pressure was just 330mb. The Tropopause is always a long way up but the exact height varies from day to day. Let’s just go back to the photo:

So basically we are looking at a cloud-top at almost the height of Everest. How far away was it? About 80km away. It went over a friend’s place in the western Brecon Beacons giving thunder and 10mm hailstones.

Final words from me:
Whilst researching this post I found that the top of the Stratosphere is 50 km, and that the very top of it contains the Ozone layer (I never knew that) (it is the Ozone layer that stops almost all of the dangerous-to-life radiation from space). Above the Stratosphere is the “Mesosphere” (‘meso’ comes from the Greek & means ‘middle’) and between the two is the Stratopause (I never knew that either!). The very top of the Mesosphere is at about 95 km (60 miles); the temperature there is -80°C (-112°F) (kerumbs, that’s cold). It is also a pretty dangerous place, because it is totally exposed to ionising radiation from space. And that is where the SR-71 Blackbird flies.

Alex Kemp