Three types of rain…

Bits and pieces by Lois

I was writing about the British fascination with weather the other day… and then today I came across some interesting facts from the Meteorological Office… did you know there is an actual word to describe the smell of rain after a long period of dry summer weather? Petrichor… and I know exactly what it smells like, and just thinking about it takes me back to an afternoon in 1970; it must have been June or July and it was the last day of term, or the day we finished our exams, or the day our results came out… We were in Manchester, at what was then the new Polytechnic (‘the Rolls Royce of Polytechnics‘ the director, Dr Smith described it… and we know what happened to Rolls Royce…) I was sharing a flat with a friend, and all our other chums came round… maybe we had been to the pub, maybe we’d had some drinks at the student union, or at home, maybe we weren’t drunk but drunk with joy at finishing the first year!

It had been tremendously hot, and we had spent the past couple of months revising, working, finishing our first dissertation, doing exams, working really hard; we had a good work ethic I think, looking back, and also we had a much fuller timetable than students have these days, lectures, seminars, tutorials, contrasting studies… we were in college every day for long hours, and then studying in the work rooms, or library, or the Manchester Central reference Library, or at home…

We were free! It was done! We had a two month holiday! It was roasting hot, and then the rain came down and we went outside into the street and cavorted about shouting and laughing and singing in the rain (yes we actually did!) Just thinking about it I can smell the scent of the rain hitting the road and pavements, and almost hear us shouting and acting the fool! So that is petrichor.

The title of this post is ‘Three types of rain’, which are frontal, orographic and convective:

  •  Frontal rainfall is a type of condensation that occurs when a cold front meets a warm front. Warm air is less dense than cold air; when the two air masses meet, warm air is forced over the cold air, because it is less dense.
  • Orographic rainfall is  is produced from the lifting of moist air over a mountain. Moist air rises and cools, producing orographic clouds, which are the source of the rain.
  • Convective rain happens when  warm air deflected from a landform rises and forms rain clouds.

… and rain drops can be as big as 6 mm in diameter… which is about the average size of  a pea… so maybe we should say ‘it’s peaing it down’, not ‘its peeing it down’.

Here are some other facts about British rain from the Met Office:

  • the longest consecutive number of days of rain was 156 in the year 2000
  • the driest location is Shoeburyness in Essex, with on average 495 mm of rain…
  • … and the wettest in Cumbria, Seathwaite with 3304 mm
  • the most rain in an hour was the 12th July 1901 in Maidenhead in Berkshire, with a fantastic 92 mm…
  • … and the most rain in a day, 24 hours, was again in Cumbria, on the Honister pass on the 5th December, 2015,  341.4 mm – that is a heck of a lot of rain!

There is loads or other interesting information here:

http://www.metoffice.gov.uk/

You will have to wait until the end of this video to see it’s relevance – but it’s worth waiting for… it’s always worth waiting for the Mavericks!

http://https://youtu.be/s_AeLQJeTd0

12 Comments

  2. David Lewis
    Reply

    We have a trading post north of the city that is more of a tourist trap. They have rock hanging outside from a leather thong which is supposed to be an old Indian weather forecaster. The sign says that if the rock is wet it’s raining, and if the rock is white it’s snowing etc. The best item I like is a trout covered with fur telling you how cold it gets around our parts. There used to be an old native that used to come on the radio in the fall to tell us how bad the winter was to be. I met him in a bar once and the more beer I bought him the nicer the forecast became. Fancy that!

    Liked by 1 person

    1. Lois
      Reply

      That sounds similar to something over here… hanging a piece of seaweed up is supposed to be an indicator too… I remember doing it when I was little and it just got more and more dried up and didn’ tell me anything!

      Like

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