Yacht Forum UK

Yep, cooler air is drawn in off the sea in your example, if there is a big temp difference between the land and sea, you can get an anabatic wind forming. A lesser version of this is seeing sea birds cruising the uplifting airs (or thermals if you're a handglider). For a good katabatic wind, you need a slope, where a good covection current can set up during the day and push air up where it cools (relative) to the underlying air. Once the convection current begins to collapse, the cooler air wants to sink back down and the katabatic effect begins. Optimum slope angle is beow 35 degrees. The longer the slope, the better. Many moons ago, I did some field work in southern Spain trying to quantify the optimum conditions for the katabatic effect. Caveat here is it wasn't my main geographical focus. Now if anyone is interested in fluvial geomorphology.......................

Ok. Here's one for you. Was the Grand Canyon created in a sudden catastrophic flood event, or over many many years?

Fieldwork in Spain trying to find the perfect beach sounds like tough work!

Ah, Grand Canyon is an interesting one. On first look, the Colorado River seems to have done a pretty impressive job of forming the features but it had some 'assistance' with some geological uplift causing more rapid erosion and a considerable amount of non fluvial weathering. It is still classed as an arid land formation even though the river is the primary erosion medium. Flood events would have accelerated erosion locally but even a catastrophic flood event couldn't result in this type of canyon formation.

Fieldwork in Spain............. fond memories, life seemed a bit simpler back then!





Bet your eyelids are feeling heavy after reading this

Only because I just woke up! I find this side of geography really interesting. Can't believe how much of how things are the way they are is now quite well understood considering how many different processes have been at work over such a long time. It's the GDP, demographics, etc etc that gets me drifting off.

Did you ever do volcano field trips? They must be quite exciting! Micro tremors seem to be a good pre indicator of imminent eruption don't they think now?

I have gcse geography btw

Oooooh, volcano field trips would have been fantastic. Alas, no such luck, although I did do a demographic survey of Budleigh Salterton in 1992. It was riveting!
If only it was all like Dante's Peak!



Mind you, I'm no Pearce Brosnan - but I would give the foil suits a try!

Back to the grind

Rob

Sorry to have started a hare running with this katabatic stuff but the discussion is interesting. Being a simple soul I only had a vague idea of how the physics worked..
I presumed that warm daytime air was cooled on clear nights due to radiation, which made it denser and thus rush down the hill and rock my little boat and ruin my sleep. I never gave any attention to where the air to replace the downwards going air came from... or the air to replace the replacement air and so on....

I read this. But I'm not much wiser really.

http://en.wikipedia.org/wiki/Katabatic_wind

Dwells on the extreme katabatic winds of the Arctic and Patagonia.. Hope that I never meet one of those babies.

best

Jim

No need for an apology Jim, it's very interesting stuff!!