In this course you can learn about the mechanics of global weather, the foundations of ocean meteorology, predictive modeling and how sailors receive data via satellite and use high-performance navigation software. This course looks at oceanic meteorology and climatology through the lens of the sport of sailing. You will gain a basic knowledge of meteorology needed by sailors to take part in a regatta such as the Barcelona World Race, the only double-handed, round the world regatta with no stops. You will learn about the strategies employed during a round the world regatta and how these are put to use on board the latest ocean racing yachts.
Video 3.2.2 Short term
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來自 Universitat de Barcelona 的課程
Strategies for winning. Meteorology in a round the world regatta
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從本節課中
The sailor as meteorologist
In this module you will learn how sailors use meteorology to sail around the world and to win round the world regattas.
All of their interest is focussed on the wind and they need theoretical, but above all practical, knowledge to help them to take the correct decisions at sea.
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If you are experiencing difficulty learning or accessing course content, or if you simply want more information.
與講師見面
Tomàs Molina
[MUSIC]
So we talked about strategy long term, strategy medium term.
There's also a strategy, it's not even a strategy,
it's part of the really short term, is that you need to deal with clouds.
You need to deal with, a lot of stuff on a boat, you have to make the boat go fast.
You have to eat, you have to sleep, you have to deal with clouds.
Especially in the tropics in the trade winds, they're very active.
Basically starting off with two simple types of clouds,
this cloud, this is the sea, this is the typical cumulus cloud.
And this cloud has become cloud like that's called cumulus.
And then once it starts raining it becomes cumulonimbus,
when the head gets pretty dark and gray.
Typically at the end of the day, when it starts cooling down, it starts raining.
This blue dash lines is the rain,
and what happens at that moment is there's a downpour out of that cloud.
The air is coming down together with the rain.
The air can't go down because here's the sea.
So what happens, the air comes out on the sides of the cloud.
And this is going to massively influence what is happening to the overall winds you
are having at that moment.
If you're having a northeasterly trade wind
and one of those clouds comes through it can completely cancel the wind.
It can accelerate it, you might to have to change sails to deal with it.
It can have a big impact, you can you can have
a few hours with being extremely busy dealing with a cloud like that.
We've spoken about long term strategy,
medium strategy, weather routing, all that sort of stuff.
But sometimes it's a lot simpler,
sometimes it's some really short term stuff.
There's a cloud in front of you,
you have to deal with it, especially in the tropics.
Tropics, tradewinds, doldrums, clouds are a big part of your daily life.
Especially the end of the day, and the end of the night.
Clouds are building up all day with the heat, typical cumulus clouds,
cauliflower type.
Then it starts cooling down at the end of the day looking like anvil head,
like this.
And they become cumulonimbus,
nimbus for precipitation, mostly rain if you're lucky.
It can massively change the wind you're sailing in.
You've been nicely sailing along with trade winds 15 to 20 knots northeasterly,
and you start having these clouds around.
That is really short term strategy.
Overall you want to go there, but
above all you want to take benefit of the clouds.
And above all you want to avoid having any disadvantage of the clouds.
This cloud, for instance,
has just started raining, that's the blue stuff falling out of it.
Here's the sea, and with this rain coming down there's also massive downpour of air.
The air is falling down out of the clouds basically, this air can't go anywhere.
It sticks on the surface, which is the sea, so it goes to the sides.
We'll see later on what it means to an actual wind field when it happens.
The other thing is the closer the cloud is to the sea
the less space there is for it to go out of the sides.
So if the cloud is close to the sea, the air coming out of it is a lot stronger.
To put it simply, start off with two simple type of clouds,
one that spits, and one that sucks, basically.
One with air coming down, one with air coming up.
This is the case of the air coming down, because the cloud has started raining.
And sometimes, you're doing your whole short term strategy dealing with
a cloud that is still convective, still sucking air in.
And all of a sudden the cloud changes on you and
it starts raining and you have to adapt your strategy to it.
That's really short term strategy, try to keep the boat going and
the avoid the pitfalls basically.
OK so here's the second type of clouds, the one that's still convective.
Still the air is still rising,
the cloud is still building becoming becoming more and more vertical.
In the doldrums, around the Equator,
sometimes these clouds can reach into eight, nine kilometers high, it's amazing.
So this one is still sucking the air in, like that, the air going in.
This is a very simple scheme, because this one is only sucking it in,
the other one is only dropping it out.
Sometimes it's more complex than that, the clouds are bigger.
Once one part of it is still sucking in the other ones already started to drop it.
So just to get an idea in the next drawing
I will explain what it does to the wind field.
Okay, we just had a look at these rain clouds and
this convective clouds still growing in height.
Now it's looking from the upside down, what does it mean to us?
What does it mean to have a raining cloud?
Just explained that the raining clouds has got the air coming out,
the air's coming down, falling down, can't go anywhere.
It will come out of the cloud like this, those are all the red arrows.
That's fine, but in the meantime our overall wind,
our general wind, trade winds, is this blue thing.
As you can see here, if there's a cloud here, pouring air down, going that
way while trade winds are coming from that way this whole green area has no wind.
It's what we call the wake of the clouds.
On the sides, with the wind coming out like that and trade winds being like that.
It combines, and you get a nice what we call a right hand shift,
the wind has turned right.
And here you get a nice left hand shift, the wind has turned left.
The best however,
The best, however, is to be in front of the clouds.
Not only you have the trade winds, also you have the downpour out of the clouds.
They add together and
get a really strong push of favorable winds here ahead of the clouds.
The trick is, of course,
to stay ahead of the clouds because if the cloud overtakes you and you end up here.
You will lose everything you've just gained and a bit more.
So it is about keeping those rain clouds on the radar,
calculating how close they are to you.
Are they gaining on you, are you gaining on them?
You want to stay over here,
you don't want to get any closer to it because it might overtake you.
And you'll end up beneath it and behind it and it could be very long and
painful before those blue winds build again.
