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When
Alina isn't busy trying to present the weather to the world, she
takes the odd time out to answer your weather questions. Just fill
in the form below if you want to ask
her anything which is puzzling you...
Mark
in Wincheslea Beach, East Sussex
"Good to see a new face, but where has Dorcas Henry gone
to?" |
Alina
says: Dorcas left the BBC sometime ago to take up a new job
with the Met Office helping to train budding young TV weather
presenters. She says she's having a wonderful time down towards
Devon and enjoys it very much.
I must admit it's quite daunting following such a class act,
but I'll do my best! |
Karen
in Wokingham
"do you like telling the weather?" |
Alina
says: Yes. I love it. I wouldn't do it otherwise! People are
always fascinated by the effect the wind, rain, temperature,
pressure has, not only on landscapes, but directly on themselves.
It amazing when you think about things like Seasonal Affective
Disorder (SAD), which have such a major effect on people's moods.
When the sun comes out people really do seem to smile more,
and be more relaxed.
It's also really nice for me to provide people with comfort,
telling them that those long nights will soon be ending, and
we're in for sunny spells literally brightens up my day! |
Brian
Davies in Farnborough
"Why does the temperature decrease as elevation increases.
As you climb you are getting closer to the sun, so it should
get warmer." |
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Alina
says: You'd think so, but in meteorological terms, the effect
on altitude bringing you closer to the sun is actually minimal.
Given that the sun is some 93 million miles away moving towards
it, even by many thousands of feet, doesn't actually mean
you get warmer.
Its scientific name is environmental lapse rate: the rate
of decrease of air temperature as altitude increases.
Mountains are very interesting as they develop their own climates.
Mountain climates occur in all major ranges where land rises
above or near the permanent snowline, generally exceeding
3,000 m (10,000 ft) in height.
Mountains
create their own climate, no matter where they are located.
The climate of a mountain or mountain range can be divided
vertically into a number of sub-zones.
While foothills may have a tropical climate, peaks may be
covered in ice.
The sub-zones of a mountain climate get progressively colder
with increased altitude.
The vegetation on the lower slopes largely depends on which
climate zone the mountain is in.
On the upper slopes, needleleaf trees reach to the tree line.
Above this level are found alpine plants which can withstand
the harsh conditions.
The uppermost level is bare rock and snow. Tibet and the Himalayas
and other mountain ranges such as the Rocky Mountains or the
Andes are good examples of this.
In Africa, only the isolated peaks of Mount Kenya and Kilimanjaro
and the Ruwenzori range are high enough to carry permanent
snow.
Once you're above the clouds, the sun is able to warm you
up, but the effect is reduced because the air is thinner and
you're competing with the mountain's own climate. It is possible
to get immensely sunburnt on top of Mount Everest, even while
you will be at risk of dying from cold.
I
hope I've answered your question!
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Alan
Holden in Brighton
"Why is it that the strongest winds always seem to be round
the southern side of a low pressure ?" |
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Alina
says: Wind moves from high pressure to low pressure. That's
pretty obvious, but the relationship between wind and pressure
is not always clear cut.
You
have to take into account 'highs' and 'lows'
Anticyclones,
or 'highs', usually bring fine, settled weather. Depressions,
or 'lows', bring rain, strong winds and changeable conditions.
Changeable
weather is a feature of British weather, depressions are responsible
for much of this.
In
Britain, most depressions cross the country from west to east,
starting in the Atlantic Ocean.
As
a depression passes there are distinct changes in weather
conditions.
Air
moves in clockwise and anti-clockwise whirls like water in
a rocky stream.
These
whirls move around warm and cold air in the form of air masses
- with uniform temperature and humidity characteristics often
from the region in which they formed.
Fronts
develop at the boundaries of the air masses because masses
of air at different temperatures do not mix but move up and
over each other.
This
might be why you feel there are stronger winds to the south
of low pressure.
You
also need to bear in mind that as the isobars on the pressure
charts become more tightly packed, so then the wind will strengthen
- this being depicted by the larger arrows!
And
it's worth noting that the wind direction cuts across the
pressure isobars (effectively the wind arrows will point in
a direction of deepening pressure).
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Tony
Marvin in Verwood
"Dear South Today,
Having again seen the sight of the suns rays showing through
the clouds radiating to the earth is it possible that one of
your weather personnel would know if there is a name given to
this effect.
It is a question that has arisen more than once and having tried
several sources it does not seem to be information easily found.
Thank you for your attention" |
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Alina
says: I'm glad I can help then! It's called diffuse sky radiation,
where the sun's rays are obscured and scattered by clouds,
molecules or another obstructions.
It's
particularly noticeable with low thick and dark clouds, when
there is still lots of moisture in the air, e.g. after rain.
The rain streams each part of the sun's rays in lines you
can see as part of the diffuse sky radiation process.
I
always think it's a bit like God looking down on us.
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You
can ask Alina your weather question by filling in the form below.
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