26/08/2017 Weather World

This time on Weather World we are the highest point of the UK's is the

city, uncovering the secrets of urban weather. And finding out why

heatwaves hit cities and those of us who live in them the hardest. We

take to the rooftops of London to see just how man-made environment

can change the weather forced what are you hoping to achieve in the

future? When we do weather forecasts we will give more detailed forecasts

so there will be differences between different parts of the city. Also on

Weather World: Out of nowhere. A view of mudslides and storms, as we

take a meteorological view of the world. Scorching summer in southern

Europe and the deadly consequences of wildfires that rage out of

control. Watch the birth of a flood as it surges down a dry riverbed to

the floods that sweep away everything in their path and the

disaster they cause. Plus, cold comfort. The blanket response to

melting glaziers in the Austrian alp. Scientists have realised there

has an unprecedented glacial melt, so the question now is how serious

is that melts and what can they do to stop it? Welcome to Weather World

and a view you will never forget. The skyscraper that stands above

everything else in London. From up here you can see the haze that

stretches over this urban landscape and tells you that the areas

different compared to win the countryside. And it is the unique

properties of urban air which produces weather and climate

differences which in packed everyone who lives and works in a city. It's

called the urban heat island effect. That is built up or man-made area

that significantly warmer than the surrounding countryside for not it

is often most noticeable overnight when the temperature difference can

be as much as 12 Celsius between the inner city and the rural

surroundings. There are several causes of the urban heat island

effect. Firstly, dark surfaces and the types of materials used in

cities, like concrete and tarmac, tends to absorb more solar radiation

on the day and heat up quicker than the countryside. This heat is then

released into the city air, creating the warming effect. With high levels

of pollutants in the cities, that air is more capable of holding onto

the heat, whereas in the countryside where the air is often clearer more

of that he can pass through the atmosphere. There's also a lack of

evaporation in cities due to less vegetation and fewer bodies water.

In more rural areas this evaporation from trees and water removes heat

from the surrounding area. As well as the materials used in cities, the

other major contributing factor is the topography of the structure of

urban areas. Imagine for instance wind flowing in a relatively

straight line across open countryside will stop when that

blows across an urban area, the buildings create more friction to

the flow, aching it slow and more to be learned. This in turn reduces its

capacity to disperse heat. So with more than half the world's

population living in urban areas, this heat island effect has a huge

impact on our weather and daily lives. We are swapping one high-rise

for another, as we cross the city from south to north, joining a team

of investigating urban weather. What they are discovering could one-day

narrow down weather forecast from hold to parts of the city and

perhaps even individuals reads. Behind me you can see the Shard on

the London skyline and it is part of the research project here where

various pieces of meteorological equipment are taking readings of

different elements of the weather. One of those pieces of equipment is

inside the silver box and that's a thermal imaging infrared camera.

This camera is looking down at the city and is taking measurements of

temperature coming of different materials, like buildings, roads and

vegetation. To tell us more about this camera and what is its

measuring the going to meet a Ph.D. Is due to end. Talk me through this

camera. -- student. What is enjoying us? This infrared camera is

sensitive to radiation which can be used to determine surface

temperatures. If I was to point the camera at different surfaces, like

my hand, surfaces of different to bridge will appear a different

colour? Yes, this is a thermal graph of the temperatures which you can

see through the camera. Your hand is appearing cooler than the

surroundings. The different colours represent different temperatures.

Have a look at how this works down the city. You've got several of

these infrared cameras positioned at different places around the

building. This one here is looking down at some buildings and roads and

vegetation down below us. Talk as through what it looks like and what

we are seeing on the infrared image. This is a time lapse of imagery. You

can see the same principle as with your hand, different colours

representing different temperatures. There's variety of colours, meaning

the surface and temperatures are highly variable. Why are we

interested in these measurements? Typically we use a satellite base of

measurements, looking straight down at the surface. That means they have

a preferential view of the roof and ground surfaces as opposed to all

surfaces. I'm doing a ground proving exercise here, with lots of

measurement of different angles. These temperatures are really

important for evaluation and input. We will have more from the rooftop

later. When the going gets hot, you do what

you can to stay cool. It's been a summer of extreme heat in southern

Europe. Temperatures soaring well into the 40s Celsius from Spain,

across to the Balkans. In Italy, the heat exacerbated drowned. The pope

ordered the famous fountains of the Vatican to be turned off to show

solidarity with the people of Italy and Rome, where temperatures hit 43

Celsius. Hot, dry and now on fire. Wildfires

led to thousands being evacuated from campsite here in France, in

July, spending the night on beaches as the smoke billowed above them.

Portugal, in June. The catastrophic forest fire kills more than 60

people. The country's worst disaster for more than 25 years. The majority

of people were killed on this road, rapidly engulfed by fire as families

already fleeing from their home is where trying to drive to safety.

More fire, but a different continent. This is South Africa,

near Cape Town, in June, as the drought combined with strong winds

spread wildfire sparked by lightning. They followed a major

storm that inundated the coastline here, with high seas and big waves.

The South African weather service said was the worst winter storm here

in 30 years. Big storms have hit Europe too. This is Moscow, in May.

A severe thunderstorm, the worst in a century, killed 16 people,

toppling trees, with winds of up to 70 mph. And astonishing scenes from

Poland, in August, as storms bring down tens of thousands of trees,

killing six people. It was declared the worst disaster of polish and

possibly European forest history. Storms brought devastating

downpours. Turkey, Istanbul, in July. Roads turn to readers. There

have been a number of flooding Storms in the city this dud summer.

In the UK storms followed a hot start. This was Cornwall in July.

The torrential rain and hail lasted over an hour, causing a flash flood

to sweep through the village, taking everything it could carry towards

the sea. This woman found her elderly mother's walking frame

amongst the piles of debris and next to it even her kitchen sink. It's

happened. You can't put it back. You just have to get on and carry on and

do what we can. We'll get back to normal. We're Cornish! Earlier in

the summer heatwave provoke an unusual protest at a Devon school.

Boys were told they couldn't wear shorts, because it wasn't official

uniform. So they wore a skirt instead. They can't stop us doing

it. Girls are allowed to wear skirts. They get cold legs and we

have to sit there sweating! The school says as hot weather becomes

more common, it may consider a change. Protest is real!

We are back at our urban experiment on the rooftop in London. Earlier,

we saw thermal imaging to look at how different surfaces, grass,

concrete, humans, heat and release the heat at different levels. That's

enough of that. That's really important because those different

surfaces are also heating the air above them at different levels.

Different writing of that air. That goes on to affect the air around us

and also the weather. Ben Crawford is monitoring how much the air

moving around -- how much the air is moving around us. This measures wind

speeds in three dimensions. With this piece of equipment we can

measure the cumulative effect of all the different surfaces and their

heating of the air. Importantly, I'm filling the air blow right at me

sideways, but when you are talking about different surfaces heating the

air above, it's rising from ground upwards, which is also measured with

this. You would expect that air to be writing differently, depending on

where it's come from. Exactly. You can imagine a natural environment

like a field or forest and replace that with the city, with glass and

concrete and brick, you will change the thermal properties of that and

change how the air flows and moves. This is measuring what's going on

just here, but you've also got another piece of kit, measuring over

a big distance? This measures disturbances from the air, from the

heat rising, the military shimmers coming off a hot roof or it piece of

concrete. This is pointed across the city towards the foot tower, about

four kilometres away. So this really is the invisible world of what's

going on in the air right above the cityscape? That's right. With the

data from this instrument we can make the invisible visible. Here we

have a series of days in the summertime in London and we can see

during the mid- day, the hottest part of the day, we have the

greatest heat emissions and we can see this rise in the graph.

Overnight when the surfaces cool we can see less heat emission coming

off the surface. What does it matter? How does knowing about all

of this turbulent air possibly improve the weather forecast for the

city? That's a good question. It emissions and turbulence affects a

lot of things. It affects air cabbage, wind speed, it affects the

dispersal of pollutants and can even impact things like clowns. -- air

temperatures. We can narrow down the forecast to a smaller part of the

city? That's right. We can give a specific forecast for a city, and

even perhaps later different neighbourhoods in the city. Thanks

for revealing the hidden world on what's going on in the air around

us. You're very welcome. Turbulence and updraughts when

airborne Our Watch hotair balloons try to avoid. But getting airborne

is the problem here. We are trying to get air app. Two balloons collide

in June. Swirling winds blow them off course. Luckily what could have

ended in tragedy only left one man with minor injuries.

Lightning sparks across the south Wales guy in May. The earth's

surface is struck about 100 times every second and were never

lightning strikes you can be sure BBC Weather Watchers will try to

succeed where many of us fail to get a good photo of it. This will all

taken when storms swept through the UK in July. Become a BBC Weather

Watchers by signing up online. Coming up, how a blanket could help

produce a phenomenon known as glacial melt.

So far on Weather World we've been getting very high-tech at this open

weather experiment on this windy rooftop in London. But along with

the high-tech, I found something that's a little bit more familiar,

at least to me, which is a weather station. We've seen a lot of these

on our travels on Weather World. In Northumberland we saw a fully

working weather station there. Insight here we've got a thermometer

and it is measuring humidity with this gauge. All inside a very clever

box which takes it from the direct sunshine and excessive wind.

Of course that weather station had a screen kind which it had a

thermometer. Although this isn't the same as that, it similarly protects

that the monitor so we can measure the temperature of the air, rather

than the sun. And we've also got an anemometer. We've been to the

birthplace of these on our travels on Weather World, the Northern --

Northern Ireland. It all started here. A simple design. The four cups

that spin in the wind and you can measure the wind speed. This

anemometer is getting a good workout today, but it's really good to know

that wherever we go on Weather World we can find a weather station. But

we will get a little bit more high-tech again later in the

programme when we come back a time in south-east England. -- but

becoming. Engenhao dash-cam technology can now

do as a driver's eye view of what it is like to negotiate a flooded road.

But things are about to get much worse. -- in-car dash-cam. China and

July, and a flash flood after many days of rain leaves many needing

rescue. Here, and the injuries, in June, a desperate search for

survivors as heavy rain triggers a landslide that kills more than 100

people. From Sri Lanka to Nepal, millions are affected. In Nepal, the

float is worst in August. Alison is used to rescue people trapped in

water. In June, torrential rain in Taiwan. -- elephants use. More 100

600 millimetres in six hours. Similar scenes in Japan in July,

where rain causes more than half a million people out of their homes.

When a flash flood Russia is a major city, disaster strikes. Freetown, in

August. And a massive downpour causes muddy water to certain

industries. Then a mountainside collapses, bearing whole communities

and families as they slept. Hundreds are under this flood, and the death

toll may never be known. It is the rainy season here, but this year it

has come with unusual and deadly ferocity. And just how quickly can

rain transform a trader Rusty weather -- transform a rusty river

bed into it a river? A happy surprise to some of the southern

hemisphere for winter, as Santiago is hit with snowfall in July. The

snowfall caused treacherous driving conditions, not that these motorists

seem to care. But unusual cold stats look like local anomalies against a

tide of record warned. Alaska. Parts of this US state had its warmest

July on record. A council meeting he assigned an agreement accepting the

need to tackle climate change. But less than a month later, this. In

order to fulfil my solemn duty to protect America and its citizens,

the United States will withdraw from the Paris climate accord. Donald

Trump's announcement brought international condemnation. The

world meteorological association said that in the worst case, it

could add 0.3 degrees Celsius to be covered by 2020 three. -- 2022. I'm

at the top of this Glazer in the Austrian Alips at about 3,000m high.

It is an area very popular for skiing. Actually, there are about 80

separate glaciers in this area. -- glacier in the Austrian Alps. This

woman is a world renowned glaciologist. She has come up with a

surprising answer to our stock, a blanket. On a very small, local

scale, we could prevent some very tiny areas. -- protect. But only

about 1% of glazier area can be preserved with this method, and of

course, it is very cost intensive and needs much labour. -- glacier.

To save 1% of a glacier seems futile. But officials say it is

worth it. There are 5000 Alpine glaciers in the world. Experts say

that half will be gone within only a few years, and those that are left

will be much smaller. But it is clear this inexpensive local

solution can help on a global scale. Here on the ice sheet, the problem

is super-size. There are fears that the melting is happening faster than

expected. This is in part due to allergy on the service of the ice.

Darker than the ices, it absorbs more of the son of a warmth. --

algae. Bevvy as saying that is going to melt in the next decade, next

100, or even 1000 years. -- nobody is saying. But it does not need to

be completely melted for people to be in danger. Only a small portion

is required to raise sea levels, and that threatens coastal communities

around the world. And the expansion of renewal, renewable energy is a

huge development. -- expression of renewable energy. This is the

world's first floating wind farm. So, you have look down towards the

ground, and we have seen equipment measured the weather at this level.

But now we look into the skies. To do that, I enjoy by Natalie. Talk us

through this piece of equipment,. This is a laser that takes a

snapshot of the atmosphere. You can't see the laser. It measures

outside the vehicle spectrum. So this looks 7000, viz in the sky.

What is it measuring? It is measuring reflector from particles

in the atmosphere. This could be clad droplets or pollution. -- cloud

droplets. So you can get a picture of the clouds and have a picture of

how things are at any moment. So now we will talk about the data and how

we use it. Sue is an urban climatologist with the university of

Redding. -- University of Reading. How is the information useful to

you? Is helping us with our weather forecast. But we can also see where

clouds form. What we are looking at now is the green is the rural area,

and the greater city. You can see the clouds are forming, and what

happens to them over cities, and how that is different. We can compare

the difference in the real city with what we can see in forecasts like

this. So with all the research going on here, had us that tie together,

and what are you hoping to achieve in the future? As we think about

forecasting into the future, what we are expecting is that models will

allow us to look at things in much more detail, so we can look at, for

example, the differences between the northern part of the city and the

southern part of the city. Hopefully this will make it better for

citizens within the city and living in different neighbours. Wonderful.

So we're looking at more accurate urban forecasting the future. They

you for joining us, Sue, and to all your team, too. Sometimes you need

to look of your shoulder to see what the weather is doing. This photo of

a man unwilling to abandon me his lawn in Canada in June took certain

media by storm. Apparently, the Tornado was further away than it

looked. We offers see pictures of the Northern Lines, but these are

the southern hemisphere equivalent. It put on a spectacular show in the

skies above Australia and New Zealand in May. And finally, the

weather can make us all a little hot and bothered in times. Apparently

the same goes for gorillas. -- at times. Zola creating a splash at

Dallas Zoo. And that is it for this time on Weather World. We will be

back later in the year. Until then, keep checking the forecast.