Can you Steer a Hurricane...?

Water is one of our most fundamental needs, and many natural disasters can remove our source of clean fresh water. One inexhaustable source of water is of course the sea, but the salt makes it no use for drinking. There are various ways of desalinating this water, but most of them don't scale down very well, even reverse osmosis - essentially filtering out the salt with a special membrane - requires large pressures, which requires a pump and the membranes tend to get gummed up by contaminants.

A new energy-efficient desalination system utilizing ion concentration polarization as the core mechanism. Both salts and any charged colloids in seawater are diverted into the brine channel, leaving the other channel relatively salt- and particle-free. The system could be made portable and operated by current battery technolgy. © Credit: Sung Jae Kim/Jongyoon Han - Nature Nanotechnology

Sung Jae Kim from MIT and colleagues have come up with an alternative. Instead of using a membrane to separate the salt from the water they are using electricity. They have made a y shape of channels about half a mm wide. The dirty water comes in along the stem of the Y and on one of the two arms is a nafion nanojunction. This is a material which will let positively charged ions flow through it but not negative ones. This is made negatively charged and a current flows along the arm in the wrong direction. This leaves lots of negatively charged ions piling up and flow up the other arm. These take any other charged species with it, including the ions in salt and bacteria and other contaminants leaving water with 99% of the salt removed.

It isn't as efficient as reverse osmosis, but it is intrinsically a much smaller scale process so you could build a machine consisting of maybe 1600 of these junctions to purify maybe 15l of water a day and because the contaminats are pushed away from the sensitive parts of the system it doesn't clog up like a membrane.

Ceramics - materials like pottery - have all sorts of very useful properties, they are very hard, resistant to heat, some are very strong etc.  but their use has been very limited because they are very brittle. They are not tough which means they can't absorb energy from an impact without shattering, and once a crack starts in the ceramic it keeps on going to the edge of the material.

For a while scientists have been fascinated by shelled animals, their shells are made up tiny plates of the brittle ceramic calcium carbonate - effectively limestone - mixed with proteins to give a very tough material which can survive an incredible amount of abuse. This is because a crack can only travel through a single plate and then stops at the edge. Many scientists have been interested in these properties and have tried making various materials in the lab with interesting properties.

Andreas Walther, from Helsinki in Finland, has managed to make a similar structure out of a clay which is made up of microscopic plates and PVA glue that is very easy to make and could be painted onto walls or an aircraft skin.

The properties are very similar to fibreglass but it can be applied more easily and is much thinner. Apparently tests with flamethrowers also show that it is very fire resistant as well.

Ben - Most of us are familiar with the long trails left behind by airplanes as they pass overhead.  But those trails, or contrails as they're called, can actually give rise to clouds.  We're joined by Dr. Jim Haywood who's from the Met office.  Now thank you for joining us, Jim.  My first question really to get a broad idea is how were clouds normally formed?

Jim -   Well, clouds almost invariably form when the air that contains the water vapour cools.  Cooling is almost always initiated by a lifting action.  For example, air flowing over mountains can cause the air to cool to such an extent that the water in it condenses, forming a cloud.  Alternatively, you can have things like cool air undercutting warm air and forcing it to rise in frontal systems associated with low pressure systems in the mid latitudes.  So really, it's just a case of air being forced to cool, the relative humidity - as meteorologists call it - exceeds 100% and the water in it condenses.

Ben -   When we see these big lines up in the sky, these contrails from airplanes, what are they actually made of?

Jim -   Obviously, most clouds that we can see from down here are made up of water droplets.  Contrails tend to be made up of ice crystals that grow when the conditions are favourable.

Ben -   How do these then go on to create a cloud?

Jim -   What you can get is - under certain conditions, which is basically cold and moist conditions  - the ice crystals that are initially formed by the aircraft contrail can grow.  It's a bit like a physics experiment that you probably did at school where you grow crystals of copper sulphate or things in supersaturated solutions.  That's exactly what's happening here.  When the conditions are right, it's cold enough and moist enough up in our atmosphere then the crystals that are initially injected can just grow tremendously and spread with the metrological flow.

Ben -   So we're not talking about lots of individual particles like we will be for a normal cloud.  This is actually a very large ice crystal that just happens to be light enough to float about.  Is that right?

Jim -   The ice crystals, when they're initially injected are about a 1000th of a millimetre typically in terms of size.  But as they grow, they can actually get many times that up to about 100 microns.  So, they do form very large crystals which are important in the earth's radiation budget.

Ben -   These clouds are a bit different than normal clouds.  How do they affect the weather?  Are they rain clouds?  Are we likely to see rain from them or just perhaps a bit of shading or will they not affect us much at all?

Jim -   Well they do affect us in terms of the amount of sunlight that they let through.  That's quite important.  They tend to reflect sunlight back out to space and lead to a cooling of the weather and consequently, the climate.  But they also trap out going long wave radiation.  So, heat radiation if you like, rather like the greenhouse effect.  So there's these two competing effects.  You've got the reflection of solar radiation or sunlight back out to space and you've also got a greenhouse type of effect.  And what's critical is really the balance between the cooling from the reflection of solar radiation and the warming due to the greenhouse type of effect of these crystals.

Ben -   So if they need particular conditions in which to form, does this mean that certain flight paths are actually more likely to create these clouds and therefore, we're more likely to have this warming effect or this reduction of sunlight effect in certain areas?

Jim -   Yes, that's right.  I mean, one of the area that's particularly good for forming cirrus types of particles - these ice crystals - actually coincides with the air traffic corridors, particularly the one linking North America with Europe.  That's a particular area that's good for crystal formation and crystal growth.

Ben -   We've had a very, very relevant question from Neil Briscoe.  He said that he heard a while ago - thanks to the 9/11 attacks - when they grounded all the flights, people were able to work out the contrails during daylight hours, helped to prohibit warming by reflecting light back out into space.  But during night time, they actually increased warming.  Is this the same stuff that we're talking about here?  Does it matter whether it's day or night?

Jim -   Yes, it does indeed.  It's exactly what that question is about.  Really, we're talking about a cooling, if you like from the reflection of sunlight and a warming during the night time which can cause a reduction in what's called the diurnal temperature range.  After 9/11, there was certainly evidence of a reduction in the diurnal temperature range from a particular study.  But it's quite difficult to disentangle that signal, if you like from the natural meteorological events that can occur.  And when they looked at it in a little bit more detail, it became almost impossible to distinguish from other events that had nothing to do with 9/11.  You still could see this signal in diurnal temperature range, just due to the natural variability of the atmospheric system.

Ben -   So it may have an impact that we can't see because it's no bigger than noise.

Jim -   It's just difficult to detect.  That's right.

Ben -   And speaking of detecting it, how do we actually study these things?

Jim - Well, we study it by a number of ways.  We've been simulating these contrails and contrails induce cirrus in the state-of-the-science atmospheric models that we use at the Met office and the Hadley Centre for Climate Change.  We've also been having a look at various different aircraft measurement campaigns.  I'm involved with an aircraft measuring campaign where we're trying to create contrails and actually measure the amount of reflected sunlight, and the amount of infrared heat energy that these contrails affect.  So, you can do it from a purely modelling perspective but it's always better to base it on objective measurements.

Ben -   And, just finally, these contrails obviously tend to stay in one place in the sky.  When they go on to create this cirrus type clouds, do they also stay where they were created or do we find that they drift across the country and have that sort of effect on a slightly wider area?

Jim -   Yes.  We studied one particular contrail that was formed by an Awacs aircraft over the north sea and what we found was although that aircraft had only travelled 1500 kilometres, the area of cloud that it created was actually over 50,000 square kilometres.  This area of cloud - this was created last March - you could see quite clearly being vectored over the UK and lasted for several hours.  It actually lasted for around about 18 hours before the ice crystals started to dissipate.

Ben -   So that's certainly something to think about next time you're 30,000 feet above the UK.  You might actually be making it literally cooler for us down on earth in the daytime, possibly a little warmer at night.  That was Jim Haywood.  He's from the Met Office.

Dave -   Now moving away from clouds and over to the extremes of weather, more specifically windstorms.  For example, the winter storm Anatol blew through Europe, including the UK, Sweden and Germany, and caused economic damages and approximately 2.9 billion Euros.  Much of this was claimed on insurance.  And so, insurance companies are very interested in predicting these extreme weather events.  A team from the University College London's Climate Extremes group have created just the tool to do this and formed the company Eurotempest to help European insurers to help prepare for the billions of pounds weather damage that may be coming their way. 

Meera Senthilingam went to visit them in London and met Operations Director, Frank Roberts to find out what they need to know for these predictions and how these weather forecasting data is collected in the first place.

Frank -   Well in the first instance, the modelling agencies - that's the national meteorological agencies of any country and in the UK, that's the UK Met office - will collate observations from all over the world.  I think the Met office collect about half a million per day at the moment and that can be from any source. So satellites, weather balloons, surface observation stations, buoys at sea, aircraft.  From that, they need to build a complete picture of the atmosphere because obviously, these observations were only taken at certain points, and this is what they called the assimilation process.  They have complex mathematical models to do this.  And from that, they will then use what they call their numerical weather prediction system.  The atmosphere is broken into - on the surface- latitude longitude grid squares, so just like you're looking at a map, and various levels, so you have these cubes of atmosphere.  You apply then the physical equations to each cube of the atmosphere in order to be able to predict the various parameters that you're interested in.

Meera -   So parameters such as?

Frank -   Temperature, wind speed, wind direction, humidity, the amount of rainfall that you might expect, cloud cover...

Meera -   To what resolution is it usually possible to predict the weather?  Say, to what area?

Frank -   Well the current global model that the UK Met office use is on the resolution of about 60 kilometres.

Meera -   Here at Eurotempest though, you focus on the parameter of wind speed and essentially then try to predict windstorms across Europe?

Frank -   Yes, that's right.  We focus on wind specifically because we provide a summary of information, not for the general public but to the insurance industry.  Severe wind causes, over the long term average, about 80% of the insurance loss from natural hazards in Europe.

Meera -   So how do you go about collecting data for wind speed and therefore, what kind of information are you putting together to help insurers plan for windstorms that may be coming up?

Frank -   Okay, well we take the surface level output from the UK Met office numerical weather prediction model for wind speed and from that, build up a picture of the wind speed forecast for the country in the coming five days, we go out to five days.  Also, our customers who are insurance companies have provided us with information about where their insured properties are.  So, by postcode, we have information about what we would call their exposure.  That's the total value of the insured properties in those locations.  And then we use what we call a vulnerability model.  This is built up from historical observations of claims and wind speeds in given locations and it's a statistical model which allows us to estimate the proportion of buildings which will be damaged in a given postcode area from a given wind speed.  So, you can't say necessarily, of course, that this particular building is going to be damaged, but if you've got enough buildings of a certain type in a large enough area, then you can say what proportion of damage is going to occur.  We can do that for a country as a whole for each of our customers and then they have a good idea of what the ultimate payout is going to be from a severe wind forecast.

Meera -   What kind of wind speeds does it take to really damage property?

Frank -   Well typically, the serious damage really only begins at about 60 miles per hour and that's not particularly usual.  It's not an everyday occurrence in the UK.  Insurance companies tend to get interested at around about 40 miles per hour, and you can get small levels of damage at those sorts of wind speeds as you might expect - a few tiles or the odd branch breaking a window, or something like that.

Meera -   Now, in terms of actual damages and costs, how much damage can be done by wind?

Frank -   Well in the UK, on average, it's about half a billion pounds a year which is obviously an awful lot.  You might remember fairly recently, just at the beginning of the month, there was this severe windstorm in France, called wind storm Cynthia.  Now the estimates for their losses from that are well over a billion pounds.

Meera -   So, as well as helping insurers prepare essentially for maybe a large amount of payouts that are about to come out, how else does this benefit them?

Frank -   They can prepare for the large amounts of payouts but of course, if there's a severe event, there is likely to be an awful lot of claims coming in all at once.  So that helps them to manage their human resources to make sure that they've got enough people in their call centres to be able to answer the phone, to answer the claim from each of their customers.  It's obviously extremely important to them that they're able to settle claims very quickly from a customer satisfaction point of view, but also from the point of view that the longer the damage is left unfixed, the higher the bill tends to be ultimately. 

We also provide a system for insurers which allows them by postcode and date to interrogate the observation data set.  So, when a claim comes in, they will be able to look at their system and they'll see the distribution of observation stations around the postcode, and it will report the wind speed or the rainfall, whatever it might be, so they can check back to see that there were damaging conditions prevailing on the day that the damage happened and then they can validate the fact that the damage that's been reported by the insured is actually consistent with storm damage.

Meera -   But now, what makes this vulnerability model better than insurers just keeping an eye on weather forecasts?

Frank -   Well the public and media weather forecasts are specifically designed for public consumption and for public safety, and that will be couched,  often, in terms of  "we may see 80 miles an hour gusts at peak".  It doesn't really say in any great detail where exactly that might be expected.  And that's a sort of high resolution information you need to predict for an insurer.  So, translating a verbal media forecast into a forecast of loss is actually very difficult for anybody to do and in the past, we've had examples from customers who said that had they only had the media forecast available and tried to interpret that in terms of what their exposure was, they would've been out by a factor of 10, compared to what we were correctly saying.

Dave -   With all that saving, hopefully, our insurance payments will be more efficient in the future and hopefully a bit cheaper.  We'll have to keep our fingers crossed on that one.

Ben -   Indeed, we will.  Yes, that was Frank Roberts, Operations Director at Eurotempest talking to Meera Senthilingam.

Dave - You can do it electrically with about 1.3 volts of electricity. However, to do it thermally, you've got to heat it up to over 2,000 degrees centigrade. It's one of these things whereby the hotter you get, the more complete the dissociation - you split the molecules up. It is actually a suggested way of making hydrogen - you heat up water at very high temperatures. You then have to somehow separate out the hydrogen and oxygen because otherwise, it's easily hot enough to burn and condense back to water again, so you need some kind of membrane to separate the two. This does exist - it's a special kind of ceramic membrane, and you can separate the two gases and you get hydrogen out.

So, yes, it can happen somewhere about 2,000 degrees C.

Ben - And would it help if you were to add a catalyst? I know that they've been looking at using platinum to help do this. You find catalysts that help reactions happen at different temperatures. Could we find the right catalyst that therefore meant it didn't need to be quite so hot as 2,000 degrees?

Dave - Catalysts certainly help with electrolysis, doing it electrically. My knowledge of high temperature chemistry is very limited, but I think the fundamental thing that you're working against is the actual energy you need to split apart water molecules and thermally, that's an awful lot of energy. So, I would be surprised if you could gain that much.