Turn on, tune in, drop out

Decision made. This is quite an achievement for me, because I’m generally terrible at making decisions. I even disagree with Magic 8 Balls.

I’ve dropped out. Dropped out of S216, but not out of my OU degree. But that is a good thing: there is no guilt here (hoorah!) because I just don’t have the time or motivation for this course at the moment.

Having found myself needing a week’s extension for TMA04, then watching the week’s extension fly past with a satisfying “whoosh” sound, then coming to the realisation that I hadn’t even thought about my project, I arrived at the conclusion that I have too much going on at the moment.

I feel lighter already. It’s an enormous weight off my mind; I can concentrate on building my new business (did I mention it’s called Sunflower Communications?), make sure I actually enjoy my holiday to Germany in September, and look forward to starting S207 The Physical World in October. I’m very excited. It’s all about physics!

The OU has a very good system: I’m transferring 30% of my S216 course fee to S207, so I’m getting 30% off my next course. I’m fine with that, because I’ve got all the course books and materials for S216, so I’ll read them at my leisure over the next few months.

I can’t help feeling that if the course had been more like S104, I would have struggled far less to find time for it. I hope so. S216 has been a disappointment to me, but I suspect that is at least partly my fault – although I still say to the authors: please discover and embrace paragraphs!

So off I go. Good luck to those still doing S216; and bring on S207! Physics ROCKS.

The wrong type of rain; or, why there are floods during a hosepipe ban

This country is in a recession. Are we not all miserable enough without the recession spreading to our weather, dammit? We do not have enough water. But how can this be, people cry despairingly, when there is all this wet stuff pouring out of the sky constantly?

My favourite explanation comes from an old schoolfriend – Ashwin – who is a gentleman, a scholar, and a wit. He posits that “the first 22% of rainfall goes to Her Majesty’s Revenue and Customs, unless there is lots of rain, in which case, Her Maj takes 40%”.

The popular press (and by this I mean the Daily Mail and its ilk) will, inevitably, go for the most attention-grabbing, frothworthy headlines they can. They will scream about flood warnings while moaning about a hosepipe ban, shouting: “Why why why? Look at all this water – how can there possibly be a drought on?”

Often, they then go on to blame the Met Office for the droughts, then the floods. Which is funny in itself. Unless these pesky meteorologists really are sitting in a secret volcano lair somewhere controlling the weather. In which case, the Daily Mail has been right all along and life as we know it is coming to a soggy end.

There are floods during a drought. And there are very good reasons why. They are also interesting reasons, so it’s a real shame that most people aren’t given the facts.

In Warwickshire, it’s been raining. A lot. More on than off for the past two weeks, and almost continuously for the past three days. That’s quite a lot of rain – 50mm in some places on Wednesday alone – and it has followed two unusually dry winters.

Several factors cluster together to pose a flood risk. But first things first: where did all this rain come from in the first place?

Water, water, all around…

A particularly strong jet stream is currently separating warm, moist air in the south (an area of high pressure) from cool air in the north (low pressure), creating a front. Jet streams are fast-flowing, narrow currents of air high in the atmosphere (near the top of the troposphere – the tropopause) which blow from west to east. Their locations are not fixed; they tend to meander around, but their position helps with weather prediction.

At the moment, the warm, moist air from the Mediterranean is flowing north (air travels from areas of high pressure to areas of low pressure) into the low pressure zone over the UK. Because warm air is less dense than cool air, it is forced upwards above the cool air.

As the warm, moist air rises, it cools and its water content condenses into rain-clouds (cool air can carry less water vapour than warm air). If the front stays steady, the rain will persist as long as the clouds are being fed by a flow of warm, moist air from the south.

Unfortunately for us (but fortunately for our gardens) the front is persisting, as is the seemingly endless precipitation…

But we’re suffering from a drought, aren’t we?

But why then, you may ask, is there a hosepipe ban across much of the country? As mentioned above, the UK has experienced two unusually dry winters. These two dry winters mean that the UK is now suffering from a water shortage. Reservoirs of water have been depleted and it takes time – and a lot of rain – to refill them.

Almost everyone knows about freshwater reservoirs – man-made lakes created specifically to provide stores of drinking water. These are replenished by rain and by rivers and streams. Fewer people realise that an awful lot of our fresh drinking water is stored as groundwater, in the rocks themselves. Just one per cent of all freshwater is accessible to humans, and of that, four million cubic kilometres is located underground. In the pores and cracks in the bedrock, and between the grains of rock themselves.

Water in the ground

Rock that is porous and permeable enough to store water and allow it to flow through easily are called aquifers, and most of the UK’s aquifers are located in the southeast of England – notably the Chalk (which is a soft, white limestone with a network of fine cracks, giving it high permeability). Individual boreholes in the Chalk can yield more than 10 million litres of water each day, which can provide for around 70,000 people.

That’s a lot of water.

Groundwater is not only accessed via boreholes, it also helps to replenish rivers. If rivers were only fed by runoff from the land, they would quickly dry up after the rain stopped. Rainwater that passes through the surface of the land soaks down through the underlying soil and rock until it reaches the water table – a level when all the pore spaces in the rock are full of water. The water table separates the unsaturated zone from the saturated zone – and the saturated zone is called groundwater.

The drought persists even after prolonged heavy rain because recharging the saturated zone takes time. There’s an awful lot of ground for the water to soak through, and the water table level will recover only slowly. And the first bout of heavy rain after a prolonged dry period, such as that the UK experienced in March, won’t do much to help – parched, hard ground won’t absorb water easily, so it simply runs off the top. It will, of course, gradually soak in, but not straight away…

Which leads us to why there are flood warnings

Most river floods result from extremely heavy and/or prolonged rain. Several factors can affect the intensity of flooding – area, slope and altitude of the river catchment, soil type, geology, vegetation cover, the nature of the drainage basin network, and the shape of the river channel.

However, in this instance there are two main reasons. Firstly, the sheer amount of water being pushed into the rivers by the rain itself and the runoff from the land surface. There is only so much extra water a river can take in a relatively short space of time before it bursts its banks.

Secondly, if there is a large volume of water dumped on the ground, the unsaturated zone will become saturated – it won’t have time for the water to soak down to the saturated zone before all the upper pore spaces are filled. So there will be even more runoff than usual.

So although drought and floods are both caused by precipitation (or the lack of it), different mechanisms are at play. Drought is a long-term problem that cannot be solved by a lot of rain in a short period of time. Floods are a short-term problem that are often caused by a lot of rain in a short period of time.

There are really cool (and by that, I mean nerdy) ways to predict how severe a flood is likely to be. In fact, the whole topic is pretty interesting – aquifers are marvellous things.

It’s really not that complicated at this level (of course, there are other aspects to consider, such as the deforestation of the British Isles, the amount of concrete and tarmac laid down, and the effects of vegetation on water movements, but in a nutshell, this is how you get floods in a drought). Yes, you could dig a little deeper and find an entire aquifer full of interesting scientific details to do with groundwater supplies, but a basic understanding of what causes droughts and floods is not out of the grasp of most people, so it’s a real shame that journalists don’t have the time to research and explain this. And it’s more of a shame that the press releases from the Met Office and the BBC don’t include simple, easy-to-follow explanations (and if they do – then why don’t the papers use them?).

I keep hearing wits on the radio commenting that this is a very wet drought, isn’t it? Ha ha ha. Well yes. Yes, it is a very wet drought. Two weeks’ worth of rain will not, sadly, make up for two winters’ worth of unusually dry weather. So put your hosepipes away and start conserving your water. It’s a precious natural resource, and deserves to be treated as such.

Puddles, puddles, everywhere…

I think the water table in our garden in Warwickshire has risen to the actual surface of our garden. There has been so much rain here – and crazy hailstorms – over the past week or so that the ground is saturated. The lawn goes *squidge* when you walk on it.

This is the first of (probably) several posts about water and how cool it is. H₂O is a marvellous, and profoundly odd, substance. But more about that later. It is the stuff of life, and knowing where and how it is stored and how it moves around is pretty important.

So: it rains. (At the moment, it seems to do nothing but rain, but that’s by-the-by.) Water falls onto the Earth – but then what? Some of it falls directly into water courses and drainage channels (streams, rivers, etc.). Some of it falls onto trees and plants; some of that evaporates or reaches the ground.

Only about a third of precipitation results in runoff (also known as streamflow or discharge). Runoff is the water that flows over the land and increases flow in rivers, and is measured in cumecs (cubic metres per second).

Then it starts to get complicated, with flow diagrams, code letters and fiddly rivulets finding their way into nooks and crannies unseen by you and me.

In a nutshell, here is where the rain goes:

• Into rivers and streams (channel precipitation) OR over the land (overland flow)
• Infiltrates into the ground below the water table as groundwater flow OR above the water table as throughflow
• The infiltrated water becomes subsurface runoff
• Subsurface runoff, channel precipitation and overland flow come together in channel flow (i.e. a river or stream)
• The mouth of the river spits out the total runoff.

It’s pretty important to keep an eye on these processes, and be aware of how topography, soil type and land use will affect water courses, because that’s what helps with flood preparation.

…lots of drops to drink

What I find interesting is what happens to the rain when it disappears beneath the surface.

You’ve got the ground surface, then soil water, then unsaturated rock, then the capillary fringe, then the water table, then saturated rock. That’s quite a lot of groundwater, and much of it is available for our purposes.

Capillary action means that water is drawn into the spaces between rock grains – and into cracks and fissures – and is held there by surface tension. The larger the surface area of the rock particles, the higher the surface tension and the more water can be potentially be stored. Hold the edge of a sugar cube in a cup of hot chocolate and see what I mean. The liquid will creep up the sugar lump.

So, the amount of groundwater stored in rocks depends on their porosity, which can be calculated by dividing the volume of void space by the total volume of rock, then multiplying by 100.

V_p/V_tot x 100

Unconsolidated rocks – not compacted or cemented – are the most porous, while consolidated rocks and dense crystalline rocks are usually less porous. But just because a rock is very porous, doesn’t mean it is necessarily permeable…

Rocks with large pores, or with pores that join together, make it easier for water to flow through them. Sandstones and gravels are permeable rocks. But clay, which has high porosity (due to lots of very small pores) holds its water virtually immobile because of the high surface tension.

Porous, permeable rocks are great natural water storage vessels. They are aquifers, and most of those in the UK are found in the south-east of England. The Chalk – the White Cliffs of Dover and the rest of this particular limestone formation – has a network of fine cracks making it very permeable to water. A single borehole in the Chalk can yield enough water to provide for around 70,000 people per day. That is a LOT of water, because we use way more than we should.

There are two types of aquifer:

1. Unconfined: the aquifer sits on a floor of impermeable rock and soaks up rain. When it becomes saturated, marked at the top by the water table, the water flows out as a spring.
2. Confined: the aquifer lies between two layers of impermeable rock, trapping water at a higher pressure than atmospheric pressure. Boreholes – artesian wells – drilled into the aquifer allow the water to rise until the pressure equalises.

What is the potentiometric surface?

If several boreholes were drilled into a confined aquifer, the water level in each would rise to a maximum. An imaginary line can be drawn linking these maximum water levels – and this is the potentiometric surface.

If the potentiometric surface is above the ground surface, water will flow freely from the well; if it is below the surface, then water must be pumped from the well. Essentially, it is the level at which the weight of each column of water balances the  water pressure in the aquifer.

Magic

Oases in the desert are often portrayed as magical, mystical things – how, in such an arid and inhospitable place, does water flow? Aquifers; that’s how. Porous and permeable rocks lying underground can transport water many miles from a source of precipitation to the middle of a desert.

You can see why people were mystified by oases. Now we understand how they work, the appearance of water is no less wondrous.

I don’t know about you, but the more I know, the more I want to know…

Clouding the issue

Just a quickie. I found this site via the S216 tutor group forum, and think it’s fabulous. Images of clouds from space, looking like you’ve never seen them before. Splendid stuff.

http://www.wired.com/wiredscience/2010/05/gallery-clouds/all/1

Enjoy!

What a lot of hot air.

Well that was a resounding disappointment. I hate to begin a post on such a negative note, but frankly, everything is so shrouded in grey cloud at the moment, it was almost inevitable.

I’ve just finished Block 1: Air. Never has such an interesting topic been made so dull, by so few. It was written by people whose skill in communication is limited to “dry and dusty”. I’ve had teachers like that in my time, and it’s thoroughly depressing.

Honestly – I know I’m a massive geek – but it’s global weather systems. It’s not only fascinating, but useful to us all – knowing what the weather is going to do from one day to the next is handy.

And I now understand why predicting short-term weather is so difficult. Long-term weather: not so much.

Although, as previously alluded to, the book is so densely written that I’m going to have to give it another once-over if I’m going to come close to getting a distinction for S216…

The basics are relatively simple – it’s just beginners’ physics. The wind blows across a horizontal pressure gradient, from high to low pressure. The fact that the Earth spins on a tilted axis affects temperatures and wind directions profoundly. Seasons are rather groovy.

I don’t really see why the book needed to preface many of its explanations with “imagine an Earth that does not rotate”. Why? Why would I do that? The Earth does rotate. Don’t go confusing things by explaining something that is irrelevant. Particularly when the concept of the Coriolis Effect is not difficult to grasp.

(The Coriolis Effect, for those who don’t know, is what causes an object to deviate from a straight path. Imagine you’re trying to land a rocket ship on a particular spot on the Earth’s surface. It’s not enough to simply aim for it and shoot; the Earth’s spin means that when you get there, the spot you were aiming for will have moved. Make sense? Or, imagine you’re firing some kind of a deadly weapon from the North Pole straight down a line of longitude to That London. Unless you correct for the Coriolis Effect, your missile will drift off to the west and end up somewhere in the Atlantic Ocean. The Earth spins through around 15° of latitude in an hour, so after one hour it would be 15° off course.)

It reminds me of an old friend, who had a physics lecturer who once began a lesson with the immortal words: “Assume a cylindrical duck”. At least that little gem has provided amusement over the years…

Anyway. The aspect of Air that i found most interesting was the El Niño Southern Oscillation (ENSO). El Niño is Spanish for “little boy”, and is so called because the event occurs every year around Christmas time. The name relates specifically to the birth of Jesus. At the end of each year, a warm current invades the coastal waters off Peru and Ecuador, warming the sea for a few weeks before the cold currents return.

But once or twice a decade, a much stronger warming effect occurs, which has far-reaching consequences for far-flung places. It lasts for several months and can lead to very severe flooding in places that do not normally receive a lot of rainfall – the normally arid coastal regions of Peru and Ecuador.

It is linked to a similar warming across the central and eastern equatorial Pacific Ocean, as well as a link between the warming and a large-scale, pan-tropical-Pacific variation in the mean sea-level pressure.

The high pressure over the tropical Pacific, and the low over Australia and much of Indonesia, can change gradually, with the high weakening (decreasing in pressure) and the low filling (increasing in pressure). The horizontal pressure gradient decreases dramatically, causing the Trade Winds to weaken or even reverse in direction.

This, in turn, causes the warm water to migrate slowly eastwards across the Pacific – and this patch of anomalously warm water is followed by cumulonimbus clouds formed by the surface heating. The clouds bring torrential rain to Pacific island groups that normally don’t get that wet.

The clouds are extremely tall, pushing a lot of heat into the upper troposphere, which strengthens the jet streams and extends them eastwards. Which is how El Niño can have such dramatic effects far outside its usual arena.

Although the event is not predictable in the sense that it occurs every two to seven years, there is plenty of warning that it will occur. Our understanding of how this works enables experts to put plans in place to deal with unusual weather, lessening the impact of droughts in some places and floods in others.

El Niño was one of the few sections of Air that was reasonably well explained. Such a shame that the rest of the book was overcomplicated, self-indulgent rambling. Speaking of self-indulgent rambling, I really hope that the rest of the course improves. It’s going to be extremely hard going if not.

All this was compounded by the fact that I only got 75% for TMA01. This was partly due to some silly and careless errors by me, and partly because the Open University is continuing its policy of cloudy and impenetrable question styles. I’m going to have to pull my socks up if I want a distinction. I have a feeling it’s going to be considerably more difficult than S104.

Sex on two wheels

Positive thinking will return. I’m sure of it. It’ll start on Friday lunchtime when I test ride the 2012 Triumph Street Triple. Oh, did I mention that I’m buying a brand new motorbike? It’ll help, honestly. Because four wheels move the body, but two wheels move the soul.

Pseudo-philosophical and navel gazing rambles aside, it’s at moments like these you need to step back and say: “Where’s the bloody knife party?”

I wandered lonely as a cloud…

I know it’s not the done thing to diss the Romantic poets, but I’m not sure clouds are really lonely, are they? Let’s anthropomorphise them for a moment, and consider the evidence in a logical and scientific manner.

Cumulus

Cumulus clouds. They don't look lonely.

Cumulus is a lumpy cloud. Its name comes from the Latin for “mass” or “heap”. It’s a good description; a lumpy heap of cloud.

It has clearly-defined edges, and looks like cotton wool. In my head, I can sleep in them because they look so very comfy. And when I’m in aeroplanes, I always think it would be nice to jump out and land in one. In fact, it is the type of cloud drawn expertly by children everywhere, and can be found moonlighting as Father Christmas’s beard as and when required. A cloud such as this could not possibly be lonely.

Interesting fact about cumulus clouds: they form “streets” when they get together. And have street parties because they are harbingers of good weather; they don’t generally grow tall, and so do not participate in precipitation.

Stratocumulus

Stratocumulus cloud. A cumulus with a hangover.

Stratocumulus is a “flattened lump or heap”. So, basically, it’s a cumulus cloud with a hangover. It doesn’t get high, forming in the lowest two kilometres of the atmosphere and, like it’s more portly brethren, is not associated with precipitation.

I suppose an argument could be made for this cloud being lonely, but I would take issue with that. It has formed from a squishy mass of cumulus clouds, which is pretty neighbourly, and chose its own hungover state. It’s usually found in the company of others, which makes it fairly sociable.

Arguably, this cloud is not lonely either. Also, it indicates high pressure and stable winter weather. So it is a pleasant fellow.

Cirrostratus

Cirrostratus. Wispy. Friendly.

So named from the Latin cirrus, “wisp” or “curl”, and stratus, “layer”. A wispy layer of cloud. They spend their time high up in the atmosphere (between five and ten kilometres) as a veritable veil of ice crystals.

Cirrostratus halo. Spooky.

They often produce a halo effect (see photo) and indicate moist air and an approaching warm front. Cirrostratus and altostratus form from each other. Such close relationships indicate that cirrostratus are unlikely to be lonely clouds. Quite the opposite, in fact.

Cirrus

These wisps are the aloof clouds of the cloud world. They form in the highest and coldest regions of the trophosphere, are composed of ice crystals, do not bring rain, and they spawned Will ‘o’ the Wisp, Kenneth Williams’ alter ego and entertainer of children of the 80s.

There is a variety of different cirrus clouds – cirrostratus, described above, is just one type. Others include cirrus intortus, tools of the Spanish Inquisition. Nobody expects the Spanish Inquisition to use clouds as instruments of torture. Cirrus castellanus is another type of cirrus cloud, used to build castles in the sky; and cirrus vertebratus has no backbone.

Cirrus clouds can be artificial too; contrails from aeroplanes are a type of cirrus cloud. You can judge wind direction up there by looking at how contrails are scattered. And if they persist, you know the relative humidity is quite high. If they disappear quickly, the air up there is very dry. So they’re useful things too.

But they all join with each other, and with other cloud types, and are most definitely not lonely.

Nimbostratus

Nimbostratus. Lonely, perhaps, but not wandering.

These are low-lying clouds that bring rain. They are named from the Latin “nimbus”, meaning rain, and “stratus”, meaning spread-out. They are big, with flat bases, and are often to be found engulfing the top of a hill. Of course, from the hill’s point of view this stratus cloud would be fog. They are the bullies of the cloud world, being big grey brooding miseries, and are the friends of the hills.

They produce dull and gloomy wet days, with the cloud base often touching the ground. The word “fug” describes them nicely.

I suppose that these clouds could be described as lonely. But they don’t wander, so my original point stands.

Anyway.

As part of Block 2: Air and Earth, we are studying weather systems. This is, sadly, not as interesting as I thought it might be. I think the extreme weather comes in later in the course. For now, the only thing that has held my interest is the clouds.

I love clouds. They bring depth and mood to the sky, and can often be found making interesting shapes – like pigs, and teapots, and – on the odd occasion – snakes and slippers.

They can also give you a clue as to what the weather may do next, if you know what you’re looking for. So this post was really for my benefit; to make sure I’ve got a vague idea of what clouds look like, and what they herald weather-wise.

I still think cumulus clouds would make a grand bed though. The laws of physics and common senses be damned.

Snow, pain and science

This is going to be a mostly science-free post, as I have been busy for the last couple of days. Busy being a tough cookie, and busy recovering from said toughness.

However, a quick recap of where I’m at now: I am almost at the end of my virtual study tour in the Teign Valley, having just taken a look at the water composition of the river and its tributaries. I’ve got to be honest, the course isn’t gripping me so far. BUT – the books look much more interesting, so I shall not be disheartened.

It’s most definitely more of a “geography with science benefits” course, and I am very much looking forward to getting stuck into the pure science again after this course. Astrophysics all the way, baby!

I am, though, learning a lot about spreadsheets. This is useful, but dull. It’s driving me to drink.

Enough of that, though. I spent yesterday evening doing this: the Grim Night Terror. Here is what it looked like:

Grim.

Yes, that is snow. Basically, we ran seven miles (it was supposed to be eight, but the ice necessitated a change of course) in an hour and ten minutes. In the snow. It was bloody good fun, and felt fabulous!

During the last mile, I was struggling to put one foot in front of the other – and then there were the crowds of onlookers. It’s astonishing the difference a bunch of strangers shouting encouragement can make. Suddenly, with their help and a man to overtake, I found a burst of speed and crossed the line at pace with a huge grin on my face.

That was nothing compared to the journey home though – four hours in heavy snow, with vehicles spinning off the motorway left, right and centre. It was quite exciting, and completely exhausting. Driving snow gave me flashbacks to my misspent youth…

With a swollen knee – not to mention the swollen sense of pride – I’ve just signed up for this one too: The NUTS Challenge. And I’m probably going to do the Tough Mudder in the summer.

I am this: NAILS. Factoid.

Sign up now. It is fun most excellent.

Cool scientific instruments

Of these, there are many; this much is true. However, by far the coolest scientific instrument I have seen recently is this: the sunshine hours recorder.

Coolest scientific instrument of the day

I came across this during my virtual fieldtrip to the Teign Valley, where I am having a crash course in climate in the local area. We’re trundling around a meteorological station and poking about in the instrumentation.

This device is a thing of beauty. It’s a crystal ball, for goodness’ sake. What’s not to like? And it is simplicity itself. The glass ball focuses sunlight onto the paper chart, and burns a small hole in it. When the sun is behind a cloud, no hole is burned.

Useful things don’t have to be ugly. Here endeth today’s (very short) lesson. I’m off to get me a crystal ball.

The virtues of virtual field trips

After a certain amount of technology woe (the laptop DVD drive died a horrible, grindy death), the IT manager at my workplace managed to do the (as it turns out, simple) job of installing the Teign Valley DVD on my work computer. What a splendid fellow. (We now have a new DVD drive on the laptop, so I’m currently studying at home. Win!)

On starting up the “tour guide” section of the DVD, I took the tour. Now, I’m the kind of girl who likes being told what to do.

1. Start here.
2. Click this.
3. No, not that, you muppet, THIS.
4. Listen and absorb.
5. Keeping clicking the “next” arrows at the end of each section.
6. Do the activities in order when prompted.

What I got was a rather fuzzy and chaotic set of non-instructions, leaving me unsure as to when the tour finishes, and the actual activities start. I’m still a little unsure, but I’m plodding on, and have completed my first activity – Differences on Dartmoor.

This takes you through a series of places in the Teign catchment, and asks you to look at various maps. You’re provided with a spreadsheet, and you’ve to fill in the missing information. So far, so Sesame Street. One problem: the resources window on screen is tiny. Really, really tiny. And when you have an overlay on the map (e.g. contour lines, so you can give the altitude of the locations you’re talking about), you can’t zoom in. So you kind of have to guess at the exact measurements you’re asked to take at the relevant locations.

This displeases me greatly, because I am, after all, a budding scientist. And there’s no room for guesswork in precise measurements.

I’m about to embark upon activity 2 – The Heather Hypothesis. I’ll keep you posted.