Saturday, 1 August 2009

Noctiluscent Clouds

I recently did a radio interview about a rare type of cloud known as noctiluscent - rare in the sense that they are rarely seen by us because of the special nature of how they occur.

The clouds are very high up, some 75 to 85 km (50 miles) high, in our mesosphere. Because they are so high they are usually too faint to see with the naked eye, but when the sun shines up from below the horizon (on nights when there is no low cloud) it can reflect light from the bottom of these clouds and they become visible.

These clouds are, to give them their proper name, polar mesospheric clouds. They are called noctiluscent because they ‘shine at night’. As far as I know they were first photographed by a German observer in 1887 and the clouds are thought to prevalent around that time as a result of the cooling of the mesosphere caused by the Krakatoa eruption in Indonesia in 1883.

You can see a fine example on the Cloud Appreciation Society’s website at:’06/

If you have ever been lucky enough to see these clouds you will know that it can be an eerie but quite stunning sight. They often have a purple-blue colour in large part caused by the absorption of the light due to atmospheric ozone.

These clouds do only occur under fairly restrictive conditions. They need water vapour to form which is very unusual in the mesosphere as the water molecules are often broken down by the UV light. Therefore they are more prevalent in weaker solar cycles when the UV is weakest. Also they tend to occur when the mesosphere is at its coldest, that is close to the poles and during summer.

Interestingly the increase in greenhouse gases leads to a warming of the troposphere and a cooling of the mesosphere. Some have suggested that the increase in the frequency of sightings of these clouds in recent years might be a visible impact of global warming. So perhaps it’s true that every cloud does indeed have a silver lining of sorts.

Wednesday, 29 July 2009

BBQ Summer

I’ve been a gas BBQer over recent years and I have been thinking of late that I need to return to more traditional methods – to be honest it’s probably because I have always wanted one of those oil-drum BBQs. Well I am kind of glad that I didn’t in the end do something about it this year as the cover has stayed on the BBQ so far this summer.

The seasonal forecast was half right (if a probability forecast can ever be deemed right or wrong) in that it has been a warm summer, but it’s also been a wet summer so far and by all accounts it doesn’t look a great deal different for August (you can see the Met Office’s seasonal forecast at So what did this year’s summer forecast not pick up on? It would seem that we have the Polar Jet Stream to blame yet again.

The Jet has once again been further south than we would expect for this time of year. This has helped to transport the weather systems across the Atlantic to the UK and stopped the development of one of those welcome ‘blocking high pressure systems’ from the south that brought our few weeks of warm sunny weather at the end of May.

So what’s caused this you could rightly ask? And the truth is that we don’t really know. We do know that there is a link with the ocean temperature patterns, and the natural cycles in El Nino and the North Atlantic Oscillation, but I don’t believe as yet that we have a good enough understanding of how these systems effect the wider global circulation. That being said it is remarkable what information the seasonal predications can provide and what an advance in our capabilities it has been to be able to produce this type of information which, despite the wet weather so far this summer, I would argue strongly holds real value.

I might not have had occasion to BBQ this summer but recently I did have the chance to visit my great Aunt who is a very remarkable 101 years old. We were talking about the vagaries of another wet summer and she recited a poem to me that I had long since forgotten. It’s a poem called ‘Rain in Summer’ by Henry Longfellow. It’s too long to reproduce here, but to give you a taster here is the first couple of verses:

How beautiful is the rain!
After the dust and heat,
In the broad and fiery street,
In the narrow lane,
How beautiful is the rain!

How it clatters along the roofs,
Like the tramp of hoofs
How it gushes and struggles out
From the throat of the overflowing spout!

Odd that it takes an American to so eloquently describe to us the British obsession. It’s a beautiful poem that I would definitely recommend having a look at in a quiet moment, perhaps best left until it’s too wet to go outside and you can read it whilst staring out of your window at the wet and rusting BBQ sitting in the corner of the patio.

Thursday, 9 July 2009

Word Bingo at the Conference Dinner

Our conference dinner is always a fun event for several reasons. I enjoy it because it’s one of the few opportunities to see our many academic members come together as a UK community. The other reason is that we present our awards at the dinner, and it’s nice to celebrate success.

A good night was had by all, but it did make me feel as though I’m well and truly in middle-age. Looking out to the dinner audience when it came to my bit to speak, it was great to see lots of young scientists there. And some of them confessed t playing the games that I used to play when I came to those kinds of events at their age, like word bingo.

If you’ve never played it, you basically put together a bingo sheet but instead of numbers you have words that you expect people to say. The first to fill the sheet wins. Their slight variation was to count how many times I said certain words. Amongst the highest ranked were ‘weather’ with 16 mentions, and 11 for ‘climate’ and ‘thank you’. Apparently the winner was ‘meteorology’ with 21 which beat the ‘Society’ only getting 19 mentions. My Head of Communications will want to make sure I get the ‘Society’ to the top of the ranking next time around!

Wednesday, 8 July 2009

Can we enjoy the Cricket in our BBQ Summer?

I was just relaxing on Sunday after the busy schedule of our biennial conference and looking forward to our Ashes series when two things caught my eye. The first was that we were holding a test match in Cardiff. This fairly historic event seems to have completely passed me by, but goes down well in our household – my wife’s Welsh.

The second was an article we recently published in our house journal Weather on the correlation between El Nino (the large-scale warming of the oceans off the coast of Peru) and the outcome of the Ashes test matches. Apparently there is a statistically significant link between what we call a positive El Nino phase and Ashes victories for the Australians.

Thinking about this it does make sense as a positive El Nino phase tends to lead to prolonged warm, dry conditions in Australian, and our antipodean friends must be more used to batting and bowling on hard, dry pitches than we are, that’s for sure. I know what you’re thinking; it’s nothing to do with El Nino, they are just better than us. Well that may be so, but the study also shows that in the opposite phase, which we call La Nina, we do far better in terms of Ashes results.

What does that mean for this test series I hear you ask. Well, we are just entering a positive El Nino phase, but often the effect of El Nino relatively speaking is less in the UK than in Australia – so you have to make of that what you will, but I still have my fingers crossed for us to sneak it on a gripping last test!

By the way, if you are planning to go to the Cardiff test, then Friday this week looks the best day – it looks a very cloudy and wet weekend. For the remaining part of the season, I’d aim for one of the July test matches. Climatologically July is sunnier and drier than August in the UK, so on average you’re more likely to have less rain interruptions and more sunshine. Whether that will help the home team is another matter.

Wednesday, 27 May 2009

It's good to see that people are interested in clouds again

I’m not sure that I quite understand what is at the heart of the sudden resurgence of interest in clouds, but it’s good news and Gavin Pretor-Pinney is surely part of the answer. Gavin set up the Cloud Appreciation Society and wrote his great book ‘The CloudSpotter’s Guide’ – and he seems really to have caught the public’s interest. I don’t often recommend things to people but out of all the recent books on clouds (and there are a few excellent ones for the coffee table) I very much enjoyed Gavin’s, and so did my wife (who never reads anything related to the weather as a matter of principle!). We are both looking forward to his new book coming out soon (

Clouds are truly fascinating things, whether you are a student of physics or just a casual admirer. To a trained eye they can tell you a lot about what’s happening in the atmosphere and to an untrained eye there is a lot to enjoy about the aesthetics of how something as simple as water can create such beauty. Clouds have deep cultural references in our society; they have inspired paintings, poetry, and yet we somehow seem to have lost touch with them.

If you are a sailor or a pilot you probably keep a close eye on what the clouds are doing, but most of us don’t pay, much attention at all. In times gone by when many of us spent more of our working day outside we would read the clouds as a way of knowing what to expect for the day and possibly the next. But over the generations we’ve become more detached from the environment around us. However there is no excuse; so come on teachers, take those children out of the classroom for half an hour and teach them to look up and record what they see – you can even send me a note about it here at the Society and we’ll put in on our website.

Over recent days there has been a lot of news coverage about the naming of a new cloud variety – something which hasn’t happened for over 50 years – and the name being proposed is ‘Aspiratus’, which I think is quite appropriate if you look at the images of these clouds (

Clouds are one of the few things that are free for all of us to enjoy. When was the last time that you spent a spare 5 minutes and just looked skyward?

Wednesday, 29 April 2009

Weather and Flu

I was talking on the radio this week about relationships between weather and flu and it occurred to me with all our advances in medical sciences there is still a lot we don’t know about things that are common to us, like the flu virus.

That’s not to do down the virologists as we know a lot of technical information about the virus and that it has different strains (this swine flu appears to be from the H1 N1 strain) and how viruses generally transmit across large populations thanks to some clever epidemiological studies - that by the way use the same mathematics that model the spread of new technologies, like the iPod, across populations. However we don’t really know how viruses interact with the environment in detail.

Take the weather for example. We know flu peaks in the winter months in Europe (between December and March in the northern hemisphere to be a bit more precise), but what we don’t know is whether that is due to changes in things like temperature and the UV in sunlight directly, or simply that it’s how people respond to these changing weather conditions that help transmission. For example, people tend to congregate indoors more in the winter months, where a greater number of people are in closer proximity and often humidity is higher (which perhaps helps the virus survive).

Almost certainly humidity is a factor in virus lifetime and transmission. We can see that in the tropics the flu cycle is much extended beyond the winter months, in large part because of the humidity.

After all that technical detail, the best defence we have is to wash our hands. How often does solving a difficult problem come back to basics!

Friday, 24 April 2009

Living in Different Climates

I’m recently back from Miami and a tour of some of the Caribbean islands on holiday. Great holiday and my first time to the Caribbean. Travelling south in the Caribbean Sea it occurred to me that I wouldn’t want to live in a tropical climate. I would miss the seasons. They do have changes in the weather – very hot, or very wet and very hot! It’s nice for a holiday, but it wouldn’t be for me as a way of life. I like the variability that our seasons bring - even, like this week, when I get wet through walking into the office.

We adapt to our weather pretty well in the UK, except for the occasional snow flurry, but it doesn’t really impact on our way of life in a big way! I’ve seen written that weather has a £2 – 3 billion impact on our economy each year on average, and individual events can have equally large and comparable financial and social impacts.

Businesses can now buy a wide range of services to lessen the impacts of weather on their performance (it’s no longer a feasible excuse for a business to use to their shareholders for poor performance). The Public Weather Service provides the variety of weather warnings we see on the web, TV and hear on radio that helps us manage our own lives. But that’s certainly not as simple in some countries who suffer the impacts of significant and severe weather on a regular basis. It does genuinely affect the way people live their lives and I think, interestingly, the way in which those countries will choose to move forward in their own growth and development that will certainly be founded in very different cultural (weather-driven) roots.

Now I need to balance out my reflections with something a little less philosophical so here is the temperature profiles for my flights as my regular blog readers have come to expect of me. These show my descents out of Amsterdam at 1237 UTC on 11 April (as I flew via here) and then into Miami at 2300 GMT on the same day.

You can see from the plot that although much later in the day, the atmosphere is quite a bit warmer all the way through the troposphere. The zero degrees C isotherm was almost 2 km higher in Miami in the late evening than it was in Amsterdam around midday. You can probably also tell from the profiles that it was a pretty smooth take-off and landing.

My hope is that you’ll be encouraged to collect the same information when you next take a flight and send it to the blog.


Wednesday, 25 March 2009

The Winter of 2008/09 and Spring 2009

The official statistics on the winter were produced by the Met Office's national climate information centre last week and confirmed that it was indeed a 'cold winter' - well at least colder that we have been used to since 1995/96 in England and Wales and 1996/97 in the UK, with temperatures 0.5 deg C below the 30-year average. The rainfall was more marked with some areas of the UK recording less than 70% of the average rainfall for the period.

But perhaps the thing that will stick in the minds of most of us was the significant snowfall in the first week of February which brought depths of snow greater than 15 cm across many parts of the UK. The last time we had a winter snowfall of that size was in February 1991.

Enough of weather-past. We had the Vernal Equinox at the weekend signalling Spring is with us now - so what should we expect? Well the latest Met Office seasonal forecast is suggesting that it will be a near or slightly below average Spring for temperatures and rainfall. But what is an average Spring I hear you say. For temperature that's an average of 7.4 deg C and for rainfall that's about 232 mm (or around 9 inches) in total across the three months from March to May.

If you had to guess the wettest Spring month what would it be - you might say April because of the old adage April showers bring forth May flowers, but actually its March. March accounts for 96 mm of our rainfall on average, April some 70 mm and around 66 mm in May - so you can see March is wetter by quite a bit. May as it happens is our driest and sunniest month of the year on average. That's probably enough weather statistics for one entry.

Friday, 13 March 2009

Who said meteorology isn't a laugh a minute? Weather and Meteorological Jokes

So here are some of the best jokes we had in for our Comic Relief challenge - 'best' meaning arbitrarily selected by me but probably gives you an indication of how bad the others were!

Why was the cloud late for work - because he mist the bus

What do you call a sheep with no legs - a cloud

Two weather satellite antennas got married, the wedding was good but the reception was fantastic

and my personal favourite (which is cheating because its really a glaciologists joke):

A guy walks into the doctors with a piece of lettuce sticking out of the top of his shirt. The doctor says that looks nasty and the guy says that's just the tip of the iceberg!

Tuesday, 3 March 2009

Weather and Climate Jokes

In aid of Comic Relief on Friday 13th March we are publishing a list of our favourite weather and climate jokes. So if you’d like to send any in to us you can do so at – I’m sure we are going to have an entertaining time deciding on our best ones, which we will also be including on our BBC Radio Berkshire broadcast on Wednesday 11th March, so make sure to listen in.

Monday, 2 March 2009

Spring is here - at least in the meteorological sense

No we haven’t redefined the astronomical calendar! Spring officially is still 21 March (the equinox – 12 hours of equal day and night), but in meteorology we think of the seasons in whole months. For us Spring is March to May, Summer is June to August, Autumn is September to November and Winter is December to February.

Two things to look out for: see the latest Met Office Spring 2009 forecasts ( and also if you haven’t seen it, it is interesting to look at the KEW 100 ( The KEW 100 is an index that follows the flowering of different plant species and how that responds to changes in the weather (and of course over longer periods climate).

The KEW 100 is a more recent index taken from a much longer record going back over a hundred years at least. The Royal Met Society used to publish the UK-wide phenological (species flowering) records as early as the 1870s.

Thursday, 12 February 2009

The Society and Chocolate

I learned an interesting fact today, that the value of the world’s scientific journal publishing industry is worth about the same as the UK spends on chocolate each year – apparently £2 billion.

The other interesting fact if you are thinking of renewing your Society membership is that statistically people live longer if they belong to professional and learned Societies, although I suspect that might not be the case if you are one of the people principally responsible for the UK’s turnover in chocolate!

Wednesday, 4 February 2009

Freak Weather

I’ve had occasion to look up some strange weather statistics recently and came across some very interesting records. For example I didn’t realise that the records for the hottest temperature, which previously was held by El Azizia in Libya with 58oC, was broken. Apparently in 2005 a temperature of 70.7oC (that’s 159oF) was recorded in the Lut Desert in Iran – boy is that hot! Also why is it that when we talk in extremes we always go back to Fahrenheit (or inches in rainfall) as if it makes it sounds more dramatic. Speaking of rainfall there is a place in the Hawaiian islands where they have regularly between 460 to 512 inches of rainfall a year, that’s between 11 to 13 metres.

But my most favourite freak weather records are where we get reports of when it rains strange objects, like the frogs in Llanddewi in 1998, or the worms in Jennings Louisiana in 2007.

Did you know there is even a freak weather explanation for the Loch Ness Monster – I won’t even go there.

Thursday, 15 January 2009

We think it's cold here!

I’ve spent this week in Phoenix, Arizona, at the American Meteorological Society Annual Meeting. This meeting is an important one for us, as each year we hold our exhibition promoting our scientific journals, we meet many of our international members at our evening reception and we have our bilateral meeting with the AMS executive team to discuss areas of possible collaboration. And its good to renew old friendships.

We often joke about the weather with our US colleagues as we regularly have very extreme unseasonal weather for the AMS meetings. However we seem to have broken the trend this year. Phoenix itself is used to extreme weather conditions. Average summer temperatures are amongst the hottest in the US. On 26 June 1990 they reached an all-time high of 50°C (some 122°F). Rainfall is pretty sparse but there is a period between July to September where humidity levels are high.

This time of year is seasonally the coldest in Phoenix, with temperatures falling between a maximum of 19°C (67°F) and a minimum of 7°C (45°F). This week it has been up in the high end of the climatology - about 16°C (61°F) with sunny blue skies, as a result of a large high pressure sitting over the lower south west past of the US. To the north, much of the rest of the US has been experiencing some pretty cold weather with heavy snowfalls and some of the coldest parts experiencing temperatures around -42°C (-45°F), which is pretty chilly in anyone’s book.

But it wasn’t just the weather that made this year’s meeting a particularly special one. It was that 23 of the world’s meteorological Societies (the largest ever gathering) met to establish an International Forum for Meteorological Societies, where we can discuss issues of common interest and share best practice. The framework for the new forum was put in place and its first meeting will be in January 2010 at the AMS’s next annual meeting in Atlanta in January 2010.

As usual I managed to get hold of some upper atmosphere data from the Phoenix flight, through the in cabin screen displays that show altitude and temperature. Unfortunately I only got hold of some low level temperatures from the cabin display going into Phoenix. Coming out of Phoenix I managed to get some better data.

Surface temperature was pretty much the same on both days, but it was warmer in the upper air by some 5 to 6°C consistently up through at least the first 2.5 km. What’s interesting in the data from the 15th is the drop in temperature in the lowest 500 m or so showing a cold layer of low level air around the airport – I haven’t really looked into the properly, but possibly some cold air drainage from the surrounding mountains.

Saturday, 3 January 2009

Weather Records and Average Temperatures

I was reading over the Christmas holidays that there are records of the weather that go back as far as 13th Century BC. The records were found amongst the Anyang oracle bones, which give us an historical account of the Shang dynasty in China. But it’s the way in which nature responds to our weather that gives us the long record that we use for studying our climate beyond the more systematic observations we have over the last century or so – the sorts of information that comes from tree rings or trapped air in ice cores, and that is what we call paleoclimatology. It’s these observations together with our complex climate models that help us to understand and give context to how our climate is changing.

Our recent summers haven’t been great in the UK, most likely a response to the effects of a strong La NiƱa – a large pool of cold water of the south-American coast. This natural feature of the earth’s climate has masked the underlying warming of land temperatures to some extend. That being said the climate models are telling us that by all accounts 2009 is set to be a warm year globally, although the seasonal forecasts for the UK are showing that we will have a cold start – with colder than average temperatures in January and an average February.