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Sylvia Knight, Head of Education at the Royal Meteorological Society was in conversation with John Lyon for the Geographical Association’s GeogPod podcast series. Their conversation centres on the COP26, climate change. the IPCC and some of the resources teachers can use in the classroom.
We are delighted that our “Weather and Climate: a Teacher’s Guide” resource has been awarded a Highly Commended in the Book Category for this year’s Scottish Association of Geography Teachers (SAGT) Publishers’ Awards.
There are three main requirements for snow, these are:
There must be water vapour in the air for clouds to form. In the UK, surrounded as we are by sea, this is rarely a problem. As water warms up and cools down more slowly than land, the sea around us stays at a pretty constant temperature all year round and is a constant source of water vapour into the air above, through evaporation.
It can be ‘too cold for snow’ in the centre of large land masses, such as Eurasia, Antarctica or N. America, where the wind has not encountered liquid water from which water can easily evaporate. It’s really ‘too dry for snow’ – but it’s too dry because it is so cold that the rate of evaporation from the lakes and rivers, which may be frozen, is very, very slow.
For clouds to form, the rate of evaporation must be lower than the rate of condensation. Evaporation and condensation are going on all the time, but the rate of evaporation falls as it gets colder. So, clouds can form when the air cools – there are several possible mechanisms for this
It has to be cold enough for the cloud droplets to grow as snowflakes and to not melt as they fall through the atmosphere and down to the ground. To see whether this is the case, forecasters look at the 528dam (=5280m) line. This line shows where the vertical thickness of the bottom half of the atmosphere (by mass) is 5280m i.e. the vertical distance between the 1000mb height (somewhere near the ground) and the 500mb height (somewhere in the middle of the troposphere). As warm air is less dense than cold air, the smaller this distance, the colder the air is.
If we are north of the line (i.e. the thickness is less than 528dam) then any precipitation can fall as snow, and if we are south of the line (i.e. the thickness is greater than 528dam) then we get rain.
If you look at the surface pressure forecast charts on the Met Office website, then if you go more than 24 hours into the future the thickness lines are shown. The 528dam line is shown as a blue dashed line, and the thicker/ warmer 546dam line as a green dashed line.
Another way to find out is to look at the weather forecast charts (in the charts and data menu) at http://www.netweather.tv/index.cgi?action=nwdc;sess= and select ‘HGT 500-1000’ from the ‘select chart type’ menu If the 528dam line is South of where you are, and there is a forecast of precipitation, then that precipitation is likely to be snow.
It is also worth having a look at a cross section through the atmosphere for example at http://www.wetter3.de/ – select ‘Vertikalschnitte’ which gives a longtitude/ height cross section for 50N (move the pointer on the right side of the left hand map to change the latitude of the cross section). The air between the clouds and the ground has to be cold for snow to reach the ground.
Using the information above, can your students identify which countries/ regions should have a forecast of snow? At the basic level, they can just look and see where is inside the 528 line. More advanced students should try to predict where there will be precipitation.
Nullschool is a great resource for visualising air flow and air masses.
More information from the Met Office about Snow in the UK and forecasting snow.
A nice explanation of why we had such a different November in 2011 to the weather in November 2010 from the Met Office and a report on the 2010 snow and its impacts on the UK.
And an article from the BBC about what constitutes a white Christmas.
Snow inspired science teaching ideas from Science in School.
Dreaming of a white Christmas – an article from MetMatters
Snow inspired geography teaching ideas from the GA.
How to make a snowflake, from the Institute of Physics
From Brilliant Maps; the probability of a white Christmas across Europe
The first of our very short daily bulletins from COP26 for teachers to use during registration or lessons can now be found on YouTube.
These bulletins will cover highlights about the coming day’s events as well as more general background information about how COP works. We’ll also try and bring in a bit of careers related information.
The aim of the films will be to help students engage more with this very important event which is happening in the UK, as well as giving them some context for the messages that they get through social media etc.
Please share with other teachers in your school who might be interested.
Thanks!
We will be filming very short daily bulletins from COP26 for teachers to use during registration or lessons.
They will cover highlights about the coming day’s events as well as more general background information about how COP works. We’ll also try and bring in a bit of careers related information. You will be able to find them on YouTube and we’ll try to make sure that they have been uploaded the night before, in plenty of time for morning registration.
The aim of the films will be to help students engage more with this very important event which is happening in the UK, as well as giving them some context for the messages that they get through social media etc.
The first video will be available for showing on Monday, 1st November.
Please share with other teachers in your school who might be interested.
Thanks!
In this new set of 11 short videos, we explore some of the many careers in climate change that you could do with qualifications in STEM subjects.
If you want to work in an area where you can do something positive about climate change, but don’t know how, have a look at the work that these people do, why they think it’s important and the paths they took to the jobs that they now do.
If a career in weather or climate sounds interesting, have a look at the further careers information on our website at metlink.org/careers
The Central England Temperature (CET) dataset is the longest instrumental record of temperature in the world, pre-dating the satellites and radar instruments which we now have to tell us about the state of the atmosphere.
The data represents the temperature in a roughly triangular area of the United Kingdom enclosed by Lancashire, London and Bristol.
The sources of the data include records kept by individuals around the country, all carefully combined and corrected for factors such as changing instruments over time etc. The precision of the data published for each year reflects the number, accuracy, reliability and geographical spread of the temperature records that were available for that year – so early in the record, the data may only have a precision of 1°C or 0.5°C, whereas more recent data has a precision of 0.1°C.
The mean monthly temperature record starts in 1659 (with daily data being available from 1772 and maximum and minimum daily and monthly data beginning in 1878).
The full dataset and references can be found at www.metoffice.gov.uk/hadobs/hadcet
The Royal Meteorological Society is delighted to have collaborated with CREATE Education to develop instructions to allow schools or individuals to 3D print sections of the Central England Temperature Record and use their models to learn about weather, climate, extreme weather and climate change.
These engaging, tactile resources allow students to get a hands-on experience of what climate is and how it can change, and how extreme weather relates to the climate.
Each three dimensional block shows 10 years’ worth of monthly temperature records. Printing off several blocks allows you to compare the changing weather and identify extreme weather events. The models have been designed to interlink, so students can create a series of models to represent larger timeframes.
Climate is usually defined as the average of 30 years’ weather. For easy comparison with the weather in any one year, you can 3D print an additional mini block which shows current (1981-2010) climate.
Once the 3D models have been created and 3D printed, there is a tactile resource that can be used in multiple ways in the classroom to visualise and study past weather and climate, and at how the climate of the UK has been changing over time.
The lesson resources specifically focus on
1. The difference between climate and weather
2. The current climate of the UK
3. The changing climate of the UK
4. Looking at past extreme weather events and researching their impacts on people in the UK.
We continue to add new teaching resources to Weather and Climate: a Teachers’ Guide.
Some of the latest are in the Tropical Cyclones section:
– A listening exercise extracting information from a hurricane warning podcast
– Grid reference practice based on the track of a Tropical storm.
In this article we explore air masses – the idea that, by looking at where our wind is blowing from, and what has happened to the air in the wind on its way to use, we can begin to understand why we’re getting some particular weather.
We live on an island, and the weather can come at us from any direction, although in practice, it comes from some directions more than others – this wind rose shows the direction the wind was recorded coming from at Heathrow airport, near London. The longer the bar, the more often the wind came from that direction, so you can see that our wind comes from between southwest and west most often.
Lets take a step back and remember that warm air rises – whether that’s the air being heated in a hot air balloon or the air above a radiator (watch a simple demonstration).
What happens to the rising air? As it rises it cools. Cloud and rain are caused by warm air rising, warm air rising is called convection (watch a simple demonstration).
You can often see convection going on in the atmosphere – you get puffy cumulus clouds, with flattish bases and puffy tops where the cloud is bubbling up.
More generally, Clouds form when there is more condensation going on than evaporation in the atmosphere.
The colder it is, the less evaporation happens – so cloud forms when the air cools.
This isn’t just when warm air rises.
Now we can think about air masses, they are classified according to where they have come from, and what they have passed over:
One air mass generally covers the whole country.
However, it can bring different weather conditions to different places. For example, Tropical continental air can carry Saharan dust, but it mostly falls on the south of the UK – there isn’t much left in the air by the time it reaches Scotland.
Lets consider Polar maritime (Pm) air first (click on the map to start the animation):
Polar maritime air comes towards us from further North in the Atlantic. It starts cold, but is slowly warmed by the ocean below as it travels over progressively warmer water. It also picks up moisture from the ocean.
As it is warmed, it becomes more unstable and inclined to rise, leading to convection and puffy Cumulus clouds, mainly over the ocean. As the air hits land (the western coast of Ireland, Wales, Scotland and England) the air, which was already inclined to rise, is forced up a bit more – forming more cloud, and giving rise to rainfall.
Polar maritime air, our dominant air mass, brings cloud and rain to the west of the UK and relatively dry air to the east.
This satellite image is typical of Pm air – you can see the puffy cumulus clouds over the ocean, and the belt of cloud over the western side of the country.
Returning Polar maritime air (rPm) is air which is Polar in origin but which swings round to hit the UK from the west or even slightly south of west – but if you were to follow its path back, you would see that it was Polar.
Arctic maritime (Am) air is extreme Polar maritime air, coming down to the UK straight from the north, over the Arctic ocean. It tends to bring wintry weather to Scotland and isolated snowy showers further south, triggered by air rising over the local orography.
Polar Continental (Pc) air will also be cold to start with and get progressively warmer as it moves south, so you would also expect convection. However, the air will be very dry as it passes over continental Europe, so little cloud will form. The UK is a set of islands though and to reach us, the air must pass over the North Sea, picking up water vapour as it does so. The cloud and precipitation (typically snow in winter) it brings therefore primarily affect the east coast. The longer the path it takes over the North Sea, the more precipitation there will be.
This satellite image is typical for Pc air – you can see the cloud free areas immediately to the west of the land masses, with cloud forming further east (ignore the front to the west of the UK and Ireland).
Of course, the characteristics of the air masses can be very different in the summer and the winter. Siberia, for example, is extremely cold in winter but relatively warm in summer – so a polar continental air mass can bring us bitterly cold weather and heavy snowfall (for eastern counties) in the winter, but much warmer weather in the summer.
The processes at work in Tropical Maritime (Tm) air are a bit different. This is warm air, which is being cooled from below as it moves north. You therefore wouldn’t expect any convection with air rising, cooling and forming cloud. However, the air is being cooled just by moving north and so eventually may reach the temperature at which cloud forms – flat, featureless sheets of stratus cloud because, on the whole, the air is staying at the same level.
As it is maritime air, there is plenty of water vapour available to form cloud droplets. The processes which give us big, fat raindrops are mainly associated with the vertical air motion and circulations in cumulus clouds. So Tm air at best gives a persistent drizzle.
The satellite image below shows the extensive sheet of stratus cloud over the Atlantic associated with Tm air.
We rarely experience Tropical Continental (Tc) air – air that flows up from the Sahara over continental Europe. This is the warmest and driest air we can get – any moisture picked up over the Mediterranean will be rained out before it reaches us.
Tc air gives clear skies, as you can see in the satellite image below – again ignore the front to the west of the UK. In the summer, this can mean that some areas get particularly warm – maybe because of their colour (dark) or aspect (facing the Sun) – giving rise to late afternoon localised thunderstorms
A front is where two air masses meet. In the UK, the weather fronts associated with depressions usually separate polar and tropical maritime air.
If there is a front, then different parts of the UK can be experiencing different air masses. The weather on the fronts themselves is more extreme.
Look out of the window now – what cloud types can you see? Does that tell you anything about where the air is coming from? You can have a look at earth.nullschool to see if you are right.
We have just added a new resource to our Weather and Climate: a Teachers’ Guide collection in the Changing UK Climate section.
The resource provides students with source material, graphs and maps to allow them to make a poster explaining how salt marshes can protect coastal areas from the impact of rising sea levels.
Steart Marshes – designed for adaptation to climate change.
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