Clouds from space
Satellite imagery plays a vital role in weather forecasting. As well as allowing us meteorologists to keep on eye on what is happening, the information they provide is fed into weather computer models to make predictions about the future.
When I spent a few months working as a commercial and aviation forecaster at the Met Office headquarters in Exeter, satellite imagery was such a valuable tool.
Technological advancements during the past few decades have meant that satellite imagery has not only become more detailed, but is available more frequently.
Satellite images are now available once every five minutes for some parts of the world, with special satellites that monitor hurricanes able to provide an image once every minute.
When you look at a satellite image, it’s easy to just think that it’s either cloudy or not, but given a little attention to detail, every cloud tells a story about what state of flux the atmosphere is in.
Thunderstorms over the Pyrenees
This image shows some bright white lumps of cloud over the border between Spain and France.
These clouds are cumulonimbus and show that the air over the mountains has become unstable, most likely caused by hot air either side of the Pyrenees rising upwards, converging and forming thunderstorms.
Cirrus over the southern North sea
This transparent, wispy cloud is easily identifiable as cirrus. The fact that it looks the same from above as it does from below makes it one of the easiest clouds to spot on satellite images.
These clouds form so high in the sky that they are made from ice crystals, rather than supper-cooled water droplets, giving them their wispy appearance.
Marine cumulus off the Iberian coast
These marine cumulus clouds form as the sun heats the moist air just above the sea’s surface. With the wind being easterly here at the moment, the clouds are gently blown westwards, further out to sea, growing as they travel.
Eventually, each cloud becomes so big that it leaves very little space (blue sky) between itself and the next cloud. At this point, it becomes stratocumulus formed from the spreading out of cumulus.
Snow cover over the Alps
Despite being well into July, snow cover remains over the tops of the Alps. The giveaway that it is snow rather than cloud, comes from the fact that the white hugs the rugged mountainous terrain, with a dendritic pattern of the snowless valleys in between.
Mist and low cloud along Spanish coast
This image shows how mist and low cloud is hugging the north west coast of Spain. It is common where moist air is cooled by the sea.
However, because the land heats up very quickly in the summer sunshine, the cloud is evaporated over land, with the exception of the immediate coastline where it remains cooler and cloudier.
Mountain wave cloud over Scotland
If you look towards the north east of Scotland, you can see that the cloud has a wave-like pattern. This is caused by the south westerly wind bouncing over the mountains – much as a car’s suspension would if travelling over a speed hump too quickly.
The air continues to bounce some distance beyond the mountains. Where the air rises, it cools and condenses, forming cloud. Where the air sinks, it warms and evaporates, with no cloud present – giving this noticeable pattern.
This type of cloud is an indicator that air may be moving up and down rapidly in a particular area, creating turbulence – something that is vital for aircraft to know about, especially when landing or taking off.
So, the next time you look at a satellite image, have a closer look. You never know what you may be able to tell given the types of cloud present.
If you see a cloud and are not sure what it may be, feel free to get in touch and ask me on Twitter – @liamdutton
Satellite images courtesy of EUMETSAT