vol 7, issue 11

Weather monitoring technology

19 November 2012
By Tony James
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Weather monitoring technology must keep pace with our changing weather

Weather monitoring equipment and techniques are becoming so accurate that we can predict a weather report down to little more than a square kilometre. Does this mean blaming rained-off picnics on the weatherman is a thing of the past?

October 2012 marked the 25th anniversary of the hurricane that ripped through southern England. Surely there is no more poignant reminder of the importance of accurate weather forecasting than the destruction left behind.

During a now-infamous TV weather forecast of the afternoon of 15 October, BBC weatherman Michael Fish reassured a concerned viewer who had heard that a hurricane was on the way: "don't worry, there isn't." Some 24 hours later, 18 people had lost their lives and the near-hurricane had left devastation in its wake.

Climate change is no longer a matter of debate; it affects our everyday lives, regardless of whether it has been caused by human or non-human phenomena. Over the coming decade, weather forecasting will become increasingly important as we adapt to cope.

A quick glance through the meteorological events of the last ten years bears ample witness to the changes that are already affecting us. In the summer of 2003 a heat wave ravaged Europe, temperatures soared to 40°C and 21,000 deaths were directly attributed to the heat. Just seven years later, the UK suffered its coldest December for over a century.

It is not just extremes of temperature but also rainfall and storms that are growing more severe. In June 2007, the UK was blighted by the worst flooding in 60 years following the wettest quarter since records began in 1766. Earlier that year winter storm Kyrill had devastated northern Europe, with winds in excess of 170km/hr leaving 50 people dead.

Behavioural patterns

As these weather patterns become more unpredictable and perilous, it is vital that our ability to forecast the weather improves.

The basis of a forecast is to represent the atmosphere in a computer model that treats it as a set of volumes of air. "If you take a small volume of air it behaves according to basic laws of physics – Newton's Law," Brian Golding, deputy director of weather science at the Met Office, says. "That basic set of laws describes how the air will behave. The great thing about the gas that's different from the classical application of Newton's Law is that everything is connected. So if you apply a gradient in one place that accelerates the air then that will change the pressure distribution, therefore it will change the force it's acting."

The other vital component is the rotation of the Earth: the atmosphere would be completely unpredictable if it wasn't for this. On a simple level, if the air is traveling under a pressure gradient it will veer to the right in the northern hemisphere. This plays a major part in creating the large-scale disturbance of the atmosphere such as the jet stream.

The entire system is interconnected with lots of feedback and some of these feedbacks result in a small disturbance developing into a large one. This is how depressions form. They are a means of taking energy, built up in the atmosphere as heat, and converting it into kinetic energy of the storm.

Forecasters predict the weather accurately by using data simulation. The two main ingredients of this are the set of equations represented in the model and the observations that describe or enable the model to start from the current state in the atmosphere. The most important source of observation in current weather forecasting is of the radiation emitted from the Earth into space and observed by satellite. The Met Office uses an IBM supercomputer, recently upgraded from P6 to a P7, for the model.

World Wide Weather

One of the successes of the international community in the immediate post-war period was to create a network of communications that linked all the weather services around the world. Many consider this as having been a prototype of the Internet.

"Each international service obtains observations on its territory or from its instruments in space and then they are passed to everyone else down this communications network without any restrictions on the recipients," Golding says. "It's quite a remarkable achievement and a very complex wiring diagram."

One of the key things that determines the accuracy of the modelling is the resolution of the model. Forty years ago the highest resolution that could be achieved to describe the atmosphere was 10 layers in the vertical and in 100km squares. Now it is described at 70 levels in vertical and on a scale of 1.5km and, according to Golding, there is further to go.

"The resolution has improved, but also the observations have improved because 40 years ago we didn't have satellites giving us all this information from the spectrally resolved radiation that leaves the Earth," he explains. "We didn't have aircraft carrying and reporting the real-time instruments and we didn't have ground-based radars.

"The easiest way to describe our advances is that in the 1960s there was a certain quality of forecasting the next day's forecast, while we now achieve that same quality of forecast five days ahead. It's difficult to prove that the one-day forecast has improved; it obviously has improved a lot but there isn't an easy benchmark to describe it."

At present the limit for a reliable forecast is five days, although on occasions when the atmosphere is in a stable state it is possible to predict further ahead with a fair degree of certainty. The most pressing need, however, is to predict accurately the severe weather systems that are going to become more frequent - these tend to be localised and develop rapidly.

Future challenges

The two fundamentals for greater accuracy are computer speed and power: the more you have, the more you can do, and the more accurately you can forecast. Another crucial area is improved observations. Moving forward there will be a greater use of remote sensing to improve the accuracy of the raw data.

"The other thing that is important in a low-key way is the development of the science," Golding adds. "The more we understand the atmosphere and how to use the information that comes from it, the better the forecasts."

The recent move to improve the resolution to 1.5km has been a huge step forward and, according to Golding, realising the benefits of that step will tax meteorologists for the next decade. "We can be quite optimistic about the next 10 years because we have the technology to move it forward," he says. "As the computer power comes on and as the observations get better, and as the science develops, we know we can do it. Beyond that, it depends on a number of things."

One of the big challenges beyond the next 10 years will be how computers develop. The current trend is to develop smaller processors and more of them, which could be problematic to the modelling. "We have research underway to look at how we might restructure the solution of the equations and even the way we describe the equation to the computer."

Apart from developments in forecasting, the big boon has been in mobile communications. The emergency services are increasingly not in an office waiting to be called these days: if they get a call they need to be able to pick up the information from a tablet or smartphone.

"Around 50 per cent of our website access is now coming from mobile devices," Golding says. "And social media as well, which is a very interesting area in two directions.

"In terms of communicating particularly severe weather, social media reaches a lot of people who wouldn't hear the traditional communication media. But in the other direction we are also looking at social media as a way of sourcing observations from the crowd because people will tweet each other if they have got water coming in through the front door. They will not email the Met Office or the Environment Agency but they will tweet each other and how we gain access to that information is a big challenge."

With the modern advancement of weather forecasting, the likelihood of a mistake on the scale of the 1987 'don't worry' announcement is remote. However, weather patterns will grow ever more complex and unpredictable with climate change, and technology will have to bear the burden. 

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