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Good observation

1 July 2010

Torrential rains, heavy snowfall, fledgling tornadoes... Observations are fundamental to the work of the Met Office. They tell us what's happening in real-time on the ground and in the skies — and make sure we're all prepared for high-impact weather events.

"Observations perform three key roles for the Met Office; they allow us to initialise environmental prediction models, corroborate the data from these models, and make sure we're ready for any emergencies," explains Gill Ryall, Head of Observations. "It's a system that's always evolving and improving."

Over the past year and into 2010, we have continued our move towards an Integrated Observing System (IOS). It's a three-pronged approach, with more surface observations, a new upper air network design project and a next-generation weather radar.

Together, these are helping us create more accurate, detailed forecasts, predict high-impact events and meet wider business objectives too.

On the ground

Since the 1970s, we have been collecting data from automatic weather stations - drawing together a range of measurements and using them to support our forecasts. Over the past two years this system has been replaced by a new, more modern surface observing system: the Meteorological Monitoring System (MMS).

While previously data was fed back on an hourly basis, the MMS receives per minute readings from all sensors at all MMS weather stations. As Aidan Green, Surface Networks Manager, explains, "Even though we can now get per minute data from many sites, we may still collect this on an hourly basis. But when there's a severe event we now have the capability to turn up the frequency - for example, bringing back data every minute from the South West if the rain gauges are going crazy."

This additional data also gives greater insights into the realities of the weather - especially in areas where there is significant regional variation, such as snowfall. With MMS, the Met Office can now see where snow is falling in real-time and discover if a front is moving more quickly or slowly than expected.

"Of course, more data means more information, so we have been developing algorithms and techniques to make processing this mass of data easier, pulling out key areas for forecasters to focus on," says Gill.

In the skies

Alongside these land developments, we are creating new ways of enhancing the upper air network. "More accurate boundary air readings will enable us to better initialise our weather models - which in turn leads to more accurate forecasts," Gill continues.

Currently in a testing phase, we have set up a number of sites around London with different air sensors at each location. With this knowledge, forecasters will be able to determine which kind of sensors will create the best operational network.

Upgrading our radars

Radar dome Throughout 2011, 2012 and 2013, we will be rolling out a new network of state-of-the-art weather radars across the UK. The radar is already a vital tool - showing forecasters where and how much rain is falling. But the new system, largely developed in-house, will bring numerous new benefits including:

> Doppler capabilities: measures how fast something is moving, providing valuable wind-speed information and greater awareness of high-impact weather events.

> Dual-polarisation: transmits and receives energy in horizontal and vertical planes, giving forecasters more data about the kind of target, identifying drop shape and size (sleet, snow, hail, drizzle) as well as location.

> Radar refractivity: because our facilities are developed in-house, we're able to maximise the value from the data we receive. For example, while some would discard clutter from ground readings, we can use this data to produce a map of changes in the atmospheric refractive index around each radar site. Refractivity is a strong function of relative humidity, so the new data will enable small-scale moisture convergence in the boundary layer to be located. Moisture convergence can be a critical factor in the timing and location of storm initiation.

More readings, more knowledge

With observations, the more data available, the better. But even with the planned enhancements, we're unable to monitor the weather on every stretch of coast or street corner. Which is why, during 2010 and 2011, we plan to launch a new website to collect weather observations from the general public.

This data will be compiled into an online database and will supplement the other forecasting tools. With more observations to hand, the Met Office will be able to create a more detailed picture of what's happening across the country.

Making sense of data

More data presents another major challenge: how to interpret the information. To aid interpretation, we've been working on the appropriate data management infrastructure and visualisation capabilities, giving forecasters information that makes their job easier, not harder.

These advances in creating a stronger, Integrated Observing System (IOS) will soon bring tangible benefits, especially when it comes to high-impact weather events. But there are other benefits too. By developing our weather monitoring capabilities we're able to monitor other environmental factors, such as air quality. By meeting these goals, we can provide more accurate data and records to meet climate needs and commercial demands.

The fact is that by observing more, the Met Office can achieve more.

Why invest in a new radar system?

Longevity: many of our current radars are over 30 years old and it's beginning to show - Hameldon Hill radar is 33 years old and has completed over 14 million scans.

Capabilities: the new radars will feature enhanced capabilities, enabling us to monitor snow, sleet, hail and drizzle, as well as rain, wind and relative humidity.

Emergencies: we can monitor and respond more quickly to high-impact weather events such as flash floods and heavy snowfall.

Efficiency: the new radars make use of the latest technologies, improving efficiency and reducing carbon emissions.

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