[an error occurred while processing this directive]
BBC News
watch One-Minute World News
Last Updated: Friday, 17 December, 2004, 18:11 GMT
Forecasters face losing key tools
By Alex Kirby
BBC News website environment correspondent

Aqua satellite (Nasa)
Earth observation is being made more difficult
Meteorologists fear they are losing one of their essential forecasting tools - microwave frequencies uniquely able to "see" through clouds from satellites.

They say commercial applications, for example mobile phones and collision avoidance systems, are ruining them.

The use of the bands in this way causes interference and contaminates the data from the satellites, making it useless.

Not only weather forecasting is put at risk, but also a better understanding of how climate change is developing.

Progress in both forecasting and climate studies depends on observations from space of the Earth's surface and atmosphere.

Unequal competition

Many of these observations depend in turn on using microwave frequency bands, which are increasingly in demand for terrestrial use.

We're in a David and Goliath situation, arguing to the ITU for the safety and humanitarian uses of frequencies against some applications with very strong financial backing
Dr Steve Foreman, Met Office
Examples include mobiles, wireless networking, other long-distance radio communications, and remote triggering devices. New military communications technologies are reported to pose another threat.

Dr Stephen English is manager of the satellite radiance assimilation group at the UK Met Office.

He told the BBC: "Microwave observations are vital because they see through cloud - this is not possible in any other frequency band.

"We only need a few narrow-frequency bands for Earth remote-sensing, but most of these are unique, so there is no alternative.

Gone already

"These bands are primarily used for temperature, water vapour, sea ice, clouds (ice and liquid), and rainfall and snowfall estimation.

Weather system (PA)
Meteorologists fear commercial interests will win out
"We use them as well for monitoring surface snowpack, soil moisture and sea surface temperature."

A meteorologists' working group on frequency management says protecting key regions of the microwave spectrum for passive remote-sensing is "a dramatic challenge", because of "the huge pressure of the commercial and military telecoms".

Two important bands (6.8 GHz and 10.7 GHz) have been lost already for use over land, but in the next few years the threat is likely to spread to other bands.

There is particular concern about protecting the 23.6-24 GHz band, which has the unique property of being sensitive to water vapour but not to liquid water.

Dr English said: "There is no other frequency where this occurs. But car 'radars' will now be allowed to broadcast in this frequency band."

Data lost

An instrument called the advanced microwave scanning radiometer, carried on Nasa's Aqua satellite, monitors rainfall as it "sees through" the cloud above the rain.

Land and sea look very different at this frequency (in the image, right, taken in mid-October, the ocean appears black where it is not raining, and magenta or blue where it is).

Blobs of red and yellow over the main urban areas show radio frequency interference (RFI), which is much hotter than actual surface or atmospheric temperatures over the UK in October.

Satellite image of UK   Met Office
Met Office image of UK
Dr English said: "The 'hot spots' are easy to spot, but more worrying is the fact that smaller variations may be RFI, or they may be due to rain.

"The truth is we can't tell. Therefore the channel is rendered useless not only in the hot spots but everywhere, because we can no longer uniquely interpret the variations in terms of rainfall.

"Of course, over the ocean man-made signals are limited, so we still regard this channel as useful over the ocean, but it's no longer useful over land."

Experts say this band should not be jeopardised under any circumstances, and all emissions able to cause interference should be prohibited.

The UN body which is the final arbiter on frequency use is the International Telecommunication Union.

Dr Steve Foreman of the Met Office told the BBC: "We're in a David and Goliath situation, arguing to the ITU for the safety and humanitarian uses of frequencies against some applications with very strong financial backing."

Met Office unveils supercomputer
07 Sep 04 |  Technology


The BBC is not responsible for the content of external internet sites


News Front Page | Africa | Americas | Asia-Pacific | Europe | Middle East | South Asia
UK | Business | Entertainment | Science/Nature | Technology | Health
Have Your Say | In Pictures | Week at a Glance | Country Profiles | In Depth | Programmes
Americas Africa Europe Middle East South Asia Asia Pacific