Global Warming

82 Modelling the climate

Data to initialise the model

At a major global weather forecasting centre, data

from many sources are collected and fed into

the model. This process is called initialisation.

Figure 5.4 illustrates some of the sources of data

for the forecast beginning at 1200 hours Universal

Time (UT) on 1 July 1990. To ensure the timely

receipt of data from around the world a dedi-

cated communication network has been set up, used

solely for this purpose. Great care needs to be taken

with the methods for assimilation of the data into

the model as well as with the data’s quality and

accuracy.

Figure 5.4Illustrating some of the sources of data for input into the UK Meteorological Office global
weather forecasting model on a typical day. Surface observations are from land observing stations
(manned and unmanned), from ships and from buoys. Radiosonde balloons make observations at up to
30 km altitude from land and from ship-borne stations. Satellite soundings are of temperature and
humidity at different atmospheric levels deduced from observations of infrared or microwave radiation.
Satellite cloud-track winds are derived from observing the motion of clouds in images from geostationary
satellites.

Forecast skill varies considerably between different weather situa-

tions or patterns. In other words some situations are more ‘chaotic’ (in

the technical sense in which that word is used – see box below) than

others. One way of identifying the skill that might be achieved in a