
Climate
It has been established by the IPCC that human influences on climate are unmistakable. The most important of these influences is the change in the chemical composition of the atmosphere due to anthropogenic emissions of long-lived greenhouse gases like CO2 and CH4. Anthropogenic emission of short-lived trace gases, like NO2 and HCHO, lead to a change in heating rate of the atmosphere via tropospheric ozone formation. Anthropogenic emission of aerosols can either cool or heat the atmosphere. Clouds are an important natural feedback factor, since clouds mostly cool the surface.In our division we observe the climate-related atmospheric constituents: ozone, aerosols and clouds. We use the satellite instruments OMI, SCIAMACHY, GOME-2 and SEVIRI. The main climate products of our division are: total ozone, ozone profile, aerosol absorbing index, cloud fraction, cloud height, and cloud physical properties. Data are distributed via TEMIS (ESA) and via the Ozone Monitoring SAF and the Climate Monitoring SAF (EUMETSAT).
Ozone
Ozone in the stratosphere is the Earth's natural shield for the damaging UV radiation from the sun. However, ozone is also an air pollutant when it is close to the surface (smog) and an important greenhouse gas when it is around the tropopause.In our division we measure ozone using satellites and ground-based instruments. On the basis of satellite ozone measurements we provide UV forecasts on the TEMIS website.
Satellite measurements of ozone
The satellite spectrometers OMI, SCIAMACHY, GOME-2 can measure the atmospheric ozone content by measuring the spectrum of ultraviolet sunlight that is reflected by the earth's atmosphere. We make the following ozone data products: total ozone, ozone profiles, and assimilated total ozone. Data can be found on the TEMIS website.Grondbased measurements of ozone
The Brewer spectrophotometer measures ultraviolet sunlight at 6
wavelengths between 302 and 320 nm. The extinction of sunlight by ozone varies
hugely with wavelength in this part of the spectrum. From these measurements
the total ozone content of the atmosphere above De Bilt is computed. If direct
sunlight is available, the accuracy of the measurements should be better than
2%. In cloudy conditions the accuracy is somewhat lower. Measurements are
performed automatically during daytime hours. We are currently operating
Brewer MKIII, #189.
An ozone sonde is a balloon borne instrument that measures ozone
concentration in situ between the ground and 32 km altitude. So typically 90%
of theatmospheric ozone is measured. Ozone sondes are launched at least once a
week, but more are launched when we expect unusual atmospheric conditions.
Additional sondes are also launched for satellite validation.