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

A Brewer spectrophotometer
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 ozonsonde
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.

Air Quality

Air quality is the combination of the presence of short-lived trace gases like O3 and NO2, and aerosols that affect human health, e.g. cause respiratory problems. Air quality is determined by the tropospheric chemical composition, and is mainly a local and regional phenomenon. From satellite measurements of tropospheric NO2 the sources and strengths of NO2 emissions can be determined.

Satellite observations

In our division we monitor globally the concentration of key components of tropospheric chemical composition, mainly tropospheric NO2 and ozone, from OMI, GOME-2 and SCIAMACHY. Data are available via TEMIS.

Groundbased observations

To validate the satellite measurements of tropospheric NO2, an NO2 sonde has been developed recently (Sluis et al., AMT, 2010). This sonde is a balloon borne NO2 sensor, which measures the vertical distribution of NO2. It is launched regularly from De Bilt or Cabauw. We also perform MAX-DOAS measurements to measure the tropospheric NO2 column from the surface (Vlemmix et al., AMT, 2010).

Publications

The full list of this departments publications can be found here.