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.
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.
