Data Collection - Instrumentation
GEOmon measures the levels of carbon dioxide (CO2), methane (CH4), ozone (O3), in the atmosphere as well as the quantity of aerosols (suspension of fine solid particles or liquid droplets in air), wind speed, temperature and other meterological conditions.
Ground-Based Measurements
Measurements are carried out by at observation stations throughout the world using upward-looking, ground-based remote sensing instruments including:
- Max-DOAS (Multi Axis Differential Optical Absorption Spectroscopy) instruments. These instruments are UV/visible spectrometers observing the sun light scattered by the atmosphere in different viewing directions.
To know more about Max-DOAS
- FTIR (Fourier Transform Infra-Red) spectrometers.
To know more about FTIR
- LIDAR (Light Detection and Ranging). Lidar works by transmitting laser signals using all light ranges (ultraviolet, visible, infrared) and amplifying the light that is scattered back through an optical telescope and photomultiplier tube.
Tropospheric/ Stratospheric Measurements by Aircraft
Measurements carried out by commercial aircraft in a related scientific project, CARIBIC, also add to our understanding of the composition of the atmosphere and its physical transport properties. Much of the sampling occurs at altitudes of 10-12 km which is at the limit between the troposphere and the stratosphere (the tropopause). This gives us information about the chemistry and transport mechanisms in a little-documented region that is of significant importance.
These measurements allow us to validate, calibrate and better understand the broad picture provided by satellite data.
Satellites measurements
Satellites carry remote sensing instruments that measures radiances, either solar light after reflection by the Earth surface or the atmosphere (wavelength < 3 µm), or radiance that is emitted by the Earth (wavelength > 4 µm). Algorithms are used to convert these radiance measurements to useful parameters about the Earth system. For instance, radiance measurements in the thermal infrared are used to infer the temperature profile of the atmosphere; other channels in the same spectral range can be used to estimate the concentration of greenhouse gases and ozone; the amount of solar light reflected by the atmosphere is related to the load of aerosols.
Satellites provide an homogeneous, global and continuous view of the Earth which is essential for climate studies. On the other hand, their products are, for most of them, less accurate that what is achieved by in-situ measurements. This is why a careful calibration and validation is needed before remote sensing products can be used in comparison to modeling results.
In situ and satellite data are complementary. The former provide high-frequency precise measurements at discrete locations, while the later provide an information over an extended area.
