Simon Proud, a scientist at the University of Copenhagen, explains how satellite data can help research the Earth and its atmosphere.
07, December 2020
Satellites are extremely useful tools for helping to understand large-scale processes and interactions between the Earth’s atmosphere, surface and oceans.
At the University of Copenhagen (KU) we have been using satellite data to explore many aspects of our planet - including plant growth, flooding, the temperature of the land surface and severe thunderstorms. We have even used satellites to model the orbital path of a meteor.
The aim of my work is to explore how MSG data can explore the Earth’s atmosphere, with an emphasis upon cloud processes.
Recently I have been looking at how MSG can observe noctilucent clouds, a poorly understood type of high altitude (80 km) cloud that only form during the summer. I hope that MSG, together with other satellites, will help explain some of the details behind the formation of these clouds. Noctilucent clouds case study. Simon's research paper on noctilucent clouds.
My main interest, however, is somewhat lower in the atmosphere: around around 12 km above the surface.
I examine how MSG data can help aircraft identify and avoid regions of severe weather such as large thunderstorms, turbulence and strong winds. In particular, I look at how to detect the dense clouds of ice that occasionally form near the tops of severe thunderstorms. These clouds have the potential to cause aircraft engine or sensor malfunctions, but are often invisible to the eye and to aircraft weather radar.
A satellite-based method of detecting the clouds would, therefore, be important to flight crews who may otherwise fly through these potentially hazardous clouds.
Currently I am combining the images produced by MSG with experimental data derived from work undertaken as part of Prof. Dan Cziczo’s group at the Massachusetts Institute of Technology in America.
This combination will allow a better understanding of how the dense ice clouds form and hence improve our ability to monitor them via satellite.
As well as researching atmospheric processes, the group at KU is also active in looking at the Earth’s surface to study flooding, vegetation growth and changes in land cover. For this type of work, cloud cover can be a problem as it obscures the surface features.
Because MSG is in a geostationary orbit, it can produce more images of the Earth in a given time than is possible from satellites in other orbits, therefore maximising the possibility of gaining a clear-sky view of the Earth.
For example, the MODIS instrument in polar orbit can only take images of some parts of the world two or three times per day while MSG gathers 96 images per day. The trade-off is that MSG has a lower spatial resolution, so small features that show up in MODIS data are not visible to MSG.
Professor Rasmus Fensholt, who leads KU's efforts to study the Earth's surface, explains: "MSG data offers new opportunities for estimating vegetation vigour, status and stress. The high temporal frequency guarantees that the initiation of events such as droughts are identified early and can be responded to in such a way as to minimise their impacts on society.
"This makes MSG data useful for real-time resource management and also for implementation in early warning systems that cover, for example, the vast dryland areas on the African continent."
Another aspect of our work is to validate satellite data using results collected at ground level. To support this goal we established a field-site near Dahra, Senegal.
For the last 12 years we have measured solar radiation, energy fluxes and other biophysical variables once every 15 minutes — providing a large set of data that for to compare with satellite observations.
In addition, these field data have allowed us to develop techniques that minimise the effects of atmospheric absorption, to give a clearer picture of what is actually happening at the Earth's surface.
Across all of these various topics, the MSG series of satellites provides a great selection of data for us to work with.
However, we are always searching for improvements to the data that we use and, looking to the future, the Meteosat Third Generation (MTG) series of satellites will allow us to gain an even better understanding of the Earth and atmosphere.
MTG's superior spatial resolution will enable us to examine smaller features, such as the detail of storm anvils or localised flooding events, while the higher temporal resolution will assist in monitoring the rapid development of thunderstorms and other severe weather events.