The properties of clouds can be a key to predicting coming climate changes. This is shown by research at the University of Gothenburg in Sweden - which has also studied urban pollution.
The earth's climate field is regulated by the balance between incoming solar radiation and outbound heat radiation. The aerosol content of the atmosphere, that is, the proportion of particles in the air, functions as a regulator: cooling off by reflecting incoming light, warming up by absorbing the outbound heat radiation.
But clouds also impact the climate. In various forms-from thin, indiscernible to thick, gray ones-clouds cover roughly half of the earth's surface. Clouds reflect a considerable proportion of solar radiation back into space, but, like greenhouse gases, they can also absorb outbound heat radiation. However, the uncertainties surrounding how clouds affect the climate are great - according to the UN Climate Panel, the greatest single uncertainty when it comes to estimating the sensitivity of the climate.
Now a new field of research is being established at the University of Gothenburg to fill these knowledge gaps.
In his doctoral dissertation, researcher Frans Olofson at the Department of Chemistry presents a new application of a metering technique in which a laser beam is sent up in the air to measure the aerosol content and how light is being reflected in the atmosphere. The study was carried out on cirrus clouds above northern Norway and is the first to be performed in the climate-sensitive Arctic region using this technology. The study establishes that incoming solar radiation is regulated to a great extent by the shape and size of cloud particles.
"Measurements of this type can be used to improve our descriptions of the radiation properties of cirrus clouds, which in turn can enhance the quality of climate models," says Frans Olofson.
In his dissertation Frans Olofson has also studied periodically troublesome temperature inversions, which can be seen in the winter as a lid of yellowish brown emissions over cities. Inversions have serious impacts on people's health, and the longer they are exposed to them, the more they are affected.
Based on his measurements in Gothenburg, Frans Olofson was able to establish that inversions are strongly tied to meteorological phenomena, and that the time it takes for the pollutants to dissolve varies considerably: from a couple of hours in the morning up to several hours in the afternoon. Sometimes an inversion doesn't break up all day.
Title of dissertation: Lidar Studies of Tropospheric Aerosols and Clouds
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