Explored tropical atmosphere

Atmosphere researchers investigate the causes of climate change at the equator

Measurements with LIDAR measuring device © University of Bremen
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There is a direct link between the air masses of the tropics and the polar regions, which has a lasting influence on global climate change. But so far very little is known about the atmospheric events in the tropics. Atmospheric researchers from the University of Bremen and the Alfred Wegener Institute in Bremerhaven have now captured the composition and processes in the tropical atmosphere from the ground up to a height of 30 kilometers in an international campaign using methods of remote sensing.

Using sophisticated mathematical methods, the data is now evaluated to provide information on the concentration and transport of polluting trace gases from biomass combustion, the atmospheric moisture content, the ozone layer strength, the variability of UV-B radiation, and the formation of ice clouds ( To get cirrus). This knowledge is needed to understand and predict global climate change - and to intervene, perhaps in good time, on human-induced climate issues through appropriate measures, such as those set out in the Kyoto Protocol.

global air circulation

In the tropics, there is a chimney effect for the air masses of the lower atmosphere layer, the troposphere. The air masses rise rapidly due to the very high solar radiation and the associated warming and get from the troposphere into the stratosphere. From the tropical stratosphere, the air masses are then transported to the middle and high latitudes and in the polar regions they sink and reenter the troposphere. The tropics thus play a central role in the global climate and there is a direct relationship between the air masses of the tropics and the polar regions.

Particularly important is the area between the troposphere and the stratosphere. However, apart from targeted aircraft campaigns, so far there have been few atmospheric measurements in the tropics. Within the framework of the international project funded by the European Union (Support for Tropical Atmospheric Research) and the Helmholtz Association funded virtual institute PEP (Pole - Equator - Pole), a first campaign with ground-based remote sensing tools was recently conducted in the tropics.

With active and passive methods to the goal

Under the direction of Professors Justus Notholt from the University of Bremen and Otto Schrems from the Alfred Wegener Institute in Bremerhaven, the atmospheric researchers investigated the composition of the entire tropical atmosphere from the ground up to a height of 30 km and beyond. Both "passive" and "active" methods were used. display

In the "passive" method one uses the weakening of the solar radiation by the trace substances in the atmosphere. For this purpose, high-resolution infrared spectrometers are used. With elaborate evaluation methods, the concentrations of the trace substances are obtained up to about 30 km altitude. In the "active" method, the Lidar method, a laser beam is emitted into the atmosphere, and the light scattered back by molecules or particles provides the concentration profiles of the substances to be examined.

The measurement campaign conducted by the Alfred Wegener Institute, the University of Bremen and other institutes took place in tropical temperatures and high humidity in the months of September to November 2004 in Paramaribo, the capital of Surinam. Suriname is located in the north of South America and borders French Guiana to the east, Brazil to the south, Guyana to the west, and the Atlantic Ocean to the north.

Trace substances on the track

The concentration and transport of trace substances in the atmosphere, the variability of the UV radiation arriving at the earth's surface and the water vapor content of the atmosphere were measured. The high ice clouds were also targeted, whose formation and influence on the radiation budget is still largely unknown. Such studies are of great importance for understanding the radiation budget and for studying the transport of combustion products in the atmosphere. Another measuring campaign will be in the coming dry season in February / March

2005 performed.

Together, the participating environmental scientists want to use a chain of measuring stations from the Arctic across the middle latitudes, the tropics to the Antarctic, together with model calculations to investigate how the emissions of climate-relevant substances are transported and converted in the atmosphere. Such studies are important, for example, in the context of the Kyoto Protocol. Emissions of greenhouse gases (eg CO2) are regulated by the Kyoto Protocol. By the end of the World Climate Change Conference in Buenos Aires on 16 December 2004, 132 states had ratified the Kyoto Protocol.

(University of Bremen, 10.01.2005 - NPO)