The Chinese and Israeli researchers showed that the average precipitation on Mount Hua near Xian in central China has decreased by 20 percent along with increasing levels of manmade air pollution during the last 50 years. The precipitation loss was doubled on days that had the poorest visibility due to pollution particles in the air.
This explains the widely observed trends of decrease in mountain precipitation relative to the rainfall in nearby densely populated lowlands, which until now had not been directly ascribed to air pollution.
The research study, published in the current issue of the journal Science, is titled “Inverse Relations between Amounts of Air Pollution and Orographic Precipitation” and was written by Prof. Rosenfeld of the Hebrew University’s Ring Department of Atmospheric Sciences, Jin Dai and others from the Meteorological Institute of Shaanxi Province, China, and Zhanyu Yao of the Chinese Academy of Meteorological Science.
These findings highlight the threat to vital water resources in polluted regions of the world where hilly-area precipitation makes a significant contribution to the regional water supply, as in the southwestern U.S. central and northern China, and the Middle East. The importance of that is underlined by the realization that it is not high temperatures due to global warming but rather the lack of water that makes a region into an unlivable desert.
The authors studied observations of precipitation and visibility starting in 1954 at the top of Mount Hua. They linked the decreasing visibility at its over two-kilometer-high summit with increasing air pollution particles that reach to the clouds. They were able to show that the trend of higher concentrations of these fine, airborne, pollutants (aerosols) is responsible for the observed decreasing trend of mountain precipitation. This is the first time that this link has been demonstrated so conclusively.
The precipitation inhibition process occurs as water vapor condenses on the pollution particles and creates a cloud with a large number of drops that are so small that they float with the air and are slow to coalesce into raindrops or to freeze into sleet and snowflakes. This slowing translates into a net loss of precipitation when the cloud “lifetime” is shorter than the time necessary to release its water. This is the case for clouds that form when they ascend across a ridge and then descend and evaporate on the downwind side.
By making use of precipitation and visibility records that show a direct causal link between the airborne particle pollution and the mountain precipitation losses, the unique China study can serve as a template to bear out hypotheses about the effects of pollution on rainfall that were undertaken previously by Prof. Rosenfeld in hilly regions with similar pollutive conditions. These include California and much of the western United States. Similar trends were already published also for Israel, and observed in South Africa, Portugal, France, Switzerland, Morocco, Canada, Greece and Spain.
Atmospheric aerosols have been described in earlier studies as playing a role in cooling the atmosphere by reflecting some of the incoming solar radiation back into space -- thus serving as a counterbalance to global warming resulting from the release of greenhouse gases. The latest study by Prof. Rosenfeld and his Chinese associates shows, however, that this “beneficial” effect is offset by the proven direct link between air pollution and decreased mountain precipitation, and that climate change means much more than “just” global warming.
Jerry Barach | alfa
Global threat to primates concerns us all
19.01.2017 | Deutsches Primatenzentrum GmbH - Leibniz-Institut für Primatenforschung
Reducing household waste with less energy
18.01.2017 | FIZ Karlsruhe – Leibniz-Institut für Informationsinfrastruktur GmbH
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences