Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Pollution shown cutting rainfall in hilly areas

09.03.2007
Manmade climate change due to pollution seriously inhibits precipitation over hills in semi-arid regions, a phenomenon with dire consequences for water resources in the Middle east and many other parts of the world, a study by a Chinese-Israeli research team, led by Prof. Daniel Rosenfeld of the Hebrew University of Jerusalem, has shown.

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
Further information:
http://www.huji.ac.il

More articles from Ecology, The Environment and Conservation:

nachricht Bioinvasion on the rise
15.02.2017 | Universität Konstanz

nachricht Litter Levels in the Depths of the Arctic are On the Rise
10.02.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>