Featured Research

from universities, journals, and other organizations

Droughts Aggravated By Dust In The Wind

Date:
May 16, 2001
Source:
NASA/Goddard Space Flight Center--EOS Project Science Office
Summary:
Windblown desert dust can choke rain clouds, cutting rainfall hundreds of miles away. This new discovery, made with the help of NASA satellites, suggests that droughts over arid regions, such as central Africa, are made worse by damaging land and livestock management that expand the desert.

Windblown desert dust can choke rain clouds, cutting rainfall hundreds of miles away. This new discovery, made with the help of NASA satellites, suggests that droughts over arid regions, such as central Africa, are made worse by damaging land and livestock management that expand the desert.

The findings, reported in the Proceedings of the National Academy of Sciences, present a new view of the decades-long drought in the African Sahel, which has been accompanied by increasing levels of airborne dust during the rainy season.

The higher dust frequency is not necessarily a result of the decreased rainfall, but rather its cause, according to scientists from Israel's Hebrew University and the Weizmann Institute. "This impact of desert dust on rainfall was not known before," says lead author Daniel Rosenfeld, Hebrew University, Jerusalem. "Due to the large sizes of some of these dust particles, it had been assumed that desert dust would enhance precipitation rather than decrease it."

Scientists had expected that the largest dust particles would form giant cloud condensation nuclei, which produce larger cloud droplets that speed the formation of rain. "Our laboratory analysis of the desert dust, however, showed that the particles contained very little water-absorbing matter," says co-author Yinon Rudich of the Weizmann Institute, Rehovot. "As a result, even large dust particles form relatively small cloud droplets."

The research shows dust actually amplifies the process of creating deserts. Activities that expose and disrupt topsoil, such as grazing and agricultural cultivation, can increase the amount of dust blown into the air. More dust reaching rain clouds produces less rainfall, which exacerbates the drought conditions and contributes to the desertification of the landscape.

Dust and other types of aerosol particles blowing into clouds act as nuclei where water vapor can condense to form cloud droplets. If a lot of dust enters a cloud, the available water is spread over many small droplets. These small droplets grow more slowly through collisions with one another to the size of a raindrop, and the cloud yields less rainfall over the course of its lifetime.

What the researchers saw in two separate cases, using different satellite observations, was that cloud droplets were smaller as dust concentrations increased.

NASA's Tropical Rainfall Measuring Mission (TRMM) spacecraft captured images of clouds over the Atlantic Ocean off the coast of northern Africa during a major dust storm last March. Droplet sizes steadily increased the farther the clouds were from dust-filled air. Rain was falling only from the dust-free clouds even though all the clouds contained equal amounts of water.

The researchers also observed similar behavior in clouds over the eastern Mediterranean Sea in March 1998, using data from aircraft and a U.S. weather satellite.

TRMM is a joint U.S.-Japanese mission and part of NASA's Earth Science Enterprise, a long-term research program designed to study the Earth's land, oceans, air, ice and life as a total system. Each day, the TRMM spacecraft observes the Earth's equatorial and tropical regions, including the southernmost United States and all of Africa.

Rosenfeld has used TRMM observations in two other recent studies to show that aerosols from biomass-burning smoke and urban air pollution also reduce rainfall. Combined with the negative impact of desert dust, Rosenfeld believes the aerosol rainfall suppression effect can have a major impact on regional and global climate.

"The recent observations of the impact on precipitation of all kinds of aerosols, each with a major human contribution, show a major climate change issue that has nothing to do with greenhouse gases," says Rosenfeld. "Still, this is perhaps the climate-change effect with the greatest socio-economic impact on water-scarce areas."


Story Source:

The above story is based on materials provided by NASA/Goddard Space Flight Center--EOS Project Science Office. Note: Materials may be edited for content and length.


Cite This Page:

NASA/Goddard Space Flight Center--EOS Project Science Office. "Droughts Aggravated By Dust In The Wind." ScienceDaily. ScienceDaily, 16 May 2001. <www.sciencedaily.com/releases/2001/05/010515080126.htm>.
NASA/Goddard Space Flight Center--EOS Project Science Office. (2001, May 16). Droughts Aggravated By Dust In The Wind. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2001/05/010515080126.htm
NASA/Goddard Space Flight Center--EOS Project Science Office. "Droughts Aggravated By Dust In The Wind." ScienceDaily. www.sciencedaily.com/releases/2001/05/010515080126.htm (accessed October 21, 2014).

Share This



More Earth & Climate News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional Farming Methods Gaining Ground in Mali

Traditional Farming Methods Gaining Ground in Mali

AFP (Oct. 20, 2014) He is leading a one man agricultural revolution in Mali - Oumar Diatabe uses traditional farming methods to get the most out of his land and is teaching others across the country how to do the same. Duration: 01:44 Video provided by AFP
Powered by NewsLook.com
Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com
White Rhino's Death In Kenya Means Just 6 Are Left

White Rhino's Death In Kenya Means Just 6 Are Left

Newsy (Oct. 20, 2014) Suni, a rare northern white rhino at Ol Pejeta Conservancy, died Friday. This, as many media have pointed out, leaves people fearing extinction. Video provided by Newsy
Powered by NewsLook.com
New Organic Fertilizer Helps Reforestation of Monarch Butterflies’ Winter Retreat

New Organic Fertilizer Helps Reforestation of Monarch Butterflies’ Winter Retreat

Reuters - Innovations Video Online (Oct. 20, 2014) Using an organic fertiliser, a conservationist from the National Autonomous University of Mexico (UNAM), leads an award-winning project to reforest the sanctuary of monarch butterflies. Sharon Reich reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins