Featured Research

from universities, journals, and other organizations

New data reveals how storms are triggered in the Sahel

Date:
June 27, 2011
Source:
CNRS (Délégation Paris Michel-Ange)
Summary:
In the Sahel, the frequency of storms increases when soil moisture varies over a few kilometers. Such contrasts cause air circulation between dry and humid areas, contributing to the development of storms. For the first time, these contrasts have been studied on a small scale. The new data that should help researchers to address the issue of drought in the Sahel.

Initiation of a storm in a semi-desert area in Mali during the monsoon.
Credit: © F. Guichard

In the Sahel, the frequency of storms increases when soil moisture varies over a few kilometers. Such contrasts cause air circulation between dry and humid areas, contributing to the development of storms. For the first time, these contrasts have been studied on a small scale by a collaboration between French researchers from the Groupe d'Etude de l'Atmosphère Météorologique (CNRS/Météo France) and UK researchers from CEH , as part of the AMMA project.

Their findings, published in the July 2011 issue of Nature Geoscience, provide new data that should help to address the issue of drought in the Sahel.

The Sahel is a semi-arid tropical region where annual rainfall depends on a few dozen storms that form during the monsoon season. The number of storms is therefore crucial in this region of the world, where insufficient precipitation can lead to a year of drought. Intense rainfall during these storms causes marked contrasts with neighboring areas in terms of humidity and temperature. Such contrasts play a role in the stability of the lower layers of the atmosphere. French researchers from the Groupe d'Etude de l'Atmosphère Météorologique (CNRS/Météo France) and UK researchers from CEH focused on the potential connections between storm formation and variations in soil properties caused by rainfall in the preceding days. They developed a statistical approach to perform individual, daytime analysis of several thousand cases of storm development identified by satellite observations at high spatial and temporal resolution during five monsoon seasons.

They found that, at the 100-km scale, storms develop more frequently above the driest and hottest surfaces. Series of satellite observations of surface temperatures at high spatial resolution (3 kilometers) were used to estimate variations in soil moisture at scales of a few tens of kilometers. The results obtained show that the number of storms significantly increases over surfaces with high contrasts in soil moisture, and more specifically in transitional areas where winds blow from a dry area towards a humid area. This suggests that atmospheric circulation starts up in the opposite direction to the wind, blowing from the more humid areas towards the drier areas, thus facilitating the formation of storms. Meteorological analyses have shown that this type of pattern is especially pronounced when the atmospheric environment is unfavorable to storms. Such contrasts therefore play a significant role in storm formation in the Sahel.

This is the first time that a study has shown, on the basis of observations, a positive feedback mechanism at this scale, namely preferential initiation of storms in areas with high soil moisture contrasts caused by intense localized rainfall. These findings shed a new light on the role of surface/atmosphere interactions in the mechanisms of storm formation and provide data that should help to address drought issues in the Sahel. The climate sensitivity of such interactions remains to be explored since current studies do not yet take it into account.


Story Source:

The above story is based on materials provided by CNRS (Délégation Paris Michel-Ange). Note: Materials may be edited for content and length.


Journal Reference:

  1. Christopher M. Taylor, Amanda Gounou, Françoise Guichard, Phil P. Harris, Richard J. Ellis, Fleur Couvreux, Martin De Kauwe. Frequency of Sahelian storm initiation enhanced over mesoscale soil-moisture patterns. Nature Geoscience, 2011; DOI: 10.1038/NGEO1173

Cite This Page:

CNRS (Délégation Paris Michel-Ange). "New data reveals how storms are triggered in the Sahel." ScienceDaily. ScienceDaily, 27 June 2011. <www.sciencedaily.com/releases/2011/06/110621101323.htm>.
CNRS (Délégation Paris Michel-Ange). (2011, June 27). New data reveals how storms are triggered in the Sahel. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2011/06/110621101323.htm
CNRS (Délégation Paris Michel-Ange). "New data reveals how storms are triggered in the Sahel." ScienceDaily. www.sciencedaily.com/releases/2011/06/110621101323.htm (accessed July 30, 2014).

Share This




More Earth & Climate News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

In Virginia, the Rise of a New Space Coast

In Virginia, the Rise of a New Space Coast

AP (July 30, 2014) — Every summer, tourists make the pilgrimage to Chincoteague Island, Va. to see wild ponies cross the Assateague Channel. But, it's the rockets sending to supplies to the International Space Station that are making this a year-round destination. (July 30) Video provided by AP
Powered by NewsLook.com
Climate Change Could Cost Billions, According To White House

Climate Change Could Cost Billions, According To White House

Newsy (July 29, 2014) — A report from the White House warns not curbing greenhouse gas emissions could cost the U.S. billions. Video provided by Newsy
Powered by NewsLook.com
Climate Change Could Cost Billions According To White House

Climate Change Could Cost Billions According To White House

Newsy (July 29, 2014) — A report from the White House warns not curbing greenhouse gas emissions could cost the U.S. billions. Video provided by Newsy
Powered by NewsLook.com
Jane Goodall Warns Great Apes Face Extinction

Jane Goodall Warns Great Apes Face Extinction

AFP (July 29, 2014) — The world's great apes face extinction within decades, renowned chimpanzee expert Jane Goodall warned Tuesday in a call to arms to ensure man's closest relatives are not wiped out. Duration: 00:58 Video provided by AFP
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:
from the past week

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