Featured Research

from universities, journals, and other organizations

Major step in improving forecasts of weather extremes such as floods and droughts

Date:
June 6, 2011
Source:
Columbia University
Summary:
Moisture and heat fluctuations from the land surface to the atmosphere form a critical nexus between surface hydrology and atmospheric processes, especially those relevant to rainfall. While current theory has suggested that soil moisture has had a positive impact on precipitation, there have been very few large-scale observations of this. Now, a team of researchers has demonstrated that evaporation from the land surface is able to modify summertime rainfall east of the Mississippi and in the monsoonal region in the southern U.S. and Mexico.

Researchers have found that evaporation from the land surface is able to modify summertime rainfall east of the Mississippi and in the monsoonal region in the southern U.S. and Mexico.
Credit: © Demydenko Mykhailo / Fotolia

Moisture and heat fluctuations from the land surface to the atmosphere form a critical nexus between surface hydrology and atmospheric processes, especially those relevant to rainfall. While current theory has suggested that soil moisture has had a positive impact on precipitation, there have been very few large-scale observations of this. A team of researchers from Columbia Engineering, Geophysical Fluid Dynamics Laboratory, and Rutgers University has now demonstrated that evaporation from the land surface is able to modify summertime rainfall east of the Mississippi and in the monsoonal region in the southern U.S. and Mexico. One of their main findings is that evaporation from the land is, however, only able to modify the frequency of summertime rainfall, not its quantity.

"This is a major shift in our understanding of the coupling between the land surface and the atmosphere, and fundamental for our understanding of the prolongation of hydrological extremes like floods and droughts," said Pierre Gentine, Assistant Professor of Applied Mathematics at The Fu Foundation School for Engineering and Applied Science at Columbia University, and co-author of the paper "Probability of Afternoon Precipitation in eastern United States and Mexico Enhanced by High Evaporation," published online June 5 in the journal Nature Geoscience. The other co-authors are Kirsten Findell (Geophysical Fluid Dynamics Laboratory), Benjamin Lintner (Rutgers University), and Christopher Kerr (Geophysical Fluid Dynamics Laboratory).

The researchers used data from the National Centers for Environmental Prediction (NCEP) to quantify the impacts of continental evaporation on the frequency and intensity of summertime rainfall over North America. They discovered that higher evaporation increases the probability of afternoon rainfall east of the Mississippi and in Mexico, while it has no influence on rainfall over the Western U.S. The difference is due to the humidity present in the atmosphere. The atmosphere over the western regions is so dry that no matter what the input of moisture via evaporation is from the surface, an added source of moisture will not trigger any rain since it will instantaneously dissipate into the atmosphere. The atmosphere over the eastern regions is sufficiently wet so that the added moisture from the surface evaporation will make it rain.

"If it starts getting really wet in the east," noted Gentine, "then the surface will trigger more rain so it becomes even moister, and this sets up a vicious cycle for floods and droughts. Nature -- i.e. the land surface and the vegetation -- cannot control the rainfall process in the west but it can in the east and in the south. This is really important in our understanding of the persistence of floods and droughts."

Consequently, once a flood or a drought is triggered by large-scale processes, such as sea surface temperature anomalies, the flood/drought conditions are most likely to persist in the eastern and southern U.S. But in the West, the duration and frequency of floods/droughts are controlled only by oceanic processes: the surface cannot modify the rainfall process. Whether the soil is dry or wet doesn't change subsequent rainfalls: consequently the surface will not help hydrological extremes persist (e.g. floods/droughts).

Gentine is developing a theoretical framework to understand the precipitation and cloud formation over land and says this should be an important breakthrough in our understanding of how soil moisture and vegetation controls cloud formation and the precipitation process. "I find this work fascinating because it's a great blend of theoretical research -- understanding how nature works -- and practical applications that affect our world -- like flood/drought/water management. My lab is right outside: observing clouds and precipitation!"

The study was funded by the National Science Foundation (NSF).


Story Source:

The above story is based on materials provided by Columbia University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Kirsten L. Findell, Pierre Gentine, Benjamin R. Lintner, Christopher Kerr. Probability of afternoon precipitation in eastern United States and Mexico enhanced by high evaporation. Nature Geoscience, 2011; DOI: 10.1038/ngeo1174

Cite This Page:

Columbia University. "Major step in improving forecasts of weather extremes such as floods and droughts." ScienceDaily. ScienceDaily, 6 June 2011. <www.sciencedaily.com/releases/2011/06/110605132427.htm>.
Columbia University. (2011, June 6). Major step in improving forecasts of weather extremes such as floods and droughts. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2011/06/110605132427.htm
Columbia University. "Major step in improving forecasts of weather extremes such as floods and droughts." ScienceDaily. www.sciencedaily.com/releases/2011/06/110605132427.htm (accessed July 31, 2014).

Share This




More Earth & Climate News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Visitors Feel Part of the Pack at Wolf Preserve

Visitors Feel Part of the Pack at Wolf Preserve

AP (July 31, 2014) — Seacrest Wolf Preserve on the northern Florida panhandle allows more than 10,000 visitors each year to get up close and personal with Arctic and British Columbian Wolves. (July 31) Video provided by AP
Powered by NewsLook.com
Big Waves In Arctic Ocean Threaten Polar Ice

Big Waves In Arctic Ocean Threaten Polar Ice

Newsy (July 30, 2014) — Big waves in parts of the Arctic Ocean are unprecedented, mainly because they used to be covered in ice. Video provided by Newsy
Powered by NewsLook.com
Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) — Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com
Weather Kills 2K A Year, But Storms Aren't The Main Offender

Weather Kills 2K A Year, But Storms Aren't The Main Offender

Newsy (July 30, 2014) — Health officials say 2,000 deaths occur each year in the U.S. due to weather, but it's excessive heat and cold that claim the most lives. Video provided by Newsy
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