Featured Research

from universities, journals, and other organizations

Elucidating heavy precipitation events

Date:
November 29, 2013
Source:
CNRS (Délégation Paris Michel-Ange)
Summary:
It is difficult to forecast heavy precipitation events accurately and reliably. The quality of these forecasts is affected by two processes whose relative importance has now been quantified. The French researchers have shown that these processes should be taken into account in low wind speed events. Their findings should help forecast these events, which repeatedly cause significant damage.

Comparison of simulated precipitation (in mm) in two simulations carried out with the Meso-NH model for a heavy rainfall event on 6 September 2010. In the upper simulation, the value of the time tendency of raindrop evaporation was reduced by 50%; in the lower simulation, the value of the tendency was increased by 50%.
Credit: © LA

It is difficult to forecast heavy precipitation events accurately and reliably. The quality of these forecasts is affected by two processes whose relative importance has now been quantified by a team at the Laboratoire d'Aérologie (CNRS / Université Toulouse III-Paul Sabatier). The researchers have shown that these processes should be taken into account in low wind speed events. Their findings should help forecast these events, which repeatedly cause significant damage, especially in south-eastern France. They are first published online the November 28, 2013 in the Quarterly Journal of the Royal Meteorological Society.

Related Articles


Nearly every autumn, the countries of the Mediterranean Basin are stricken by heavy rainfall and flash floods, which endanger populations and can cause significant property damage. South-eastern France is frequently affected by these events, caused by the interaction between topography and the still warm and moisture-laden air masses from the Mediterranean Sea. Weather forecasters are able to predict these events and issue weather warnings. However, simulating their evolution on different time scales remains difficult, just like forecasting the strength and location of precipitation, the two parameters that broadly determine the extent of flooding.

Researchers from CNRS and Université Toulouse III-Paul Sabatier at the Laboratoire d'Aérologie investigated two phenomena that play a key role in meteorology: the microphysics of hydrometeors (rain, snow and ice pellets)[1] and atmospheric turbulence. The aim was to determine the relative effect of these two processes on forecast sensitivity. To do this, the scientists looked at five heavy rainfall episodes that took place between September 2010 and November 2011 in south-eastern France and for which measured data was available. For each event, ensemble simulations were carried out using the Meso-NH[2] atmospheric research model, giving more or less importance to each of the two processes.

Two main results emerged. For high wind speed events, precipitation is scarcely affected by the perturbations introduced. It is therefore unnecessary to take account of these two processes to improve heavy precipitation forecasting. In this case, it is the interaction with the topography that determines the onset of precipitation. However, when wind speed is low, both the intensity of precipitation and its location (upstream of the topography) are far more sensitive to these two processes. In this case, the microphysics of hydrometeors and atmospheric turbulence need to be better represented so as to improve forecast sensitivity.

These results suggest that in low wind speed situations, errors related to the representation of microphysical and turbulent processes make a significant contribution to the total error in the forecasting system. Taking greater account of these errors would improve heavy precipitation forecasting when wind speed is low. The study was also used to test a methodology that may be implemented as part of the HyMeX[3] international research program, launched in 2010 for a period of ten years and coordinated by Météo-France and CNRS.


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. A. Hally, E. Richard, S. Fresnay, D. Lambert. Ensemble simulations with perturbed physical parametrizations: Pre-HyMeX case studies. Quarterly Journal of the Royal Meteorological Society, 2013; DOI: 10.1002/qj.2257

Cite This Page:

CNRS (Délégation Paris Michel-Ange). "Elucidating heavy precipitation events." ScienceDaily. ScienceDaily, 29 November 2013. <www.sciencedaily.com/releases/2013/11/131129101903.htm>.
CNRS (Délégation Paris Michel-Ange). (2013, November 29). Elucidating heavy precipitation events. ScienceDaily. Retrieved November 21, 2014 from www.sciencedaily.com/releases/2013/11/131129101903.htm
CNRS (Délégation Paris Michel-Ange). "Elucidating heavy precipitation events." ScienceDaily. www.sciencedaily.com/releases/2013/11/131129101903.htm (accessed November 21, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Friday, November 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Nations Pledge $9.3 Bn for Green Climate Fund

Nations Pledge $9.3 Bn for Green Climate Fund

AFP (Nov. 20, 2014) — Nations meeting in Berlin pledge $9.3 billion (7.4 bn euros) for a climate fund to help poor countries cut emissions and prepare for global warming, just shy of a $10bn target. Duration: 00:46 Video provided by AFP
Powered by NewsLook.com
What's The Point Of Climate Conferences?

What's The Point Of Climate Conferences?

Newsy (Nov. 20, 2014) — There's optimism about the U.N.'s climate conference in Paris next year, and if climate conferences past are anything to go off, that's notable. Video provided by Newsy
Powered by NewsLook.com
Mysterious Glow Worms Found in the Amazon

Mysterious Glow Worms Found in the Amazon

Buzz60 (Nov. 20, 2014) — Wildlife photographer Jeff Cremer teamed up with entomologist Aaron Pomerantz and others to investigate a predatory glow worm found in the Amazon. Patrick Jones (@Patrick_E_Jones) explains. Video provided by Buzz60
Powered by NewsLook.com
N.Y. Snowfall Renews Climate Change Discussion

N.Y. Snowfall Renews Climate Change Discussion

Newsy (Nov. 20, 2014) — Record snowfalls in New York are helping to reinforce new climate catchphrases. 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:

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