Abu Dhabi: The National Centre of Meteorology (NCM) hosted a virtual session titled ‘Direct and Indirect Effect of Dust on Rainfall’ as part of the ‘Rain Enhancement Hub’ webinar series organised by the UAE Research Programme for Rain Enhancement Science (UAEREP).
Dr. Sagar P. Parajuli, a research scientist at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, presented his investigations of the direct and indirect effect of dust over the Red Sea coast using high-resolution (1.5x1.5 km) WRF-Chem model simulations.
Reflecting its status as a global rain enhancement science and innovation hub, the UAEREP is presenting the latest advances in knowledge from international experts, scientists, and researchers in a series of interactive webinar sessions that are covering all aspects of rain enhancement and weather modification research.
The paper was then followed by a discussion on the impact of dust on rainfall distributions across the Middle East and North Africa (MENA) region and potential use of rain enhancement techniques to replenish depleted surface water and groundwater resources. While it has long been established by scientists that interactions between clouds and atmospheric aerosol particle such as dust create condensation, much more research is needed to understand this process.
Cutting-edge insights
Dr. Abdulla Al Mandous, director of NCM and president of the Regional Association II (Asia) of the World Meteorological Organisation (WMO), said: “We are proud to host our UAEREP’s Rain Enhancement Hub webinar series as a means of sharing cutting-edge insights and from leading experts working on rain enhancement and water sustainability.”
“Our fifth session in the series demonstrates the NCM’s leading role in enhancing our understanding of atmospheric phenomena such as dust by drawing on the latest research from international experts. Through its commitment and success in bringing together the best minds in this field, the UAE is leading global efforts to develop new sources of water to replenish depleted groundwater sources and secure this precious resource for the benefit of future generations.”
Alya Al Mazroui, director of the UAE Research Programme for Rain Enhancement Science, said: “This webinar gave participants an excellent opportunity to discuss to the effects of dust on rainfall and enhance our understanding of how this phenomenon impacts on weather patterns. The UAEREP is leading the way in developing the new science and technologies need to boost water security for vulnerable populations around the world. As a hub for a global research network, the Programme is also facilitating the knowledge transfers needed to nurture new innovations and secure a sustainable future.”
Far-reaching impact
Atmospheric dust is one of a range of aerosol particles naturally found in cloud formations. Once dust has been lifted into the upper atmosphere the particles can be widely distributed: for instance, mineral dust from the Sahara Desert and China has been detected in rainwater collected as far away as California in the US.
Dr. Parajuli’s investigations of the effects of dust over the Red Sea Coast covered an area where rainfall was very predictable due to local moisture availability being governed by recurring sea breezes. The study found that there was up to ten-fold increase of dust-cloud interaction, making dust a major factor in local precipitation patterns.
Direct effect
The ‘direct effect’ of dust, which depended on the local circulation of the sea breezes, was found to suppress rainfall for normal rain events due to cooling, while enhancing precipitation during extreme rain events through a warming effect.
Indirect effect
Atmospheric dust had an ‘indirect effect’ through droplet growth, as high dust concentration led to cloud droplets growing in the presence of sufficient moisture. Dr. Parajuli’s research found that while dust might be a threat to air quality, atmospheric particles could also positively contribute to modulating rain.
Further study could enhance our understanding of extreme rainfall events and minimise the risk of heavy flooding and loss of public property. In terms of rain enhancement, Dr. Parajuli’s project suggests that the presence of background dust aerosols in dusty regions must be considered. Therefore, targeted modelling experiments for cloud-seeding applications could take into account the location and height of the injection of seeding particles when dust was already present.
