Spells of heavy rain that can cause flash flooding in the UAE have become longer lasting over the past two decades, a study has found.
Khalifa University of Science and Technology in Abu Dhabi and the National Centre of Meteorology (NCM), also in the UAE capital, found these events in the southeastern Arabian peninsula “may be even more impactful in a warming world”.
However, while they create the risk of floods, such episodes also offer opportunities in a country where precipitation is limited.
In a study recently published in the journal Atmospheric Research, scientists looked at mesoscale convective systems (MCSs), a weather pattern that most commonly causes severe weather in March or April.
They analysed 95 of these between 2000 and 2020, and found they were caused by particular wind patterns and moisture coming from the Arabian Sea, Arabian Gulf or Red Sea.
They looked at observational data and records from satellites, for example, and found that, over time, these events over the UAE were lasting longer.
Some of the most severe episodes happened in 2016 when there was severe flooding after more than 240mm of rain fell in Dubai, and Abu Dhabi experienced winds of nearly 80mph.
Climate change key to changing weather patterns
“We believe that global warming and climate change are likely responsible for the increase in the duration of MCSs over the study region,” said Dr Diana Francis, an author of the study.
Dr Francis, who heads the environmental and geophysical sciences laboratory at Khalifa University, said a warmer atmosphere could hold more water vapour, meaning extreme events last longer.
This ties in with the latest Intergovernmental Panel on Climate Change report which, Dr Francis said, “clearly identified … that there is an intensification of the global water cycle due to increased warming”.
“We would expect to see similar trends in the future with a possible additional increase in the strength of the MCSs and a resulting larger amount of rain,” said Dr Francis, who also recently identified a strengthening of a warm-weather system over the UAE called the Arabian heat low.
More rainfall to boost agriculture
While in many countries extreme weather is solely a danger to life and property, Dr Francis said arid nations such as the UAE, where many areas receive an average of less than 100mm of rain each year, should plan for benefits too.
“Rainwater storage strategies and water water evacuation plans in big cities need to be included in the country’s urban planning strategies to both avoid the damage from flooding, and benefit from the large amount of precipitation,” she said.
Cloud seeding proves successful
A separate study by NCM researchers evaluating the impact of the UAE’s cloud seeding programme has concluded that seeded areas experience an average of 23 per cent more rain.
The analysis was based on comparing rain gauge results without cloud seeding, recorded between 1981 and 2002, with those where cloud seeding took place, recorded between 2003 and 2019.
Previous studies elsewhere have indicated that cloud seeding does increase rainfall, although the question of whether it is effective is still debated.
In the new study, published in the journal Atmosphere, the NCM researchers, two of whom were also authors of the study Dr Francis was involved with, indicated their findings could influence whether cloud seeding work goes ahead in the UAE and similar areas in the future.
“The work provides new insights for assessing long-term seeding impacts and has significant implications for policy and decision-making related to cloud seeding research and operational programmes in arid regions,” they wrote.
Dr Francis said the seeding efficiency reported by the NCM researchers focused on summertime rain events linked to the development of local clouds and convection, which is the process by which heat and moisture moves vertically in the atmosphere.
The MCSs, by contrast, develop in the spring and are large-scale events associated with the global water cycle, so their formation and development cannot be affected by cloud seeding.
“However the amount of rain obtained from these systems can be increased by seeding the clouds associated with them once they reached over the UAE,” Dr Francis said.
