Researchers from KU’s ENGEOS Lab carried out the first fog microphysics measurements over the UAE, filling a gap in the existing studies of fog microphysics and contributing to region-specific prediction models that can help mitigate the impact that fog can have on society

Despite being a desert country, the UAE has all the necessary ingredients for fog, seeing up to 50 foggy nights per year. Dry desert conditions exist next to the warm seas of the Gulf, with moist air carried inland by the afternoon sea breeze cooled by the desert surface at night. This type of fog is known as radiation fog.

Fog can be considered a low-lying cloud; it’s a visible aerosol of miniscule water droplets hovering above the ground. This aerosol impacts visibility and can have a major impact on societal activities, particularly transportation, where low visibility can result in flight delays or create hazardous driving conditions.

Dr. Michael Weston, Dr. Diana Francis, Dr. Narendra Nelli, Dr. Ricardo Fonseca, Dr. Marouane Temimi and Dr. Yacine Addad published their results in the

“Fog microphysics characteristics play a key role in fog life cycle, radiation and visibility,” Dr. Francis said. “Measurements of fog microphysics are important to understand and improve existing model parameter schemes for more accurate fog forecasting. We carried out the first fog microphysics measurements over the UAE, where fog is a frequent occurrence in the winter months. The results from this study are the first of their kind in the region, and expected to advance our current knowledge on fog dynamics and characteristics.”

Once fog develops, it will persist for as long as moisture can continue to condense out of the air. When the condensation process is slowed by rising temperatures or other factors, the fog will begin to dissipate. Much of the fog seen in the UAE is radiation fog, but some develops via a different mechanism known as advection fog. This type of fog forms over the surrounding seas and moves over the UAE. Regardless of the type of fog, when the sun rises and warms the country in the morning, the fog dissipates.

“The stages of fog from onset, to maturation, and finally dissipation, are dependent on the complex interactions of droplet microphysics, aerosol chemistry, radiation, turbulence, and surface conditions,” Dr. Francis said. “For example, the number of fog droplets gives an indication of the number of activated cloud condensation nuclei, which is an important interaction in understanding fog onset and persistence.”

The research team collected the microphysical measurements of fog in the UAE from 28 January to 17 February 2021. These measurements are novel as they were collected at a site next to a warm water body and in an arid subtropical region. While fog microphysics have been reported for arid regions, they are normally associated with cold oceans located on the western coast of continents. The team’s results fill a gap in the existing studies of fog microphysics.

“Knowing the microphysical properties of fog helps in developing a more accurate forecast of the fog life cycle,” Dr. Francis said. “Previously, we were applying the generally known properties of fog because we didn’t have information on fog microphysics in the UAE available to us.”

To understand what’s happening during foggy periods, forecasters need to know the aerosol content and quantity in the atmosphere to determine the number of cloud droplets that will form around the aerosols.

The depth of the fog and the resulting reduction in visibility depends on the number of droplets that form, but research has shown that neither the number of fog droplets nor their shape remains constant during the different stages of the fog lifecycle.

For numerical prediction models to reflect these processes, the fundamental properties of the single droplets and aerosol particles must be considered.

The team’s results are useful for future work on fog harvesting as knowing the microphysical properties of fog droplets helps in the design of fog harvesting systems.  The current observations are the first part of a long-term data set on fog microphysics for this region and future measurements are planned for the next winter season in the UAE.

Jade Sterling
Science Writer
22 March 2022

The post KU Researchers Making Fog Forecasting Models More Precise in the UAE appeared first on Khalifa University.

A Khalifa University team has found warming global temperatures may be making springtime rainfall last longer in the UAE, and possibly become more common. 

A team from the Khalifa University Environmental and Geophysical Sciences Lab (ENGEOS) investigated spring season rain in the UAE, finding a positive trend over the past 20 years. Meaning, more rain is occurring during the spring now than in previous decades.

To better predict and model these rainy days, the team characterized the atmospheric conditions that favor their occurrence and explained that springtime rain will be more likely in the future as the global climate continues to warm and the global water cycle accelerates.

Additionally, globally averaged rainfall has increased since 1950, with human influence likely contributing to this.

A warmer atmosphere can hold more water, noted Dr. Francis, the senior author on the study, meaning rainfall can last longer. While this can be beneficial to a region known for its lack of rain, it can also be detrimental, since much of the city infrastructure is not designed to handle large amounts of rainfall.

Dr. Narendra Nelli, Postdoctoral Fellow, Dr. Diana Francis, Senior Research Scientist and Head of the ENGEOS Lab, Dr. Ricardo Fonseca, Postdoctoral Fellow, Dr. Rachid Abida, Research Scientist, Michael Weston, Research Engineer, Dr. Youssef Wehbe, Graduate Research and Teaching Assistant, and Taha Al Hosary from the UAE National Center of Meteorology, analyzed 95 springtime rain events that affected the UAE between 2000 and 2020. They published their findings in.

These systems are known as mesoscale convective systems (MCS). An MCS is a cluster of storms that moves as a single system. For one to develop in a hyper arid environment like the UAE, a combination of factors ranging from local to regional scale is needed, including a steep temperature gradient on the ground between the land and the surrounding seas. If cold air from the sea meets hot air from the desert, there is potential for an MCS to form.

“In arid regions, MCSs account for most of the annual rainfall and are associated with heavy rain that can cause flooding, landslides, and associated disruption to daily life,” Dr. Nelli said. “Past extreme weather events over the Arabian Peninsula have had devastating impacts on the local population so understanding how they start and develop is crucial for better simulation and prediction of future events and impact.”

despite their large contribution to the total amount of rain per year. What’s more, Dr. Nelli said, they may occur more frequently under a warmer climate.

The study found that MCSs occurring in spring over the UAE are large-scale features of the global water cycle which drifts over the UAE, contrary to summertime MCSs which develops locally over the UAE.

The study highlighted that the duration of these springtime MCS is becoming longer and the resulting amount of rain larger.

A better understanding of what causes MCSs in a region known for its aridity is an important step toward accurately predicting them and benefit from their associated rainfall, especially as they are expected to become more frequent as the global climate changes, Dr. Nelli said. 

Jade Sterling
Science Writer
28 September 2021

The post More UAE Rain in the Springtime as Climate Change Impacts Local Weather Patterns appeared first on Khalifa University.