Evaluating the U.A.E.’s Orographic Cloud Seeding Techniques: A Comprehensive Analysis of Cloud Seeding Microphysics and Particle Microstructures.

Divraj Singh

doi:10.32388/rk9jx2.3

Abstract

Although our knowledge of cloud seeding techniques has increased substantially over the past few decades, there remains a lack of overview of its efficacy and procedures across spatial scales. (1) In this paper, we analyze the 219 cloud seeding events conducted by the U.A.E.’s National Center Of Meteorology. (2) These events aimed to improve agriculture and mitigate the negative effects of summer drought. We analyze the microstructures of cloud particles and the microphysics of air volume and sediment interaction to identify which of the U.A.E.’s cloud seeding techniques were most efficient. First, we evaluate the conditions conducive to cloud condensation nuclei (CCN) formation through the collision-coalesce model and nucleation. Second, we consider cloud particle sedimentation, collision rates and aerosol concentrations to explain cloud behavior and cloud stability during seeding. Third, we analyze the surface tension of spherical particles and how they affect CCN grouping and collision success. Lastly, we examine current static, hygroscopic, dynamic and nanotechnology cloud seeding techniques implemented globally and identify which techniques are most suitable for the U.A.E. to adopt. We find that given the natural U.A.E. climate and the safety concerns associated with uncertain nature of emerging cloud seeding technology, it is best to use non-chemical hygroscopic methods to maximize condensation and rainfall in a sustainable way.

Highlights

Our knowledge of cloud seeding techniques has increased substantially over the past few decades, there remains a lack of overview of its efficacy and procedures across spatial scales. (1) In this paper, we analyze the 219 cloud seeding events conducted by the U.A.E.’s National Center Of Meteorology. (2) These events aimed to improve agriculture and mitigate the negative effects of summer drought
We analyze the microstructures of cloud particles and the microphysics of air volume and sediment interaction to identify which of the U.A.E.’s cloud seeding techniques were most efficient
We find that given the natural U.A.E. climate and the safety concerns associated with uncertain nature of emerging cloud seeding technology, it is best to use non-chemical hygroscopic methods to maximize condensation and rainfall in a sustainable way

Summary

Cloud Formation and the Microphysics and Microstructure of Clouds

When hot air rises up into the atmosphere, it carries water vapor up with it. As this air cools and the atmospheric pressure drops, this vapor becomes small water droplets or ice crystals that come together to form a cloud. The most common way relative humidity builds up is through water vapor condensing upon particles of dust, pollen, or other condensation nuclei Another way clouds form includes the collision of two large mass of air (especially warm and cold air mass) near the Earth's surface, which forces the warm air mass to rise and form a cloud. Cloud microphysics involves studying the aqueous (water-like) particles that make up a cloud, their classification, and the way they change with time These particles, either liquid or solid (ice), vary significantly in size and shape. There are two processes by which water mass enters or leaves a particular air volume – 1) atmospheric motions carrying vapor at a rate r*-1 and 2) cloud particles falling fast relative to this air. The ‘mixed-phase’ of a cloud is when both liquid and solid water is present simultaneously (between the melting level 0 °C and −40 °C i.e. the practical lower limit for liquid water to exist in the supercooled’ state). (8)

Droplet Formation

Technological Advances in Cloud Microphysics

Cloud Seeding Techniques

Findings

Conclusion and Limitations