An agricultural aircraft flies over Prachuab Khirikhan in a bid to seed clouds, about 300 km (186 miles) south of Bangkok, April 4, 2007. REUTERS/Sukree Sukplang An agricultural aircraft flies over Prachuab Khirikhan in a bid to seed clouds, about 300 km (186 miles) south of Bangkok, April 4, 2007. REUTERS/Sukree Sukplang

When the Rains Come

Wed, Mar. 27, 2019
Climate change has been taking its toll on many countries, and a main concern is its impact on the consistency and predictability of rainfall. But recently, to balance things out, more than 50 countries have been using cloud seeding programs, according to the World Meteorological Organization (WMO), and the numbers have been increasing in the past five years. The number rose from 47 in 2013, to 52 in 2015, and then 56 in 2016. Countries with active cloud seeding programs include the US, Canada, China, Russia, India, Indonesia, the UAE and several Latin American and European countries.

The technology may soon be adopted in Egypt, as the Head of the Egyptian Meteorological Authority Ahmed Abdel tells Business Today Egypt that a feasibility study and a review of application possibilities of cloud seeding in Egypt are underway.

As global warming leads to a hike in heat-trapping greenhouse gases, heavier rainfall and snow and a higher risk of flooding have been recorded. Research shows that in areas where the air is very hot, we can expect longer spans of drought, and then shorter periods of heavy rains. In Egypt, rainfall varies between 2 millimeters per year in desert areas, to 180 millimeters per year in the North Coast, according to a “The Future Impact of Climate Change on Egyptian Population.” The report maintains that, “The first impact of climate change in Egypt is likely to be felt in the water domain. Water is already a limited resource, with per capita share at the edge of poverty line, below 1000m3 per year. . . . . Both water supply and demand are expected to be [affected] by climate change. It is expected by 2050 that climate change will raise water demand by an average of 5% [and] agriculture will be the most affected economic sector from the shortage of water, consum[ing] 80% of the water budget.”

Abdel Aal explains that the impact of climate change in Egypt is most evident in high temperature, but that rain would not increase as the heat is in the core of the Earth, and not its atmosphere, which means that precipitation over coasts driven by surface evaporation wouldn’t increase with rising temperatures. He affirms, however, that global warming would reduce the frequency of rainfall in Egypt, but make it more intense.

What Is Cloud Seeding?

Cloud seeding means adding “aerosol particles” to the cloud that compete with the naturally existing ones. These small particles are suspended in the atmosphere and range in size from a few nanometers, up to tens of micrometers. They are essential for cloud formation because they function as the surface on which liquid or solid condensation is initialized.

The cloud seeding process is carried out by aircraft, artillery shells and small-sized rockets, special high-altitude fireworks (ejected up to 200 meters in the atmosphere) or from ground-based generators. “The most common seeding material is silver iodide (AgI), which nucleates ice particles at temperatures below about -5 ° C,” according to the WMO’s “Peer Review Report on Global Precipitation Enhancement Activities.” The process can be improved by adding common salt.

As mountains force moist air to rise, contributing to cloud formation and rainfall, spreading ice particles above in the atmosphere along with other substances have given “encouraging results,” according to WMO’s “Peer Review Report on Global Precipitation Enhancement Activities.” The process, known as glaciogenic cloud seeding, produces best results when implementing silver iodide aircraft seeding of clouds that have a natural tendency for precipitation formation, according to the 2018 report. The parameters used to measure the success of the seeding are the stability of the flow over a mountain, the geometry of the mountain, the temperature and stratification of the deeper atmosphere.

Cloud seeding mainly targets two types of clouds in mid-latitude. The first is called frontal systems, where clouds form outside the tropics, most commonly near the mountains peaks during winter. The second type is called liquid or mix-phased convective cloud systems, where clouds form in tropical and subtropical areas in summertime. Those are often intertwined with surface heating, and can be subject to influences by orography (mountain features and formation), as well as convergence of air zones.

In August 2016, the Egyptian Meteorological Authority held a conference and a workshop in collaboration with the German Company WeatherTech under the auspices of the Ministry of Civil Aviation to study how cloud seeding can be implemented in Egypt having an annual amount of precipitation of 1.3 billion cubic meters.

The project should have been officially announced by December of the same year as a committee comprising representatives from the ministries of irrigation, agriculture, environment, and defense would have finished the feasibility study. However, no news on the project has come through since then.

The areas nominated by WeatherTech to implement the project are the Delta and the North Coast. Regardless, the committee would have the final say on the locations as various factors must be taken into consideration such as the suitability of infrastructure in those zones. Southern parts of the country along with moist areas can be included in the project, according to media reports.

The UAE Model

The National Centre for Meteorology (NCM) at the Gulf country - where the annual rainfall rate is around 100 mm - estimates that cloud seeding can boost rainfall by 30-35% in a clean atmosphere, and by up to 10-15% in a dusty atmosphere like the UAE’s.

The NCM started seeding in the 1990s, collaborating in the following decade with NASA and the National Centre for Atmospheric Research in the US. The institution executed 242 and 177 missions in the years 2017 and 2016 respectively.

In the morning after cloud observation by meteorologists, a pilot positions a twin-propeller beneath a cloud base firing salt flares attached to the wings. These flares are composed of potassium chloride (70%), and sodium chloride (13%), in addition to other substances that include magnesium (5%) to control the flame. Both potassium chloride and sodium chloride attract water droplets, and it takes two to three minutes to fire the flares, and 20 minutes to take effect. Convective clouds are detected by radars before cloud seeding, which is almost 60 times cheaper than desalination, is executed. Operations are carried out by six planes four days a week from July to September.
 
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