The connection between desert dust and air pollution and the deadly flood that occurred at the beginning of the year in Tel Aviv has been revealed

In the disaster that happened on January 4, 2020, two people were killed in the elevator and many infrastructures were damaged. In the last week, two storms swept the coastal cities of Israel. Is the reason for the existence of these storms solely related to climate change? A study led by researchers from the Hebrew University and IDC Herzliya, found a fascinating synergy between several factors, including aerosols and dust particles, which may lead to lightning storms and rains that have increased recently in our region

Google article Prof. Yoav Yair from the School of Sustainability at the Interdisciplinary Center Herzliya and Dr. Barry Lin from the Institute of Earth Sciences at the Hebrew University of Jerusalem, Chinese Academy of Sciences, which was funded by the National Science Foundation and recently published in the "Journal of Geophysical Research", analyzed the factors that led to the extreme storm that happened on January 4 this year that caused a flood in Tel Aviv and a severe disaster in the south of the city. As I recall, Tel Aviv was flooded in the rainstorm of the beginning of the year, in just three hours, following an extremely unusual amount of precipitation (80 year record) which caused a complete collapse of the urban infrastructure, mainly in the city center and in the south. Many streets in the Florentine neighborhood and around Bloomfield Stadium quickly turned into rivers, and many cars were submerged by the flooding. Dozens of people needed medical treatment. During that storm they drowned Two young men in an elevator in a residential building, and the case shocked an entire country.

Last weekend Israel found itself again surprised by the amount of rain that hit the coastal cities throughout the country. Many cities were flooded, citizens were outraged at the infrastructures that are unable to cope with the heavy rains and a lot of damage was caused to public and private property. "Thus we find ourselves in the same bush every year with the beginning of the rainy season, that as a result of climate change the number of extreme rain events is only increasing with the amount of precipitation decreasing in short periods of time", was written in the local media. Is the reason only related to climate change?

Through a model they developed in their various studies, which included the use of the separation-of-variables technique, they succeeded Prof. Lin and Prof. Yair To understand in their new research to what extent the synergy between desert dust particles, air pollution by aerosols from continental and urban sources, affects the strength and nature of winter rainfall systems in the Israel region. The researchers performed a simulation of the atmospheric conditions that prevailed in the area during the disaster in January, in order to simulate the fatal event, and the results showed that it was the combination of urban pollution and desert dust that intensified the rate of lightning and the amount of precipitation over the city in that storm.

"The possible effect of urban pollution on lightning and rainfall was investigated using a sophisticated cloud model embedded in a weather forecast model. The cloud model took into account the influence of various dust sources, including desert dust. The day chosen for the simulation was one of the days with a large amount of lightning and even deadly floods observed in Israel in the Tel Aviv city area. The results showed that urban pollution intensifies the rate of lightning and the amount of precipitation over the city. We found that when large raindrops formed on large dust particles collided with small droplets formed on urban particulate pollution, intense lightning storms and downpours occurred in the area causing deadly flooding. Therefore, to predict the intensity of severe storms, forecasts need to take into account different sources of dust and pollution." written in the scientific article.

In other words, the researchers assumed that the rapid development of the storm in January manifested itself in very active electrical activity, with high amounts of lightning, thanks to those dust and pollution particles that were in the air in higher than normal quantities that resulted in very efficient charge separation processes and the creation of strong electric fields in the clouds. The real-time lightning observations collected from the ENTLN system (Israel Total Lightning Network which operates as part of the Earth Networks Total Lightning Network) and the pollution data collected from the detectors of the monitoring systems of the Ministry of Environmental Protection, made it possible to confirm the research hypothesis and the results of the model. "Understanding the relative effects of desert dust and air pollution may improve the forecast of such extreme events, the frequency of which will increase in the future due to climate change processes in the Middle East region", Dr. Lin explains.

At the beginning of November, a unique lightning storm raged in the Mediterranean sky, between the Sinai Peninsula and Cyprus, which according to the meteorological maps included amounts of tens of thousands of lightning, and no less than 15 "super-lightning" storms. Are such storms going to happen more and more in the coming years in our region? Are such storms expected to reach Israel's shores soon? "It is too early to determine this, but it is important that we listen to nature and learn lessons from these events. We have already counted seven cases of extremely intense lightning storms in the last three years, which is a non-negligible amount of storms in our region, and we as researchers are trying to understand, especially the initial conditions that cause these systems to develop." Prof. Yair clarifies. "The disaster in Nahal Tsafet and the electrocution to death of a 14 year old At Zikim Beach A year ago, as well as the extreme event in October 2015 in the center of the country, should make us all understand how dangerous such storms are. The huge storm that recently occurred in the Mediterranean Sea, at the beginning of the month, which fortunately did not come close to Israel's shores, could have been dangerous for the drilling rigs that are several tens of kilometers from the coast. I don't want to think about what might happen if lightning, God forbid, hits a rig or a ship or an airplane on its way to Israel."

In conclusion, Prof. Yair noted that with the help of the student Mordechai Yaffe from the Hebrew University who processed the rain and lightning data over several years, indications were found of the existence of the "weekend effect" in Israel, which states that there is a greater chance of rain and lightning storms in the middle of the week than on Friday-Saturday: "why? Because transportation is less active these days in Israel and therefore there is a decrease in the amount of particles in the air. In countries around the world, by the way, the effect is revealed mainly on Saturdays and Sundays, which are less busy with traffic. We estimate that the results of the study regarding the effect will be published in the near future."

for the scientific article

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