Meet the Team

Navot continued our study of superbolts of lightning.  Superbolts are defined as the very strongest lightning flashes around the globe.  But how do you define a superbolt?  In the early years of satellite observations using optical sensors, superbolts were defined by their optical brightness.  More recently, they have been categorized by their radio EM signals.  Navot tried to compare the optical signals with the radio  signals of superbolts, and surprisingly we found little if any overlap between these superbolts of different definitions.

Ziv carried out research using the pressure sensors in smartphones.  These sensors are very sensitive with sampling rates of 1 Hz.  They measure the "weight" of the atmospheric column on the sensor, and hence are accurate both inside and outside buildings.  Ziv studied a number of storms using global data collected from smartphones around the globe.  She showed that smartphones can easily detect pressure changes due to hurricanes and extra-tropical storms.  She also showed that wind intensity can also be obtained using pressure gradients between different regions/smartphones.

Omri studied the link between air pollution and bats.  This was a joint project between Geophysics and Zoology, with Prof. Yosi Yovel.  Omri placed air pollution sensors in a number of bat colonies in Israel to monitor their activity during pollution events.  The bats were also sampled for blood Hemoglobin levels, and unsuprisingly we found that the Hemoglobin levels were lower in the bats that experience more air pollution.   This was the first quantitative study showing the impact of air pollution on bats.

Yanai studied superbolts of lightning, which are the most powerful lightning flashes on Earth.  Recently it was shown that when looking at the most intense lightning on the planet, using VLF radio methods, the eastern Mediterranean is a hotspot for superbolts.  Why?  Yanai attempted to understand why we have so many superbolts in our region of the globe.  Is this related to the special meteorology of winter storms that occur over the Mediterranean Sea?  Is it due to the salinity of the sea?  Something else?

Moran researched how the insurance industry in the United States will be impacted by future changes in Atlantic hurricanes due to climate change.  While the number of Atlantic hurricanes may not change in the future as a result of global warming, the intensities are predicted to increase dramatically.  Moran's modelling showed that US insurance agencies could possibly go brike by 2060 if nothing is done to curb climate change.  She suggests that the insurance industry should think of investing now in GHG mitigation to prevent the damages they will face in the future.

Maayan studied the relationship between VLF waveforms of lightning and infrasound signals from lightning.  While VLF waveforms from lightning are electromagnetic waves that travel over great distances (close to the speed of light), infrasound are pressure or acoustic waves that travel at the speed of sound, and hence arrive later than the VLF waves.  Taking into account the different propagation times, comparisons were made between the two types of signals produced by lightning.

Dekel studied the link between lightning activity in Israel and flash floods.  He looked at the spatial and temporal relationships between rainfall and lightning activity.  As expected we found a general positive correlation between thunderstorms with high rain rates, and thunderstorms with high lightning activity.  In particular, a sever flash flood that killed 10 youth on a hiking trip showed a lightnign jump before the flash flood occurred.

Tair studied the link between thunderstorms and upper tropospheric water  vapor (UTWV), a strong greenhouse gas. This was a joint Israel-India collaboration, using ELF and VLF lightning data.  Tair showed that tropical cyclones with lots of lightning activity also transported large amounts of water vapor into the upper troposphere.  This is an important climate feedback that could amplify surface warming if tropical cycles become stronger in the future.

Raam studied the long-term trends in thunderstorm activity over Africa and South America using ERA5 reanalysis data and an empirical model to estimate the number of thunderstorms based on large-scale meteorological data.  One surprising find from his research was that the deforestation in the Amazon over the past decades has resulted in a decrease in the number of thunderstorms over South America.  The reduction in forests results in the reduction in latent heat release from the surface, with a reduction in convection, clouds, lightning and precipitation.  This results in further drying of the region, and results in a positive feedback amplifying the drying trends.

Orly studyied the impact of sea level rise resulting from climate change on the coastlines of Israel.  Both past trends and future predictions, and the implications on the coastline infrastructures.  Orly developed a Coastal Vulnerability Index (CVI) for the Israeli coastlines, with an in depth analysis of the index for the Netanya coastline.  These CVIs depend on many factors from: rising sea levels, the wave heights during storms, the type of coastlines, vegetation, construction, infrastructures, and more.

Aviad carried out research related to the link between rainfall and lightning activity in thunderstorms.  Since rainfall is often a parameter difficult to measure in remote regions, while lightning is an easier paramter to monitor from great distances, finding relationships between lightning and rainfall may provide a proxy measurement for rainfall around the globe.  Aviad studied the relationship between rainfall and lightning using two independent satellite data sets.  The Global Lightning Mapper (GLM) and the Global Precipitation Mission (GPM).

Tamir carried out research on the ground level enhancement of gamma rays at the Mt. Hermon cosmic ray observatory.  In recent years long term (hours) enhancements of gamma radiation has been observed with ground detectors, and often associated with thunderstorms and stormy weather.  There are two hypotheses as to the source of these enhancements in gamma rays.  The first is from the high electric fields within the thunderstorms above the station, accelerating charged particles to relativistic speeds.  The second is the washout of radon daughters by the rain below the storms.  Tamir found that the majority of enhancements are associated with rainfall, but not all.

Uriel carried out research related to Space Weather.  This was a joint thesis under the supervision of Dr. Sari Katz (Soreq Nuclear Research Center) as well.  The research looked at satellite failures are malfunctions as a result of solar storms.  Uriel investigated many different satellite malfunctions, some published in the literature, others not.  He developed a empirical model to try to predict the type of damage to satellites based on different types of solar storms.

Maayan was studying the link between thunderstorms and climate change.  Using the clustering scheme of Keren Mezuman (above) we were looking at the link between regional temperatures, instabilities, water vapour, etc. and the number, size and intensity of thunderstorm clusters.  Will warmer temperatures result in more thunderstorms with the same intensity, less storms but more intense, or more storms that are also more intense?  Hopefully Maayan's research will allow us to better understand what may happen in the future to thunderstorms.