The Effects of Middle and Upper Tropospheric Relative Humidity on Microbursts

Microbursts are intense downdrafts that spread out at the surface, resulting in strong winds that can have negative impacts on aviation. Several studies have been conducted on environmental factors that contribute to microbursts, but most are focused on these characteristics in the boundary layer. This study will focus on the importance of relative humidity in the middle and upper troposphere for a thunderstorm to generate a microburst using a series of large eddy simulations (LESs). Relative humidity (RH) values in the middle and upper troposphere were varied among simulations to assess the impact of RH on microburst characteristics. We identified microbursts in these simulations as regions of downward velocity exceeding a threshold of 10 m/s, consistent with definitions in past literature. Simulations showed that higher relative humidity values led to increased precipitation rates and condensate loading, increasing the frequency of microburst activity. This suggests that microburst activity is not only dependent on the low-level environment, but also indirectly dependent on the moisture of the free troposphere. This study could be expanded to vary rates of evaporative cooling to see how much of an impact it has on downbursts.