Observation of cloud formation caused by low-level jets

Abstract:

We present the results of analyses performed on high-resolution remotely-sensed and in situ atmospheric measurements of the boundary layer and lower atmosphere centered over the northeast coast of the Hampton Roads body of water in southeast Virginia. This region is adjacent to the confluence of the Chesapeake Bay and the Atlantic Ocean where often times, low-level jets (LLJs) are found in the boundary layer during summer months. An East Hampton Roads Aerosol Flux (EHRAF) campaign, was conducted from the campus of Hampton University (HU) to examine small-scale aerosol transport using aerosol, Raman, and Doppler lidars, as well as rawindsondes over a one-week period in May 2014 . LLJs were observed from evening of 20 May to the morning of 21 May, and were found to lead to cloud formation. In this paper, the cloud formation caused by LLJs is analyzed using data that includes high-resolution profiles of: aerosol backscatter, turbulence structure, temperature, wind speed and direction, and water vapor. It is found that enhanced nighttime turbulence triggered by LLJs causes the aerosol and water vapor content of boundary layer to be lifted up forming a well-mixed region. We show that this region contains the cloud condensation nuclei that are very important for the formation of clouds.