In 2018, the Atmospheric Radiation Measurement Aerial Facility (AAF) deployed its G-1 research aircraft to the Sierras de Córdoba mountain range in north-central Argentina to support the research of environmental factors on deep convective cycles as part of the Cloud, Aerosol, and Complex Terrain Interactions (CACTI) field campaign. The aircraft was fitted with a suite of instruments to holistically measure in situ the current state of the atmosphere. In this study, we organize the campaign’s 22 flights by environmental conditions. Data from each flight was transected by the aircraft’s position relative to cloud, allowing for in depth analysis of cloud processing on aerosol populations. My project was a case study of selected flights where warm, shallow orographic cumulus clouds were observed.
During my time at PNNL, I worked towards my goals for the internship, which were both professional and educational goals. I learned about some of the instruments AAF uses on their aircraft campaign and utilized data from those instruments to perform my analysis. I improved my skills in the programming language Python. I gained the confidence to analyze data critically and independently, which has further encouraged and prepared me for graduate school level research. I also met many amazing scientists at PNNL.
II INTRODUCTION
Climate models are used to predict future climate and study processes that occur to better understand the climate system. Aerosols are solid or liquid particles suspended in the atmosphere. The biggest uncertainty in climate models are clouds and how aerosols can interact with and impact clouds1. The uncertainty from climate models is largely due to geographically limited datasets. Instrumentation is necessary to quantify the number of aerosols in the atmosphere. A large fraction of aircraft data is collected in the northern hemisphere. Most aircraft campaigns are away from severe storms due to dangerous atmospheric conditions or are over oceans that have horizontally uniform clouds.
Aerosols have a direct effect on the amount of radiation absorbed on Earth’s surface and an effect on clouds2,3. A fraction of aerosols, called cloud condensation nuclei (CCN), are needed for water to condense on to form cloud droplets. The number of aerosols in clouds is one factor that determines how long a cloud’s lifetime is and if a cloud will precipitate or not4 .The more aerosols that are in a cloud, the smaller the droplets and smaller droplets are less likely to precipitate because they cannot get large enough to precipitate 2. Climate models that model cloud and aerosol interactions have uncertainty regarding aerosol concentrations.
While we can observe aerosols from the surface, which is cheaper and easier to operate, it is important to consider where aerosols are vertically. Where the aerosols are vertically determines their atmospheric lifetime, which extends their spatial and temporal effect on the climate. Aerosols in the boundary layer, the layer in the atmosphere that is in contact with the surface, have a shorter lifetime, in the scale of hours, than in the free troposphere which is on a scale of days to weeks to months5. Aerosols in the boundary layer are the ones interacting with clouds. However, aerosols in the free troposphere can transport across the world and can get pulled into the boundary layer if there are strong vertical winds. Only in-situ measurements can give the true picture of where aerosols are vertically.
In 2018, the Department of Energy’s Atmospheric Radiation Measurement (ARM) group conducted the Cloud, Aerosol, and Complex Terrain Interactions (CACTI) to study environmental factors on deep convective cycles in north-central Argentina. The campaign included the use of the ARM Mobile Facility (ARM) ground site as well as the use of the ARM Aerial Facility’s (AAF) G-1 research aircraft. While the campaign was conducted for a total of 6 months, the aircraft flew for an intensive period of 6 week