Climatology of aerosol and cloud properties observed by multiple LIDAR systems at the ARM ENA site

Remote sensing observations from LIDARs are crucial for understanding atmospheric processes in the boundary layer and the troposphere. The Atmospheric Radiation Measurement (ARM) user facility (https://www.arm.gov/) operates comprehensive suites of instruments to collect in-situ and remote sensing observations for research on Earth system sciences from multiple sites worldwide. Here, we present aerosol and cloud properties retrieved from the ARM Raman Lidar, Doppler Lidar, and Ceilometer observations at the Eastern North Atlantic (ENA) site on Graciosa Island in the Azores, located in the northeastern Atlantic Ocean west of Portugal. Aerosol light extinction at 355 nm is retrieved using the Raman Lidar Feature detection and EXtinction (RLFEX) retrieval algorithm (https://www.arm.gov/publications/tech_reports/doe-sc-arm-tr-224.pdf). Particulate extinction and cloud base height (CBH) are observed with Raman Lidar, while CBH is also measured with Doppler Lidar and Ceilometer at the same site. All available observations from 2015 to the present are used to develop the climatology of particulate extinction and cloud base altitudes. Diurnal and seasonal variations in aerosols and clouds are observed by all LIDARs. The highest extinction is observed in March-April during the afternoon hours, while the lowest cloud base altitude is recorded in July during the late morning. The seasonal and diurnal patterns observed by all LIDARs and Sun-photometer are consistent and closely aligned. Detailed results on aerosol extinction, optical depth, and CBH will be presented to better understand the atmospheric processes over the ARM ENA site.