Airborne In-situ Measurements during JATAC/CAVA-AW 2021/2022 campaigns - First Climate-Relevant Results

Abstract

<div class="WordSection1"> <p class="paperabstract"><span lang="EN-US">The JATAC campaign in September 2021 and September 2022 on and above Cape Verde Islands have resulted in a large dataset of in-situ and remote measurements. In addition to the calibration/validation of the ESA’s Aeolus ALADIN during the campaign, the campaign also featured secondary scientific objectives related to climate change. The atmosphere above the Atlantic Ocean off the coast of West Africa is ideal for the study of the Saharan Aerosol layer (SAL), the long-range transport of dust, and the regional influence of SAL aerosols on the climate.</span></p> <p class="paperabstract"><span lang="EN-US">We have instrumented a light aircraft (Advantic WT-10) with instrumentation for the in-situ aerosol characterization. Ten flights were conducted over the Atlantic Ocean up to over 3000 m above sea level during two intense dust transport events. PollyXT</span><span lang="EL">, and </span><span lang="EN-US">EvE lidars were deployed at the Ocean Science Center, measuring the vertical optical properties of aerosols and were also used to plan the flights.</span></p> <p class="paperabstract"><span lang="EN-US">The particle light absorption coefficient was determined at three different wavelengths with Continuous Light Absorption Photometers (CLAP). They were calibrated with the dual wavelength photo-thermal interferometric measurement of the aerosol light-absorption coefficient in the laboratory. The particle size distributions above 0.3 µm diameter were measured with two Grimm 11-D Optical Particle Size Spectrometers (OPSS). These measurements were conducted separately for the fine aerosol fraction and the enriched coarse fraction using an isokinetic inlet and a pseudo-virtual impactor, respectively. </span></p> <p class="paperabstract"><span lang="EN-US">The aerosol light scattering and backscattering coefficients were measured with an Ecotech Aurora 4000 nephelometer. The instrument used a separate isokinetic inlet and was calibrated prior to and its calibration validated after the campaign with CO2. We have measured the total and diffuse solar irradiance with a DeltaT SPN1 pyranometer. CO2 concentration, temperature, aircraft GPS position altitude, air and ground speed were also measured.</span></p> <p class="paperabstract"><span lang="EN-US">The in-situ single-scattering albedo Angstrom exponent and the lidar depolarization ratio will be compared as two independent parameters indicating the presence of Saharan dust. We will show differences between homogeneous Saharan dust layer in space (horizontally and vertically) and time and events featuring strong horizontal gradients in aerosol composition and concentration, and layering in the vertical direction. These layers often less than 100 m thick, separated by layers of air with no dust. </span></p> <p class="paperabstract"><span lang="EN-US">Complex mixtures of aerosols in the outflow of Saharan dust over the Atlantic Ocean in the tropics will be characterized. We will show the in-situ atmospheric heating/cooling rate and provide insight into the regional and local effects of this heating of the dust layers. These measurements will support of the research on evolution, dynamics, and predictability of tropical weather systems and provide input into and verification of the climate models.</span></p> </div>

An Overview of the ASKOS Campaign in Cabo Verde

“…Particles within the dust layers were collected through impactor samples onboard the UAVs [5]. In September 2021 and 2022, the JATAC CAWA-AW component [6] conducted 10 light aircraft flights equipped with continuous light absorption photometers (CLAPs) providing measurements of particle light absorption coefficient at three wavelengths, optical particle size spectrometers (OPSSs) for particle size distributions above 0.3 µm diameter separately for fine and coarse mode, a nephelometer for aerosol light scattering and backscattering coefficients, and a pyranometer for the total and diffuse solar irradiance. The light aircraft and the UAVs collected in situ measurements at 0-3 km and 0-5 km above sea level (ASL), respectively, collocated with the ASKOS remote sensing measurements.…”