Correlation between marine aerosol optical properties and wind fields over remote oceans with use of spaceborne lidar observations

Abstract

Abstract. By utilizing Level 2A products (particle optical properties and numerical weather prediction data) and Level 2C products (numerical weather prediction wind vector assimilated with observed wind component) provided by the Atmospheric Laser Doppler Instrument (ALADIN) onboard the Aeolus mission, and Level 2 vertical feature mask (VFM) products provided by Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission, three remote ocean areas are selected and the optical properties at 355 nm of marine aerosol are derived. The combined analysis of marine aerosol optical properties at 355 nm and instantaneous co-located wind speeds above the remote ocean areas are conducted. Eventually their relationships are explored and discussed at two sperate vertical atmospheric layers (0–1 km and 1–2 km, correspond to the heights within and above marine atmospheric boundary layer (MABL)), revealing the marine aerosol related atmospheric background states. Pure marine aerosol optical properties at 355 nm are obtained after quality control, cloud screening and backscatter coefficient correction from the ALADIN observations. The spatial distributions of marine aerosol optical properties and wind speed above the study areas are presented and analysed, respectively, at two vertical layers. The statistical results of the marine aerosol optical properties along with the wind speed grids at two vertical layers together with the corresponding regression curves fitted by power law functions are acquired and analysed, for each remote ocean area. The optical properties present increasing trends with wind speed in all cases, implying that the atmosphere of the two vertical layers will both receive the marine aerosol input produced and transported by the wind and the turbulence. The marine aerosol enhancement caused by the wind speed at the lower layer is more intensive than at the higher layer. As derived data from ALADIN, the averaged marine aerosol optical depth (AODmar) and the averaged marine aerosol lidar ratio (LRmar) at 355 nm are acquired and discussed along the wind speed range. The marine aerosol optical properties distributions, wind speed bins, and the marine aerosol variation tendencies along wind speed above the individual study areas are not totally similar, implying that the development and evolution of the marine aerosol above the ocean might not only be dominated by the drive of the wind, but also be impacted by other meteorological and environmental factors, e.g., atmospheric stability, sea and air temperature, or relative humidity. Combined analysis on the aerosol optical properties and wind with additional atmospheric parameters above the ocean might be capable to provide more detailed information of marine aerosol production, entrainment, transport and removal.

HSRL-2 Retrievals of Ocean Surface Wind Speeds

“…Although CALIPSO retrievals of surface wind speeds have been used in many studies (e.g., Hu et al, 2008;Josset et al, 2010a;Josset et al, 2010b;Kiliyanpilakkil and Meskhidze, 2011;Nair and Rajeev, 2014;Murphy and Hu, 2021;Sun et al, 2023), the main drawback is that one must have an accurate calibration of the measured ocean surface reflectance. This presents a difficulty for elastic backscatter lidars like CALIPSO, for which the signal is typically calibrated high in the atmosphere where molecular backscatter dominates and aerosol backscatter is insignificant or can be accurately estimated.…”

Characterisation of dust aerosols from ALADIN and CALIOP measurements

“…Additionally, ALADIN's Level-2 backscatter and extinction coefficients are subject to independent Quality Control (QC) procedures. Despite these challenges, it has been demonstrated that ALADIN is capable of retrieving lidar ratios from smoke (Baars et al, 2021), dust (Flament et al, 2021) and marine aerosols (Sun et al, 2023).…”