Correlation between marine aerosol optical properties and wind fields over remote oceans with use of spaceborne lidar observations
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.
Kangwen Sun et al.
Status: open (until 05 Jul 2023)
- RC1: 'Comment on egusphere-2023-433', Anonymous Referee #1, 04 Jun 2023 reply
Kangwen Sun et al.
Kangwen Sun et al.
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The paper makes an important contribution to the literature and can provide input to the modeling community regarding the sea-salt emissions.
Some minor comments before publication:
Using ECMWF model constraints for RH would not necessarily remove clouds from L2A measurements (it is well-known that clouds are not well-represented in models)
It is better to use marine particle depolarization at 355nm from the Delian model (Floutsi et al., 2023). Gross' paper reports depol values at 532nm (even though the difference is not large, 1.3 vs 2%).
CALIPSO cannot verify the presence of a specific aerosol type, since the aerosol type is inferred based on assumptions on the surface type. Even though the regions selected are dominated by marine particles, it is better to rephrase as it concerns CALIPSO and further validate through a global model that there are no other types present (e.g. from ship emissions).
In 4.2 the comparison of Aeolus with CALIPSO on extensive properties (a, b), should be restricted for backscatter only (CALIPSO cannot deliver extinction). Extinction could be evaluated against passive sensors such as MODIS AODs over the region.