Preprints
https://doi.org/10.5194/acp-2022-374
https://doi.org/10.5194/acp-2022-374
 
07 Jun 2022
07 Jun 2022
Status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

In Situ and Satellite-based Estimates of Cloud Properties and Aerosol-Cloud Interactions over the Southeast Atlantic Ocean

Siddhant Gupta1,2,a, Greg M. McFarquhar1,2, Joseph R. O'Brien3,b, Michael R. Poellot3, David J. Delene3, Ian Chang2, Lan Gao2, Feng Xu2, and Jens Redemann2 Siddhant Gupta et al.
  • 1Cooperative Institute for Severe and High-Impact Weather Research and Operations, University of Oklahoma, Norman, OK, USA
  • 2School of Meteorology, University of Oklahoma, Norman, OK, USA
  • 3Department of Atmospheric Sciences, University of North Dakota, Grand Forks, ND, USA
  • aBrookhaven National Laboratory, Upton, NY, USA
  • bArgonne National Laboratory, Lemont, IL, USA

Abstract. In situ cloud probe data from the NASA ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) field campaign were used to estimate effective radius (Re), cloud optical thickness (τ), and cloud droplet concentration (Nc) for marine stratocumulus over the southeast Atlantic Ocean. The in situ Re, τ, and Nc were compared with co-located Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals of Re and τ, and MODIS derived Nc. For 145 cloud profiles, a MODIS retrieval was co-located with in situ data with a time gap of less than 1 hour. On average, the MODIS Re and τ (11.3 μm and 11.7) were 1.6 μm and 2.3 higher than the in situ Re and τ with Pearson’s correlation coefficient (R) of 0.77 and 0.73, respectively. The average MODIS Nc (151.5 cm-3) was within 1 cm-3 of the average in situ Nc with R of 0.90.

The 145 cloud profiles were classified into 67 contact profiles where aerosol concentration (Na) greater than 500 cm-3 was sampled within 100 m above cloud tops and 78 separated profiles where Na less than 500 cm-3 was sampled up to 100 m above cloud tops. Contact profiles had higher in situ Nc (by 88 cm-3), higher τ (by 2.5) and lower in situ Re (by 2.2 μm) compared to separated profiles. These differences were associated with aerosol-cloud interactions (ACI) and MODIS estimates of the differences were within 5 cm-3, 0.5, and 0.2 μm of the in situ estimates when profiles with MODIS Re > 15 μm or MODIS τ > 25 were removed. The agreement between MODIS and in situ estimates of changes in Re, τ, and Nc associated with ACI was driven by low biases in MODIS retrievals of cloud properties across different aerosol regimes. Thus, when combined with estimates of aerosol location and concentration, MODIS retrievals of marine stratocumulus cloud properties over the southeast Atlantic can be used to study ACI over larger domains and longer timescales than possible using in situ data.

Siddhant Gupta et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-374', Anonymous Referee #1, 12 Jul 2022
    • AC1: 'Reply on RC1', Siddhant Gupta, 29 Aug 2022
  • RC2: 'Comment on acp-2022-374', Anonymous Referee #2, 13 Aug 2022
    • AC2: 'Reply on RC2', Siddhant Gupta, 29 Aug 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-374', Anonymous Referee #1, 12 Jul 2022
    • AC1: 'Reply on RC1', Siddhant Gupta, 29 Aug 2022
  • RC2: 'Comment on acp-2022-374', Anonymous Referee #2, 13 Aug 2022
    • AC2: 'Reply on RC2', Siddhant Gupta, 29 Aug 2022

Siddhant Gupta et al.

Data sets

Suite of Aerosol, Cloud, and Related Data Acquired Aboard P3 During ORACLES 2016, Version 2 ORACLES Science Team https://doi.org/10.5067/Suborbital/ORACLES/P3/2016_V2

Suite of Aerosol, Cloud, and Related Data Acquired Aboard P3 During ORACLES 2017, Version 2 ORACLES Science Team https://doi.org/10.5067/Suborbital/ORACLES/P3/2017_V2

MODIS Atmosphere L2 Cloud Product (06_L2) Platnick, S., Ackerman, S., King, M., et al. http://dx.doi.org/10.5067/MODIS/MOD06_L2.061

Suite of Aerosol, Cloud, and Related Data Acquired Aboard P3 During ORACLES 2018, Version 2 ORACLES Science Team https://doi.org/10.5067/Suborbital/ORACLES/P3/2018_V2

Model code and software

University of Illinois/Oklahoma Optical Array Probe (OAP) Processing Software G. M. McFarquhar, J. A. Finlon, D. M. Stechman, W. Wu, R. C. Jackson, and M. Freer https://doi.org/10.5281/zenodo.1285969

Airborne Data Processing and Analysis Software Package (Version 3981) David J. Delene, A. Skow, J. O'Brien, N. Gapp, S. Wagner, K. Hibert, K. Sand, and G. Sova https://doi.org/10.5281/zenodo.3733448

Siddhant Gupta et al.

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Short summary
The ability of NASA’s Terra and Aqua satellites to retrieve cloud properties and estimate the changes in cloud properties due to aerosol-cloud interactions (ACI) was examined. There was good agreement between satellite retrievals and in-situ measurements over the southeast Atlantic Ocean. This suggests that, combined with information on aerosol properties, satellite retrievals of cloud properties can be used to study ACI over larger domains and longer timescales in the absence of in situ data.
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