Abstract
Abstract. The challenge of using satellite observations to retrieve aerosol properties in a cloudy environment is to prevent contamination of the aerosol signal from clouds, while maintaining sufficient aerosol product yield to satisfy specific applications. We investigate aerosol retrieval availability at different instrument pixel resolutions using the standard MODIS aerosol cloud mask applied to MODIS data and supplemented with a new GOES-R cloud mask applied to GOES data for a domain covering North America and surrounding oceans. Aerosol product availability is not the same as the cloud free fraction and takes into account the techniques used in the MODIS algorithm to avoid clouds, reduce noise and maintain sufficient numbers of aerosol retrievals. The inherent spatial resolution of each instrument, 0.5×0.5 km for MODIS and 1×1 km for GOES, is systematically degraded to 1×1, 2×2, 1×4, 4×4 and 8×8 km resolutions and then analyzed as to how that degradation would affect the availability of an aerosol retrieval, assuming an aerosol product resolution at 8×8 km. The analysis is repeated, separately, for near-nadir pixels and those at larger view angles to investigate the effect of pixel growth at oblique angles on aerosol retrieval availability. The results show that as nominal pixel size increases, availability decreases until at 8×8 km 70% to 85% of the retrievals available at 0.5 km, nadir, have been lost. The effect at oblique angles is to further decrease availability over land but increase availability over ocean, because sun glint is found at near-nadir view angles. Finer resolution sensors (i.e., 1×1, 2×2 or even 1×4 km) will retrieve aerosols in partly cloudy scenes significantly more often than sensors with nadir views of 4×4 km or coarser. Large differences in the results of the two cloud masks designed for MODIS aerosol and GOES cloud products strongly reinforce that cloud masks must be developed with specific purposes in mind and that a generic cloud mask applied to an independent aerosol retrieval will likely fail.
Highlights
Atmospheric aerosols are important short-lived climate forcing agents in Earth’s atmosphere
We explore the availability of an aerosol retrieval in a cloudy environment.Availability is defined as the number of product boxes available for aerosol retrieval divided by the total number of boxes in the region or time period of interest
Using the MODerate resolution Imaging Spectroradiometer (MODIS) aerosol cloud mask (Martins et al, 2002) applied to MODIS radiances, we explore the availability of an aerosol retrieval in a cloudy environment
Summary
Atmospheric aerosols are important short-lived climate forcing agents in Earth’s atmosphere. Remer et al.: Retrieving aerosol in a cloudy environment agencies and communities in mitigating and warning populations of potential dangers (Al-Saadi et al, 2005) Both climate and air quality applications require continual monitoring of aerosol loading over broad geographical regions. Even if interest is more regional, there is need for a more complete coverage and higher density of spatial sampling than a network of ground-based in situ monitoring stations can provide (Chu et al, 2003; Prados et al, 2007; Gupta and Christopher, 2009) Both these applications are increasingly relying on satellite retrievals of aerosol information to provide the observational constraints on models, offer new insights on aerosol distributions, and provide day-to-day coverage and accumulated statistics of aerosol properties (Stier et al, 2005; Yu et al, 2006; van Donkelaar et al, 2006, 2011). In the end we discuss the implications of these results to currently proposed satellite missions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
