Abstract
Abstract. Cloud occurrence, microphysical and optical properties, and atmospheric profiles within a subtropical cloud regime transition in the northeastern Pacific Ocean are obtained from a synergistic combination of the Atmospheric Infrared Sounder (AIRS) and the MODerate resolution Imaging Spectroradiometer (MODIS). The observed cloud parameters and atmospheric thermodynamic profile retrievals are binned by cloud type and analyzed based on their probability density functions (PDFs). Comparison of the PDFs to data from the European Centre for Medium Range Weather Forecasting reanalysis (ERA-Interim) shows a strong difference in the occurrence of the different cloud types compared to clear sky. An increasing non-Gaussian behavior is observed in cloud optical thickness (τc), effective radius (re) and cloud-top temperature (Tc) distributions from stratocumulus to trade cumulus, while decreasing values of lower-tropospheric stability are seen. However, variations in the mean, width and shape of the distributions are found. The AIRS potential temperature (θ) and water vapor (q) profiles in the presence of varying marine boundary layer (MBL) cloud types show overall similarities to the ERA-Interim in the mean profiles, but differences arise in the higher moments at some altitudes. The differences between the PDFs from AIRS+MODIS and ERA-Interim make it possible to pinpoint systematic errors in both systems and help to understand joint PDFs of cloud properties and coincident thermodynamic profiles from satellite observations.
Highlights
Earth’s cloud types are highly variable in both their frequency of occurrence and optical properties, and have strong relevance to climate sensitivity
The occurrence for Atmospheric Infrared Sounder (AIRS)/MODerate resolution Imaging Spectroradiometer (MODIS) and for ERA-Interim is normalized relative to clear sky: 100 % translates as the same occurrence of the cloud type as clear-sky occurrence for this month, whereas 200 or 300 % translate as 2 or 3 times more occurrence of this type than clear sky
A novel pixel-scale application of cloud properties and thermodynamic profiles obtained from the NASA Aqua MODerate resolution Imaging Spectroradiometer (MODIS) and Atmospheric Infrared Sounder (AIRS) is presented for a subtropical cloud regime transition in the northeastern Pacific Ocean
Summary
Earth’s cloud types are highly variable in both their frequency of occurrence and optical properties, and have strong relevance to climate sensitivity (see, e.g., Cess et al, 1989, 1996; Bony and DuFresne, 2005; Wyant et al, 2006; Vial et al, 2013; or IPCC, 2007). The spatial and temporal variation in cloud types are controlled to a significant degree by the large-scale atmospheric dynamic circulation and thermodynamic structures (Stephens, 2005; Bony and Dufresne, 2005; Su et al, 2008) in combination with variations of water vapor (Stevens, 2005). On a smaller scale, the water vapor within clear-sky conditions can be influenced by adjacent clouds (Stevens, 2005), resulting in variations of water vapor. Quantifying the variations of potential temperature (θ ) and water vapor (q) profiles within each cloud type is essential for understanding the spatial and temporal variability of clouds in a present and future climate. Based on early ideas (Sommeria and Deardorff, 1977; Cuijpers and Bechthold, 1995), the importance of cloud-dependent statistics for θ and q has been pointed out by, for example, Pincus and Klein (2000), Larson et al (2001), Gierens et al (2007), Pressel and Collins (2012), Published by Copernicus Publications on behalf of the European Geosciences Union
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