Stratocumulus properties retrieval method from NOAA-AVHRR data based on the discretization of cloud parameters

Abstract

A method is presented for determining the optical thickness, eVective droplet radius and temperature of oceanic stratocumulus clouds from NOAA-AVHRR infrared channels. The satellite data used in the present study correspond to night-time images in which large-scale stratiform clouds overlay the ocean. The procedure is based on the inversion of an atmospheric radiative transfer model that makes use of the discrete ordinates method called DISORT. A detailed study is presented which shows that cloud parameter retrieval is ambiguous, resulting in several possible solutions, because some pairs of eVective particle radius and optical thickness produce the same brightness temperatures. The discretization of these two parameters, based on the cloud layer radiative behaviour, is proposed to avoid these multiple solutions. In addition, the model inversion presents some diYculties that have been solved using a genetic algorithm. The current retrieval scheme is applied to satellite data to compare results with local in situ measurements and a good agreement is obtained in those pixels near the sample site.

Aerosol optical depth retrievals at the Izaña Atmospheric Observatory from 1941 to 2013 by using artificial neural networks

“…The ANNs have been employed in diverse applications and fields such as robotics, pattern recognition, forecasting, medicine, power systems, etc. In atmospheric science the use of ANNs is quite recent, for example, ANNs have been successfully used for estimating solar radiation values (Mohandes et al, 1998;Dorvlo et al, 2002;López et al, 2005;Feister and Junk, 2006;Junk et al, 2007;Feister et al, 2008;Paoli et al, 2009;Linares-Rodríguez et al, 2011 or cloud properties (González et al, 2002;Cerdeña et al, 2006). However, their use for AOD estimations is quite recent and limited to short periods.…”

Artificial Intelligence Methods in the Environmental Sciences

“…used hybrid GAs to tune fuzzy sets in order to identify bounded weak echo regions, which are radar return features associated with supercell thunderstorms. Gonzalez et al (2002) were able to determine cloud optical thickness, effective droplet radius, and temperature of night-time largescale stratiform clouds over the ocean by inverting an atmospheric radiative transfer model. Since the inversion displays multiple local minima, a GA was needed to produce a global minimum that agreed well with local in situ measurements.…”

Remote Sensing of Water Cloud Parameters Using Neural Networks

“…Recently, these techniques have been extended to include data from other spectral bands provided by new-generation sensors, such as the Moderate Resolution Imaging Spectroradiometer (MODIS), on board Earth Observing System (EOS) satellites (Terra and Aqua). Thus, new procedures have been developed for the cloud properties' retrieval for both daylight imagery (Kokhanovsky et al 2003;Platnick et al 2003) and nighttime data (Perez et al 2002;Baum et al 2003).…”

“…The neural network's ability to learn and generalize, beginning with data used during the training stage, together with its low computational cost, turns it into a powerful and attractive tool to solve this kind of problem. Once the neural networks have been trained, their application to satellite data to perform the model inversion is faster than other methods, such as iterative approaches (Kawamoto et al 2001), dual-channel correlation techniques (King et al 1997), or evolutionary numerical methods (Gonzalez et al 2002).…”

“…During nighttime the retrieval procedure is more complex, because the radiances received in the middle and thermal infrared bands depend on all cloud parameters. In this case, applied methods (Baum et al 1994;Perez et al 2000;Gonzalez et al 2002) are based on the fact that the optical properties of clouds are different at each available band. Recently, these techniques have been extended to include data from other spectral bands provided by new-generation sensors, such as the Moderate Resolution Imaging Spectroradiometer (MODIS), on board Earth Observing System (EOS) satellites (Terra and Aqua).…”