Retrieval of aerosol optical thickness over snow and ice surfaces in the Arctic using Advanced Along Track Scanning Radiometer Larysa Istomina Universität Bremen 2012 _____________________________________________ Retrieval of aerosol optical thickness over snow and ice surfaces in the Arctic using Advanced Along Track Scanning Radiometer _____________________________________________ Vom Fachbereich Physik, Elektro- und Informationstechnik der Universität Bremen genehmigte Dissertation zur Erladung des akademischen Grades Doktor rer. nat. von: Dipl.-Phys. u. Astron. Larysa Istomina aus Bremen eingereicht am: 07. September 2011 Tag des mündlichen Kolloquiums: 16. December 2011 1. Gutachter: Prof. Dr. John P. Burrows 2. Gutachter: Prof. Dr. Justus Notholt _____________________________________________ Abstract Atmospheric aerosols influence energy balance of the Arctic region via scattering solar radiation, influencing albedo and lifetime of clouds, and via deposition on snow and ice surfaces. To know about the impact of arctic aerosols is crucial, because the Arctic region is a very sensitive area and an important factor in global circulation and climate. Due to severe conditions and remoteness of the area, there are few ground based or airborne data available on atmospheric aerosols in the Arctic. Remote sensing has therefore a strong potential to provide the necessary spatial and temporal observation coverage of the area. Passive remote sensing of aerosols in the Arctic region is a challenging task: the underlying snow and ice reflect much more than aerosol layer in the atmosphere, i.e. the underlying surfaces compose most of the top of atmosphere signal observed by the satellite. State-of-the art algorithms are not able to resolve this task, leading to gaps in aerosol data in the Polar regions. This thesis describes an algorithm, which takes into account the bright reflecting underlying surface and establishes the retrieval of the atmospheric aerosol amount in the Arctic region using passive remote sensing. The goal of this work is to provide the maps of aerosol optical thickness over snow and help to better understand the global aerosol distribution. The algorithm is a multi-angle approach, based on the dual-viewing Advanced Along-Track Scanning Radiometer (AATSR) onboard ENVISAT. A number of conducted simulation and modeling studies preceded the establishment of automatic snow/cloud discrimination algorithm and aerosol optical thickness retrievals in the visible and infrared spectral regions. Extensive validation and application studies, which have been chosen in order to cover possibly greater spatial and temporal range of data, show the ability of the developed methods to provide the maps of aerosol optical thickness over various snow types, for different aerosol types. The results of the aerosol retrieval for pollution events featuring mineral dust, volcanic aerosol, biomass burning and pollution associated with boreal forest fires are compared to independent space borne and ground based observations and showed coinciding temporal and spatial dynamics of the aerosol distribution. Additionally, a cloud screening routine, based on visible and infrared AATSR observations, was also successfully validated against independent space borne and ground based data and ensures the absence of cloud contamination in the resulting aerosol product. Applied together, these methods allow for the first time the retrieval of aerosol amount over snow and ice on local to global scales. The developed methods and resulting aerosol product are of major importance for better understanding of aerosol distribution over snow and its effect on the local and global energy balance, which is necessary for the evaluation of the Arctic climate status. The resulting aerosol product can be also used as the atmospheric correction for the snow surface retrievals not only in the Arctic region, but also over any snow covered surface. List of publications 1. Publications in peer-reviewed journals As first author: • Istomina L., W. von Hoyningen-Huene, A. A. Kokhanovsky, and J. P. Burrows. The detection of cloud free snow covered areas using AATSR measurements, Atmos. Meas. Tech., 3, 1-13, 2010. • Istomina L., von Hoyningen-Huene, W., Kokhanovsky, A. A., Schultz, E., and Burrows, J. P.: Remote sensing of aerosols over snow using infrared AATSR observations, Atmos. Meas. Tech., 4, 1133-1145, 2011. • Istomina L., W. von Hoyningen-Huene, A. A. Kokhanovsky, and J. P. Burrows. Retrieval of aerosol optical thickness over snow and ice using dual-view AATSR observations in the visible spectral region, in preparation. As coauthor: • Stankevich D., Istomina L., Shkuratov Yu., Videen G. Electromagnetic phase differences in the coherent backscattering enhancement mechanism for random media consisting of large non-transparent spheres, Applied Optics, Vol. 46, Issue 9, 1562-1567, 2007. • Stankevich D., Istomina L., Shkuratov Yu., Videen G. The coherent backscattering effects in a random medium as calculated using a ray tracing technique for large non- transparent spheres, Journal of Quantitative Spectroscopy and Radiative Transfer, 106, 1- 3, 509-519, 2007. • W. von Hoyningen-Huene, J.M. Yoon, M. Vountas, L.G. Istomina, G. Rohen, T. Dinter, A.A. Kokhanovsky, and J.P. Burrows. Retrieval of spectral aerosol optical thickness over land using ocean color sensors MERIS and SeaWiFS , Atmos. Meas. Tech., 4, 151-171, 2011. • C. Schlundt, A. A. Kokhanovsky, W. von Hoyningen-Huene, T. Dinter, L. Istomina, and J. P. Burrows. Synergetic cloud fraction determination for SCIAMACHY using MERIS, Atmos. Meas. Tech., 4, 319-337, 2011. • Krijger, J. M., Tol, P., Istomina, L. G., Schlundt, C., Schrijver, H., and Aben, I.: Improved identification of clouds and ice/snow covered surfaces in SCIAMACHY observations, Atmos. Meas. Tech. Discuss., 4, 1113-1138, 2011. 2. Conference and workshops contributions: • Istomina L.G., W. von Hoyningen-Huene, Kokhanovsky A. A., Rozanov V. V., Schreier M., Burrows J.P. The Algorithm of AOT retrieval over snow and ice: developing and testing on simulated radiative-transfer data // 2nd EUFAR Summer School on Airborne Cloud and Aerosol Science, 17-25 April, 2008, Utrecht, The Netherlands, 2008. • Istomina L.G., W. von Hoyningen-Huene, Kokhanovsky A. A., Rozanov V. V., Schreier M., Stock M., Treffeisen R., Herber A., Burrows J.P. Sensitivity study of the dual-view algorithm for aerosol optical thickness retrieval over snow and ice // Proceedings of 2nd MERIS/(A)ATSR user workshop, ESRIN, Frascati, Italy, 22-26 Sept. 2008, ESA SP-666, 2009. • Istomina L., W. Von Hoyningen-Huene, A. Kokhanovsky, M. Schreier, V. Rozanov, and J.P. Burrows. Retrieval of aerosol optical thickness over snow using dual-view satelliete observations // Book of abstracts, General Assembly of European Geosciences Union, Vienna, Austria, 18-24 April 2009. • Istomina L., W. von Hoyningen-Huene, A. Kokhanovsky, J. P. Burrows. The retrieval of aerosol optical thickness in Arctic region using dual-view AATSR measurements // POLARCAT workshop, 2-5 June 2009, Durham, New Hampshire, 2009. • Istomina L., W. von Hoyningen-Huene, A. Kokhanovsky, J. P. Burrows. The determination of AOT over snow using AATSR observations // 439. WE-Heraeus Seminar on Determination of Atmospheric Aerosol Properties Using Satellite Measurements, 17-19 August 2009, Bad Honnef, Germany, 2009. • Istomina L., W. von Hoyningen-Huene, A. Kokhanovsky, J. P. Burrows. The retrieval of aerosol optical thickness over snow using AATSR observations // Abstracts of American Geophysical Union Fall Meeting, 14-18 December 2009, San Francisco, California, 2009. • Istomina L.G., W. von Hoyningen-Huene, A.A. Kokhanovsky, and J.P. Burrows. Retrieval of aerosol optical thickness in Arctic region using dual-view AATSR observations // Proceedings of ESA Atmospheric Science Conference, Barcelona, Spain, 7-11 Sept. 2009, ESA SP-676, 2010. • Istomina L.G., W. von Hoyningen-Huene, A.A. Kokhanovsky, and J.P. Burrows. Remote Sensing of Aerosols in Arctic Region // AWI-IUP Blockseminar “Polar Processes - II”, 13 July 2010, Bremerhaven, Germany, 2010. • Istomina L.G., W. von Hoyningen-Huene, A.A. Kokhanovsky, and J.P. Burrows. Retrieval of aerosol optical thickness over snow using AATSR observations // 38th COSPAR Scientific Assembly, July 18-25 2010, Bremen, Germany, 2010. • Istomina L.G., W. von Hoyningen-Huene, A.A. Kokhanovsky, and J.P. Burrows. Aerosol remote sensing over snow using infrared AATSR observations // Book of abstracts, General Assembly of European Geosciences Union, Vienna, Austria, 03-08 April 2011. Contents Abstract .................................................................................................................................... 5 List of publications .................................................................................................................. 7 Contents ................................................................................................................................... 9 1 Introduction and motivation ............................................................................................. 11 1.1. Aerosol satellite remote sensing .................................................................................. 14 1.2 Aim of this work ........................................................................................................... 18 1.3 Outline of this thesis ..................................................................................................... 19 2