Influence of spatial heterogeneity of local surface albedo on the area-averaged surface albedo retrieved from airborne irradiance measurements

Author:

Jäkel E.,Wendisch M.,Mayer B.

Abstract

Abstract. Spectral airborne upward and downward irradiance measurements are used to derive the area-averaged surface albedo. Real surfaces are not homogeneous in their reflectivity. Therefore, this work studies the effects of the heterogeneity of surface reflectivity on the area-averaged surface albedo to quantify how well aircraft measurements can resolve the small-scale variability of the local surface albedo. For that purpose spatially heterogeneous surface albedo maps were input into a 3-dimensional (3-D) Monte Carlo radiative transfer model to simulate 3-D irradiance fields. The calculated up- and downward irradiances in altitudes between 0.1 km and 5 km are used to derive the area-averaged surface albedo using an iterative retrieval method that removes the effects due to atmospheric scattering and absorption within the layer beneath the considered level. For the case of adjacent land and sea surfaces a parametrization is presented which quantifies the horizontal distance to the coastline that is required to reduce surface heterogeneity effects on the area-averaged surface albedo to a given limit. The parametrization which is a function of altitude, aerosol optical depth, and the ratio of local land and sea albedo was applied for airborne spectral measurements. In addition, the deviation between area-averaged and local surface albedo is determined for more complex surface albedo maps. For moderate aerosol conditions (optical depth less than 0.4) and the visible wavelength range, the altitude and the heterogeneity of the surface albedo are the dominant factors determining the mean deviation between local and area-averaged surface albedo. A parametrization of the mean deviation is applied to an albedo map that was derived from a Landsat image of an area in East Anglia (UK). Parametrization and direct comparison of local and area-averaged surface albedo show similar mean deviations (20% vs. 25%) over land.

Publisher

Copernicus GmbH

Reference31 articles.

1. Anderson, G., Clough, S., Kneizys, F., Chetwynd, J., and Shettle, E.: AFGL Atmospheric Constituent Profiles (0–120 km), Tech. Rep. AFGL-TR-86-0110, AFGL (OPI), Hanscom AFB, MA 01736, 1986.

2. Aoki, T., Mikami, M., and Liu, W.: Spectral albedos of desert surfaces and size distributions of soil particles measured around Qira and Aksu in the Taklimakan Desert, J. Arid Land Stud., 11, 259–266, 2002.

3. Bierwirth, E.: Airborne measurements of the spectral surface albedo over Morocco and its influence on the radiative forcing of Saharan dust, Ph. D. thesis, Johannes Gutenberg University Mainz, Germany, 2008.

4. Bierwirth, E., Wendisch, M., Ehrlich, A., Heese, B., Tesche, M., Althausen, D., Schladitz, A., Müller, D., Otto, S., Trautmann, T., Dinter, T., von Hoyningen-Huene, W., and Kahn, R.: Spectral surface albedo over Morocco and its impact on the radiative forcing of Saharan dust, Tellus , 61, 252–269, 2009.

5. Bowker, D., Davis, R., Myrick, D., Stacy, K., and Jones, W.: Spectral Reflectances of Natural Targets for Use in Remote Sensing Studies, NASA RP-1139, NASA Langley Research Center, Hampton, USA, 1985.

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