ALBERT

Beschreibung: ABSTRACT Twelve-year satellite observations between 2002 and 2013 from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the satellite Aqua are used to quantitatively assess the water property changes in the Aral Sea. The shortwave infrared (SWIR) atmospheric correction algorithm is required and used to derive normalized water-leaving radiance spectra nL w ( λ ) in the Aral Sea. We used radiance ratio nL w (555)/ nL w (443) as a surrogate to characterize the spatial and temporal variations of chlorophyll-a (Chl-a) in the Aral Sea. Both seasonal variability and significant interannual changes were observed when the Aral Sea desiccated between 2002 and 2013. All three separated regions of the Aral Sea show increased nL w (555)/ nL w (443) ratio (a surrogate for Chl-a) and the diffuse attenuation coefficient at the wavelength of 490 nm ( K d (490)) during the fall season. Of the three regions, the North Aral Sea has had the least interannual variability, while South-East (SE) Aral Sea experienced drastic changes. Waters in the SE Aral Sea are the most turbid with significantly higher K d (490) than those in the other two sub-regions. K d (490) gradually increased from ∼2 m −1 in 2002 to ∼3.5 m −1 after 2008 in the SE Aral Sea. In comparison, both radiance ratio nL w (555)/ nL w (443) and K d (490) were relatively stable for the North Aral Sea. In the South-West (SW) Aral Sea, however, nL w (555)/ nL w (443) values reached peaks in the fall of 2007 and 2010. A possible link between the Aral Sea water property change and the regional climate variation is also discussed. This article is protected by copyright. All rights reserved.