[1] In this study we prove the feasibility of the advanced very high resolution radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer sea surface temperature algorithms to derive operational lake surface water temperature (LSWT). A validation study covering 2 years was done using data from the AVHRR on NOAA 12, 15, 16, and 17, the MODIS on TERRA, and AQUA and with different method-ingested in situ data from different sized lakes. Best results were found for NOAA 16 nighttime data at Lake Geneva (bias of 0.18 K and standard deviation of 0.73 K) and TERRA nighttime data at Lake Constance (satellite-buoy bias of À0.08 K and standard deviation of 0.92 K). For all sensor families an overall scatter ranging from 0.9 to 1.6 K was found. Bias of MODIS is larger, À1.73 to 1.9 K, than the one of the AVHRR (À0.28 to 1.5 K). The current orbital configuration of the platforms used revealed the diurnal evolution of the lake surface temperature amplitude from space. The damped mixing found for a typical calm and clear-sky regime is different from open ocean conditions. As the main error source, we found undetected cloudy pixel. Furthermore, the physical difference between skin and bulk temperature, especially its relation to the diurnal thermocline, solar insolation, and wind stress contributes to the bias and scatter within the match-up data set. The data sets have been validated to allow further application for LSWT climatology and assimilation into numerical weather prediction models.Citation: Oesch, D. C., J.-M. Jaquet, A. Hauser, and S. Wunderle (2005), Lake surface water temperature retrieval using advanced very high resolution radiometer and Moderate Resolution Imaging Spectroradiometer data: Validation and feasibility study,

[1] Aerosol optical depth was retrieved from a time series of NOAA-16 AVHRR data from May 2001 through December 2002 for Central Europe (40.5°N-50.0°N, 0°E-17°E). In contrast to classical methods, no a priori knowledge of the surface reflectance is necessary, but instead the surface reflectance is estimated from a time series including the previous 44 days. Additionally, the area where aerosol optical depth can be retrieved is no longer limited to certain land cover types. Only bright surface targets are excluded in the retrieval. To retrieve the aerosol optical depth, the radiative transfer code SMAC is used. Afterwards the data are averaged within a 25 Â 25 pixel region to increase the retrieval precision. The resulting standard deviation of the aerosol optical depth within this region is used as a quality control parameter and suitable for a post-processing of the initial aerosol retrieval. This post-processing leads to a substantial increase in the retrieval accuracy when compared to ground-based AERONET measurements. Over 650 co-incident AVHRR retrievals and AERONET measurements were compared, and a correlation coefficient of 0.70 was found. Altogether, the proposed method offers the potential to generate an aerosol climatology based on NOAA AVHRR data, which dates back to the early 1980s.

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