Abstract. We use the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite aerosol optical thickness (AOT) product to assess the impact of reduced swath width on global and regional AOT statistics and trends. Ten different sampling strategies are employed, in which the full MODIS dataset is sub-sampled with various narrow-swath (~400–800 km) and curtain-like (~10 km) along-track configurations. Although view-angle artifacts in the MODIS AOT retrieval confound direct comparisons between averages derived from different sub-samples, careful analysis shows that with many portions of the Earth essentially unobserved, the AOT statistics of these sub-samples exhibit significant regional and seasonal biases. These AOT spatial sampling artifacts comprise up to 60% of the full-swath AOT value under moderate aerosol loading, and can be as large as 0.1 in some regions under high aerosol loading. Compared to full-swath observations, narrower swaths exhibit a reduced ability to detect AOT trends with statistical significance, and for curtain-like sampling we do not find any statistically significant decadal-scale trends at all. An across-track sampling strategy obviates the MODIS view angle artifact, and its mean AOT converges to the full-swath mean values for sufficiently coarse spatial and temporal aggregation. Nevertheless, across-track sampling has significant seasonal-regional sampling artifacts, leading to biases comparable to the curtain-like along-track sampling, lacks sufficient coverage to assign statistical significance to aerosol trends, and is not achievable with an actual narrow-swath or curtain-like instrument. These results suggest that future aerosol satellite missions having significantly less than full-swath viewing are unlikely to sample the true AOT distribution well enough to determine decadal-scale trends or to obtain the statistics needed to reduce uncertainty in aerosol direct forcing of climate.
Sampling Artifacts from Conductive Silicone Tubing