Earth Observation Data Group

Abstract:

The most widely used satellite products are averages of data onto a regular spatiotemporal grid, known as Level 3 data. Some atmospheric variables can vary rapidly in response to changing conditions. Over the scales of Level 3 averaging, the combination of observations across different conditions may result in data that is not normally distributed, such that a simple mean is not representative. The problem is illustrated by the distribution of aerosol optical depth from different sensors and algorithms. A simple statistical technique is proposed to better convey the diversity of satellite observations to users whereby a multimodal log-normal distribution is fit to the distribution of data observed within each grid cell. Allowing multiple modes within each cell is shown to improve the agreement between satellite products by highlighting regions of significant variability and isolating systematic differences between instruments.