The Spatial and Temporal Distribution of Commercial Aircraft Weather Observations Available for Assimilation into Numerical Weather Prediction Models

Weather observations from commercial aircraft constitute a critical component of the global observing system, and have been shown to be the most valuable observation source for frequently updated numerical weather prediction (NWP) systems over North America. However, the distribution of aircraft observations is highly irregular in space and time. In this study, we describe the spatial and temporal distribution of commercial aircraft weather observations, as well as changes over time. Coverage is most dense over the contiguous United States and Europe, with secondary maxima in East Asia and Australia / New Zealand. High-altitude observations are generally available only along frequently used flight routes, particularly over the North Pacific and North Atlantic Oceans, with diurnal patterns that are relatable to normal flight schedules. Ascent and descent observations, which provide important vertical profiles of the atmosphere for numerical weather prediction initialization, cover a much smaller area globally, as do observations of water vapor mixing ratio. Networks of regional carriers, such as TAMDAR, and new reporting protocols such as MODE-S or ADS-B provide an opportunity to widely expand coverage of aircraft observations and to improve short-term NWP.