Understanding the Atmosphere: Constraints on Astronomical Observation

The atmosphere, in terms of the prevailing climate as well as everyday weather, places limits on what we can view during astronomical observation. Specifically, cloud cover, precipitable water vapour, atmospheric stability and turbulence,
relative humidity, the direction and magnitude of the wind vectors, and aerosol (dust) loadings are the principal natural atmospheric parameters which constrain viewing conditions. These cover a huge range of physical scales spanning at least 10 orders of magnitude, from millimetres to thousands of kilometres. The spatio-temporal variability of these parameters, however, is often governed by broader synoptic-scale geophysical parameters such as latitude, altitude, season, and the prevailing weather and climate conditions themselves. Fortunately, the knowledge and prediction of many of these parameters is possible today, using a range of observational and modelling products. This short paper overviews the basic meteorology and climatology in the context of the constraints that the atmosphere places on astronomical observations.