On the computation of several “insolation” quantities relevant to climatology or planetology

Abstract. There are many possible “insolation” quantities. When looking for some astronomical forcing, geologists, paleoclimatologists and climate modellers are often limited by the available software or web sites that compute or distribute some specific time series, often with a quite limited documentation. Furthermore, the astronomical forcing has several subtleties that some people might not be aware of, especially the key difficulty of defining a calendar. This paper aims therefore at presenting and documenting a rather complete python library designed to compute many astronomical and insolation quantities relevant to climate: standard ones like for instance daily insolation; less classical ones like integrated insolation over time or over space (or both); but also new quantities that are sometimes discussed in the literature on a qualitative basis, like the semi-precessional forcing at low latitudes, something which involves computing minima and maxima of the solar forcing over the year, a surprising complex endeavour when looking at generic planetary situations with arbitrary eccentricity or obliquity. Overall, the aim is here to provide not only a useful toolbox for scientists, but also a pedagogical introduction of some subtle difficulties for students. This is done using the widely used computer language python so that the code is easy to understand, to reuse or modify for various different contexts.