Towards an aviation weather forecast for green operations

Kurzfassung

Aviation contributes about 3.5% of the total anthropogenic global warming through both CO2 and non-CO2 effects. This problem is aggravated by the large growth rate of the aviation sector (>4% per year), which was only temporarily interrupted by the Covid-19 pandemic. It is evident that measures need to be taken to lessen the climate impact by aviation. CO2 has a very long residence time, such that its climate impact does not depend on when and where it is emitted. In contrast, non-CO2 emissions act on shorter time scales and their effect thus depends on the weather and synoptic situation at the time and location of the emission. This is particularly evident for contrails whose individual impacts range from strong cooling to strong warming, depending on the actual situation. It is thus possible to lessen the climate impact of aviation by planning flights such that climate-sensitive regions (i.e. regions where emissions would have a particularly strong warming impact) are avoided. To make such ideas real, new developments in aviation weather forecast are needed. One example is the implementation of so-called algorithmic climate change functions which provide measures of potential climate impact of emissions depending on actual weather variables (e.g. temperature and geopotential). The result can be provided in different ways, e.g. as costs, such that they can be used directly as additional cost-functions in flight routing. Another example is the prediction of persistent contrails in order to avoid them either tactically (by directives of air traffic control to pilots en-route) or strategically (as above, during flight routing). As one requirement for contrail persistence is ice supersaturation, this atmospheric state must be represented by the numerical weather prediction models, which is currently challenging. Another possibility is a probabilistic prediction of contrails using the standard weather variables. In this talk we will present how ideas from several projects for a better mitigation of contrails and other aviation non-CO2 effects on climate can be incorporated into aviation weather forecast models.