Stability requirements of observation systems to detect long-term stratospheric ozone trends based upon Monte Carlo simulations
Abstract. For new observing systems, particularly satellites, specifications on the stability required for climate variables are provided in order to be useful for certain applications, for instance, deriving long-term trends. The stability is usually stated in units of percent per decade (%/dec) and is often associated with or termed instrument drift. A stability requirement of 3 %/dec or better has been recently stated for tropospheric and stratospheric ozone. However, the way this number is derived is not clear. In this study we use Monte Carlo simulations to investigate how a stability requirement translates into uncertainties of long-term trends depending on the lifetime of individual observing systems, which are merged into timeseries, and the period of available observations. Depending on the need to observe a certain trend over a given period, e.g. typically +1 %/dec for total ozone and +2 %/dec for stratospheric ozone over thirty years, stability for observation systems can be properly specified and justified in order to achieve statistical significance in the observed long-term trend. Assuming a typical mean lifetime of seven years for an individual observing system and a stability of 3 %/dec results in a 2 %/dec trend uncertainty over a period of 30 years, which is barely sufficient for stratospheric ozone but too high for total ozone. Having two or three observing systems simultaneously reduces the uncertainty by 30 % and 42 %, respectively. The method presented here is applicable to any variable of interest for which long-term changes are to be detected.
Status: open (until 29 Feb 2024)
Viewed (geographical distribution)