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- Title
An assessment of the climatological representativeness of IAGOS-CARIBIC trace gas measurements using EMAC model simulations.
- Authors
Eckstein, Johannes; Ruhnke, Roland; Zahn, Andreas; Neumaier, Marco; Kirner, Ole; Braesicke, Peter
- Abstract
Measurement data from the long-term passenger aircraft project IAGOS-CARIBIC is often used to derive trace gas climatologies. We investigate to what extent such derived climatologies can be assumed to be representative for the true state of the atmosphere. Using the chemistry-climate model EMAC we sample the modelled trace gases along CARIBIC flight tracks. Different trace gases are considered and climatologies relative to the mid-latitude tropopause are calculated. Representativeness can now be assessed by comparing the CARIBIC sampled model data to the true climatological model state. Three statistical methods are applied for this purpose: the Kolomogorov-Smirnov test, and scores based on the variability and relative differences. Generally, representativeness is expected to decrease with increasing variability and to increase with the number of available samples. Based on this assumption, we investigate the suitability of the different statistical measures for our problem. The Kolmogorov-Smirnov test seems too strict and does not identify any climatology as representative - not even long lived well observed trace gases. In contrast, the variability based scores pass the general requirements for representativeness formulated above. In addition, even the simplest metric (relative differences) seems applicable for investigating representativeness. Using the relative differences score we investigate the representativeness of a large number of different trace gases. For our final consideration we assume that the EMAC model is a reasonable representation of the real world and that representativeness in the model world can be translated to representativeness for CARIBIC measurements. This assumption is justified by comparing the model variability to the variability of CARIBIC measurements. Finally, we show how the representativeness score can be translated into a number of flights necessary to achieve a certain degree of representativeness.
- Subjects
CLIMATOLOGY; ATMOSPHERIC models; CLIMATE change; ATMOSPHERIC chemistry; ATMOSPHERIC aerosols
- Publication
Atmospheric Chemistry & Physics Discussions, 2016, Vol 16, Issue 4, p1
- ISSN
1680-7367
- Publication type
Article
- DOI
10.5194/acp-2016-179