6 merge requests!319add all changes of dev into release v1.4.0 branch,!318Resolve "release v1.4.0",!299Draft: Merge default data handler and preprocessing support parameter use_multiprocessing....,!298Lukas issue307 bug data handler fails if no chem variable is used,!296index array was missing,!259Draft: Resolve "WRF-Datahandler should inherit from SingleStationDatahandler"