The ATLAS Backward Trajectory Dataset for the Palau Atmospheric Observatory (PAO) Balloon-borne ozonesonde record V1.0 provides backward trajectory data in NetCDF format calculated by the transport module of the Lagrangian Chemistry and Transport Model ATLAS (Wohltmann and Rex, 2009; Wohltmann et al., 2010) for coinciding Electrochemical Concentration Cell (ECC) ozonesonde measurements from the PAO located in Koror, Palau (7.3420° N, 134.4722° E), in the Tropical West Pacific (TWP) from 2016- October 2019 (Müller 2020, Müller et al. 2023). 30-days backward trajectories with a time step of 10 minutes were initialized at the time of an ozonesonde measurement at the PAO for every tenth ozonesonde reading within a profile and for a total number of 138 soundings (= days) and between 0 and 20 km altitude. The model was driven by 3D wind fields, temperatures and diabatic heating rates from the ECMWF ERA5 reanalysis dataset (1.125° x 1.125°) with a 3 hour temporal resolution (compare Hoffmann et al., 2019). The model uses a hybrid vertical coordinate (zeta) which gradually transforms from "pressure" at the surface to "potential temperature" in the stratosphere (see Wohltmann and Rex, 2009). The corresponding vertical velocities change from vertical winds in pressure coordinates to diabatic heating rates. The Palau ECC record is currently being continued, will be available in the SHADOZ database in SHADOZ standard format in the near future, and can for now be found here: https://zenodo.org/record/6920648. Please email katrin.mueller@awi.de and let us know what your intended purpose for the use of the data is. You will then receive updates if an improved version becomes available.