Merged Datasets for the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Central Observatory in the Arctic Ocean (2019-2020) version 2

Major changes to the dataset with version 2 (see below for full description of dataset): - Data files have been separated into 'drift1' (October 2019-July 2020) and 'drift2' (August-September 2020) to highlight the spatial discontinuity in measurement sites. - Precipitation data is now provided for June 18 - July 31 of drift 1 and drift 2. - The code recipes for producing merged datasets were found to be infeasible to run on systems with limited random access memory (RAM). The code (https://doi.org/10.5281/zenodo.14633302) has been reorganized and a minutely-averaged version of the Atmospheric Radiation Measurement (ARM) ship-based radiation data is provided for convenience. - Ship-based radiation data has been updated to level b1 and now includes downwelling longwave data. Please see the methods (addendum 1) for a summary of the differences in downwelling radiation: Full description of the dataset: - The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) produced a wealth of observational data along the drift of the R/V Polarstern in the Arctic Ocean from October 2019 to September 2020. These data can further process-level understanding and improvements in models. However, the observational records contain temporal gaps and are provided in different formats. One goal of the MOSAiC Model Forcing Dataset Working Group (MMFDWG: https://mosaic-expedition.org/science/cross-cutting_groups/) is to provide consistently-formatted, gap-filled, merged datasets representing the conditions at the MOSAiC Central Observatory (the intensively studied region within a few km of R/V Polarstern) that are suitable for driving models on this spatial domain (e.g., single column models, large eddy simulations, etc). The MSCMWG is an open group, please contact the dataset creators if you would like to contribute to future versions of these merged datasets (including new variables). - This dataset contains version 2 of these merged datasets, and comprises the variables necessary to force a single column ice model (e.g., Icepack: https://zenodo.org/doi/10.5281/zenodo.1213462). The atmospheric variables are primarily derived from Met City (https://doi.org/10.18739/A2PV6B83F), with temporal gaps filled by bias and advection corrected data from Atmospheric Surface Flux Stations ( https://doi.org/10.18739/A2XD0R00S, https://doi.org/10.18739/A25X25F0P, https://doi.org/10.18739/A2FF3M18K). Some residual gaps in shortwave radiation were filled with ARM ship-board radiometer data. See addendum 2 in the methods for a summary of the data sources for atmospheric data. - The MOSAiC expedition drifted with two distinct sets of drifting ice floes. 'drift1' began in October 2019 north of the Laptev Sea and ended in July 2020 in the Fram Strait. 'drift2' was from August to September 2020 in the vicinity of the North Pole. Distinct files are provided for drift1 and drift2. - Three different options for snowfall precipitation rate (prsn) for drift 1 are provided, based on in-situ observations that precipitation greatly exceeded accumulation on level ice, and accumulation rates varied on different ice types. See methods for a description of the different precipitation rates. Besides precipitation, the other atmospheric variables for these files are identical. - Oceanic variables are in MOSAiC_ocn* files and are derived from https://doi.org/10.18739/A21J9790B. Data format: The data are netCDF files formatted according to the Merged Data File format (https://doi.org/10.5194/egusphere-2023-2413, https://gitlab.com/mdf-makers/mdf-toolkit). Code availability: The code 'recipes' that were used to produce these data are available at: https://doi.org/10.5281/zenodo.14633302. References: If you use these datasets, please also cite the appropriate publications: - Meteorological variables (excluding precipitation): Cox et al., 2023 (https://doi.org/10.1038/s41597-023-02415-5) - Oceanographic variables: Schulz et al., 2024 (https://doi.org/10.1525/elementa.2023.00114) - Ka-band ARM Zenith Radar (KAZR)-derived precipitation: Matrosov et al., 2022 (https://doi.org/10.1525/elementa.2021.00101) - Accumulation-derived pseudo-precipitation: Raphael et al., 2024 (https://doi.org/10.1525/elementa.2023.00040). - Summertime precipitation: Smith et al., 2024 (https://doi.org/10.5194/egusphere-2024-1977) Known issues: The following are known issues that will be addressed in future dataset releases: 1. Residual gaps occupy approximately 7% of the data record (see addendum) 2. Measurement Data Format (MDF) format does not currently include a field for point-by-point data source 3. There is no precipitation data for the leg 3-4 crew transition (May 15 - June 19).