Linking Warm Conveyor Belts to the TEM Circulation in Northern Hemisphere Midlatitude Winter

This dataset provides gridded daily warm conveyor belt (WCB) frequency of occurrence for boreal winter (December–February) from 1 December 1980 to 28 February 2022 (3790 days). It includes WCB occurrence frequency on a 0.5° × 0.5° latitude–longitude grid in WCB_daily_1980_2022_DJF_latlon.nc, reported for the total field and separated into three vertical phases: inflow (GT800; pressure > 800 hPa), ascent (MIDTROP; 800–400 hPa), and outflow (LT400; pressure < 400 hPa). The file WCB_daily_1980_2022_DJF_preslat.nc provides the daily zonal-mean total WCB frequency (WCBSUM) on a latitude–pressure grid with 0.5° meridional resolution and pressure levels from 1 to 1015 hPa at 5-hPa intervals. WCB occurrence fields are derived from the ERA5-based LAGRANTO trajectory dataset generated by Heitmann et al. (2024) using the LAGRANTO Lagrangian analysis tool (Sprenger and Wernli, 2015) applied to ERA5 winds: kinematic forward trajectories are initialized every six hours in the lower troposphere and integrated forward for up to 96 hours, with the first 48 hours used to identify WCB ascent; air parcels ascending by at least 600 hPa within 48 hours and associated with extratropical cyclones are classified as WCBs following established trajectory-based criteria. The six-hourly trajectory output is aggregated into daily frequency fields, where frequencies represent the fraction of grid cells influenced by WCB trajectories during each day. Heitmann, K., M. Sprenger, H. Binder, H. Wernli, and H. Joos, 2024: Warm conveyor belt characteristics and impacts along the life cycle of extratropical cyclones: Case studies and climatological analysis based on ERA5. Weather Clim. Dynam., 5(2), 537–557, doi:10.5194/wcd-5-537-2024. Sprenger, M., and H. Wernli, 2015: The LAGRANTO Lagrangian analysis tool – version 2.0. Geosci. Model Dev., 8, 2569–2586, doi:10.5194/gmd-8-2569-2015.