TCOM-HCl : Daily global gap-free stratospheric hydrogen chloride profile data set based on TOMCAT CTM and Occultation Measurements

Methodology:  TOMCAT simulation is performed at T64L32 resolution for the 1991-2021 time period. Collocated hydrogen chloride (HCl) profiles are divided in five latitude bins: SH polar (90S-50S), SH mid-lat (70S-20S), tropics (40S-40N), NH mid-lat (20N-70N) and NH polar (50N-90N). Initially, model-measurement  differences are calculated for each zonal bins (46 height levels, 15km to 60km). Separate XGBoost regression models are trained for the  differences between TOMCAT and measurements at each level for a given latitude bin. XGBoost model is then used to estimate error corrections for all the TOMCAT grids ( day/night, 2 X11323 time steps).  TOMCAT output sampled at 1.30 am and 1.30 pm local time at the equator. Estimated corrections for a given model grid that are added to the original TOMCAT simulated day and night time HCl profiles. Height resolved data are then interpolated on 28-pressure levels (300 - 0.1hPa). For overlapping latitude bins, we use averages and then calculate daily zonal mean values.  For more details see attached presentation.

Dataset also includes two files containing daily mean zonal mean HCl  profiles on height (15-60 km) and pressure (300-0.1 hPa) levels:

zmhcl_TCOM_hlev_T2Dz_1991_2021.nc – height level data (15 to 60 km)

zmhcl_TCOM_plev_T2Dz_1991_2021.nc – pressure level data (300 to 0.1 hPa)

Daily 3D profiles on height and pressure levels would be made available upon request