0. SECTIONS ------------- 1. Project 2. Dataset 3. Terms of Use 4. Content 5. Method and Processing 1. PROJECT ------------ Title: Understanding atmospheric circulation from a surface perspective Funding organisation: EU Horizon 2020 Grant no.: 654492 2. DATASET ------------ Title: Missing orographic drag leads to climate model biases in jet streams and storm tracks Description: UM model experiments used in the paper 'Missing orographic drag leads to climate model biases in jet streams and storm tracks', submitted to Geophys. Res. Lett. State-of-the art climate models generally struggle to represent important features of the large-scale circulation. Common model deficiencies include an equatorward bias in the location of the mid-latitude westerlies and an overly zonal orientation of the North Atlantic storm track. Orography is known to strongly affect the atmospheric circulation and is notoriously difficult to represent in coarse-resolution climate models. How the representation of orography affects circulation biases in current climate models is not understood. Here, we show that the effects of switching off the parameterisation of drag from low-level orographic blocking in one climate model resemble the biases of the CMIP5 ensemble: An equatorward shift in the Southern Hemispheric jet, an overly zonal wintertime North Atlantic storm track, and an increase in the Southern Annular Mode timescale. This suggests that the representation of the extratropical circulation in coarse-resolution climate models can be improved considerably by improving the parameterisation of low-level drag. In the file listing, "UM std" refers to a 30-year AMIP-II run of the UM at N96 resolution with standard parameters. "UM noblock" refers to an experiment in which the low-level drag scheme is effectively switched off by setting a tuning parameter to zero, all else being equal to "UM std". Publication Year: 2016 Creator(s) Name(s): Felix Pithan Organisation(s): University of Reading 3. TERMS OF USE ----------------- Terms of use will be supplied on request. 4. CONTENT ------------ File listing xlgta_mslp_all_daily.nc daily mean sea-level pressure for the UM std run xlgtj_mslp_all_daily.nc daily mean sea-level pressure for the UM noblock run xlgta_z500all_daily.nc daily 500 hPa geopotential heights from UM std xlgtj_z500all_daily.nc daily 500 hPa geopotential heights from UM noblock xlgta_u850all_6h.nc 6-hourly 850 hPa zonal winds in UM std xlgtj_u850all_6h.nc 6-hourly 850 hPa zonal winds in UM noblock xlgta_v850all_6h.nc 6-hourly 850 hPa meridional winds in UM std xlgtj_v850all_6h.nc 6-hourly 850 hPa meridional winds in UM noblock xlgta_u_mean.nc time mean zonal wind in UM std xlgtj_u_mean.nc time mean zonal wind in UM noblock File formats and structure: netcdf files 5. METHOD and PROCESSING -------------------------- The experiments leading to the data are described in 'Missing orographic drag leads to climate model biases in jet streams and storm tracks' by F. Pithan, T.G. Shepherd, G. Zappa and I. Sandu, submitted to Geophy. Res. Lett.