The Impact of Parameterized Convection on Climatological Precipitation in Atmospheric Global Climate Models

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.Convective parameterizations are widely believed to be essential for realistic simulations of the atmosphere. However, their deficiencies also result in model biases. The role of convection schemes in modern atmospheric models is examined using Selected Process On/Off Klima Intercomparison Experiment (SPOOKIE) simulations without parameterized convection and forced with observed sea surface temperatures. Convection schemes are not required for reasonable climatological precipitation. However, they are essential for reasonable daily precipitation and restraining extreme daily precipitation that otherwise develops. Systematic effects on lapse rate and humidity are likewise modest compared with the inter-model spread. Without parameterized convection Kelvin waves are more realistic. An unexpectedly large moist Southern Hemisphere storm track bias is identified. This storm track bias persists without convection schemes, as does the double intertropical convergence zone and excessive ocean precipitation biases. This suggests that model biases originate from processes other than convection or that convection schemes are missing key processes.PM, GKV and PGS are funded by the Natural Environment Research Council and Met Office as part of the EuroClim project (grant number NE/M006123/1), ParaCon project (grant number NE/N013123/1) and the Royal Society (Wolfson Foundation). MJW is supported by the Joint UK BEIS/Defra Met Office Hadley Centre Climate Programme number GA01101. SCS acknowledges the Australian Research Council (grant number FL150100035)