WGNE Systematic Error Survey Results Summary

The Fifth Workshop on Systematic Errors in Weather and Climate Models was hosted by Environment and Climate Change Canada under the auspices of the Working Group on Numerical Experimentation (WGNE), jointly sponsored by the Commission of Atmospheric Sciences of the World Meteorological Organization (WMO) and the World Climate Research Programme (WCRP). This major event held in Montreal in June 2017 welcomed over 200 scientists from the weather and climate communities. The workshop’s primary goal was to increase understanding of the nature and cause of systematic errors in numerical models across time scales. The Working Group on Numerical Experimentation (WGNE) subsequently conducted a survey among modelling centers, to determine the priority of the 17 major systematic errors produced as an outcome of the workshop. 14 centers responded to the survey, contributing 35 surveys in total (most centers contributed multiple surveys corresponding to their different modeling systems). Modeling system characteristics (i.e., global, regional, NWP, monthly-annual, climate, and atmosphere-ocean coupling) were collected such that results could be stratified by the type and purpose of the system.

While priorities naturally reflected the type of system being developed, four issues stand out as of almost uniform concern. Chief among them is “Convective precipitation—including diurnal cycle (timing and intensity); the organization of convective systems; precipitation intensity and distribution; and the relationship with column-integrated water vapor, SST, and vertical velocity”. This is followed by “Outstanding errors in the modeling of surface fluxes”; “Surface temperature errors (land and sea) including errors in the diurnal cycle of surface temperature”; and “Cloud microphysics—including errors linked to mixed-phase, supercooled liquid cloud, and warm rain”. These community priorities on convection, microphysics, and surface fields and fluxes should serve as a guide as WGNE and other groups organize community efforts to address these pressing problems. There are already ongoing and proposed efforts to look at some of these biases and issues. For example, the WGNE surface flux intercomparison project should help to benchmark the current status of surface flux errors and uncertainties in different modeling systems. Likewise, the WGNE MJO Task Force is examining the ability of models to capture aspects of convective organization.