On-line diagnostics of boundary layer processes in numerical weather predication and climate models

Atmospheric boundary layer (ABL) processes influence the atmosphere’s general circulation. Thus, representing the ABL processes correctly in global climate and numerical weather prediction models (NWP) is important. For example, surface and turbulent friction affect the transport of mass across the globe. Cross-isobaric mass flow then plays a significant role in the lifecycle and intensity of extratropical cyclones at the midlatitudes. The direction and magnitude of it depends on both synoptic scale and ABL conditions such as friction and thermal stratification. This transport can be studied using the turning of the wind with height, from the surface up to the ABL top, to understand where, when and how much mass is transported across isobars.

In a new era of increasing resolution of climate and NWP models, storing data remains a challenge even with greater capacity. The full vertical structure, and high temporal resolution needed to study the ABL well, is rarely all stored nor easily accessible due to the great amount of storage required. We have therefore implemented on-line diagnostics into the open version of the European Centre for Medium Range Weather Forecast’s (ECMWF) Integrated Forecast System (IFS), the OpenIFS. During the computation of simulations, the process diagnoses the turning of the wind with height, as well as the vertically integrated cross-isobaric mass flow, both from the surface to the ABL top. These diagnostics makes it possible, in more detail, to study the role of the boundary layer turbulence on the evolution of the flow in various regimes such as mid-latitude cyclones and the trade regions as well as sensitivity to modelling of turbulence and friction. All without having to store great amounts of data. We’ve run experiments focused on the global scale, and on a more local scale, tracking an extratropical cyclone in one of the storm tracks. Here the first results of this study are presented as well as a walkthrough of the basics of the online diagnostics.