Mesoscale simulations of atmospheric CO₂ variations using a high‐resolution model system with process‐based CO₂ fluxes

Abstract

A new coupled high-resolution biosphere-atmosphere model (TerrSysMP-CO 2 ) is applied to simulate mesoscale and diurnal variations of atmospheric CO 2 mixing ratios. The model is characterized by process-based parametrization calculating atmospheric dynamics and biogenic processes considering the prognostically varying CO 2 content at the surface. An advanced parametrization of soil respiration is used distinguishing between heterotrophic and autotrophic respiration and explicitly considering the effect of varying soil moisture. In addition to biogenic CO 2 fluxes, high-resolution anthropogenic emissions are included in the simulations.The model performance is verified with eddy-covariance fluxes and meteorological and CO 2 concentration measurements at various heights of a tower. It is found that a correct representation of turbulent mixing is most critical for a precise prediction of nearsurface CO 2 mixing ratios and respective vertical gradients. High-resolution simulations were performed for a region with complex terrain, heterogeneous land use and densely populated areas. The relative influence of diverse land use, orography as well as of synoptic and mesoscale transport on the spatio-temporal CO 2 distribution is analyzed. The results indicate that, in regions with hilly terrain at night and in the morning, the CO 2 patterns are strongly influenced by terrain-induced local circulations. Moreover, in densely populated regions, fossil fuel emissions are an important source of atmospheric CO 2 . Finally, the simulated canopy fluxes and atmospheric conditions, calculated using two different crop physiological parameter sets, are compared.

Influence of complex terrain and anthropogenic emissions on atmospheric CO2 patterns–a high‐resolution numerical analysis

“…This allows us to initialize the high‐resolution simulations (inner domain) with a heterogeneous three‐dimensional CO 2 distribution according to the predominant dynamical situation. Additional information on initialization and nesting of TerrSysMP‐CO 2 can be found in Uebel et al ().…”

“…The mesoscale application of TerrSysMP‐CO 2 in Uebel et al () pointed out that, additionally to the synoptic flow, in regions with hilly terrain the CO 2 distribution within the PBL is strongly influenced by terrain‐induced local circulations. In order to analyze the thermo‐dynamical processes explaining this behaviour in detail, at first the spatio‐temporal variability of near‐surface CO 2 patterns is described for the two selected case studies.…”

“…For the numerical simulations we apply the model system TerrSysMP-CO 2 , which is based on the Terrestrial Systems Modelling Platform (TerrSysMP: Shrestha et al, 2014), extended by a prognostic treatment of CO 2 dynamics in the atmosphere (Uebel et al, 2017). TerrSysMP-CO 2 consists of the non-hydrostatic limited-area numerical weather prediction (NWP) model developed by the Consortium for Small-scale Modelling (COSMO, version 4.21: Baldauf et al, 2011) coupled to the Community Land Model (CLM, version 3.5: Dai et al, 2003;Oleson et al, 2010) via the external coupler OASIS3 (Valcke, 2013).…”

“…the biogenic CO 2 source/sink that influences the atmospheric CO 2 content (see below). For a more detailed description of the process-based parametrizations of TerrSysMP-CO 2 , the reader is referred to Uebel (2016) and Uebel et al (2017).…”

“…CO 2 emissions from road networks and settlements in rural regions are considered explicitly. Uebel et al (2017) indicated heterogeneous mesoscale CO 2 patterns in a region characterized by complex terrain and urban areas. The objectives of this subsequent study are, at first, a detailed analysis of the thermodynamic processes responsible for strong near-surface CO 2 gradients in mountainous regions.…”