High-resolution simulations of atmospheric CO₂ over complex terrain – representing the Ochsenkopf mountain tall tower

Abstract. Accurate simulation of the spatial and temporal variability of tracer mixing ratios over complex terrain is challenging, but essential in order to utilize measurements made in complex orography (e.g. mountain and coastal sites) in an atmospheric inverse framework to better estimate regional fluxes of these trace gases. This study investigates the ability of high-resolution modeling tools to simulate meteorological and CO₂ fields around Ochsenkopf tall tower, situated in Fichtelgebirge mountain range- Germany (1022 m a.s.l.; 50°1′48" N, 11°48′30" E). We used tower measurements made at different heights for different seasons together with the measurements from an aircraft campaign. Two tracer transport models – WRF (Eulerian based) and STILT (Lagrangian based), both with a 2 km horizontal resolution – are used together with the satellite-based biospheric model VPRM to simulate the distribution of atmospheric CO₂ concentration over Ochsenkopf. The results suggest that the high-resolution models can capture diurnal, seasonal and synoptic variability of observed mixing ratios much better than coarse global models. The effects of mesoscale transports such as mountain-valley circulations and mountain-wave activities on atmospheric CO₂ distributions are reproduced remarkably well in the high-resolution models. With this study, we emphasize the potential of using high-resolution models in the context of inverse modeling frameworks to utilize measurements provided from mountain or complex terrain sites.