Plake, D; Moravek, A; Tsokankunku, A; Breuninger, C; Welling, M; Foken, T; Andreae, MO; Meixner, FX*: Vertical profiles of reactive trace gases (NO, NO2, O3) in a forest ecosystem
Poster, Workshop on Atmospheric Chemistry: Kinetics and Spectroscopy, Bayreuth: 24.02.2010 - 26.02.2010

Within the framework of EGER (ExchanGE processes in mountainous Regions), tower-based vertical profiles of both reactive (NO, NO2, O3) and non-reactive (CO2, H2O) trace gas mixing ratios were measured during the two Intensive Observation Periods (IOP I from 6th of September to 3rd of October 2007 and IOP II from 05th of June to 11th of July 2008). Measurements were made at several heights (IOP I: 9 heights and IOP II: 11 heights) between 0.005 m and 31.5 m in a spruce forest ecosystem (mean canopy height: 23 m) using two identical, but independently operating analyzing units. Special emphasis was given on resolving vertical gradients at the soil–trunk space and canopy–roughness sublayer interfaces. Accompanying measurements comprise vertical profiles of wind speed, air temperature, relative humidity, global and photosynthetic active radiation, as well as the NO2 photolysis rate. Additionally, fluxes of momentum, sensible and latent heat, NO, NO2 and O3 were measured above the forest (32.5m) using the eddy covariance technique (EC). Vertical profiles are a useful tool for the interpretation of the measured EC fluxes of reactive compounds. Due to reduced turbulence within the forest canopy the residence time of the in-canopy air mass increases. Additionally, radiation and, thus, the NO2 photolysis frequency is attenuated non-uniformly throughout the forest canopy. Biogenic soil emissions of NO and subsequent conversion to NO2 by the reaction with O3 are investigated using the vertical profiles as well as the influence of advection of NOx from nearby anthropogenic sources during the morning hours. Both chemical interconversion and advection have a significant impact on the direction and magnitude of the reactive trace gas fluxes.

Letzte Änderung 20.03.2010