Volume 23 (Kristina Brust 2017)
Kristina Brust, 2017
Impact of Climate Change on
the Storm Water System in
Al Hillah City / IRAQ
ISBN 978-3-86780-417-2
Abstract
Changes in climate and land use interact in a complex system with various feedbacks including water, carbon (C), and nitrogen (N) fluxes. In this dissertation, firstly measurements of surface fluxes were conducted via two different measurement systems, a Bowen Ratio (BR) and an Eddy Covariance (EC) system. Over two succeeding years, fluxes and gradients of heat, water vapour, and CO2 over winter barley and rapeseed were simultaneously measured at Klingenberg, a long-term cropland site in eastern Germany. The two independent systems (EC/BR) are compared with respect to energy and CO2 fluxes. Inspection as well as a neutral regression analysis show that differences between the systems were largest for latent heat LE. EC detects apparently lower LE due to the lack of closure of the energy balance of approximately 30%, whereas the fluxes of CO2 show only smaller differences up to 10%. Therefore, Bowen Ratio setups remain an alternative to EC systems when gradients are large and analysers with high measurement frequency are not available. Encouraged by this analysis, the Modified Bowen Ratio system was used to measure the vertical gradients of mixing ratios of nitrogen oxides (NOx) and ammonia (NH3). Fluxes of these nitrogen species are analysed and associated to the corresponding growth status of two crops within two growing periods. Integration of these nitrogen fluxes results in a net emission into the atmosphere of 1.25 kg N ha-1 for the total measurement period of 77 days, differing in the proportion of NOx and NH3. However, this net emission does not largely reduce the fertilization of the crop site.
In a second step, the atmospheric boundary layer model HIRVAC (HIgh Resolution Vegetation Atmosphere Coupler) was improved and applied to three different land uses within the TU-Dresden-cluster for selected time periods in 2009 and 2010. Simulated fluxes of H2O and CO2 with the improved model HIRVAC show good agreement with measurements. Realistic fluxes were obtained with respect to the diurnal cycle as well as the order of magnitude. Modelling of energy and trace gas fluxes also gives the opportunity to assess effects of changing climate conditions on surface fluxes. Since in the improved HIRVAC version a coupled model for stomatal conductance is used, an increase in CO2 concentration is linked with a decrease of stomatal conductance in the simulation. Therefore, simulations of changes in climate condition along with elevated CO2 concentrations and their effect on latent heat fluxes are analysed. The grassland and agricultural site revealed increased evapotranspiration with elevated temperatures and CO2 concentrations, whereas the forest site came up with reduced evapotranspiration rates. Concerning the flux of CO2, all land uses considered here increased the amount of assimilated carbon, whereby the forest site increased the most. Finally, the scenario calculations revealed that regarding evapotranspiration and CO2, differences of land use dominate over differences of climate change.