Field and simulation experiments for analysing regional land-atmosphere interactions of the West African Climate System -

Transcription

1 Field and simulation experiments for analysing regional land-atmosphere interactions of the West African Climate System - Titelmasterformat Experimental set-up and durch first results Klicken , Gothenburg, IAHS-IAPSO-IASPEI Assembly J. BLIEFERNICHT 1, H. KUNSTMANN 1,2, L. HINGERL 1, J. ARNAULT 1, C. KLEIN 1, M. WAONGO 1, T. RUMMLER 1, S. ANDRESEN 2, M.MAUDER 2, R. STEINBRECHER 2, R. FRIEß 1, D. GOCHIS 4, U. GESSNER 3, E. QUENSAH 6, A. AWOTUSE 6, F. NEIDL 2, C. JAHN 2,D. HEINZELLER 2, S. GUUG 5, I. BOUBACAR, B. SYLLA 5 & B. BARRY 5 Untertitelmasters 5 WASCAL Competence Centre, durch Burkina Faso Klicken 1 Chair for Regional Climate and Hydrology, University of Augsburg, Universitätsstraße 10, Augsburg, Germany 2 Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Germany 3 German Aerospace Centre, Earth Observation Center, German Remote Sensing Data Center, Land Surface, Germany 4 National Center for Atmospheric Research, United States 6 Graduate Research Program on the West African Climate System, Federal University of Technology Akure, Nigeria WASCAL 9/9/ West African Science Service Center on Climate Change and Adapted Land Use

2 High Climate Variability in West Africa e.g. annual precipitation amount [mm], Volta basin, GPCC Sahel Drought 9/9/2014 2

3 Severe Land Cover Changes in West Africa 9/9/ Le Monde, Institute of Research for Development (IRD), 1996; UNEP, International Soil Reference and Information Centre (ISRIC), World Atlas of Desertification,

4 Tremendous Population Increase in West Africa e.g. Benin Titelmasterformat durch 9% per year! Klicken Faostat, 2005 > 80 % of the West African population are living from the income produced in agriculture Savannah and rainfall forest has been converted to agricultural land This is expected for the future, too! 9/9/2014 4

5 Key Questions What is the impact of land surface changes on hydrometeorological fluxes under changing climate conditions? Can land surface changes even amplify the frequency and magnitude of hydro-meteorological extremes such as droughts? To find answers: Field experiment using micro-meteorological stations (EC stations) Simulation experiments with two-way coupled atmospherichydrological modelling systems (WRF-Hydro) 9/9/2014 5

6 Study Region Titelmasterformat Sahelian Zone durch Klicken Source: White 1983 Sudanian Zone Rain Forest Zone Guinean Zone The study region is located in the Sudanian savanna belt which is considered as the potential breadbasket of West Africa 9/9/2014 6

7 Watersheds and EC Stations 9/9/2014 7

8 Land Cover/Use Situation for the Study Region (GLC, 2000) 9/9/2014 8

9 Micro-Meteorological Stations (EC Stations) Nazinga Zumbrungu near-natural, Nazinga National Park, reference agricultural heavily-used, soil is highly degraded Formatvorlage Kayooro des Kayooro, mixture between Nazinga and 9/9/2014 Zumbrungu 10

10 Flux Measurements: October 2012, Kayooro Precipitation event: October 26, 2012; P = 11.4 mm/d the day before the day after the latent heat fluxes moderately increases after the rainfall event due to a higher evapotranspiration 9/9/

11 Measurement Equipment of EC Stations EC stations are very rare in West Africa: 3 from 10 belong to WASCAL (Fluxnet, 2013)! 9/9/

12 EC Network in West Africa (Fluxnet, 2012) Mali: barren Mali: open scrublands grassland - cropland New EC sites January Ghana, rainforest Niger: cropland fallow degraded land Benin: forest - mixed agricultural land 9/9/

13 Components of a Regional Climate Model (RCM) Dynamical Core Parameterisation/Model Physics Schemes 3-dim simulation of the atmospheric circulation for a limited geographical region e.g land-atmosphere exchange simulation of subgrid-scale processes: e.g convection/cloud formation processes land surface model Chen and Dudhia, /9/

14 Key Limitations of Land Surface Models (e.g. Noah LSM) I. Poor representation of bio-physical land surface properties that describe the vegetation dynamic evapotranspiration! assumption: vegetation is not changing from year to year!!! key parameters: green fraction index, leaf area index II. Lack of available and reliable observations highly important for model assessment implement EC stations and further hydrometeorological stations III. Hydrological processes are missing e.g. surface runoff use an LSM model with additional process descriptions: NDHMS 9/9/

15 WRF-Hydro WRF NDHMS dynamical core (3-dim: x,y,z) land surface model (1-dim, z) 2 dim (x,y) WRF = Weather Research Forecasting model (Skamarock et al., 2005) NDHMS 9/9/2014 = Noah Distributed Hydrological Modelling System (Gochis 16 et al.,

16 Stepwise Evaluation of WRF-Hydro Components 1. WRF simulations using global fine-resolution reanalysis information Experiment 1: Impact of domain size and model resolution on Experiment 2: Impact of parameterization/model physics schemes on Experiment 3: the simulation accuracy of daily precipitation and daily temperature characteristics (primary focus) 2. NDHMS simulations using semi-observed and simulated weather information Experiment 1: NDHMS simulations using simulated surface weather information from WRF Experiment 2: NDHMS simulations using observed precipitation fields instead of simulated precipitation fields 9/9/

17 Sissili basin Titelmasterformat durch agricultural Klicken land no big reservoirs: less regulated small portion of long-term daily discharge measurements at two gages! long-term daily precipitation measurements will be equipped with additional climate and hydrological stations this year precipitation stations climate stations discharge stations 9/9/

18 Example of a Simulation Domain for WRF-Hydro ca. 30 km x 30 km ca. 10 km x 10 km ca. 2.5 km x 2.5 km 9/9/

19 Experiment 2: Impact of Parameterisation Schemes Precipitation, May October 1999, 70 precipitation stations with daily measurements Ghana and Burkina Faso overestimation for daily precipitation can be clearly improved in comparison to a standard model configuration Key questions fur further model simulations: How is the model transferrability for a simulation period with different climate and land use characteristics? 9/9/

20 Summary/Conclusions 1. EC stations have been established recently in North Ghana and South Burkina Faso along a transect of increasing agricultural activity to investigate the impact of land surface changes on hydrometeorological fluxes (long-term experiment) to gain additional information for model assessment e.g. for Noah LSM, NDHMS, WRF and WRF-Hydro 2. Novel two-way coupled atmospheric-hydrological modelling system: WRF-Hydro Stepwise evaluation of WRF-Hydro components Problem: Daily precipitation characteristics are not simulated adequately further analysis is essential 9/9/

21 When would data and information become available for others? Thank You! This work is part of the Core Research Program of WASCAL, the West African Science Service Centre on Climate Change and Adapted Land Use, funded by the German Ministry of Education and Research 9/9/2014 and coordinated by the Centre of Development Research of the University 22 of Bonn