1. Effects of Documented Land Use Change on Climate in Hungary
Áron Drüszler University of West Hungary, Institute of Environmental and Earth Sciences
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

2. Workshop in Landscape History, Sopron, Hungary, 22 April 2010
Introduction
Final aim of climate research: create correct forecasts of the changing climate
→ identifying all the different climate forcing processes
→ evaluating their impacts on the climate
What do we call climate forcing processes?
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

3. Workshop in Landscape History, Sopron, Hungary, 22 April 2010
Climate System
natural climate forcing processes:
solar variability
volcanic activity
changes in solar orbital parameters
Anthropogenic climate forcing processes:
greenhouse gases
aerosols
ozone depletion
jet contrails
land use change
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

4. Workshop in Landscape History, Sopron, Hungary, 22 April 2010
(IPCC, 2007)
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

5. Processes through which vegetation affects climate
Indirect:
Greenhouse gases (CO2)
Mineral dust aerosols
→ global climatic effects
Direct:
Albedo
Evapotranspiration
→ Primarily regional effects
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

6. Indirect Effects of Land Use Change
Carbon cycle in forests:
Sinks:
plants take in carbon through photosynthesis
Transfer of carbon to soil through litter fall → build-up of carbon in the soil
Sources:
return carbon to the atmosphere through autotrophic and heterotrophic respiration
Forest fire
net uptake of carbon by growth
→ Large scale changes in forest cover can affect climate
Plants take in carbon dioxide from the atmosphere through the process of photosynthesis, and although they return some to the atmosphere through autotrophic respiration, there is a net uptake of carbon enabling them to grow. Some carbon is transferred from plants to the soil through litter fall, leading to a buildup of carbon in the soil which itself can be returned to the atmosphere through heterotrophic respiration as part of the process of decay.
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

7. Indirect Effects of Land Use Change
Mineral dust aerosols:
Less vegetated, dry landscapes can be significant sources of dust
Dust can exert climatic effects by:
modifying the fractions of incoming solar radiation (cooling)
altering the absorption and transmission of outgoing terrestrial long wave radiation (warming)
→ The net climatic effect is still an open question
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

8. Direct Effects of Land Use Change
Albedo
Forests are generally darker than open land (lower albedo)
→ less sunlight is reflected
→ more available energy (warming effect)
Evapotranspiration (ET)
If the soil stores enough moisture then the afforestation can increase evapotranspiration
→ greater proportion of the available energy flows to the atmosphere through latent heat
→ (cooling effect at the surface)
The rate of ET depends on:
- current weather condition (moisture availability)
- vegetation-specific parameters (LAI, roughness length, rooting depth, etc.)
(Latent heat)
(Sensible heat)

9. The Net Climatic Effects of Afforestation
Tropics:
Net carbon uptake (cooling)
The influence of increased transpiration (the moisture is nearly limitless available) outweighs the impact of decreased albedo (cooling)
Boreal Forests:
Rates of carbon storage is much slower then in the tropics (cooling)
The impact of decreased albedo is much higher than the effect of increased transpiration (warming)
What can be the direct climatic effects of Hungarian land use change?

10. The MM5 Model The Fifth-Generation NCAR/Penn State Mesoscale Model
Equations of impulse-, mass- and energy conservation
Nonhydrostatic dynamic → Nowcasting
A number of physics options
OSU Land-Surface Model
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

11. Investigation the Climatic Effects of Land Use Change with MM5
The lower boundary conditions are generated for two selected time period (1900, 2000)
The MM5 land use map for 1900 is based on different maps (3rd Military Mapping Survey of Austria-Hungary, Synoptic Forestry Map of Hungarian Kingdom (1895) and on the database of Hungarian Central Statistical Office
The MM5 land use map for 2000 is based on the CORINE 2000 land cover database
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

12. Land Use Change in Hungary
1900
Forest (12.50 %)
Urban (2.43 %)
Grassland (15.99 %)
Cropland (61.0 %)
Vineyard (2.49 %)
Water (2.26 %)
Wetland (3.22 %)
2000
Forest (21.07 %)
Urban (5.69 %)
Grassland (9.53 %)
Cropland (56.8%)
Vineyard (1.51 %)
Water (1.86 %)
Wetland (1.12 %)
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

13. Investigation the Climatic Effects of Land Use Change with MM5
The dynamical model has been run with the same detailed meteorological conditions of selected days from 2006 and 2007 but with modified lower boundary conditions (resolution 2.5 x 2.5km)
The set of the 26 selected initial conditions represents the whole set of the macrosynoptic situations (Péczely, 1983) for Hungary.
The effects of land use change under the different weather situations are further weighted by the long-term ( ) mean frequency of the corresponding macrosynoptic types
→ Climatic effects
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

14. Effects of Land Use Change on the Regional Climate
Temperature
Dewpoint
Precipitation °C °C mm
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

15. Workshop in Landscape History, Sopron, Hungary, 22 April 2010
GyMS county:
Temperature
Dewpoint
Precipitation
+ 0.1 °C °C mm
Pest county:
Temperature
Dewpoint
Precipitation °C °C mm
Workshop in Landscape History, Sopron, Hungary, 22 April 2010

16. Workshop in Landscape History, Sopron, Hungary, 22 April 2010
Conclusions
Climatic effects of land use changes are not negligible (especially regional)
In urban areas (e.g. Budapest) the changes are more significant
Land cover differences can perturb the precipitation fields
→ Further process studies are needed in this region:
- New field and process-oriented studies that focus on processes critical to the temperate forests (length and frequency of droughts → new model running for longer time period)
- Observing and improving vegetation-specific land surface parameters which influence the rate of evapotranspiration in the model results
Workshop in Landscape History, Sopron, Hungary, 22 April 2010