12th Alps-Adria Scientific Workshop
Opatija, Doberdò, Venezia – Croatia – Italy 2013
THE IMPACT OF SOIL TEXTURE AND LAND USE ON LANDSURFACE/ATMOSPHERE INTERACTIONS IN AN
ANTICYCLONIC WEATHER TYPE
Ferenc ÁCS 1 – András Zénó GYÖNGYÖSI 1 – Hajnalka BREUER 1 – Kálmán RAJKAI 2
1
2
Department of Meteorology, Institute of Geography and Earth sciences, Faculty of Science, Eötvös Loránd
University, Pázmány Péter sétány 1/A., 1117 Budapest, Hungary, [email protected]
Centre for Agricultural Research, Institute for Soil Science and Agricultural Chemistry, Hungarian
Academy of Sciences, Hermann Ottó út 15., 1022 Budapest, Hungary, [email protected]
Abstract: Earth is going trough fast global change involving its important resources as climate and soil
fertility as well. Both of them substantially determine the carrying capacity of the biosphere. Climate and soil
fertility as well as their changes are closely linked in many aspects. In spite of this there are more unknown
processes in this tightly coupled system. Both parts are highly depending on land use and soil texture because
these two factors determine not only the biophysical but also the biogeochemical processes. In this work landsurface/weather relationships are treated involving the biophysical - energy and water transport - processes
since they act as „drivers” of the biochemical processes. The land-surface/weather interaction is analyzed
investigating the sensitivity of planetary boundary layer height to land use and soil texture types. The
presented sensitivity studies are performed above the Carpathian basin for shallow convection typical for
anticyclonic weather type. The research tool used is the WRF (Weather Research Forecast) modeling system;
the results are analyzed visually. The first results suggest that planetary boundary layer height changes are
more sensitive to soil texture than to land use. The results can be applied in the WRF-GHG (Greenhouse Gas)
modeling framework used for soil quality estimations.
Keywords: planetary boundary layer height, soil texture, land use, anticyclonic weather
Introduction
Biosphere is one of the most important features of the Earth. This ancient, sophisticated,
aestetic, and extremely flexible system can also be scientifically treated by using
DGVM-GCM (Dynamic Global Vegetation Models – Global Circulation Models)
models since couple of decades. In this modeling system there are basically three types
of processes: vegetation-atmosphere (V-A), soil-atmosphere (S-A) and vegetation-soil
(V-S) exchange processes. Among these the less known processes are related to V-S
interactions which also fundamentally determine the ecosystems’ functioning.
DGVM-GCM modeling systems can also be used for investigating soil fertility/climate
relationships. So DGVMs are proper tools for treating soil fertility. They are concerned
with soil’s C, N and P turnover, net nitrogen mineralization and plant species
composition in a range of agro-ecosystems of arable croplands, grasslands and forests
and peatlands. N cycle is tightly coupled to V-S C dynamic, so the N availability also
affects the structure and functioning of the ecosystem. For instance, low nitrogen
availability leads to lower nitrogen and higher lignin content in litter slowing
decomposition rate and reducing nitrogen release. Vice versa, high nitrogen availability
results high nitrogen but low lignin content in litter producing a faster decay rate and
higher nitrogen availability. The importance of tightly coupled C-N cycling in V-S
system was demonstrated, for instance, by Thornton et al. (2007) in the framework of
the Community Land Model – Carbon, Nitrogen (CML-CN). Thornton et al. (2007)
obtained that global terrestrial C uptake under elevated atmospheric CO2 concentration
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was reduced in CLM-CN by 74% with respect to CLM-C the version when N limitation
was included (Ostle et al., 2009). GCMs are standard tools for simulating global
climate. Climate is mainly governed by V-A and S-A interactions represented by
processes spanning across the whole time-space range. Both the climate and soil fertility
depend on many factors. Among them, in our opinion, special attention is to be paid to
soil texture and land use.
In Hungary, DGVM-GCM modeling systems are not in use. Only weather (e.g. WRF,
Weather Research Forecast) and regional climate models (e.g. REMO, Regional
Model) are run either for scientific or for operational purposes. Our group uses WRF
modeling system as research tool since 2010s. Up to date the soil-atmosphere
relationships were investigated. In this work WRF will be used as surrogate of DGVMGCM. Research related to soil-atmosphere relationships is extended by land useatmosphere interaction aspects. More precisely, it will be compared the sensitivity of
planetary boundary layer height to different soil textures and land uses to get more
insights into short term land-surface-atmosphere interaction characteristics. These tests
serve good basis for investigating climate/soil fertility relationships.
Materials and methods
WRF modeling system: WRF is a well-known mesoscale model constructed for both
research and operative goals. This USA product is used world-wide as research tool; in
Hungary since couple of years.
Noah land-surface model: Noah is a well known land-surface parameterization scheme
which is the result of a long term evolution (Mahrt and Pan, 1984; Pan and Mahrt, 1987;
Chen and Dudhia, 2001). It possesses a multilayer soil and a single layer snow and
canopy model. More about the soil and the vegetation modules can be found e.g. in
Horváth et al. (2009).
Atmospheric data: The day chosen for analysis is 5th July, 2012. On this day
anticyclonic weather type prevailed. The sky above Great Plain of Hungary was
completely cloud-free, above the Transdanubian part of the country only partly.
Atmospheric boundary conditions are taken from the GFS global model every 6 hours
started from 00 UTC.
Land-surface data: Noah uses a dozen land-surface parameters. Many of them are
highly dependent on the land use and the soil texture type. Therefore we paid more
attention to these two factors. The land use is specified after USGS (United State
Geological Survey) categorization. 21 land cover types are distinguished, among them
only a few (e.g. crop, crop/grass, forest, bare ground, water, urban) are used since in
Hungary mainly the „crop/grass” and „forest” land cover types are frequent. According
to parameter values these land cover types differ mostly in roughness length, z 0 (z0 for
forest is about 0.5 m, while for crop/grass it is about 0.1 m). Soil texture categorization
is given after USDA (United State Department of Agriculture), this means that in total
11 soil texture classes are distinguished. The areal distribution of these classes is
specified according to FAO (Food and Agriculture Organization). Among 11 soil
textural classes only 7 classes occure in Hungary, sand and clay alike.
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12th Alps-Adria Scientific Workshop
Opatija, Doberdò, Venezia – Croatia – Italy 2013
Sensitivity tests: Four runs are performed for sensitivity tests to test the major
differences. In each run a specific land use/soil texture combination is used to Hungary.
In Run 1, „actual” land use of the USGS is used. The soil texture is specified as sand. In
Run 2 the soil texture is clay. In Run 3, Hungary is completely covered by land use type
of „crop/grass”, the soil texture is specified by FAO. In Run 4 land use type of „forest”
is used.
Table 1. Main land-surface characteristics of the runs used in this study
Run type
Run 1
Run 2
Run 3
Run 4
Main land-surface conditions as used in Hungary
Land use
Soil texture
actual
sand
actual
clay
crop/grass
actual
forest
actual
Comparison of the results obtained by Run 1 and 2 enables us to analyze sensitivity to
changes of soil texture (sand/clay). This will be referred as comparison 1. Similarly,
comparing results of Run 3 and 4 we will get the sensitivity to crop, grass/forest land
use differences. This will be noted as comparison 2.
Results and discussion
The areal distribution is analyzed. The chosen term was 12 UTC. For actual land use,
the planetary boundary layer height (pblh) sensitivity to soil textures is shown in
Figure 1. Areal distribution of planetary boundary layer height differences obtained in comparison 1
Figure 1. According to weather situation, there are two distinct areas: the Great
Hungarian Plain and Transdanubia. In Transdanubia the areal heterogeneity of pblh
differences is large because of variable cloud cover. The pblh differences range between
a few and -1000 meters. For taking the actual soil texture territorial distribution, the
sensitivity of planetary boundary layer height to the two different land use types is
presented in Figure 2.
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Figure 2. Areal distribution of planetary boundary layer height differences obtained for comparison 2
The largest pblh differences are about -1000 m, that is they are as large as the
differences obtained in comparison 1.
Conclusions
In this study, WRF modeling system is used as surrogate of DGVM-GCM for analyzing
a not enough investigated aspect of land-surface/atmosphere interactions: the sensitivity
of planetary boundary layer height to changes of soil texture and land use. In our
opinion, these tests could serve as a good basis for investigating climate/soil fertility
relationships. The preliminary results suggest that planetary boundary layer height is
about equally sensitive to soil texture and land use changes in an anticyclonic weather
type when the process of shallow convection is prevailing.
Acknowledgements
The work was supported by the contract OTKA K81432, and by the European Union
and co-financed by the European Social Fund (TÁMOP-4.2.2/B-10.1-2010-0030).
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