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| Titel |
Area integrated emission of biogenic nitric oxide by Lagrangian dispersion modeling (LASAT): Milan oasis, Taklimakan desert (Xinjiang, PR China) |
| VerfasserIn |
M. Badawy, Z. Wu, T. Behrendt, A. D. Fechner, F. X. Meixner, M. O. Andreae, B. Mamtimin |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250070180
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| Zusammenfassung |
| Today’s knowledge of soil biogenic NO emission rates from arid and hyper-arid land is based
on a total of about 20 experimental studies. Nevertheless, biogenic NO emissions even from
non-managed arid and hyper-arid soils are significant and may range between 1-10
ng m-2 s-1 (in terms of nitrogen, if conditions for soil NO production are favourable
(optimum soil moisture, high soil temperatures). Irrigated and fertilized oases, ranging about
3000 km long around the great Central Asian Taklimakan desert form the backbone of the
agricultural output (80% of the Chinese cotton production) of the Xinjiang Uygur
Autonomous Region (NW-China). Recent and future development of farmland and
intensification of agriculture will definitely impact the regional soil NO emission and
consequently the budget of nitrogen oxides and ozone. Up to today, only a few studies
have preliminarily addressed soil biogenic NO emissions from the Taklimakan
desert.
In our contribution, we will focus on the quantification of the area integrated NO
emission from the Milan oasis located on the most southern fringe of the Takalimkan
desert (39.26Ë N, 88.91Ë E). At a first step, the 3D distribution of ambient NO
concentration is calculated using a state-of-the-art commercially available dispersion
model (LASAT 3.2, Lagrange Simulation of Aerosol-Transport). Performing the
dispersion simulation, transport and turbulent diffusion are simulated for a group of
representative "simulation particles" by means of a stochastic process (Lagrange
simulation). Surface sources (individual cotton fields, Jujube orchards) are known:
their geographical location as well as their areal extent, their stage of vegetation
growth as well as irrigation and fertilization events and amounts, soil temperatures
and soil water contents. This information is used to up-scale our results of field
specific potential net NO emission, which has been parameterized in terms of soil
temperature, soil water content, and soil nutrient content. Meteorological input for
LASAT (wind speed and wind direction, atmospheric stability, roughness length,
radiation intensity) is provided by the results of an automatic weather station network,
consisting of six individual stations which have been distributed over the entire
oasis.
Given the 3D distribution of ambient NO concentration, vertical cross-sections of NO
concentrations up-wind and down-wind the Milan oasis will be constructed (perpendicular to
the main wind direction). The height- and cross-wind integrated horizontal NO
fluxes at the up-wind and down-wind end of the oasis is then calculated by double
integration of the product of NO concentration and horizontal wind speed (from ground
to height of mixing layer and along the cross-wind extension of the oasis). The
difference between the down-wind and up-wind integrated horizontal NO fluxes is
considered to be equal the area-integrated NO emission of the entire oasis, provided the
horizontal NO Flux at the up-wind end of the oasis is known (most likely equal
zero, since the oasis is isolated by the Taklimakan desert for more than 100-150
km).
Results of a three week period (June 2011) will be presented and will be discussed in
comparison to up-scaled, field-specific in-situ measured NO fluxes (dynamic chamber and
aerodynamic gradient techniques). |
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