 |
| Titel |
A COsmic-ray Soil Moisture Interaction Code (COSMIC) for Use in Data Assimilation |
| VerfasserIn |
W. J. Shuttleworth, R. Rosolem, M. Zreda, T. Franz |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060568
|
|
|
|
|
|
| Zusammenfassung |
| If the cosmic ray induced above-ground fast neutron count is to be used to update the soil
moisture status in a Soil-Vegetation Atmosphere Transfer Scheme (SVATS) using data
assimilation, a model is required to accurately calculate the above-ground neutron count rate
from the profiles of soil moisture modeled by the SVATS. An accurate model, the Monte
Carlo N-Particle eXtended (MCNPX; http://mcnpx.lanl.gov/) exists to do this but, because
this is a time consuming Monte-Carlo model, using it in the context of data assimilation is
impractical. Consequently an alternative and efficient model is needed which can be
calibrated to accurately reproduce the calculations made by MCNPX and used to substitute
for MCNPX during data assimilation. This paper describes the construction and calibration of
such a model, COSMIC, which is simple, physically-based and analytic and, because it runs
approximately 5000 times faster than MCNPX, is appropriate for in data assimilation
applications. The model includes description of (a) degradation of the incoming high
energy neutron flux, (b) creation of fast neutrons at each depth in the soil, and (c)
degradation of the resulting fast neutrons before they reach the soil surface, all of
which processes have parameterized dependency on the chemistry and moisture
content of the soil. The comparative performance of SPAM relative to MCNPX when
applied to represent cosmic-ray/moist soil interactions at several deployment sites
within the COsmic-ray Soil Moisture Observing System (COSMOS) is described. |
|
|
|
|
|
|