The modeling efforts for the UMRB Pilot Project are
discussed here as they relate to the three specific UMRB science objectives:
- The first UMRB science objective will be addressed by
using the surface and subsurface components of a coupled atmosphere-land
surface-subsurface hydrology model. The working hypotheses is:
Ground water in aquifers is an important
component of the water budgets and water resources in the Upper Missouri River Basin on
seasonal to interannual scales.
The model will be driven by surface inputs obtained
through the GCIP Data Management and Service System (DMSS): precipitation from NEXRAD
products and other variables from Regional Mesoscale Model (RMM) data sets. A simlulation
run over an extended period, say one water year, will bring the aquifer groundwater
components as well as the surface flows into play. This will illuminate the linkage
between surface and groundwater and the importance of the latter to the overall water
budget and water resources of the region. The coupled model is currently being tested for
an ISA-sized region in the Black Hills, and data from the Black Hills Hydrology Study
(BHHS) will be available for model validation.
- The second UMRB science objective will be addressed
through numerical modeling studies using nested models existing or under development. The
working hypothesis is:
Models with resolution finer than that used in
current RMMs will be needed to depict precipitation and other components of the water
budget adequately in orographic terrain.
The critical questions to be examined involve
evaluations of fundamental issues for modeling orographic precipitation: 1) Resolution of
orography needed to correctly capture its effect on precipitation; 2) importance of local
and mesoscale variations in evapotranspiration and input soil moisture on clouds and
precipitation; 3) importance of spatial and temporal variations of moisture advection on
the ISA and mesoscale.
The Clark model has already been used to simulate
precipitation episodes over the Black Hills region. A coupled
atmospheric/surface/subsurface model involving the ARPS atmospheric model is being
constructed at the South Dakota School of Mines and Technology (SDSM&T) under a National Science Foundation (NSF) EPSCoR (Experimental Program to
Stimulate Competetive Research) project. Model runs will be initialized from available
case study data or from the Eta or RUC RMM. We will use observational data from the BHHS
as well as from the URMBPP special IOP observations fromthe GCIP DMSS for model
validation. Simulations at multiple grid resolutions will assess the effect of model
resolution of topography and atmospheric processes on clouds and precipitation in
orographic terrain. Additionally, sensitivity of simulated precipitation to
evapotranspiration rates and initial soil moisture conditions will be determined.
Simulations of the sensitivity of precipitation to
spatial and temporal variations of atmospheric moisture advection will provide a context
for evaluating the importance of observed variations of moisture advection obtained in the
IOP.
Since ARPS can be a nested component of the Eta
model, the transition to regional mesoscale modeling will be facilitated. This work
contributes directly to the GCIP objective to understand the physics of precipitating
clouds and their relation to the storm environment and the produced precipitation fields
by helping to understand the effects of orographic influences.
- The third UMRB science objective will be approached by
a combined observational and coupled modeling study of the Black Hills ISA. The working
hypothesis will be:
The normal observational system needs to be
augmented to obtain adequate water budgets on ISA, and perhaps larger, scales in
orographic terrain.
This component will take advantage of the
infrastructure established by the BHHS. The UMRBPP builds on the BHHS database with
enhanced observations of atmospheric fluxes. The mesoscale modeling studies will use the
observational data for validation and also provide values for unobserved components. The
coupled atmospheric-surface-subsurface model will produce component and total water
budgets for comparison with the observations and for assessment of dominate terms and
major uncertainties in the budgets. An improved snowpack/snowmelt module will be added to
the model to facilitate the simulations. This model is initiated from the Eta model, and
its nesting feature permits evaluating the effect of model resolution on the results.
The coupled model will simulate one or more
well-observed episodes from the Spring 1999 Intensive Observational Period (IOP). Values
of the fluxes and precipitation, as well as surface and subsurface flows, will be
validated against the observations. Variables and flux components from the model as well
as from the Eta and RUC RMMs will be compared with the observations, and budgets computed
to assess their usefulness, the dominant terms, and the potential uncertainties on the ISA
scale. The results will assist in understanding the uncertainty in GCIP data sets.
The observations, both routine and enhanced, will
provide spot check points for model validation and, under favorable circumstances, enough
data to compute rough budget estimates. Budgets will also come from the RMMs for the full
IOP duration and from the coupled atmospheric/surface/subsurface model for intensively
observed episodes within the IOP. The latter will contribute towards the GCIP objective to
"develop energy and water budgets for selected ISA/SSA...". This work will focus
on cold season precipitation issues in orographic terrain, which links to the science
agenda developed from the GCIP Coupled Modeling Workshop.
Go to UMRB Tasks :
Observational
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