CEH/NERC funded PhD studentships
CEH Wallingford, Maclean Building, Crowmarsh Gifford, Wallingford,
OX10 8BB
The Centre for Ecology and Hydrology (CEH), part of the Natural
Environment Research Council (NERC), carries out large-scale and
long-term research in the terrestrial and freshwater sciences to
support a broad user community. We address key environmental issues
through integrated monitoring, process studies and predictive
modelling, and the development of essential infrastructure and
facilities.
CEH Wallingford invites applications for the projects below from
graduates or final year students who have, or expect to have, a First
or Upper Second Class Honours Degree in a relevant subject. The start
date will be October 2003. UK residents will receive £12k pa. European
residents can apply for the post, but will not receive the grant.
Applicants should forward a CV and the names of two academic referees
to Lisa Stewart, [log in to unmask], by 16 June 2003.
Spatial dependence in flood and rainfall occurrence
The research is needed to estimate the probability of several areas
being flooded at the same time, or within a certain time period. This
is important for the co-ordination of flood mitigation activities,
estimation of the required capacity of the emergency services, and for
the re-insurance industry. The objectives are to identify areas where
spatial dependence in river flooding is particularly strong, and
possibly analyse what meteorological situations cause the flooding in
these areas. The concept of "collective risk" involves the estimation
of the probability of a flood of a certain return period occurring
somewhere in a particular area in any one year. Analysis of dependence
in precipitation data will be used to aid in the interpretation of the
results.
The techniques available for estimating collective risk of flooding
are not as well-developed as those available for single sites. Using a
simple pair-wise method on a sparse network of flow gauges in eastern
Britain, a previous study carried out at CEH Wallingford suggested
that spatial dependence is stronger in some areas than in others, and
that topography and seasonality play a part in determining the areas
in which dependence is important. The project involves a combination
of climatology/meteorology and statistics, and the emphasis on one or
the other will depend on the applicant. However, the candidate must be
numerate and computer literate.
Multi-cause uncertainty in hydrological modelling
A probabilistic model of, for example, the relationship between
rainfall and runoff, involves estimating probability distributions for
the inputs to the model and projecting those distributions through the
model in order to generate a probability distribution on the output.
This is usually, but not exclusively performed using Monte Carlo
simulation. It may also be necessary to calibrate the model in order
to represent a site of interest, and there are mechanisms available to
account for the uncertainties in this calibration process. Global
sensitivity analysis involves decomposing the variance in the model
output and attributing it to the uncertainties in the various inputs.
It is therefore possible to identify the inputs, or combinations of
inputs, that contribute the most uncertainty to the model prediction.
The proposed research will explore and develop these methods in the
context of rainfall-runoff models. In particular it will seek to
extend existing methods to deal with models driven by real or
simulated time series of rainfall data, in the first instance averaged
over a catchment and subsequently spatially distributed rainfall. The
work will be applied to a variety of rainfall-runoff models operated
by CEH Wallingford. Subject to satisfactory progress the study will
proceed to use a spatially distributed rainfall-runoff model to look
at changes in climate and land use and analyse the contribution that
the uncertainty in these different processes makes to the
uncertainties in runoff predictions.
The research will involve a combination of statistical analysis and
process-based modelling of the rainfall-runoff process. The candidate
must be numerate and computer literate and be willing to dedicate
themselves to a project involving a substantial quantity of
statistical analysis and computer modelling.
Carl Scarrott, PhD web : www.nwl.ac.uk/staffpages/cjsc
CEH Wallingford email : [log in to unmask]
Maclean Building tel : 01491 692291
Wallingford, OX10 8BB fax : 01491 692424
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