ELDAS URD (draft)
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ELDAS User Requirements Document
(DRAFT)
Project ID
EVG2-2001-00013
Date of preparation
12-2-2016
Contents
1. Introduction
2. Identification of sectors
3. List of institutions & requirements
ELDAS URD (draft)
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1. Introduction
As a first iteration of the ELDAS User Requirements Document (URD) an inventory
of potential types of institutions (companies, governmental services, research
institutions, …) that has a potential interest in ELDAS products has been compiled in
section 2. This compilation is based on the experience of members of the ELDAS
team, who represent a wide range of potential users of soil moisture fields at regional
European scale. Section 3 provides a list of potential institutions and their specific
requirements with respect to the ELDAS product. This section is to be completed in a
later stage of the ELDAS project.
2. Identifications of sectors
ELDAS aims at the design and test of an infrastructure for soil moisture assimilation
at the regional to global scale. During the project period, a prototype system will be
designed and implemented, and experiments will be carried out addressing the
validation and application of the soil moisture fields produced with the ELDAS
system.
The motivation of this project is based on a number of potential impacts of regional
scale soil moisture:
 Short- and medium-range Numerical Weather Prediction (NWP) is shown to
be sensitive to the treatment of soil moisture in the prediction models. The
land surface routines used in these applications are necessarily simplifications
of reality and suffer from systematic shortcomings. NWP forecasts need to be
kept on a realistic track by means of corrections derived from available routine
observations. ELDAS is designed to be highly compatible with this data
correction practice, by its choice of spatial and temporal resolution, type of
data used and algorithms applied.
 Seasonal predictions by these NWP-centers are known to be sensitive to the
hydrological memory of the soil water reservoir. In particular the occurrence
of persistent droughts is related to systematic interaction between the soil
moisture reservoir and the atmospheric hydrological cycle. ELDAS products
are assumed to contain potentially useful information on the soil moisture
conditions that can be related to the hydrological cycle on a seasonal time
scale, and may therefore serve as indicator for seasonal weather prediction,
including the prediction of droughts.
 Surface floodings is partially dependent on the state of the soil moisture
reservoir at the moment of excessive precipitation events. An accurate
monitoring of soil moisture evolution by a system similar to ELDAS may help
in assessing the risk of these floodings when excessive precipitation is
expected.
 Future climate predictions using numerical climate models show a wide range
of hydrological conditions for a given greenhouse gas scenario. This is
partially related to differences between (and uncertainties of) land surface and
soil moisture parameterization schemes used in these climate models. ELDAS
products may help in the creation of a soil moisture database compatible to the
quantity that is actually simulated in these climate models, and serve as
verification material to assess and improve the quality of climate models.
Emphasis of the ELDAS system design is the application of soil moisture assimilation
at a regional to continental scale. Methodologies developed and implemented for this
ELDAS URD (draft)
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spatial scale may well be applicable at smaller scales (individual small river
catchments or agricultural regions), but this is not explicitly addressed by the ELDAS
consortium.
Summarizing this discussion, the following sectors may be identified as potential
users of ELDAS products:
 National and European centers for Numerical Weather Prediction and
Seasonal Prediction
 Hydrological services monitoring soil moisture evolution in areas sensitive to
floodings after strong precipitation events
 Climate modeling institutions with expertise on land surface modeling and
evaluation of land surface models, in particular the soil hydrological
components of these land models.
These sectors all require soil moisture fields that extend over spatial scales varying
from large river basins to the global scale. The required spatial resolution depends on
the application, and varies from order 5  5 km for flood forecasting and mediumrange NWP applications to 252 km2 for seasonal and climate modeling applications.
In these large scale applications, temporal resolution is determined by the memory of
the soil water reservoir. Updates once per week are deemed sufficient. For short term
flood and weather forecasting daily updates of soil moisture fields are necessary.
3. List of institutions and requirements
To be compiled
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ELDAS End User Requirements – Draft Summary
The table below gives an overview of end user requirements. Shown are the potential end users and the (numbered) applications for which they
potentially benefit from ELDAS achievements. Also shown are their requirements and the way in which ELDAS may contribute to this. A final
column lists a number of relevant institutes in Europe.
End user group
Application
Numerical
1. Operational
Weather Prediction
weather
(NWP) centres
forecasting –
global scale
2. Operational
weather
forecasting –
regional scale
Requirements
ELDAS achievements
Examples of institutes
Near real-time soil moisture fields
For European area: see regional
expressed in quantities compatible to scale NWP (2).
the definition of root zone soil
moisture in the NWP model used.
Spatial resolution between 50 and
100 km. Temporal resolution 3 – 5
days. Areal coverage of soil
moisture fields must preferably be
global
European Centre for
Medium-range Weather
Forecasts (ECMWF)
Same as above, but spatial resolution
between 10 and 25 km, temporal
resolution daily, areal coverage at
least Europe
HIRLAM-consortium
(NWP centers in Spain,
Netherlands, Ireland,
Sweden and others)
Set-up of infrastructure to make
compatible soil moisture
estimates; demonstration of the
system in case of availability of
forcing data covering Europe
only. Near real-time requirement
not met.
German Weather
Service (DWD)
Météo-France
DWD
Météo-France
ELDAS URD (draft)
End user group
Hydrological
services
Climate research
groups
5
Application
Requirements
ELDAS achievements
Examples of institutes
3. Seasonal weather
prediction
Same as global scale NWP
application (1), but less stringent on
near real-time requirement (delay of
about a week is allowed). Temporal
resolution is 10-daily.
See regional scale NWP (2),
which is relevant as European
sub-set for a global application
ECMWF
4. Flood forecasting
Root zone soil moisture content in
big river catchments at 1 – 10 km
resolution for estimation of
infiltration-excess and flood peak
timing and intensity
ELDAS-infrastructure may be
applied here, but typical ELDAS
resolution (20 km) probably too
coarse for application
UK Environmental
Agency, Dept. of Flood
Prediction
5. Routine
monitoring
Near real-time daily precipitation
and evaporation estimates at 10 – 20
km resolution
Demonstration data bases of
evaporation and precipitation
fields are produced within
ELDAS, but near real-time
requirement not met
same as above
6. Development and
evaluation of
climate models
Weekly – monthly fields of
evaporation, runoff, soil moisture
and precipitation at 50 – 100 km
resolution, covering at least Europe
and preferably global (retrospective
analysis possible)
Products of ELDAS system
compatible with climate model
requirements. Analysis of
potential value of ELDAS
products
Laboratoire de
Météorologie
Dynamique (LMD)
Netherlands Institute
for Inland Water
Management (RIZA)
Rossby Centre Sweden