COSTA
www.costapse.org
Common Set of Tools for Assimilation of Data
COSTA
An Introduction
Nils van Velzen
email: [email protected]
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
www.costapse.org
Common Set of Tools for Assimilation of Data
Outline
•
•
•
•
Data assimilation and calibration
Existing software and programming issues
COSTA
Application of COSTA with
WAQUA/TRIWAQ
• Conclusions
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Data assimilation and calibration
• (Dynamic) simulation models
– Weather forecast
– Air quality
– Shallow water (storm surge)
– Ocean modelling
– Reservoir
• Predictions are not perfect!
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Data assimilation and calibration
• Measurements:
– Satellites
– Buoy
– Radar
– Weather stations
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Data assimilation and calibration
– Make model perform better using the
available observations:
•
Calibration: change model parameters
in order to reduce the difference
between the model predictions and
observations
•
Data assimilation: combine the model
forecast and observations into a
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Existing software and
programming issues
• Simulation software is complex
• More complex is combined with Data
assimilation and/or Calibration methods
• Expensive to develop and maintain
• Splitting up software is in general a
good idea
– Less complex
– Possible to reuse (parts of) the code
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Existing software and
programming issues
• Why people think they have to develop a
custom implementation of a DA method:
– Computational efficient
– Need to handle model specific issues
• Are these assumptions correct? Issues are:
–
–
–
–
Which method to implement?
Expensive
Incompatible
Potentially full of bugs
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
COSTA
• A problem solving environment for data
assimilation and calibration
– Components and their interface
– Data assimilation methods
– Platform for exchanging models and methods
• Free software (LGPL)
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Steps to prepare model codes for
implementing data assimilation
• Identify the state-vector of your model and
those parameters and forcing (you think)
you want to use
• Isolate the model time step
--This is 90% of the work and has to be done
for a custom data assimilation
implementation as well
--COSTA provides tools to simplify this work
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
COSTA
• A generic environment where user can
easily try out different DA-methods to their
models
• A generic environment where method
developers can easily implement their
method to different models
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
COSTA
• Most data assimilation actually only requires
information about model state and
observation at the same time.
• This makes it possible to implement model,
observation and data assimilation methods
separately as independent components.
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
COSTA components
Model, observations and DA-method
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Model Component
• Model component in COSTA (formal)
d
x
t



M
x
t
,,
p
uw
t
,
t







d
t
• State of a model instance x,u,p, w,t
• Methods to get or change the state of
model instance
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Model Component
• Propagate the model state-vector
t


t
x
t

M
xp
t
,,
u
t
,
w
td









t

t
t ,p
,u
t ,w
t
• Get, set, axpy for x



t
Hx
• GetObsValues: yt
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Using COSTA
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Using COSTA
• Use the “costawb” program to combine
a model with a DA-method without any
programming
• Model components are dynamic
libraries and are linked to the “costawb”
program
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
WAQUA/TRIWAQ
• Simulation model for shallow water
• Used operational by the Dutch
Rijkswaterstaat
• Long history of data assimilation
– Too expensive
– Inflexible
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
WAQUA/TRIWAQ
• Domain decomposition and parallel
computing
• COSTA
model
component
• RRSQRT
Filter
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
The WAQUA/TRIWAQ model

Deterministic model:
[
φ t i+ 1 =A φ t i ,u t i ,g

Stochastic model:
A [φ t ,u t +W
φ t
t
t
i+1
pu t i+ 1 =
p
A
or
t i+ 1
f
i
u
i
diag α
diag α
[
]
]
p u t i ,g +W A p A t i
A
u
A
p
u
p
ti
ti
]
x t t i+1 =M i x t i +η t i
Data Assimilation Summer School, Sibiu, 6th August 2009
0
η u ti
η
A
ti
COSTA
Common Set of Tools for Assimilation of Data
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Deterministic and Stochastic

We want a separation between
deterministic and stochastic model

Use deterministic model for other applications

Play with alternative
noise models
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Deterministic and Stochastic


WAQUA/TRIWAQ uses ADI-scheme:

One time step consist of two half time steps

Time correlation applied each half time step
New approach:

Time correlation
each whole
time step

Different results!
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data


Can we:
Challenge

Separate filter and
method Method?

have same results?

Similar performance?
Is the COSTA model
interface sufficient
for this task?
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Conclusions
• COSTA offers a flexible framework for
using and developing data assimilation
methods.
• Successful coupling with “real” models:
– WAQUA/TRIWAQ
– Lotos-Euros
– Chimere
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Conclusions
• Easy to use
• Complete basic functionality available:
– Implementation available for all basic
building blocks
– Growing number of available methods
• Support for parallel computing
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Thank you!
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Existing software and
programming issues
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Tools for creating COSTA
models
• Simple model builder
– Handles the “object oriented” aspects of the model
– You only need to implement 4 functions
• Model combiner
– Combine multiple COSTA models in one composite
model
– Create a stochastic model from a deterministic model
• Black Box model builder
– Create a COSTA component for a model without
changing the model code
• Support for parallel models
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Automatic parallelization
Data Assimilation Summer School, Sibiu, 6th August 2009
COSTA
Common Set of Tools for Assimilation of Data
Using parallel models
Data Assimilation Summer School, Sibiu, 6th August 2009