ceh-gear dataset (bhs2014 birmingham)
TRANSCRIPT
Maliko Tanguy, V. Keller, I. Prosdocimi, J. Terry,
O. Hitt, S. Cole, M. Fry, D. Morris and H. Dixon
BHS 2014, Birmingham 2-4 September
The new CEH-GEAR dataset:
Fine resolution daily and monthly
areal rainfall estimates for the UK
Contents
1 Introduction
2 Methodology
3 Analysis
4 Examples of use
5 Access
Contents
1 Introduction
2 Methodology
3 Analysis
4 Examples of use
5 Access
Introduction Method Analysis Examples Access
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What does CEH-GEAR stand for?
Gridded Estimates of Areal Rainfall
Introduction Method Analysis Examples Access
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What is CEH-GEAR dataset?
MAIN PRODUCT: 1 km gridded rainfall
DAILY and MONTHLY totals for the UK 1890-2012
UPDATED YEARLY
SUB-PRODUCTS: DAILY and MONTHLY grids of the distance to
the closest gauge Ancillary grids:
- grid of first year of missing data - grid of last year of missing data - grid of total days/months of missing data
Introduction Method Analysis Examples Access
Hydrological purposes
Long record (back to 1890)
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CEH-GEAR: Main Features
Based on observed data
FREE (terms & conditions apply)
0
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Nu
mb
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of
rain
gau
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Year
GB daily gauges
Introduction Method Analysis Examples Access
Raingauge network density varies in time.
Peak in 1975: ~5000 gauges
Pre-1961: few stations digitised (500 in 1960)
From1961: most gauges been digitised Decrease since mid-70s:
currently around 2700 raingauges
Introduction Method Analysis Examples Access
Raingauge network density varies in time.
1910 1940 1961
Contents
1 Introduction
2 Methodology
3 Analysis
4 Examples of use
5 Access
NATURAL NEIGHBOUR method
Based on THIESSEN polygons
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Complies with BS 7843-4:2012 from the British Standards Institution
rci,t = calculated rainfall for point i at time interval t i
rj,t = measured rainfall for raingauge j at time interval t
j=1 j=2
j=3
j=…
j=p
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Wi,j,t = Weight for raingauge j in time interval t, when used in the estimation of rainfall for target grid point i
Si , Sj = Standard-period Average Annual Rainfall (SAAR) at point i and j
Intro Methodology Analysis Examples Access
Natural neighbour method
Normalisation by SAAR
For GB: Met Office SAAR (Spackman, 1993)
For Northern Ireland: Met Eireann SAAR (Walsh, 2012)
Intro Methodology Analysis Examples Access
Intro Methodology Analysis Examples Access
Monthly correction factor daily and monthly grids consistent
=
Sum of daily rainfall totals for 1 month
Monthly rainfall total
Contents
1 Introduction
2 Methodology
3 Analysis
4 Examples of use
5 Access
Intro Method Analysis Examples Access
For validation: 14 sites chosen
Intro Method Analysis Examples Access
Sites chosen in areas with high spatial variability in rainfall
Intro Method Analysis Examples Access
Error: Some outliers
(Scotland)
Larger error for bigger rainfall events
On average: slightly underestimates biggest rainfall events
Low rainfall High rainfall
rcp: calculated rainfall rco: observed rainfall
Erro
r
Small error when no or little rain
Intro Method Analysis Examples Access
For assessing the effect of network density: 138 SEPA TBRs (Tipping bucket raingauges)
Intro Method Analysis Examples Access
Effect of network density: Median absolute error vs. Distance to the closest gauge
Low rainfall High rainfall
Error with distance for BIGGEST rainfall events
Error when distance to the closest gauge
Ab
solu
te e
rro
r
Distance (km)
Intro Method Analysis Examples Access
Error when distance to the
closest gauge
MINIMUM DISTANCE GRIDS: Grid of the distance to the
closest gauge
Contents
1 Introduction
2 Methodology
3 Analysis
4 Examples of use
5 Access
Intro Method Analysis Examples Access
Drought Monitoring Drought indicator: SPI (Standardised Precipitation Index)
March 2010 June 2010 May 2011 March 2012 June 2012
Intro Method Analysis Examples Access
Land surface model CHESS: JULES applied to the UK CEH-GEAR used as one of the 7 driving variables
to run CHESS. CEH-GEAR
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Will use CEH-GEAR dataset to derive catchment averaged rainfall time series.
National River Flow Archive
www.ceh.ac.uk/data/nrfa/
Catchment averaged rainfall time series
This data is fictitious. Used for illustration purpose. only
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Contents
1 Introduction
2 Methodology
3 Analysis
4 Examples of use
5 Access
Intro Method Analysis Examples Access
https://gateway.ceh.ac.uk
Intro Method Analysis Examples Access
CEH GEAR
First result
Intro Method Analysis Examples Access
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Data stored in NetCDF format • array oriented scientific data • highly portable • built-in metadata
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Will be fully operational in
November 2014
http://doi.org/10.5285/5dc179dc-f692-49ba-9326-a6893a503f6e
THREDDS DATA SERVER
In the meantime: [email protected]
Summary of key ideas
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UK 1km gridded rainfall DAILY and MONTHLY totals
Back to 1890 and updated yearly
CEH-GEAR
COME AND SEE ME AT THE STAND !
For more info: CEH stand at BHS 2014, Birmingham
Contact:
Twitter: @MalikoTanguy
@CEHScienceNews
Thank you