CEH-GEAR dataset (BHS2014 Birmingham)

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

Introduction Method Analysis Examples Access

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What does CEH-GEAR stand for?

Gridded Estimates of Areal Rainfall


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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


Hydrological purposes

Long record (back to 1890)

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CEH-GEAR: Main Features

Based on observed data

FREE (terms & conditions apply)

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GB daily gauges


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


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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Intro Methodology Analysis Examples Access

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


Natural neighbour method

Normalisation by SAAR

For GB: Met Office SAAR (Spackman, 1993)

For Northern Ireland: Met Eireann SAAR (Walsh, 2012)



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


Sites chosen in areas with high spatial variability in rainfall


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


For assessing the effect of network density: 138 SEPA TBRs (Tipping bucket raingauges)


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

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rro

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Distance (km)


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


Drought Monitoring Drought indicator: SPI (Standardised Precipitation Index)

March 2010 June 2010 May 2011 March 2012 June 2012


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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http://www.ceh.ac.uk/data/nrfa/

Contents

1 Introduction

2 Methodology

3 Analysis

4 Examples of use

5 Access


https://gateway.ceh.ac.uk


CEH GEAR

First result


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Data stored in NetCDF format • array oriented scientific data • highly portable • built-in metadata


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]










mailto:[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:

[email protected]

Twitter: @MalikoTanguy

@CEHScienceNews

Thank you









CEH-GEAR dataset (BHS2014 Birmingham)

Science

Transcript of CEH-GEAR dataset (BHS2014 Birmingham)