Wednesday, March 28, 2012


date: Wed, 20 May 2009 13:01:49 +0100
from: Clare Goodess <>
subject: Fwd: Re: CIRCE urban heat island simulations for Athens


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>Subject: Re: CIRCE urban heat island simulations for Athens
>From: Mark McCarthy <>
>Cc: Clare Goodess <>, maureen agnew <>
>Date: Tue, 19 May 2009 12:16:32 +0100
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>Hi Christos,
> Thanks for this. Glad you downloaded the data OK. Answers to your
>questions are:
>1) In section 3.1 of my report I use the urban tile from NoUrbNoAnth and
>define the urban heat island as the difference between the urban tile
>and the gridcell mean. In this particular experiment the urban coverage
>is set to zero so that there is no feedback of the urban surface onto
>the gridcell mean. This was done for simplicity. For section 3.2 I also
>reference the other experiments, but I do use the urban tile
>2) Yes the missing gridcells are sea points in the model.
>3) Model resolution is 25km. It is on a rotated pole grid so the cells
>are not aligned N-S. I attach a file of lat-lon coords for the corners
>of the gridcells. You will also notice that it does not fit neatly over
>Athens. The model will have the peak heat island where there is peak
>urban coverage. Therefore gridcell 5 is defined as the "Athens" gridcell
>for the model because it has the highest urban fraction (40%). You
>should already have the fractional coverage of surface types for each
>gridcell but let me know if you do not.
>4) No I do not use neighbouring grid cells. There are significant
>temperature differences between the "central" athens gridcell and its
>neighbours even without the inclusion of urban areas. Therefore I
>defined the urban heat island using the NoUrbNoAnth experiment (see
>answer to quest. 1 above). This will be an underestimate because we do
>not account for the feedback into the atmosphere. Defining what the
>urban heat island actually is for both model and observations is rather
>With reference to your plots:
>Fig.1 What are the observations? Are they a single station or from a
>gridded product?
>The model appears to have a significant summer warm bias. For such a
>local comparison we shouldn't expect to achieve quantitative agreement
>between the model and the observations. The purpose of the frequency of
>hot nights/days in the report is to show the sensitivity of extremes to
>urbanisation and climate change. You could always try applying a simple
>bias correction to the model temperatures and then recalculate the
>exceedences to see if that brings the model and observations more in-
>Kind regards,
>On Fri, 2009-05-15 at 13:12 +0300, CHRISTOS GIANNAKOPOULOS wrote:
> > Dear Mark,
> >
> > we have started to process the UHI data for Athens from the data we have
> > dowloaded from the website you have pointed out.
> > Our first task was to try to reproduce the figures in your CIRCE UHI
> > report. The attached file contans some of our graphs where we have also
> > added the observations from the station of NOA in the centre of the city.
> > Some questions remain:
> > 1) we believe that in your figure reports you are using the
> temperature from
> > the tiles and not the gridcell mean. Pls confirm
> > 2) for Athens some gridcells are missing (7, 8,9) from the files we have
> > downloaded. We believe they are missing becasue they are sea gridcells. Pls
> > confirm.
> > 3) Can you provide us the exact coordinates of the cells for the files in
> > the website? What is the model resolution (25km?)?
> > 4) In your report to calcuate the UHI, you use all the neighboring cells of
> > the city?
> >
> > Please let me know if you want more clarifications on these.
> > We will be happy to provide more plots if needed.
> > Best,
> > Christos
> >
> > Dr. Christos Giannakopoulos
> > Senior Researcher
> > Institute for Environmental Research and Sustainable Development
> > National Observatory of Athens
> > V.Pavlou and Metaxa Str., P.Pendeli
> > GR-15236 Athens, Greece
> > Tel: +30-210-8109128
> > Fax: +30-2108103236
> > email:
>Mark McCarthy Climate Impacts Scientist
>Met Office Hadley Centre, Fitzroy Road, Exeter, EX1 3PB
>Tel: +44(0)1392 884672 Fax: +44(0)1392 885681

Dr Clare Goodess
Climatic Research Unit
School of Environmental Sciences
University of East Anglia

Tel: +44 -1603 592875
Fax: +44 -1603 507784


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