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Alina Premrova,b *, Matthew Saundersb, Florence Renou-Willsona
a School of Biology & Environmental Sci., Science Centre –West, University College Dublin, Belfield, Dublin 4, b Botany Dept., School of Natural Sci., Trinity College Dublin, Dublin 2, * Corresponding author: premrova@ucd.ie
Biogeochemical modelling of Irish peatland
sites - Insights into the procedures for
estimating potential evapotranspiration for
long-term average climate input data
Peatlands are known to represent one of the most important terrestrial carbon (C) stores, and in their natural state they can act as an important C
sink. However, if they are exposed to anthropogenic changes (such as drainage) peatlands can act as C source. Biogeochemical models are
often used for modelling the greenhouse gas (GHG) emissions from different systems [1].. This work is performed as part of the EPA funded
AUGER project (“AUGER - Peatland properties influencing greenhouse Gas Emissions and Removals”)[1], which uses the ECOSSE (“Estimating
Carbon in Organic Soils-Sequestration and Emissions”)[2] process-based biogeochemical model to model and predict GHG emissions associated
with different land use/management of Irish peatlands[1]. During the model spin-up, the ECOSSE requires long-term (30 yrs.) average climate input
data –i.e. monthly mean temperature (Temp), rain (Rain) and potential evapotranspiration (PET)[2]. Insights into the procedures for estimating
PET from other climate-parameters (e.g. Temp) obtained from Met Éireann 30 year averages (1981-2010) climate data [3] are presented here.
30 years average Temp and Rain climate gridded data at 1km resolution were obtained from Met Éireann (1981-2010 averages) [3]. PET was not
included in the Met Éireann datasets and had to be estimated using computation methods that would require minimum number of parameters.
Used was the Thornthwaite (1948) method for estimating PET, which is well known for its simplicity [5],[6],[7]. First the annual heat index (I) was
calculated from monthly indices (i) using Temp. This was necessary because the coefficient α, required for computation of PET, is a function of I
[5],[6] [7]. The maximum number of sun hours N(also required for computing PET), was calculated from the hourly angle of sun rising (ωs), which
was obtained from the latitude in radians (latrad)and solar declination (δ)[8]. Computing steps are illustrated with examples presented in Figs. 1a,
1b, and 1c. Equations for computing PET using Thornthwaite (1948) method [5] and methods for computing δ,ωsand Naccording to the FAO
guidelines [8] are presented in Fig. 1b.
●Procedures for estimating potential evapotranspiration
IGRM - The 63rd Irish Geological Research Meeting –28th Feb. to 1st March, 2020, Athlone, Co. Westmeath, Ireland
LITERATURE
[1] AUGER, 2018. http://www.ucd.ie/auger/.
[2] Smith, J. et al. 2010. ECOSSE. User Manual.
https://www.abdn.ac.uk/staffpages/uploads/soi450/ECOSSE%20User%20manual%20310810.pdf
[3] Met Éireann, (2012) 30 year averages. Met Éireann - The Irish Meteorological Service, Ireland. URL:
https://www.met.ie/climate/30-year-averages.
[4] R Core Team. 2019. R v.3.6.0 https://www.R-project.org/.
[5] Thornthwaite, C.W. (1948) An Approach toward a Rational Classification of Climate. Geographical Review 38, 55-
94.
●Introduction & background
●Acknowledgements
The AUGER project is funded under the Irish Environmental Protection Agency (EPA) Research Programme 2014-2020. The EPA Research Programme
is a Government of Ireland initiative funded by the Department of Communications, Climate Action and Environment. It is administered by the EPA,
which has the statutory function of co-ordinating and promoting environmental research. Many thanks go to Dr Jagadeesh Yeluripati from The James
Hutton Institute, Aberdeen, Scotland, UK, for providing ECOSSE v.6.2b and for his advice and support.
[6] Werner, C., Nolan, P. and Naughton O. (2019) High-resolution Gridded Datasets of Hydroclimate
Indices for Ireland. ICHEC. http://www.epa.ie/pubs/reports/research/water/Research_Report_267.pdf
[7] Wayne, C.P., Vaughn Havens, A. (1958) A graphical technique for determining evapotranspiration by
the Thornthwaite method. 86, 123-128.
[8] FAO, (1998) Crop evapotranspiration - Guidelines for computing crop water requirements - FAO
Irrigation and drainage paper 56. http://www.fao.org/3/X0490E/x0490e07.htm#solar%20radiation
[9] Images adapted from http://www.ucd.ie/ferg/Research/Projects/BOGFOR//, http://www.ucd.ie/bogland/,
http://www.ucd.ie/auger/communicationhub/
Land Use & Management
Fig. 1a
Site parameters
Long-term average climate data (AVEMET.DAT)
Fig. 1b
Fig. 1c
[2]
[Note: figures are provided for illustrative purpose, scale may be distorted]
Modelling using ECOSSE 6.2b
[9]
[9]
[5],[6], [7], [8] [3]
