ICHEC researchers lead Environmental Protection Agency (EPA) report on Irish hydro-climate

Two members of the ICHEC team have led an EPA report on climate downscaling published this month. The report describes the application of numerical weather prediction (NWP) simulations to develop high-quality, long-term, climate datasets of hydro-climate variables for Ireland, covering the period 1981–2016.

According to Chris Werner, computational scientist at ICHEC, who led the work, “hydroclimate variables such as evapotranspiration and soil moisture conditions are among the most crucial factors in estimating water sustainability, understanding groundwater recharge, agronomic management and the management of flood and drought risk.”

“Because of this, there is constant demand for these datasets from industry, research and governmental agencies for use in fields such as agriculture, water resource estimation and management, hydrology and hydrogeology, public health, energy and planning,“ he said.

High resolution climate datasets, which include important variables such as evapotranspiration and soil moisture deficits, are measured at a limited number of weather stations across Ireland. But the current lack of widespread data represents a serious knowledge gap in Irish hydrological and agro-climatic modelling. Until now, with the exception of temperature and precipitation, spatially (in space) and temporally (in time) homogeneous, multi-decadal, observational climate datasets have not been readily available for hydro-climatic research applications in Ireland.

“The hydro-climate variable, evapotranspiration, is a major process in the hydrological cycle,” said Dr. Owen Naughton, a researcher at the Department of Built Environment, Carlow Institute of Technology, who is a co-author on the report.  “It can account for large differences between incoming rainfall and the water available in our streams, rivers, lakes and groundwater systems. However, it is one of the most difficult processes to quantify and the lack of a gridded evapotranspiration dataset for Ireland represented a significant knowledge gap.

The new high-resolution datasets will lead to a better understanding, not only of the physical climate system, but also of the interaction of climate and Irish society. The datasets produced will allow for an assessment of the impact of model resolution, data assimilation, and NWP model choice on simulation accuracy. In addition, it is envisaged the datasets will be used as a basis for more-focused hydro-climate impact studies.

How it works

In order to generate the datasets the researchers used an approach which involves the use of NWP downscaled simulations. NWP models use mathematical approximations of the atmosphere to forecast weather based on current atmospheric conditions. So the NWP models here were downscaled in space to produce gridded climate datasets of the key hydro-climate variables for Ireland.

“Global reanalysis datasets, such as the ERA-Interim dataset from the European Centre for Medium Range Weather Forecasts (ECMWF) have resolutions on the order of 80km, which is too coarse to be of use in high resolution studies,” said lead author Chris Werner. “Thus the need for a regional climate model (RCM) or numerical weather prediction model (NWP) is required to downscale these coarser datasets.”

For the study the performances of three NWP models (COSMO-CLM, WRF and the Met Éireann Reanalysis (MÉRA) dataset) were compared and analysed to assess their ability to accurately represent hydro-climate variables. Additionally, the Teagasc Indicative Soil Drainage Map was implemented to capture the actual soil conditions throughout the country.

An additional project output was to facilitate an update to the Agroclimatic Atlas for Ireland. Met Éireann high-resolution (1 km) daily gridded datasets of temperature and precipitation were used to derive agro-climate variables such as the Standardised Precipitation Index (SPI) and growing season. "The research provides an important data resource for Irish researchers, policy makers and industry by providing, for the first time, high-resolution gridded datasets of hydro-climate variables such as evapotranspiration and soil moisture deficits,” said ICHEC’s Dr. Paul Nolan.

“To promote the use of the data and enhance climate research in Ireland, the datasets are made publicly available through the Irish Centre for High-End Computing (ICHEC).”

All datasets are available for download through the ICHEC ERDDAP server, which can be found at https://erddap.ichec.ie/erddap/files/EPA_Hydroclimate/.

The report can be found here: http://www.epa.ie/researchandeducation/research/researchpublications/researchreports/research267.html