John Sweeney

Geographical variations in precipitation yields and circulation types in Britain and Ireland

The geographical distribution of daily precipitation with each of the Lamb-classification circulation types is examined for 65 locations in Britain and Ireland. Substantial differences in spatial receipt are related to exposure at the location concerned and length of ocean passage for the air mass involved. Airflow contrasts occurring at regional scales are also instrumental in producing geographical variability in receipt. Cyclonic south westerlies are identified as the most prolific precipitation-producing synoptic type for the area as a whole, while anticyclonic northerlies and north easterlies are the driest. Changes in the frequency of the 27 categories identified by Lamb are then examined over 130 years of record. A significant change in the make-up of the synoptic circulation is seen to have occurred in recent decades. Declining westerlies and increasing cyclonic and anticyclonic airflows are suggested as being primarily responsible for recent changes in precipitation geography. Future precipitation will be determined partly by such changes in airflow types.

The sensitivity of fluvial flood risk in Irish catchments to the range of IPCC AR4 climate change scenarios

In the face of increased flood risk responsible authorities have set out safety margins to incorporate climate change impacts in building robust flood infrastructure. Using the case study of four catchments in Ireland, this study subjects such design allowances to a sensitivity analysis of the uncertainty inherent in estimates of future flood risk. Uncertainty in flood quantiles is quantified using regionalised climate scenarios derived from a large number of GCMs (17), forced with three SRES emissions scenarios. In terms of hydrological response uncertainty within and between hydrological models is assessed using the GLUE framework. Regionalisation is achieved using a change factor method to infer changes in the parameters of a weather generator using monthly output from the GCMs, while flood frequency analysis is conducted using the method of probability weighted moments to fit the Generalised Extreme Value distribution to ~20,000 annual maximia series. Sensitivity results show that for low frequency events, the risk of exceedence of design allowances is greater than for more frequent events, with considerable implications for critical infrastructure. Peak flows for the five return periods assessed were found to be less sensitive to temperature and subsequently to potential evaporation (PET) than to rainfall. The average width of the uncertainty range for changes in flood magnitude is greater for low frequency events than for high frequency events. In all catchments there is a progressive increase in the peak flows associated with the 5, 25, 50 and 100-year return periods when moving from the 2020s to the 2080s.

A three-century storm climatology for Dublin 1715-2000

A need to quantify belter the hazard posed by storms in Ireland exists, particularly during a lime of imminent climate change. To assist this, a rudimentary storm chronology lor the Dublin region was constructed for the period 1715- 2000 using documentary and instrumental records. The former, using early newspapers and other weather catalogues, indicates a period of marked storm activity in the early eighteenth century which corresponds to the later stages of the Little Ice Age in Ireland. Instrumental records, though also imperfect, suggest that the twentieth century had a number of stormy intervals, particularly in the 1920s, 1960s and early 1990s. These were probably comparable to the early eighteenth century in storm frequency and severity. A clear link between storm frequency and cyclonic synoptic circulation types was established, with stormy decades evident at times of high frequencies of Jenkinson-Lamb cyclonic types. Preliminary analysis of some of the most severe storms indicated that rapid deepening of sometimes quite small wave depressions close to Ireland are the most common occurrence, though this may not have been so in the past. An expectation of increases in storm activity in the vicinity of Ireland exists for the medium term as global warming proceeds, though in the longer term a decline in vigour of the westerly circulation can be anticipated.

Statistical downscaling of temperature, radiation and potential evapotranspiration to produce a multiple GCM ensemble mean for a selection of sites in Ireland

Abstract Irish climate is experiencing changes which have been found to be consistent with those occurring at a global scale. Consequently there is now growing confidence that these changes are largely attributable to global warming. Based on the data from four long-term monitoring, synoptic stations, between 1890 and 2004, mean annual temperatures in Ireland rose by 0.7oC. In the absence of strict emissions controls, a doubling of global atmospheric concentrations of CO2 is likely by the end of the twenty-first century. As a consequence, global temperatures are projected to increase by between 1.8oC and 4oC over the same period depending on the climate sensitivity to increased levels of greenhouse gases. In order to determine the likely impact on Irish temperatures and related climatic variables, this paper illustrates a technique for downscaling Global Climate Model (GCM) output for a selection of sites in Ireland. Results of a weighted ensemble mean, derived from multiple GCMs, are presented in an atte...

Technology-aided participative methods in environmental assessment : An international perspective

Provisions for citizen involvement in the assessment of potential environmental effects of certain plans, programmes and projects are present in current legislation. An international survey revealed that public participation is common practice in European and some other countries worldwide. However, a number of issues are observed to affect public involvement in EIA/SEA processes and expert opinion differs when evaluating the effectiveness of existing participative methods. Results suggest that technology-aided methods can improve traditional participation processes. In particular, GIS has the potential to increase community knowledge and enhance involvement by communicating information more effectively. Variable accessibility to technology and data quality remain issues. Combining technology with more conventional ways of gathering, evaluating and presenting data are seen as offering a solution to the need to promote the integration of public perceptions in environmental assessment procedures. Recommendations to improve current public participation methods and measures for making GIS available to the general public are provided.

Climate change in Ireland‐ recent trends in temperature and precipitation

Abstract This paper presents an assessment of indicators of climate change in Ireland over the past century. Trends are examined in order to determine the magnitude and direction of ongoing climate change. Although detection of a trend is difficult due to the influence of the North Atlantic Ocean, it is concluded that Irish climate is following similar trajectories to those predicted by global climate models. Climatic variables investigated included the key temperature and precipitation data series from the Irish synoptic station network. Analysis of the Irish mean temperature records indicates an increase similar to global trends, particularly with reference to early‐twentieth century warming and, more importantly, rapid warming in the 1990s. Similarly, analysis of precipitation change support the findings of the United Kingdom Climate Impacts Programme (UKCIPS) with evidence of a trend towards winter increases in the north‐west of the country and summer decreases in the south‐east. Secondary climate ind...

The Changing Synoptic Origins of Irish Precipitation

Using Lamb circulation categories, daily precipitation receipt for 34 Irish sites are examined for the period since 1941. Marked gradients are apparent with particular trajectories and the influence of ocean surface temperatures and topography is described. Changes in the frequency of occurrence of synoptic types, particularly westerly and cyclonic categories, are shown to have implications for the national distribution of precipitation and also for particular areas in terms of annual receipt.

The Urban Heat Island of Dublin City

Automobile traverses revealed an intense urban heat island in Dublin city during winter nights with light winds and clear skies. Urban rural contrasts of over 6.5°C may be anticipated, and a close correspondence between building density and temperature exists. The citys location close to warm sea and cold uplands appears to be responsible for the generation of active mesoscale air movement during such nights. These circulations bring both cold mountain air into the southern suburbs and warmer oceanic air into the eastern fringes and are responsible for creating substantial variations in temperature within the urban area itself. Cold air drainage along surprisingly gentle slopes occurs, channelled along the valleys of small streams particularly in the south of the city. Considerable intra-urban differences in aggregate energy demand may be anticipated as a consequence.

Multi-level climate policies in Ireland

Global greenhouse gas concentrations continue to rise even though there are binding international agreements and national commitments for emission reductions. While some states and local governments around the world are taking action to reduce emissions and adapt to the inevitable climate change impacts, overall collective goals are not being realised and this implementation gap may be due to multi-level governance failures. To date there has been limited research of Irish climate measures, with a significant gap at the sub-national level. This research explores whether city and county councils are the lowest most effective level for climate change actions in Ireland through a nationwide survey and a review of all relevant government policies at local, regional and national levels. The study reveals that local climate measures are isolated best-practice examples rather than being widespread throughout the country. This study concludes that there is limited vertical integration among Irish government level...

Identification of frequency changes in synoptic circulation types and consequences for glacier mass balance in Norway

The cumulative net mass balances of maritime glaciers in Norway display a net surplus during the period 1963–2000. The article seeks to establish the causal mechanisms that resulted in the positive net balances occurring on Norwegian maritime glaciers. To achieve this, a Temporal Synoptic Index (TSI) was derived for a 30-year period for a number of synoptic meteorological stations in Norway. The TSI is derived using Principal Components Analysis (PCA) and subsequent clustering of component scores to classify days for both winter and summer seasons. Findings indicate that the occurrence of ‘warm’ type air masses during the summer months have increased in frequency, particularly since the late 1980s. A reduction in the frequency of ‘cold’ cluster types during the winter months is evident after this period, while the frequency of ‘warm’ types, with an increased moisture carrying capacity, has increased in frequency. The frequency occurrence of these key air mass types is shown to be significantly related to glacier mass balance during both the accumulation and ablation season. Winter air mass types from maritime source regions act to enhance accumulation and suppress ablation, while summer continental source types suppress accumulation and enhance ablation.