Geography

Profile

I graduated from the University of Durham in 1991 with a BSc in Geography. I went on to study in Durham for a PhD supervised by Joan Kenworthy and Nick Cox, investigating long-term climate change in the Pennines in Northern England using meteorological records. I was awarded the PhD in 1994 and in the same year moved to the University of Portsmouth as lecturer in climatology/meteorology in the Department of Geography.

In 1998 I was a visiting scientist for six months at the Institute of Arctic and Alpine Research (INSTAAR), part of the University of Colorado at Boulder, U.S.A. I studied long-term climate change in the instrumental records kept by the Mountain Research Station at high elevations in the Colorado Rockies. This work was sponsored by a Fulbright Scholarship.

In 2003/2004 I was awarded a National Academies National Science Foundation scholarship to visit NOAA’s Air Resources Laboratory in Silver Spring Maryland, U.S.A. for 12 months as a Senior Research Associate. My work as part of the Climate Variability and Trends Research Group under adviser Dr Dian Seidel, was concerned with the comparison of temperature trends from a variety of global datasets (surface, radiosonde and reanalyses). The focus was trends at high elevations sites, since mountain summits show some of the characteristics of both the free atmosphere and the Earth’s surface (boundary layer). 

Current Research Interests

My main research interest is in assessing evidence for climate change in the mountainous areas of the globe, specifically how the high elevation signal of global warming may be different to that at sea-level (Pepin & Lundquist 2008) and that in the free atmosphere at equivalent elevations (Pepin & Seidel 2005). I am also interested in the consequences of such changes in mountain environments. High elevation areas show complex response to radiative forcing changes due both to the interaction of topography and relief with the atmosphere, and to the increased importance of snow and ice feedback.

Early work (pre-2000) concentrated on lapse rates within mountainous terrain (Pepin et al. 1999) based on long-term surface climate records (mostly temperature). Lapse rate variability can be assessed by comparison of observational records at varying elevations (Pepin 2000). In addition, a synoptic climatological approach was used to relate climate changes to changes in atmospheric circulation at different atmospheric levels (Pepin & Losleben 2002). This research has since widened to compare surface temperature trends at high elevation mountain sites with analogous free-atmospheric trends, and examine long term changes in the instantaneous surface/free-air temperature difference. Analyses using large-scale homogeneity adjusted global datasets such as GHCN (Global Historical Climate Network), CRU (Climate Research Unit), LKS (Lanzante, Klein & Seidel) radiosonde and the NCEP/NCAR reanalyses have shown surface sites to be warming more rapidly than the free atmosphere (Pepin & Seidel 2005) and that much of this difference can be explained by changes in cloudiness and snow cover, at least during the daytime (Pepin & Norris 2005). This work has been performed in collaboration with the Air Resources Lab. at NOAA and the Scripps Institution of Oceanography. 

As well as analysis of secondary datasets, I am involved in primary data collection in many mountain areas. My main field areas include the North Pennines in Northern England; Niwot Ridge, Colorado (the Mountain Research Station of the University of Colorado); the Eastern Pyrenees; Finnish Lapland (The Subarctic Research Station of the University of Turku); and Mt Kilimanjaro in Africa.

Work in the Pennines is being undertaken in collaboration with the NERC Institute of Terrestrial Ecology, and the most recent project is an attempt to produce a long-term (~40 years) homogenous climate record for Widdybank Fell, a moorland site in the Upper Teesdale National Nature Reserve, through calibration of different instrumentation with automatic weather stations. Climate monitoring is traditionally a major part of research in this area, popularised as England's Last Wilderness by David Bellamy. There is the legacy of Gordon Manley's work at Moor House and Great Dun Fell going back to the early part of this century.

My Fulbright research project in Colorado consisted of creating homogenous records for meteorological sites run by the Mountain Research Station as part of the Long-Term Ecological Research Program. Analysis revealed an increase in surface based lapse rates at high elevations over the last 50 years, not experienced in local radiosonde records (Pepin & Losleben 2002).

Research on Mt Kilimanjaro in collaboration with Doug Hardy of the Climate System Research Center at the University of Massachusetts and Dr Bill Duane at the University of Brunei has installed climate sensors at various elevations of the mountain to monitor the effects of the montane thermal circulation on transporting heat and moisture to the upper reaches of the mountain (Duane et al. 2008) . This is of particular relevance to understanding the rapid shrinkage of the summit glaciers, which has become an important issue, and the reasons for which is the subject of intense debate. During summer 2008 I led an RGS Sponsored Expedition to the mountain to obtain more recent climate data, including measurements of the surface thermal circulation and upslope moisture transport. We are now investigating the influence of deforestation on the drying of the mountain climate and comparing this with the influence of the free atmospheric flow. This work brought attention from international media, including the debate over the exact role of global warming.

Work in the Pyrenees as part of a NERC funded project (2002-2005) concentrated on the relationships between mountain climate, in particular cold-air ponding controlled by topography, and the behaviour of the common European bushcricket (Pepin & Kidd 2006). This work on cold air ponding is now being expanded in collaboration with Dr Jessica Lundquist of the University of Washington to develop generic algorithms to predict the location of cold air pools (Lundquist et al. 2008). Field monitoring in the Cerdagne is continuing in collaboration with the Servei Meteorologic de Catalunya.

A new field-site is the Kevo Sub-Arctic Research Centre in Finnish Lapland. Since September 2008 we have installed hundreds of temperature sensors in the Kevo basin as part of the EU funded LAPBIAT2 project (Pepin et al. 2008). This project is investigating the spatial patterning of low minimum temperatures (<-35 degC) which are important in the killing of the over-wintering larvae of a moth Epirrita Autumnata. The caterpillars of this moth can cause extensive defoliation of the native mountain birch forest. The current cold air pool in northern Lapland can be both intense and spatially extensive. Yet with global warming this propensity to inversion formation may be reduced.

A final emergent research focus is the changing role of the cryosphere (snow and ice) in mountain regions of the globe. This work considers a range of spatial scales from global analyses examining long term changes in snow cover in mountains and its influence on surface energy balance and mountain temperatures (Pepin & Lundquist 2008) to regional influences of atmospheric circulation on snow cover (Pepin et al. 2005), and local field investigation into factors influencing snow distribution at the altitudinal and latitudinal forest-tundra ecotones (areas which are expected to show rapid environmental response to climate change).

Local scale examination of snow distribution is focussing on the influence of spatial heterogeneity in forest vegetation on snow accumulation. Within the forest/tundra ecotone there is a transition from mature forest stands to open heathland or tundra areas. This has a strong control on snow retention since wind redistribution of lying snow can be a major factor in these environments.  Our field sites include a sub-alpine clearing within the upper forest zone in the Colorado Front Range and a similar clearing in Finnish Lapland, just south of the northern Boreal forest limit. These field sites represent altitudinal and latitudinal ecotones respectively. In both environments vegetation strongly influence the local snowpack, but the contrasting climates result in different snow distribution patterns. This work is being extended to assess the influence of future climate changes on snowpack evolution in these environments.

Other research interests include the history and development of weather lore and ritual in various parts of the world (Pepin 1996), and the consequences of varied time systems (i.e. the adoption of Double British Summer Time - DBST) on society (Pepin 1997), with special reference to meteorologically-influenced consequences such as building heating and cooling requirements.

Recent Publications

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Recent Grants