Andreas Hoy

Large-scale synoptic types and their impact on European precipitation

Atmospheric circulation strongly modulates precipitation patterns throughout Europe. A selection of synoptic types was chosen to investigate the impact of circulation on the spatial distribution of precipitation within Europe and neighbouring regions (for 1951–2010). Applied were (1) the original and one automated version of the Grosswetterlagen classification, (2) the Vangengeim–Girs classification and (3) a dataset of the North Atlantic Oscillation (NAO). Daily values of the E-OBS gridded precipitation dataset were allocated to synoptic types, visualising precipitation anomalies (in percent) during winter (October–March) and summer (April–September) half years. Anomalies from average precipitation conditions (only) contain days connected to each of the investigated synoptic types. Distinct anomaly patterns become visible and are explained by the location of pressure systems. Patterns are spatially similar between both half years for Grosswetterlagen and Vangengeim–Girs classifications, while the NAO shows pronounced seasonal changes. Precipitation anomaly maps were applied to help explain observed changes in European precipitation amounts from 1981 to 2010, as compared to 1951–1980. Changes of precipitation amounts were related to frequency changes of synoptic types, predominantly during the winter half year. Here, increasing (decreasing) frequencies of synoptic types connected to westerly (easterly) inflow supported higher precipitation amounts in northern Europe and lower amounts in southern Europe.

Spatial response of two European atmospheric circulation classifications (data 1901–2010)

Air pressure field and circulation pattern frequencies were investigated to (1) locate and compare positions of the underlying pressure fields, (2) analyse the spatial dimension of affected areas, (3) create schematic maps of important circulation types and (4) compare the classification types in their response to the data. Two manual classifications were used, selected for the length of their time series and their applicability to a larger region: the Grosswetterlagen classification (GWLc) and the Vangengeim–Girs classification (VGc). Their time series were correlated with a global set of gridded monthly sea-level pressure data. Results show the different conceptual orientation of VGc (hemispheric) and GWLc (continental). The highest correlation values and the largest affected areas are visible in winter, where patterns frequently extended into northern Africa and western Asia. Schematic maps, illustrating the average location of main pressure centres, are provided for basic classes of both classifications. Re-arranging GWLc subtypes increases the classifications comparability with the VGc. Analysis of moving correlation coefficients reveals high fluctuations in the relation of both classifications over time.

Climatic changes and their impact on socio-economic sectors in the Bhutan Himalayas: an implementation strategy

Abstract This paper contributes to an enhanced understanding of present climatic conditions, observed climate trends and regional climate vulnerability of the Bhutan Himalayas. Bhutan’s complex, often high-altitude terrain and the severe impact of the Indian summer monsoon leads to a strong exposure of the countries’ key economic sectors (agriculture, forestry, hydropower generation and tourism) to climatic changes. Climate change also threatens Bhutan’s vast biodiversity and increases the likelihood of natural hazards (e.g. glacier lake outburst floods, flash floods, droughts and forest fires). A better understanding of Bhutan’s climate and its variability, as well as observed and possible climate impacts, will help in improving the handling of regional social, economic and ecologic challenges not limited to the Himalayas. Only a few climatological studies exist for the eastern Himalayas. They mainly focus on adaptation to immediate threats by glacier lake outbursts. In contrast, this paper (1) investigates the average spatial and inner-annual diversity of the air temperature regime of Bhutan, based on local meteorological observations, (2) discusses past temperature variability, based on global datasets, and (3) relates effects of observed warming to water availability, hydropower development, natural hazards, forests, biodiversity, agriculture, human health and tourism in the Bhutan Himalayas. Results indicate a large spatial and temporal temperature variability within Bhutan and considerably increasing temperatures especially over recent decades. Implications of regional climatic changes on various socio-economic sectors and possible adaptation efforts are discussed.

Chen D, Walther A, Moberg A, Jones P, Jacobeit J, Lister D | European trend atlas of extreme temperature and precipitation records

Climate change is most visible and dangerous to society when it comes to extremes. Hence an atlas that systematically illustrates the observed changes in temperature and precipitation extremes is strongly needed and desired. Thereby, the analysis of long-term time series is particularly attractive. This atlas advertises “an easy way to identify spatial patterns for a given time period, region, season, and index”. Unfortunately, the hopes and expectations raised by the title and abstract are abated by the content and structure of the book.