A NEW HIGH-RESOLUTION BI-CENTENNIAL (1800–2003) PRECIPITATION DATASET FOR THE GREATER ALPINE REGION

A new precipitation dataset for the Greater Alpine Region (GAR; 4°E–19°E, 43°N–49°N) has been developed. It provides monthly precipitation totals for the 1800–2003 period on a 10-min resolution grid. The new ‘HISTALP 10-min-grid’ dataset is based on long-term homogenized precipitation series from meteorological stations across the study domain and a high-resolution precipitation climatology dataset for the 1971–1990 period. The effective coverage of the dataset depends on the observations available in the station network which progressively decline back to the early 19th Century (from 192 to 5 stations). To aid the use of these data in other studies, an accompanying dataset has also been developed, which provides a measure of quality of each monthly precipitation estimate over the grid: the explained variance, relative to the 1931–2000 (maximum data availability) period. The computed quality score illustrates the comparatively poorer accuracy of the dataset for regions and months with less coherent precipitation fields (i.e., over the Alps and in summer) and when the number of stations is reduced, particularly before 1840. The derived gridded field has been compared with other independently-developed datasets and is found to provide a similar description of the precipitation in the GAR for places and periods of common coverage

PATTERNS OF PRECIPITATION VARIABILITY IN THE GREATER ALPINE REGION

A recently set up and homogenised new precipitation dataset for the Greater Alpine Region (GAR) is presented here with some first preliminary analyses. Climate change patterns within the study region are analysed in terms of regionally different evolutions, seasonality, and short to long-term trends. It will be shown that precipitation presents pronouncedly different variability patterns in space as well as in terms of seasonality and at different time scales

Assessment of Maximum Possible Urbanization Influences on Land Temperature Data by Comparison of Land and Marine Data around Coasts

Global surface temperature trends, based on land and marine data, show warming of about 0.8 °C over the last 100 years. This rate of warming is sometimes questioned because of the existence of Urban Heat Islands (UHIs). In this study we compare the rate of temperature change estimated from measurements of land and marine temperatures for the same grid squares using 5° by 5° latitude/longitude grid-box datasets. For 1951–2009 the ‘land’ average warmed by 0.02 °C decade−1 relative to the ‘sea surface temperature’ (SST) average. There were regional contrasts in the trends of land/sea temperature differences: the land warmed at a greater rate compared to the SST for regions north of 20°S, but the opposite occurred further south. Given strong forcing of the climate system, we would expect the land to change more rapidly than the ocean, so the differences represent an upper limit to the urbanization effect

The March 2012 Heat Wave in Northeast America as a Possible Effect of Strong Solar Activity and Unusual Space Plasma Interactions

In the past two decades, the world has experienced an unprecedented number of extreme weather events, some causing major human suffering and economic damage. The March 2012 heat wave is one of the most known and broadly discussed events in the Northeast United States (NE-USA). The present study examines in depth the possible influence of solar activity on the historic March 2012 heat wave based on a comparison of solar/space and meteorological data. Our research suggests that the historic March 2012 heat wave (M2012HW) and the March 1910 heat wave (M1910HW), which occurred a century earlier in NE-USA, were related to Sun-generated special space plasma structures triggering large magnetic storms. Furthermore, the largest (Dst = −222 nT) magnetic storm during solar cycle 24 in March 2015 (only three years later than the March 2012 events) occurred in relation to another heat wave (M2015HW) in NE-USA. Both these heat waves, M2012HW and M2015HW, resemble each other in many ways: they were characterized by extremely huge temperature increases ΔΤΜ = 30° and 32° (with maximum temperatures ΤΜ = 28° and 23°, respectively) during a positive North Atlantic Oscillation index, the high temperatures coincided with large-scale warm air streaming from southern latitudes, they were accompanied by superstorms caused by unexpected geoeffective interplanetary coronal mass ejections (ICMEs), and the ICME-related solar energetic particle (SEP) events were characterized by a proton spectrum extending to very high (>0.5 GeV) energies. We infer that (i) all three heat waves examined (M2012HW, M2015HW, M1910HW) were related with strong magnetic storms triggered by effective solar wind plasma structures, and (b) the heat wave in March 2012 and the related solar activity was not an accidental coincidence; that is, the M2012HW was most probably affected by solar activity. Future case and statistical studies are needed to further check the hypothesis put forward here, which might improve atmospheric models in helping people’s safety, health and life

Influence of large-scale atmospheric circulation on climate variability in the Greater Alpine Region of Europe

The climatic variability in the Greater Alpine Region (GAR) of Europe has a diverse character: it exhibits differences between winter and summer, and between its individual subregions. The large-scale atmospheric circulation, as expressed by the mean sea level pressure (MSLP) patterns in the wider Euro-Atlantic region, plays a significant role in the climate variability in winter, but less in summer. In winter, high-altitude temperatures are markedly linked with the Northern Hemisphere (NH) zonal circulation, as expressed by the NH annular mode (NAM), whereas the low-level temperature field is associated more with the circulation over the NE Atlantic. The Alpine mountain chain delimits the different winter precipitation regimes between the northern and southern side of the GAR. While a British Isles-centered pressure pattern plays the principal role in influencing northern Alpine precipitation, the North Atlantic Oscillation (NAO), and in particular its Mediterranean component, is the large-scale atmospheric mode affecting precipitation over the southern Alpine region. The impact of the El Niño/Southern Oscillation (ENSO) phenomenon on GAR climate is weak, though it is distinctly manifested within intermittent multidecadal periods. The most pronounced impact is found for late-autumn and early-winter temperature and late-winter precipitation. In these cases, GAR climate exhibits significant correlations with ENSO state of the preceding early autumn and late summer. The ENSO impact is associated with atmospheric pressure anomaly patterns in the European region indicating modifications of large-scale circulation whose effects are also found in the climates of larger areas of Europe

Past and Current Climate Changes in the Mediterranean Region

Mediterranean climate change during the last 60 years is based on homogenized daily temperature and quality controlled precipitation observational data and gridded products. The estimated changes indicate statistically significant Mediterranean summer temperature increase and a reduction in winter precipitation in specific areas. Reconstructions of Mediterranean sea level suggest a rise of some 150 mm since the beginning of the nineteenth century. A 20 years long reanalysis (1985–2007) was produced, showing long term temperature variability and a positive salinity trend in the ocean layers from the surface to 1,500 m depth. A prominent increase in summer temperature extremes is found in the whole Mediterranean region, while warm bias in the mid twentieth century station data is removed by homogenization. No basin-wide trends in precipitation and droughts are found for the second half of the twentieth century, while trends in extreme winds are largely negative, as are those of the related cyclones and cut-off-lows. The role of large scale pressure patterns like the NAO for variabilities and trends is discussed for the different parameters considered

Construction of a 10-min-gridded precipitation data set for the Greater Alpine Region for 1800–2003

[1] A new precipitation data set for the Greater Alpine Region (GAR; 4°E–19°E, 43°N–49°N) has been developed. It provides monthly precipitation totals, for the 1800–2003 period, gridded at 10-min resolution. The new HISTALP 10-min-grid data set is based on 192 long-term homogenized precipitation series from meteorological stations across the study domain and a high-resolution precipitation climatology for the 1971–1990 period. The effective coverage of the data set depends on the observations available in the station network which progressively declines back to the early 19th century (from 192 to 5 stations). To aid the use of these data in other studies, an accompanying data set has also been developed, which provides a measure of the quality of each monthly precipitation estimate over the grid: the explained variance, relative to the 1931–2000 (maximum data availability) period. The computed quality score illustrates the comparatively poorer accuracy of the data set for regions and months with less coherent precipitation fields (i.e., over the Alps and in summer) and when the number of stations is reduced, particularly before 1840. The derived gridded field has also been compared for the whole and geographical subregions with other independently developed data sets and is found to provide a similar description of the precipitation in the GAR for places and periods of common coverage. The data set is publicly available at http://www.cru.uea.ac.uk/