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Bohm R.,Central Institute for Meteorology and Geodynamics ZAMG | Jones P.D.,University of East Anglia | Hiebl J.,Central Institute for Meteorology and Geodynamics ZAMG | Frank D.,Swiss Federal Institute of forest | And 2 more authors.
Climatic Change | Year: 2010

Instrumental temperature recording in the Greater Alpine Region (GAR) began in the year 1760. Prior to the 1850-1870 period, after which screens of different types protected the instruments, thermometers were insufficiently sheltered from direct sunlight so were normally placed on north-facing walls or windows. It is likely that temperatures recorded in the summer half of the year were biased warm and those in the winter half biased cold, with the summer effect dominating. Because the changeover to screens often occurred at similar times, often coincident with the formation of National Meteorological Services (NMSs) in the GAR, it has been difficult to determine the scale of the problem, as all neighbour sites were likely to be similarly affected. This paper uses simultaneous measurements taken for eight recent years at the old and modern site at Kremsmünster, Austria to assess the issue. The temperature differences between the two locations (screened and unscreened) have caused a change in the diurnal cycle, which depends on the time of year. Starting from this specific empirical evidence from the only still existing and active early instrumental measuring site in the region, we developed three correction models for orientations NW through N to NE. Using the orientation angle of the buildings derived from metadata in the station histories of the other early instrumental sites in the region (sites across the GAR in the range from NE to NW) different adjustments to the diurnal cycle are developed for each location. The effect on the 32 sites across the GAR varies due to different formulae being used by NMSs to calculate monthly means from the two or more observations made at each site each day. These formulae also vary with time, so considerable amounts of additional metadata have had to be collected to apply the adjustments across the whole network. Overall, the results indicate that summer (April to September) average temperatures are cooled by about 0. 4°C before 1850, with winters (October to March) staying much the same. The effects on monthly temperature averages are largest in June (a cooling from 0. 21° to 0. 93°C, depending on location) to a slight warming (up to 0. 3°C) at some sites in February. In addition to revising the temperature evolution during the past centuries, the results have important implications for the calibration of proxy climatic data in the region (such as tree ring indices and documentary data such as grape harvest dates). A difference series across the 32 sites in the GAR indicates that summers since 1760 have warmed by about 1°C less than winters. © 2009 Springer Science+Business Media B.V.

Gilge S.,Hohenpeissenberg Meteorological Observatory | Plass-Duelmer C.,Hohenpeissenberg Meteorological Observatory | Fricke W.,Hohenpeissenberg Meteorological Observatory | Kaiser A.,Central Institute for Meteorology and Geodynamics ZAMG | And 3 more authors.
Atmospheric Chemistry and Physics | Year: 2010

Long-term, ground based in-situ observations of ozone (O 3) and its precursor gases nitrogen dioxide (NO 2) and carbon monoxide (CO) from the four sites Hohenpeissenberg and Zugspitze (D), Sonnblick (A) and Jungfraujoch (CH) are presented for the period 1995-2007. These Central European alpine mountain observatories cover an altitude range of roughly 1000 to 3500 m. Comparable analytical methods and common quality assurance (QA) procedures are used at all sites. For O 3 and CO, calibration is linked to primary calibrations (O 3) or CO standards provided by the Central Calibration Laboratory (CCL) at NOAA/ESRL. All stations have been audited by the World Calibration Centre (WCC) for CO and O 3 (WCC-Empa; CH). Data from long-term measurements of NO 2 and CO are only available from Hohenpeissenberg and Jungfraujoch. Both sites show slightly decreasing mixing ratios of the primarily emitted NO 2 and the partly anthropogenically emitted CO between 1995 and 2007. The findings are generally consistent with shorter observation periods at Zugspitze and Sonnblick and thus are considered to represent regional changes in Central European atmospheric composition at this altitude range. Over the same period, 1995-2007, the O 3 mixing ratios have slightly increased at three of the four sites independent of wind sector. Trends are often more pronounced in winter and less in summer; highest declines of NO 2 and CO are observed in winter and the lowest in summer, whereas the strongest O 3 increase was detected in winter and lowest or even decline in summer, respectively. Weekly cycles demonstrate anthropogenic impact at all elevations with enhanced NO 2 on working days compared to weekends. Enhanced O 3 values on working days indicating photochemical production from anthropogenic precursors are only observed in summer, whereas in all other seasons anti-correlation with NO 2 was found due to reduced O 3 values on working days. Trends are discussed with respect to anthropogenic impacts and vertical mixing. The observed trends for NO 2 at the alpine mountain sites are less pronounced than trends estimated based on emission inventories. © 2010 Author(s).

Martinez-Alvarado O.,University of Reading | Weidle F.,Johannes Gutenberg University Mainz | Weidle F.,Central Institute for Meteorology and Geodynamics ZAMG | Gray S.L.,University of Reading
Monthly Weather Review | Year: 2010

The existence of sting jets as a potential source of damaging surface winds during the passage of extratropical cyclones has recently been recognized. However, there are still very few published studies on the subject. Furthermore, although it is known that other models are capable of reproducing sting jets, in the published literature only one numerical model [the Met Office Unified Model (MetUM)] has been used to numerically analyze these phenomena. This article aims to improve our understanding of the processes that contribute to the development of sting jets and show that model differences affect the evolution of modeled sting jets.A sting jet event during the passage of a cyclone over the United Kingdom on 26 February 2002 has been simulated using two mesoscale models, namely the MetUM and the Consortium for Small Scale Modeling (COSMO) model, to compare their performance. Given the known critical importance of vertical resolution in the simulation of sting jets, the vertical resolution of both models has been enhanced with respect to their operational versions. Both simulations have been verified against surface measurements of maximum gusts, satellite imagery, and Met Office operational synoptic analyses, as well as operational analyses from the ECMWF. It is shown that both models are capable of reproducing sting jets with similar, though not identical, features. Through the comparison of the results from these two models, the relevance of physical mechanisms, such as evaporative cooling and the release of conditional symmetric instability, in the generation and evolution of sting jets is also discussed. © 2010 American Meteorological Society.

Leonhardt R.,Central Institute for Meteorology and Geodynamics ZAMG | Wicht J.,Max Planck Institute for Solar System Research
Space Science Reviews | Year: 2010

Recent advances in the study of geomagnetic field reversals are reviewed. These include studies of the transitional field during the last geomagnetic reversal and the last geomagnetic excursion based on paleomagnetic observations, and analysis of reversals in self-consistent 3D numerical dynamo simulations. Field models inferred from observations estimate reversal duration in the range of 1-10 kyr (depending on site location). The transitional fields during both the Matuyama/Brunhes reversal and the Laschamp excursion are characterized by low-latitude reversed flux formation and subsequent poleward migration. During both events the dipole as well as the non-dipole field energies decrease. However, while the non-dipole energy dominates the dipole energy for a period of 2 kyr in the reversal, the non-dipole energy merely exceeds the dipole energy for a very brief period during the excursion. Numerical dynamo simulations show that stronger convection, slower rotation, and lower electrical conductivity provide more favorable conditions for reversals. A non-dimensional number that depends on the typical length scale of the flow and represents the relative importance of inertial effects, termed the local Rossby number, seems to determine whether a dynamo will reverse or not. Stable polarity periods in numerical dynamos may last about 1 Myr, whereas reversals may last about 10 kyr. Numerical dynamo reversals often involve prolonged dipole collapse followed by shorter directional instability of the dipole axis, with advective processes governing the field variation. Magnetic upwellings from the equatorial inner-core boundary that produce reversed flux patches at low-latitudes of the core-mantle boundary could be significant in triggering reversals. Inferences from the observational and modeling sides are compared. We summarize with an outlook on some open questions and future prospects. © 2010 Springer Science+Business Media B.V.

Haslinger K.,Central Institute for Meteorology and Geodynamics ZAMG | Bartsch A.,Central Institute for Meteorology and Geodynamics ZAMG
Hydrology and Earth System Sciences | Year: 2016

A new approach for the construction of high-resolution gridded fields of reference evapotranspiration for the Austrian domain on a daily time step is presented. Gridded data of minimum and maximum temperatures are used to estimate reference evapotranspiration based on the formulation of Hargreaves. The calibration constant in the Hargreaves equation is recalibrated to the Penman-Monteith equation in a monthly and station-wise assessment. This ensures, on one hand, eliminated biases of the Hargreaves approach compared to the formulation of Penman-Monteith and, on the other hand, also reduced root mean square errors and relative errors on a daily timescale. The resulting new calibration parameters are interpolated over time to a daily temporal resolution for a standard year of 365 days. The overall novelty of the approach is the use of surface elevation as the only predictor to estimate the recalibrated Hargreaves parameter in space. A third-order polynomial is fitted to the recalibrated parameters against elevation at every station which yields a statistical model for assessing these new parameters in space by using the underlying digital elevation model of the temperature fields. With these newly calibrated parameters for every day of year and every grid point, the Hargreaves method is applied to the temperature fields, yielding reference evapotranspiration for the entire grid and time period from 1961-2013. This approach is opening opportunities to create high-resolution reference evapotranspiration fields based only temperature observations, but being as close as possible to the estimates of the Penman-Monteith approach. © Author(s) 2016.

Haslinger K.,Central Institute for Meteorology and Geodynamics ZAMG | Schoner W.,Central Institute for Meteorology and Geodynamics ZAMG | Anders I.,Central Institute for Meteorology and Geodynamics ZAMG
Meteorologische Zeitschrift | Year: 2016

In this study we assess future drought probabilities in the Greater Alpine Region based on four regional climate model simulations with COSMO-CLM forced by ECHAM5 and HadCM3 under different emission scenarios. As a drought indicator, the Standardized Precipitation Evapotranspiration Index is applied. The evaluation of a hindcast run show reasonable skill of the CCLM in simulating the evolution of dry and wet phases, although decreasing skill towards the East of the Alpine domain is apparent. The results of the scenario investigations indicate a considerably higher probability for droughts averaged over the study region, but with rather diverse patterns north and south of the Alps. This signal is mainly emerging from the warm season months, whereas in winter nearly no change is detected. By differentiating between precipitation and temperature as the driving forces of the considerable drying trends in summer we found precipitation as the relevant driver north of and in the Alps, whereas we detected that temperature, as a proxy for evapotranspiration, is the main factor for the southern and eastern areas. © 2015 The authors.

Wotawa G.,Central Institute for Meteorology and Geodynamics ZAMG
Journal of Radioanalytical and Nuclear Chemistry | Year: 2013

Between 13 and 22 May 2010, multiple detections of radionuclides were recorded at monitoring stations in Eastern Asia, including Okinawa, Takasaki (both Japan) and Ussuriysk (Russia). The stations are operated as part of the CTBTO international monitoring system (IMS) to record signals from nuclear tests. Additional detections were reported from a national monitoring post of the Republic of Korea located in Geojin close the border to the Democratic People's Republic of Korea (DPRK). The scenario under investigation was unique in the history of the IMS. Possible source regions in the region and consistent release times were investigated. Subsequently, it was checked whether some known locations on the territory of DPRK could have been a possible origin of the fission products detected. As a result, it was found that two of the three DPRK locations investigated could be a possible source. It is evident, however, that the two events cannot be explained by one single release at one specific location and time. At least two releases with a time shift of about 1 day, possibly but not necessarily on the same location, are needed. Under the hypothesis that the source was in DPRK, the releases needed to explain the measurements would be about 1014 Bq for 133Xe and 5 × 1012 Bq for 140Ba. Taking all this into account and comparing the results with recently published hypotheses regarding a possible low-yield nuclear test in DPRK in May 2010, we conclude that such a test is indeed one of the possible scenarios from the meteorological point of view. © 2012 Akadémiai Kiadó, Budapest, Hungary.

Bohm R.,Central Institute for Meteorology and Geodynamics ZAMG
European Physical Journal Plus | Year: 2012

The paper uses the data potential of very long and homogenized instrumental climate time series in the south central Europe for analyzing one feature which is very dominant in the climate change debate --whether anthropogenic climate warming causes or goes along with an increase of climate extremes. The monthly resolved data of the HISTALP data collection provide 58 single series for the three climate elements, air pressure, air temperature and precipitation, that start earlier than 1831 and extend back to 1760 in some cases. Trends and long-term low frequent climate evolution is only shortly touched in the paper. The main goal is the analysis of trends or changes of high frequent interannual and interseasonal variability. In other words, it is features like extremely hot summers, very cold winters, excessively dry or wet seasons which the study aims at. The methods used are based on detrended highpass series whose variance is analyzed in discrete 30-year windows moving over the entire instrumental period. The analysis of discrete subintervals relies on the unique number of 8 (for precipitation 7) such “normal periods”. The second approach is based on the same subintervals though not in fixed but moving windows over the entire instrumental period. The first result of the study is the clear evidence that there has been no increase of variability during the past 250 years in the region. The second finding is similar but concentrates on the recent three decades which are of particular interest because they are the first 30 years with dominating anthropogenic greenhouse gas forcing. We can show that also this recent anthropogenic normal period shows no widening of the PDF (probability density function) compared to the preceding ones. The third finding is based on the moving window technique. It shows that interannual variability changes show a clear centennial oscillating structure for all three climate elements in the region. For the time being we have no explanation for this empirical evidence. We argue that it should not be an artifact of any remaining data problems, but of course a centennial cyclic effect based on 250 years of data only is not really well consolidated in terms of sample length. But it is at least an interesting new feature and the subject is open for scientific discussion and for further studies dealing with circulation effects, long-term memories in the oceans etc. © 2012, Società Italiana di Fisica and Springer.

Hofstatter M.,Central Institute for Meteorology and Geodynamics ZAMG | Chimani B.,Central Institute for Meteorology and Geodynamics ZAMG
Meteorologische Zeitschrift | Year: 2012

In this study, a systematic tracking of atmospheric cyclones at the pressure level of 700 hPa has been performed to determine three different track types and their climatologic characteristics over Central Europe from 1961 to 2002 by using ERA-40 (ECMWF - European Centre for Medium Range Weather Forecast, 40 year Re-Analysis) and ERA-Interim data. The specific focus is on cyclone tracks of type V as suggested by Van Bebber in 1891 and congeneric types, because of their association with extreme large-scale precipitation amounts and related flooding in Central and Eastern Europe. The tracking procedure consists of detecting isolated minima of the band-pass filtered 700 hPa geopotential height field and combining them over time to continuous tracks by nearest neighbour approach. Results show that the common Vb cyclone track is a rare event (3.5/year) and the probability of occurrence is largest in April with a secondary maximum in autumn. Furthermore, there is no temporal trend of any of these track types noticeable throughout the 42-years investigation period. The new 700 hPa cyclone track catalogue is used as a reference to verify the hypothesis of a coherence of Vb-tracks with certain circulation types (CTs). Selected objective and subjective circulation type classifications (CTCs) from COST (European Cooperation in Science and Technology) action 733 as well as a manual Vb-classification from the ZAMG (Zentralanstalt fürMeteorologie und Geodynamik) are utilized. This study shows both the shortcomings and the potential of CTCs to discriminate Vb cyclone tracks by certain classes of stationary circulation patterns. Subjective CTCs rank higher than objective ones in terms of Brier Skill Score, which demonstrates the power to enhance relevant synoptic phenomena instead of favouring mathematical criteria. For the first time, an objective catalogue with the famous cyclone track Vb and its climatology is now on hand for the period 1961-2002, offering a valuable basis to further improve our knowledge on the issues of Vb and related hydro-meteorological aspects. © 2012 Gebrüder Borntraeger, Stuttgart.

Hiebl J.,Central Institute for Meteorology and Geodynamics ZAMG | Hofstatter M.,Central Institute for Meteorology and Geodynamics ZAMG
Climatic Change | Year: 2012

This paper assesses the extent to which temperature variability has increased in Austria since the late 19th century using a novel objective approach. The approach focuses on multi-day temperature episodes and isolates variability from changes in the long-term mean and seasonal variation. We define and compute three different indices of temperature variability, and find-based on 140 years of data-that temperature variability has evolved independently of mean temperature but with no long-term trend. Early 21st century's relatively raised temperature variability level is known from late 19th century's pre-greenhouse climate state. © 2012 Springer Science+Business Media B.V.

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