Austrian long-term climate 1767-2000: multiple instrumental climate time series from central Europe (Österreichische Beiträge zu Meteorologie und Geophysik, Heft 25), by I. Auer, R. Böhm and W. Schöner, Central Institute for Meteorology and Geodynamics, H

2002 ◽  
Vol 22 (9) ◽  
pp. 1143-1143
Author(s):  
Ian D. Phillips
Keyword(s):  
Time Series ◽  
Central Europe ◽  
Central Institute ◽  
Climate Time Series

scholarly journals Revisiting the long-term decreasing trend of atmospheric electric potential gradient measured at Nagycenk, Hungary, Central Europe

2021 ◽  
Vol 39 (4) ◽  
pp. 627-640
Author(s):  
Attila Buzás ◽  
Veronika Barta ◽  
Tamás Horváth ◽  
József Bór
Keyword(s):  
Time Series ◽  
Electric Field ◽  
Central Europe ◽  
Electric Potential ◽  
Potential Gradient ◽  
Time Dependent ◽  
Shielding Effect ◽  
Term Variation ◽  
Atmospheric Electric Potential Gradient

Abstract. In 2003, a decreasing trend was reported in the long-term (1962–2001) fair weather atmospheric electric potential gradient (PG) measured in the Széchenyi István Geophysical Observatory (NCK; 47∘38′ N, 16∘43′ E), Hungary, Central Europe. The origin of this reduction has been the subject of a long-standing debate, due to a group of trees near the measurement site which reached significant height since the measurements have started. Those trees have contributed to the lowering of the ambient vertical electric field due to their electrostatic shielding effect. In the present study, we attempt to reconstruct the true long-term variation of the vertical atmospheric electric field at NCK. The time-dependent shielding effect of trees at the measurement site was calculated to remove the corresponding bias from the recorded time series. A numerical model based on electrostatic theory was set up to take into account the electrostatic shielding of the local environment. The validity of the model was verified by on-site measurement campaigns. The changing height of the trees between 1962 and 2017 was derived from national-average age–height diagrams for each year. Modelling the time-dependent electrical shielding effect of the trees at NCK revealed that local effects played a pivotal role in the long-term decrease. The results suggest that earlier attempts could not quantify the shielding effect of the trees at NCK accurately. In this work it is found that the reconstructed PG time series at NCK exhibits an increase between 1962 and 1997 followed by a decaying trend since 1997. It is pointed out that long-term variation in summertime and wintertime PG averages should be analysed separately as these may contribute to trends in the annual mean values rather differently.

Investigating the long-term variation of atmospheric electric potential gradient at Nagycenk, Hungary, Central Europe

2021 ◽  
Author(s):  
Attila Buzas ◽  
Veronika Barta ◽  
József Bór ◽  
Tamás Horváth
Keyword(s):  
Time Series ◽  
Central Europe ◽  
Atmospheric Electricity ◽  
Electrical Potential ◽  
Potential Gradient ◽  
Electric Circuit ◽  
Geophysical Research ◽  
Term Variation ◽  
Atmospheric Electric Potential Gradient

<p><span><span>The atmospheric electric potential gradient (PG, the reverse of the atmospheric vertical electric field) is commonly measured near the ground. The PG plays a pivotal role in studying the global electric circuit (GEC) which comprises all large scale quasi-static electrical processes occurring in between the Earth's surface and the lower ionosphere [1]. Therefore, long-term, coherent PG measurements are of high importance in atmospheric electricity research. Nevertheless, it is a challenging task to use PG as a reliable diagnostic tool for investigating global changes in Earth’s electromagnetic environment because of its high variability. </span></span></p><p> </p><p><span><span>There are few PG datasets around the globe which are long enough and have been recorded continuously for decades. One of the datasets that fulfil these requirements has been recorded in the Széchenyi István Geophysical Observatory, Nagycenk, Hungary, Central Europe (NCK, </span></span><span>47°38’ N, 16°43’ E</span><span><span>). A necessary correction of the recorded PG time series due to the time-dependent shielding effect of nearby trees at NCK was introduced earlier [2,3]. In this study, the corrected long-term (1962-2009) variation of PG at NCK is exhibited and discussed.</span></span></p><p> </p><p><span><span>In the present study, the behaviour of annual minima, maxima, means, and summer and winter means of the PG at NCK are investigated. As these PG time-series exhibited quite different characteristics, the joint analysis of these data is required. The long-term variation of these PG time series can be divided into three periods: the first period (1962-1985) is characterized by a rather steep increase and is mostly driven by the wintertime data. The increase continues with a moderate magnitude and less significantly in the second period (1986-1997) where summertime data dominate the change, whereas there is a pronounced reduction of the PG in the third period (1997-2009) with almost equal magnitude in both the winter- and summertime records. These observed trends are confirmed by independent PG observations made at other measuring sites (e.g., the Swider Observatory, Poland).</span></span></p><p> </p><p><span><span>The PG at NCK is generally greater in winter than in summer, which is a well-known phenomenon at northern hemisphere continental stations [4]. The annual minima, however, do not comply with this trend in every year. The month with the lowest average PG is in late spring (May) in most years of the examined epoch at NCK but minimum values occur in autumn and winter months as well.</span></span></p><p> </p><p><span><span>References:</span></span></p><p><span><span>[1] Rycroft, M. J., Israelsson, S., and Price, C.: The global atmospheric electric circuit, solar activity and climate change, J. Atmos. Sol-Terr. Phy., 62, 1563–1576, 2000.</span></span></p><p><span><span>[2] Buzás, A., Barta, V., Steinbach, P., and Bór, J.: Impact of local environmental conditions on atmospheric electrical potential gradient measurements, Geophysical Research Abstracts, 19, EGU2017-1193-1, 2017.</span></span></p><p><span><span>[3] Buzás, A., Horváth, T., Barta, V., and Bór, J.: Revisiting the decreasing trend of atmospheric electrical potential gradient measured in Central Europe at Nagycenk, Hungary, Geophysical Research Abstracts, 20, EGU2018-6723, 2018.</span></span></p><p><span><span>[4] Chalmers, J. A.: Atmospheric Electricity, second edition, Pergamon Press, London, pp. 168-169 1967.</span></span></p>

scholarly journals A Nonparametric Approach to the Removal of Documented Inhomogeneities in Climate Time Series

2013 ◽  
Vol 52 (5) ◽  
pp. 1139-1146 ◽  
Author(s):  
Chiara Ambrosino ◽  
Richard E. Chandler
Keyword(s):  
Time Series ◽  
Reanalysis Data ◽  
Climate Data ◽  
Nonparametric Approach ◽  
Satellite Technology ◽  
Abrupt Changes ◽  
Regression Framework ◽  
Climate Time Series ◽  
Climate Analysis

AbstractClimate data often suffer from artificial inhomogeneities, resulting from documented or undocumented events. For a time series to be used with confidence in climate analysis, it should only be characterized by variations intrinsic to the climate system. Many methods (e.g., direct or indirect) have been proposed according to the data characteristics (e.g., location, variable, or data completeness). This paper is focused on the abrupt-changes problem (when the properties of a time series change abruptly), when their timing is known, and suggests that a nonparametric regression framework provides an appealing way to correct for discontinuities in such a way as to recognize and allow for the existence of other structures such as seasonality and long-term smooth trends. The approach is illustrated by using reanalysis data for southern Africa, for which discontinuities are present because of the introduction of satellite technology in 1979.

scholarly journals Changepoint Detection in Climate Time Series with Long-Term Trends

2013 ◽  
Vol 26 (14) ◽  
pp. 4994-5006 ◽  
Author(s):  
Colin Gallagher ◽  
Robert Lund ◽  
Michael Robbins
Keyword(s):  
Time Series ◽  
Mean Shift ◽  
Asymptotic Properties ◽  
Erroneous Conclusion ◽  
Test Application ◽  
Long Term Trends ◽  
Temperature Records ◽  
Climate Time Series ◽  
Two Temperature

Abstract Climate time series often have artificial shifts induced by instrumentation changes, station relocations, observer changes, etc. Climate time series also often exhibit long-term trends. Much of the recent literature has focused on identifying the structural breakpoint time(s) of climate time series—the so-called changepoint problem. Unfortunately, application of rudimentary mean-shift changepoint tests to scenarios with trends often leads to the erroneous conclusion that a mean shift occurred near the series' center. This paper examines this problem in detail, constructing some simple homogeneity tests for series with trends. The asymptotic distribution of the proposed statistic is derived; en route, an attempt is made to unify the asymptotic properties of the changepoint methods used in today's climate literature. The tests presented here are linked to the ubiquitous t test. Application is made to two temperature records: 1) the continental United States record and 2) a local record from Jacksonville, Illinois.

scholarly journals Revisiting the long-term decreasing trend of atmospheric electric potential gradient measured at Nagycenk, Hungary, Central Europe

2021 ◽  
Author(s):  
Attila Buzás ◽  
Veronika Barta ◽  
Tamás Horváth ◽  
József Bór
Keyword(s):  
Time Series ◽  
Central Europe ◽  
Electric Potential ◽  
Potential Gradient ◽  
Time Dependent ◽  
Shielding Effect ◽  
Measurement Site ◽  
Term Variation ◽  
Atmospheric Electric Potential Gradient

Abstract. In 2003, a decreasing trend has been reported in the long-term (1962–2001) fair weather atmospheric electric potential gradient (PG) measured in the Széchenyi István Geophysical Observatory (NCK, 47°38' N, 16°43' E), Hungary, Central Europe. The origin of this reduction has been the subject of a long-standing debate, due to a group of trees near the measurement site which reached significant height since the measurements of PG have started. Those trees have contributed to the lowering of the ambient vertical electric field due to their electrostatic shielding effect. In the present study, we attempt to reconstruct the true long-term variation of the vertical atmospheric field at NCK. The time-dependent shielding effect of trees at the measurement site was calculated to remove the corresponding bias from the recorded time series. A numerical model based on electrostatic theory was set up to take into account the electrostatic shielding of the local environment. The validity of the model was verified by on-site measurement campaigns. The changing height of the trees between 1962 and 2017 was derived from national average age-height diagrams for each year. Modelling the time-dependent electrical shielding effect of the trees at NCK revealed that local effects played a pivotal role in the long-term decrease. The results suggest that earlier attempts could not quantify the shielding effect of the trees at NCK accurately. It was found that the reconstructed PG time series at NCK exhibits a significant increase between 1962 and 1997 followed by a decaying trend since 1997. It is pointed out that long-term variation in summertime and wintertime PG averages should be analyzed separately as these may contribute to trends in the annual mean values rather differently.

scholarly journals Homogenization of long-term GPS monitoring series at permanent stations in Central Europe and Balkan Peninsula

2009 ◽  
Vol 39 (1) ◽  
pp. 19-42 ◽  
Author(s):  
Ján Hefty ◽  
Miroslava Igondová ◽  
Branislav Droščák
Keyword(s):  
Time Series ◽  
Central Europe ◽  
Balkan Peninsula ◽  
Terrestrial Reference Frame ◽  
Processing Strategy ◽  
Gps Monitoring ◽  
Homogeneous Models ◽  
Physical Effects ◽  
Adriatic Region

Homogenization of long-term GPS monitoring series at permanent stations in Central Europe and Balkan PeninsulaThe network of 54 permanent GPS stations situated in Central Europe, Alpine-Adriatic region and Balkan Peninsula is analyzed by unified processing strategy, using homogeneous models for reduction of physical effects, and is uniformly referred to as the International Terrestrial Reference Frame - ITRF2005. The resulting time series of observed site coordinates and site troposphere parameters from interval 1999.5 to 2008.5 are inspected for their continuity, homogeneity, long-term drift, and seasonal variations.

Effects of climate change on runoff variability in mid-latitude montane basins

2020 ◽  
Author(s):  
Jakub Langhammer ◽  
Jana Bernsteinová
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Central Europe ◽  
Statistical Testing ◽  
Low Flow ◽  
Hydrologic Alteration ◽  
Recent Climate ◽  
Runoff Variability ◽  
Daily Discharge

<p>The study analyzed long-term changes of runoff variability of headwater montane basins in Central Europe as a response to the effects of climate change and modifications to the environment.</p><p>The aim was to compare the patterns of variability of the indicators of hydrologic alteration, derived from long-term time series of daily discharge observations in montane basins with the recent premises of climate change effects on surface runoff dynamics in the Central Europe region. In particular, there were tested the following assumptions: (i) recent climate warming will result in the shifts of the runoff seasonality and distribution and in (ii) higher variability of runoff, displayed by a higher frequency of floods and droughts, while (iii) the indicators of runoff balance will remain without significant changes.</p><p>These hypotheses were tested in a set of 8 unregulated montane catchments, spreading over the border mountain ranges of the Czech Republic - the Šumava Mountains (Bohemian Forest), Krušné hory (Ore Mountains), Jizera Mountains, Krkonoše (Giant Mountains), Orlické Mountains and Beskydy Mountains. All basins are of comparable size (30-90 km2), and without significant hydrological regulations. Their west-east geographical distribution allows for tracking the potential effects of the gradient of climate continentality in the Central European region. The uninterrupted time series of daily discharge observations from 1953 to 2018 were used for the analyses at the gauging stations. </p><p>We focused on indicators that reflect the aspects of the runoff regime, that are likely to be affected by the assumed effects of the changing climate. Variety of time series analysis and statistical techniques was applied, including the set of 33 Indicators of hydrologic alteration (IHA), 34 Indicators of Environmental flow components, frequency and distribution of the peak an low flows, statistical testing of significance of changes using Mann-Kendall test, breakpoint analysis, analysis of deficit and surplus volumes and homogeneity testing using Buishand, Petitt and SNHT tests.</p><p>The study has identified the significant shifts in the hydrological response of montane basins that are apparent in seasonality, balance, and variability of discharge. The analyses proved (i) changes in runoff response reflecting the timing of the observed changes in air temperatures, (ii) the shift of spring snowmelts towards earlier spring and a corresponding decline of may flows, occurring in all of the investigated regions, (iii) diverging trends of high flows across the basins, (iv) changing dynamics of rainfall-runoff response (v) better sensitivity of indicators, reflecting low magnitude events and (vi) decline of low flow indicators across the basins.</p>

scholarly journals Aerosol optical depth retrievals at the Izaña Atmospheric Observatory from 1941 to 2013 by using artificial neural networks

2016 ◽  
Vol 9 (1) ◽  
pp. 53-62 ◽  
Author(s):  
R. D. García ◽  
O. E. García ◽  
E. Cuevas ◽  
V. E. Cachorro ◽  
A. Barreto ◽  
...  
Keyword(s):  
Neural Networks ◽  
Time Series ◽  
Artificial Neural Networks ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Mineral Dust ◽  
Dust Particles ◽  
Filter Radiometer ◽  
Artificial Neural

Abstract. This paper presents the reconstruction of a 73-year time series of the aerosol optical depth (AOD) at 500 nm at the subtropical high-mountain Izaña Atmospheric Observatory (IZO) located in Tenerife (Canary Islands, Spain). For this purpose, we have combined AOD estimates from artificial neural networks (ANNs) from 1941 to 2001 and AOD measurements directly obtained with a Precision Filter Radiometer (PFR) between 2003 and 2013. The analysis is limited to summer months (July–August–September), when the largest aerosol load is observed at IZO (Saharan mineral dust particles). The ANN AOD time series has been comprehensively validated against coincident AOD measurements performed with a solar spectrometer Mark-I (1984–2009) and AERONET (AErosol RObotic NETwork) CIMEL photometers (2004–2009) at IZO, obtaining a rather good agreement on a daily basis: Pearson coefficient, R, of 0.97 between AERONET and ANN AOD, and 0.93 between Mark-I and ANN AOD estimates. In addition, we have analysed the long-term consistency between ANN AOD time series and long-term meteorological records identifying Saharan mineral dust events at IZO (synoptical observations and local wind records). Both analyses provide consistent results, with correlations  >  85 %. Therefore, we can conclude that the reconstructed AOD time series captures well the AOD variations and dust-laden Saharan air mass outbreaks on short-term and long-term timescales and, thus, it is suitable to be used in climate analysis.

Sign in / Sign up

Export Citation Format

Share Document