scholarly journals Investigations of long-term trends in the ionosphere with world-wide ionosonde observations*

2005 ◽  
Vol 2 ◽  
pp. 253-258 ◽  
Author(s):  
J. Bremer
Keyword(s):  
Data Series ◽  
Model Calculations ◽  
Maximum Electron Density ◽  
Model Predictions ◽  
Density Values ◽  
Long Term Trends ◽  
Experimental Values ◽  
The Individual ◽  
Global Mean

Abstract. Basing on model calculations by Roble and Dickinson (1989) for an increasing content of atmospheric greenhouse gases in the Earth’s atmosphere Rishbeth (1990) predicted a lowering of the ionospheric F2- and E-regions. Later Rishbeth and Roble (1992) also predicted characteristic longterm changes of the maximum electron density values of the ionospheric E-, F1-, and F2-layers. Long-term observations at more than 100 ionosonde stations have been analyzed to test these model predictions. In the E- and F1-layers the derived experimental results agree reasonably with the model trends (lowering of h'E and increase of ƒoE and ƒoF1, in the E-layer the experimental values are however markedly stronger than the model data). In the ionospheric F2-region the variability of the trends derived at the different individual stations for hmF2 as well as ƒoF2 values is too large to estimate reasonable global mean trends. The reason of the large differences between the individual trends is not quite clear. Strong dynamical effects may play an important role in the F2-region. But also inhomogeneous data series due to technical changes as well as changes in the evaluation algorithms used during the long observation periods may influence the trend analyses.

scholarly journals Long-term trends in the ionospheric F2 region with different solar activity indices

2013 ◽  
Vol 31 (2) ◽  
pp. 291-303 ◽  
Author(s):  
J. Mielich ◽  
J. Bremer
Keyword(s):  
Solar Activity ◽  
Geomagnetic Activity ◽  
Data Series ◽  
Radio Flux ◽  
Model Calculations ◽  
Long Term Trends ◽  
Global Mean ◽  
Good Agreement ◽  
Activity Indices

Abstract. A new comprehensive data collection by Damboldt and Suessmann (2012a) with monthly foF2 and M(3000)F2 median values is an excellent basis for the derivation of long-term trends in the ionospheric F2 region. Ionospheric trends have been derived only for stations with data series of at least 22 years (124 stations with foF2 data and 113 stations with M(3000)F2 data) using a twofold regression analysis depending on solar and geomagnetic activity. Three main results have been derived: Firstly, it could be shown that the solar 10.7 cm radio flux F10.7 is a better index for the description of the solar activity than the relative solar sunspot number R as well as the solar EUV proxy E10.7. Secondly, the global mean foF2 and hmF2 trends derived for the interval between 1948 and 2006 are in surprisingly good agreement with model calculations of an increasing atmospheric greenhouse effect (Rishbeth and Roble, 1992). Thirdly, during the years 2007 until 2009, the hmF2 values and to a smaller amount the foF2 values strongly decrease. The reason for this effect is a reduction of the thermospheric density and ionization due to a markedly reduced solar EUV irradiation and extremely small geomagnetic activity during the solar cycle 23/24 minimum.

scholarly journals Shift of subtropical transport barriers explains observed hemispheric asymmetry of decadal trends of age of air

2017 ◽  
Author(s):  
Gabriele P. Stiller ◽  
Federico Fierli ◽  
Felix Ploeger ◽  
Chiara Cagnazzo ◽  
Bernd Funke ◽  
...  
Keyword(s):  
Circulation Pattern ◽  
Transport Time ◽  
Model Calculations ◽  
Model Predictions ◽  
Southward Shift ◽  
Transport Barriers ◽  
Long Term Trends ◽  
The Mean ◽  
Middle Stratosphere

Abstract. In response to global warming the Brewer–Dobson circulation in the stratosphere is expected to accelerate and the mean transport time of air along this circulation to decrease. This would imply a negative stratospheric age of air trend, i.e. an air parcel would need less time to travel from the tropopause to any point in the stratosphere. Age of air as inferred from tracer observations, however, shows zero to positive trends in the Northern midlatitude stratosphere and zonally asymmetric patterns. Using satellite 5 observations and model calculations we show that the observed latitudinal and vertical patterns of the decadal changes of age of air in the lower to middle stratosphere during 2002–2012 are predominantly caused by a southward shift of the circulation pattern of about 5 degrees. After correction for this shift, the observations reveal a hemispherically almost symmetric decrease of age of air in the lower to middle stratosphere up to 800 K of up to −0.25 years over the 2002–2012 period with strongest decrease in the Northern tropics. This net change is consistent with long-term trends from model predictions.

scholarly journals Shift of subtropical transport barriers explains observed hemispheric asymmetry of decadal trends of age of air

2017 ◽  
Vol 17 (18) ◽  
pp. 11177-11192 ◽  
Author(s):  
Gabriele P. Stiller ◽  
Federico Fierli ◽  
Felix Ploeger ◽  
Chiara Cagnazzo ◽  
Bernd Funke ◽  
...  
Keyword(s):  
Circulation Pattern ◽  
Transport Time ◽  
Model Calculations ◽  
Model Predictions ◽  
Southward Shift ◽  
Transport Barriers ◽  
Long Term Trends ◽  
The Mean ◽  
Middle Stratosphere

Abstract. In response to global warming, the Brewer–Dobson circulation in the stratosphere is expected to accelerate and the mean transport time of air along this circulation to decrease. This would imply a negative stratospheric age of air trend, i.e. an air parcel would need less time to travel from the tropopause to any point in the stratosphere. Age of air as inferred from tracer observations, however, shows zero to positive trends in the northern mid-latitude stratosphere and zonally asymmetric patterns. Using satellite observations and model calculations we show that the observed latitudinal and vertical patterns of the decadal changes of age of air in the lower to middle stratosphere during the period 2002–2012 are predominantly caused by a southward shift of the circulation pattern by about 5°. After correction for this shift, the observations reveal a hemispherically almost symmetric decrease of age of air in the lower to middle stratosphere up to 800 K of up to −0.25 years over the 2002–2012 period with strongest decrease in the northern tropics. This net change is consistent with long-term trends from model predictions.

Solar Energy and Global Climate Change

2014 ◽  
Vol 875-877 ◽  
pp. 1767-1770
Author(s):  
Jia Lin Lin ◽  
Tao Tao Qian
Keyword(s):  
Solar Energy ◽  
Global Climate ◽  
Surface Energy Budget ◽  
The Earth ◽  
Decadal Variations ◽  
Global Dimming ◽  
The Individual ◽  
Solar Energy Input ◽  
Global Mean

Previous studies have shown that the solar energy input to the earth system underwent significant decadal variations at individual surface energy budget stations, with a global dimming from 1950s to 1980s, but a global brightening from 1980s to 2000s, and a mixed tendency at different locations thereafter. Here we use a new global gridded solar irradiance dataset to show that the previous results from individual stations represent well the regional means but not the global mean or hemisphere means. The global mean has a decadal variation that is quite different from the individual station results reported in previous studies, which comes from the fact that the southern hemisphere mean has an opposite trend with the northern hemisphere mean. No long-term global dimming trend is found associated with global warming

scholarly journals Long-term trends in the ionospheric E and F1 regions

2008 ◽  
Vol 26 (5) ◽  
pp. 1189-1197 ◽  
Author(s):  
J. Bremer
Keyword(s):  
Geomagnetic Latitude ◽  
Data Series ◽  
General Behaviour ◽  
Global Trends ◽  
Evaluation Algorithm ◽  
Ozone Trend ◽  
E Region ◽  
Long Term Trends ◽  
Source Of Information

Abstract. Ground based ionosonde measurements are the most essential source of information about long-term variations in the ionospheric E and F1 regions. Data of such observations have been derived at many different ionospheric stations all over the world some for more than 50 years. The standard parameters foE, h'E, and foF1 are used for trend analyses in this paper. Two main problems have to be considered in these analyses. Firstly, the data series have to be homogeneous, i.e. the observations should not be disturbed by artificial steps due to technical reasons or changes in the evaluation algorithm. Secondly, the strong solar and geomagnetic influences upon the ionospheric data have carefully to be removed by an appropriate regression analysis. Otherwise the small trends in the different ionospheric parameters cannot be detected. The trends derived at individual stations differ markedly, however their dependence on geographic or geomagnetic latitude is only small. Nevertheless, the mean global trends estimated from the trends at the different stations show some general behaviour (positive trends in foE and foF1, negative trend in h'E) which can at least qualitatively be explained by an increasing atmospheric greenhouse effect (increase of CO2 content and other greenhouse gases) and decreasing ozone values. The positive foE trend is also in qualitative agreement with rocket mass spectrometer observations of ion densities in the E region. First indications could be found that the changing ozone trend at mid-latitudes (before about 1979, between 1979 until 1995, and after about 1995) modifies the estimated mean foE trend.

scholarly journals Nitrogen Deposition on Danish Nature

Atmosphere ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 447 ◽  
Author(s):  
Thomas Ellermann ◽  
Jesper Nygaard ◽  
Jesper Christensen ◽  
Per Løfstrøm ◽  
Camilla Geels ◽  
...  
Keyword(s):  
Nitrogen Deposition ◽  
Critical Loads ◽  
Temporal Trends ◽  
Monitoring Program ◽  
Terrestrial Ecosystems ◽  
Marine Waters ◽  
Model Calculations ◽  
Nitrogen Loads ◽  
Long Term Trends

Eutrophication events are frequent in Inner Danish waters and critical loads are exceeded for much of the Danish sensitive terrestrial ecosystems. The Danish air quality monitoring program combines measurements and model calculations to benefit from the complementarities in data from these two sources. Measurements describe actual status, seasonal variation, and temporal trends. Model calculations extrapolate the results to the entire country and determine depositions to specific ecosystems. Measurements in 2016 show annual depositions between 7.5 and 11 kg N/ha to terrestrial ecosystems, and a load to marine waters of 5.3 kg N/ha. The deposition on Danish marine waters in 2016 was calculated to be 73,000 tons N with an average deposition of 6.9 kg N/ha. For terrestrial areas, the deposition was calculated to be 57,000 tons N with an average deposition of 13 kg N/ha. This is above critical loads for sensitive ecosystems. Long-term trends show a 35% decrease since 1990 in measured annual nitrogen deposition. At two out of four stations in nature areas, measured ammonia levels exceeded critical levels for lichens and mosses. Conclusions: Nitrogen loads and levels to Danish nature is decreasing, but critical loads and levels are still exceeded for sensitive ecosystems. Combining measurements and model calculations is a strong tool in monitoring.

scholarly journals Long-term variations of the mesospheric wind field at mid-latitudes

2007 ◽  
Vol 25 (8) ◽  
pp. 1779-1790 ◽  
Author(s):  
D. Keuer ◽  
P. Hoffmann ◽  
W. Singer ◽  
J. Bremer
Keyword(s):  
Solar Activity ◽  
Wind Field ◽  
Meridional Wind ◽  
Time Interval ◽  
Wind Component ◽  
Model Calculations ◽  
Measuring Techniques ◽  
Long Term Trends ◽  
Solar Influence

Abstract. Continuous MF radar observations at the station Juliusruh (54.6° N; 13.4° E) have been analysed for the time interval between 1990 and 2005, to obtain information about solar activity-induced variations, as well as long-term trends in the mesospheric wind field. Using monthly median values of the zonal and the meridional prevailing wind components, as well as of the amplitude of the semidiurnal tide, regression analyses have been carried out with a dependence on solar activity and time. The solar activity causes a significant amplification of the zonal winds during summer (increasing easterly winds) and winter (increasing westerly winds). The meridional wind component is positively correlated with the solar activity during summer but during winter the correlation is very small and non significant. Also, the solar influence upon the amplitude of the semidiurnal tidal component is relatively small (in dependence on height partly positive and partly negative) and mostly non-significant. The derived trends in the zonal wind component during summer are below an altitude of about 83 km negative and above this height positive. During the winter months the trends are nearly opposite compared with the trends in summer (transition height near 86 km). The trends in the meridional wind components are below about 85 km positive in summer (significant) and near zero (nonsignificant) in winter; above this height during both seasons negative trends have been detected. The trends in the semidiurnal tidal amplitude are at all heights positive, but only partly significant. The detected trends and solar cycle dependencies are compared with other experimental results and model calculations. There is no full agreement between the different results, probably caused by different measuring techniques and evaluation methods used. Also, different heights and observation periods investigated may contribute to the detected differences.

scholarly journals On the inclusion of data from solar cycle 19 to estimate F2 layer characteristic long term trends

2015 ◽  
Vol 58 (4) ◽  
Author(s):  
Blas F. de Haro Barbas ◽  
Ana G. Elias
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Solar Radio ◽  
Data Series ◽  
Radio Flux ◽  
Solar Radio Flux ◽  
Long Term Trends ◽  
Layer Characteristic ◽  
Dominant Influence

<p>The effect of including solar cycle 19 (1954-1964) in ionospheric trend estimation is assessed using experimental foF2 values. The dominant influence on the F2 layer is solar EUV radiation. In fact, around 90% of inter-annual variance of ionospheric parameters, such as foF2, is explained by solar EUV proxies such as the sunspot number, Rz, and solar radio flux at 10.7 cm, F10.7. This makes necessary to filter out solar activity effects prior to long term trends estimation, which is reduced at most to the remaining 10% variance. In general solar activity is filtered assessing the residuals of a linear regression between foF2 and Rz, or between foF2 and F10.7. Solar cycle 19 is a strong cycle during which Rz and F10.7 exceeded the values beyond which the ionosphere does not respond linearly to a further increase in EUV radiation. This effect, called saturation, implies a break down of the linearity between foF2 and EUV, and results in persistent negative residuals during this period. Since solar cycle 19 is at the beginning of the time series, trends result to be positive, or less negative, than trends without considering this period. In this case the filtering process is generating a “spurious” trend in the filtered data series which may lead to erroneous conclusions. hmF2 that do not present a saturation effect is also analyzed.</p><div> </div>

scholarly journals Inequality Dynamics in Malta: Cracks, Blips and Long-Term Trends

2021 ◽  
Vol 13 (11) ◽  
pp. 1
Author(s):  
Melchior Vella ◽  
Gilmour Camilleri
Keyword(s):  
Income Inequality ◽  
Safety Net ◽  
The European Union ◽  
Tax Reforms ◽  
Tax Progressivity ◽  
Long Term Trends ◽  
Social Transfers ◽  
The Lorenz Curve ◽  
The Individual

This study analyses changes in income inequality in Malta and its driving factors between 2005 and 2018. The study employs and analyses data collected by Malta&rsquo;s National Statistics Office, which conforms with the European Union Survey on Income and Living Conditions. Education and labour status are identified as key drivers behind income inequality changes over the period under review. While the Gini coefficient remained relatively stable between 2005 and 2018, the Lorenz curve moved further away from the line of equality at the upper end of the income distribution, showing modest increases. Over the 2014-2018 period, Government intervention has been mildly neutralizing through social transfers but not through taxes. Social transfers provided a greater safety net to citizens than they did during the 2005-2009 period, whereas tax reforms have abraded some tax progressivity. We also find that inequality was mostly attributed to differences in the individual&rsquo;s qualifications, hours worked, occupations, and household employment structure and size, highlighting an important role for policy to further reduce the barriers to economic inclusion.

scholarly journals Long-term in situ measurements of NO<sub>x</sub> and NO<sub>y</sub> at Jungfraujoch 1998–2009: time series analysis and evaluation

2011 ◽  
Vol 11 (8) ◽  
pp. 21835-21875
Author(s):  
S. Pandey Deolal ◽  
D. Brunner ◽  
M. Steinbacher ◽  
U. Weers ◽  
J. Staehelin
Keyword(s):  
Time Series ◽  
Warm Season ◽  
Data Series ◽  
Data Set ◽  
Long Term Trends ◽  
Investigation Period ◽  
Transport And Mixing ◽  
Time Required

Abstract. We present an analysis of the NOy (NOx + other oxidized species) measurements at the high alpine site Jungfraujoch (JFJ, 3580 m a.s.l.) for the period 1998–2009, which is the longest continous NOy data set reported from the lower free troposphere worldwide. Due to stringent emission control regulations, nitrogen oxides (NOx) emissions have been reduced significantly in Europe since the late 1980s as well as during the investigation period. However, the time series of NOy at JFJ does not show a consistent trend but a maximum during 2002 to 2004 and a decreasing tendency thereafter. The seasonal cycle of NOy exhibits a maximum in the warm season and a minimum in the cold months, opposite to measurements in the PBL, reflecting the seasonal changes in vertical transport and mixing. Except for summer, the seasonal mean NOx concentrations at JFJ show a high year-to-year variability which is strongly controlled by short episodic pollution events obscuring any long-term trends. The low variability in mean and median NOx values in summer is quite remarkable indicating rapid photochemical conversion of NOx to higher oxidized species (NOz) of the NOy family on a timescale shorter than the time required to transport polluted air from the boundary layer to JFJ. In order to evaluate the quality of the NOy data series, an in-situ intercomparison with a second collocated NOy analyzer with a separate inlet was performed in 2009–2010 which showed an agreement within 10 % including all uncertainties and errors.

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