Long-term trends in the relation between daytime and nighttime values of &lt;I&gt;fo&lt;/I&gt;F2

Abstract. The data from the vertical ionospheric sounding for 12 stations over the world were analyzed to find the relation between the values of foF2 for 02:00 LT and 14:00 LT of the same day. It is found that, in general, there exists a negative correlation between foF2(02) and foF2(14). The value of the correlation coefficient R(foF2) can be in some cases high enough and reach minus 0.7–0.8. The value of R(foF2) demonstrates a well pronounced seasonal variations, the highest negative values being observed at the equinox periods of the year. It is also found that R(foF2) depends on geomagnetic activity: the magnitude of R(foF2) is the highest for the choice of only magnetically quiet days (Ap<6), decreasing with the increase of the limiting value of Ap. For a fixed limitation on Ap, the value of R(foF2) depends also on solar activity. Apparently, the effects found are related to thermospheric winds. Analysis of long series of the vertical sounding data shows that there is a long-term trend in R(foF2) with a statistically significant increase in the R(foF2) magnitude after about 1980. Similar analysis is performed for the foF2(02)/foF2(14) ratio itself. The ratio also demonstrates a systematic trend after 1980. Both trends are interpreted in terms of long-term changes in thermospheric circulation.

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Long term relation between solar activity and surface temperature at different geographical regions

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312005170 ◽

2011 ◽

Vol 7 (S286) ◽

pp. 418-422

Author(s):

M. P. Souza-Echer ◽

W. D. Gonzalez ◽

E. Echer ◽

D. J. R. Nordemann ◽

N. R. Rigozo

Keyword(s):

Solar Activity ◽

Surface Temperature ◽

Temperature Series ◽

Term Trend ◽

Natural Processes ◽

Term Relation ◽

Geographical Regions ◽

Long Term Trend

AbstractGlobal suface temperature has showed a rise trend in the last 150 years. This has been mainly attributed to the anthropogenic induced grenhouse gases emissions. However, the role of natural processes is not completely understood and should not be underestimated. In this work, we compare the long term variability of solar activity (as quantified by the sunspot number) with several surface temperature series from different geographical regions (global, hemispheric and latitudinal ranges). The interval of analysis is 1880-2005. The data are analyzed with wavelet multiresolution technique. It has been found that the solar activity long term trend has a maximum around 1970, while air surface temperature series showed maximum (still rising) at 2005. There are differences in the long term trend for Northern and Southern hemispheres. These differences and the relation with solar activity are discussed in this work.

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Measurement Methods Affect the Observed Global Dimming and Brightening

Journal of Climate ◽

10.1175/jcli-d-12-00482.1 ◽

2013 ◽

Vol 26 (12) ◽

pp. 4112-4120 ◽

Cited By ~ 26

Author(s):

Kaicun Wang ◽

Robert E. Dickinson ◽

Qian Ma ◽

John A. Augustine ◽

Martin Wild

Keyword(s):

Important Implication ◽

Summation Method ◽

Measurement Methods ◽

Term Trend ◽

Summation Methods ◽

Long Term Trends ◽

Global Dimming ◽

Long Term Trend ◽

Parallel Measurements

Abstract Surface incident solar radiation G determines our climate and environment, and has been widely observed with a single pyranometer since the late 1950s. Such observations have suggested a widespread decrease between the 1950s and 1980s (global dimming), that is, at a rate of −3.5 W m−2 decade−1 (or −2% decade−1) from 1960 to 1990. Since the early 1990s, the diffuse and direct components of G have been measured independently, and a more accurate G has been calculated by summing these two measurements. Data from this summation method suggest that G increased at a rate of 6.6 W m−2 decade−1 (3.6% decade−1) from 1992 to 2002 (brightening) at selected sites. The brightening rates from these studies were also higher than those from a single pyranometer. In this paper, the authors used 17 years (1995–2011) of parallel measurements by the two methods from nearly 50 stations to test whether these two measurement methods of G provide similar long-term trends. The results show that although measurements of G by the two methods agree very well on a monthly time scale, the long-term trend from 1995 to 2011 determined by the single pyranometer is 2–4 W m−2 decade−1 less than that from the summation method. This difference of trends in the observed G is statistically significant. The dependence of trends of G on measurement methods uncovered here has an important implication for the widely reported global dimming and brightening based on datasets collected by different measurement methods; that is, the dimming might have been less if measured with current summation methods.

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Long-term Trend Comparison of Planetary Boundary Layer Height in Observations and CMIP6 models over China

10.5194/egusphere-egu21-1706 ◽

2021 ◽

Author(s):

Man Yue ◽

Minghuai Wang ◽

Jianping Guo ◽

Haipeng Zhang ◽

Xinyi Dong ◽

...

Keyword(s):

Soil Moisture ◽

Cloud Cover ◽

Climate Models ◽

Term Trend ◽

Cloud Radiative Effect ◽

Low Cloud ◽

Long Term Trends ◽

Low Cloud Cover ◽

Long Term Trend

<p>The planetary boundary layer (PBL) plays an essential role in climate and air quality simulations. Large uncertainties remain in understanding the long-term trend of PBL height (PBLH) and its simulation. Here we use the radiosonde data and reanalysis datasets to analyze PBLH long-term trends over China, and to further evaluate the performance of CMIP6 climate models in simulating these trends. Results show that the observed long-term &#8220;positive to negative&#8221; trend shift of PBLH is related to the variation in the surface upward sensible heat flux (SHFLX) which is further controlled by the synergistic effect of low cloud cover (LCC) and soil moisture (SM) changes. Variabilities in low cloud cover and soil moisture directly influence the energy balance via surface net downward shortwave flux (SWF) and the latent heat flux (LHFLX), respectively. We have found that the CMIP6 climate models cannot reproduce the observed PBLH long-term trend shift over China. The CMIP6 results show an overwhelming continuous downward PBLH trend during the 1979-2014 period, which is caused by the poorly simulated long-term changes of cloud radiative effect. Our results reveal that the long-term cloud radiative effect simulation is critical for CMIP6 models in reproducing the PBLH long-term trends. This study highlights the importance of low cloud cover and soil moisture processes in modulating PBLH long-term variations and calls attentions to improve these processes in climate models in order to improve the PLBH long-term trend simulations.</p>

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Have World, Country, and Industry Risks Changed over Time? An Investigation of the Volatility of Developed Stock Markets

Journal of Financial and Quantitative Analysis ◽

10.1017/s0022109000001794 ◽

2005 ◽

Vol 40 (1) ◽

pp. 195-222 ◽

Cited By ~ 67

Author(s):

Miguel A. Ferreira ◽

Paulo M. Gama

Keyword(s):

Sharp Increase ◽

Decomposition Method ◽

World Country ◽

The Other ◽

Term Trend ◽

The World ◽

Developed Stock Markets ◽

Long Term Trend ◽

Over Time

AbstractThis paper uses a volatility decomposition method to study the time-series behavior of equity volatility at the world, country, and local industry levels. Between 1974 and 2001, there is no noticeable long-term trend in any of the volatility measures. Then in the 1990s there is a sharp increase in local industry volatility compared to market and country volatility. Thus, correlations among local industries have declined. More assets are needed to achieve a given level of diversification, and there is more of a penalty for not being well diversified by industry. Local industry volatility leads the other volatility measures.

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