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.

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 Different long-term trends of the oxygen red 630.0 nm line nightglow intensity as the result of lowering the ionosphere F2 layer

2008 ◽  
Vol 26 (8) ◽  
pp. 2069-2080 ◽  
Author(s):  
N. B. Gudadze ◽  
G. G. Didebulidze ◽  
L. N. Lomidze ◽  
G. Sh. Javakhishvili ◽  
M. A. Marsagishvili ◽  
...  
Keyword(s):  
Electron Density ◽  
Line Intensity ◽  
Peak Height ◽  
Height Distribution ◽  
Theoretical Simulation ◽  
Type Layer ◽  
Long Term Trends ◽  
The Mean ◽  
Long Term Trend

Abstract. Long-term observations of total nightglow intensity of the atomic oxygen red 630.0 nm line at Abastumani (41.75° N, 42.82° E) in 1957–1993 and measurements of the ionosphere F2 layer parameters from the Tbilisi ionosphere station (41.65° N, 44.75° E) in 1963–1986 have been analyzed. It is shown that a decrease in the long-term trend of the mean annual red 630.0 nm line intensity from the pre-midnight value (+0.770±1.045 R/year) to its minimum negative value (−1.080±0.670 R/year) at the midnight/after midnight is a possible result of the observed lowering of the peak height of the ionosphere F2 layer electron density hmF2 (−0.455±0.343 km/year). A theoretical simulation is carried out using a simple Chapman-type layer (damping in time) for the height distribution of the F2 layer electron density. The estimated values of the lowering in the hmF2, the increase in the red line intensity at pre-midnight and its decrease at midnight/after midnight are close to their observational ones, when a negative trend in the total neutral density of the upper atmosphere and an increase in the mean northward wind (or its possible consequence – a decrease in the southward one) are assumed.

scholarly journals Evolutionary dynamics of neutral phenotypes under DNA substitution models

2020 ◽  
Author(s):  
Shadi Zabad ◽  
Alan M Moses
Keyword(s):  
Dna Sequences ◽  
Evolutionary Dynamics ◽  
Gc Content ◽  
Stabilizing Selection ◽  
Restoring Force ◽  
Dna Substitution ◽  
Long Term Trends ◽  
The Mean ◽  
Molecular Phenotypes

AbstractWe study the evolution of quantitative molecular traits in the absence of selection. Using a simple theory based on Felsenstein’s 1981 DNA substitution model, we predict a linear restoring force on the mean of an additive phenotype. Remarkably, the mean dynamics are independent of the effect sizes and genotype and are similar to the widely-used OU model for stabilizing selection. We confirm the predictions empirically using additive molecular phenotypes calculated from ancestral reconstructions of putatively unconstrained DNA sequences in primate genomes. We show that the OU model is favoured by inference software even when applied to GC content of unconstrained sequences or simulations of DNA evolution. We predict and confirm empirically that the dynamics of the variance are more complicated than those predicted by the OU model, and show that our results for the restoring force of mutation hold even for non-additive phenotypes, such as number of transcription factor binding sites, longest encoded peptide and folding propensity of the encoded peptide. Our results have implications for efforts to infer selection based on quantitative phenotype dynamics as well as to understand long-term trends in evolution of quantitative molecular traits.

Assessment of Nonresearch Industry Payments to Otolaryngologists in 2014 and 2015

2018 ◽  
Vol 158 (6) ◽  
pp. 1028-1034 ◽  
Author(s):  
Neil Pathak ◽  
Rance J. T. Fujiwara ◽  
Saral Mehra
Keyword(s):  
Annual Variation ◽  
Public Awareness ◽  
Large Change ◽  
Cross Sectional ◽  
Food And Beverage ◽  
Long Term Trends ◽  
The Mean ◽  
Open Payments ◽  
Made In

Objective To characterize, describe, and compare nonresearch industry payments made to otolaryngologists in 2014 and 2015. Additionally, to describe industry payment variation within otolaryngology and among other surgical specialties. Study Design Retrospective cross-sectional database analysis. Setting Open Payments Database. Subjects and Methods Nonresearch payments made to US otolaryngologists were characterized and compared by payment amount, nature of payment, sponsor, and census region between 2014 and 2015. Payments in otolaryngology were compared with those in other surgical specialties. Results From 2014 to 2015, there was an increase in the number of compensated otolaryngologists (7903 vs 7946) and in the mean payment per compensated otolaryngologist ($1096 vs $1242), as well as a decrease in the median payment per compensated otolaryngologist ($169 vs $165, P = .274). Approximately 90% of total payments made in both years were attributed to food and beverage. Northeast census region otolaryngologists received the highest median payment in 2014 and 2015. Compared with other surgical specialists, otolaryngologists received the lowest mean payment in 2014 and 2015 and the second-lowest and lowest median payment in 2014 and 2015, respectively. Conclusion The increase in the mean payment and number of compensated otolaryngologists can be explained by normal annual variation, stronger industry-otolaryngologist relationships, or improved reporting; additional years of data and improved public awareness of the Sunshine Act will facilitate determining long-term trends. The large change in disparity between the mean and median from 2014 to 2015 suggests greater payment variation. Otolaryngologists continue to demonstrate limited industry ties when compared with other surgical specialists.

Trends in match injury risk in professional male rugby union: a 16-season review of 10 851 match injuries in the English Premiership (2002–2019): the Professional Rugby Injury Surveillance Project

2020 ◽  
pp. bjsports-2020-102529
Author(s):  
Stephen W West ◽  
Lindsay Starling ◽  
Simon Kemp ◽  
Sean Williams ◽  
Matthew Cross ◽  
...  
Keyword(s):  
Injury Risk ◽  
Injury Severity ◽  
Rugby Union ◽  
Injury Surveillance ◽  
Injury Incidence ◽  
Match Play ◽  
Common Activity ◽  
Long Term Trends ◽  
The Mean

ObjectivesThe Professional Rugby Injury Surveillance Project is the largest and longest running rugby union injury surveillance project globally and focuses on the highest level of rugby in England.MethodsWe examined match injuries in professional men’s rugby over the period 2002/2003 to 2018/2019 and described trends in injuries over this time.ResultsOver the period 2002/2003–2018/2019, 10 851 injuries occurred in 1 24 952 hours of match play, equating to a mean of 57 injuries per club per season and one injury per team per match. The mean incidence, severity (days absence) and burden (days absence/1000 hours) of injury were 87/1000 hours (95% CI 82 to 92), 25 days (95% CI 22 to 28) and 2178 days/1000 hours (95% CI 1872 to 2484), respectively. The tackle accounted for 43% injuries with running the second most common activity during injury (12%). The most common injury location was the head/face with an incidence of 11.3/1000 hours, while the location with the highest overall burden was the knee (11.1 days/1000 hours). Long-term trends demonstrated stable injury incidence and proportion of injured players, but an increase in the mean and median severity of injuries. Concussion incidence, severity and burden increased from the 2009/2010 season onwards and from 2011 to 2019 concussion was the most common injury.ConclusionThe rise in overall injury severity and concussion incidence are the most significant findings from this work and demonstrate the need for continued efforts to reduce concussion risk as well as a greater understanding of changes in injury severity over time.

scholarly journals Changes in the reproductive parameters of female harp seals (Pagophilus groenlandicus) in the Northwest Atlantic

2009 ◽  
Vol 67 (2) ◽  
pp. 304-315 ◽  
Author(s):  
Becky Sjare ◽  
Garry B. Stenson
Keyword(s):  
Environmental Factors ◽  
Population Size ◽  
Sexual Maturity ◽  
Reproductive Parameters ◽  
Northwest Atlantic ◽  
Pagophilus Groenlandicus ◽  
Long Term Trends ◽  
The Mean ◽  
The 1950S

Abstract Sjare, B., and Stenson, G. B. 2010. Changes in the reproductive parameters of female harp seals (Pagophilus groenlandicus) in the Northwest Atlantic. – ICES Journal of Marine Science, 67: 304–315. Changes in female harp seal (Pagophilus groenlandicus) reproductive parameters from 1980 to 2004, and long-term trends since the early 1950s, are evaluated. Estimates of the total number of seals in the Northwest Atlantic declined from ∼3.0 million in the 1950s to 1.8 million in the early 1970s, then increased steadily to 5.5 million in 1996, at which relatively stable level it has remained since. Pregnancy rates increased from ∼86% in the 1950s to a high of 98% in the mid-1960s, then declined to ∼65–70% by the early 1990s; the rate then varied between 45 and 70% from 2000 to 2004. Concurrently, the mean age at sexual maturity decreased from 5.8 (s.e = 0.02) years in the mid-1950s to 4.1 (s.e. = 0.02) in the late 1970s, increased to 5.5 (s.e. = 0.03) years by the early 1990s, and peaked at 5.7 (s.e. = 0.01) in 1995. From 2000 to 2004, mean age varied from 4.9 (s.e. = 0.01) to 6.0 (s.e. = 0.01) years. Although the direction of change in each of the parameters was consistent with a density-dependent response, changes in population size explained relatively little of the variability observed, suggesting that other ecological or environmental factors were influential.

scholarly journals The Impact of Improved Thermistor Calibration on the Expendable Bathythermograph Profile Data

2017 ◽  
Vol 34 (9) ◽  
pp. 1947-1961 ◽  
Author(s):  
Marlos Goes ◽  
Elizabeth Babcock ◽  
Francis Bringas ◽  
Peter Ortner ◽  
Gustavo Goni
Keyword(s):  
Small Sample Size ◽  
Heat Content ◽  
Small Sample ◽  
Profile Data ◽  
Expendable Bathythermograph ◽  
Different Types ◽  
Long Term Trends ◽  
The Mean ◽  
The Impact

AbstractExpendable bathythermograph (XBT) data provide one of the longest available records of upper-ocean temperature. However, temperature and depth biases in XBT data adversely affect estimates of long-term trends of ocean heat content and, to a lesser extent, estimates of volume and heat transport in the ocean. Several corrections have been proposed to overcome historical biases in XBT data, which rely on constantly monitoring these biases. This paper provides an analysis of data collected during three recent hydrographic cruises that utilized different types of probes, and examines methods to reduce temperature and depth biases by improving the thermistor calibration and reducing the mass variability of the XBT probes.The results obtained show that the use of individual thermistor calibration in XBT probes is the most effective calibration to decrease the thermal bias, improving the mean thermal bias to less than 0.02°C and its tolerance from 0.1° to 0.03°C. The temperature variance of probes with screened thermistors is significantly reduced by approximately 60% in comparison to standard probes. On the other hand, probes with a tighter weight tolerance did not show statistically significant reductions in the spread of depth biases, possibly because of the small sample size or the sensitivity of the depth accuracy to other causes affecting the analysis.

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.

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