scholarly journals Total ozone variations at russian antarctic stations. Results of long-term observations

2018 ◽  
Vol 64 (3) ◽  
pp. 250-261 ◽  
Author(s):  
E. E. Sibir ◽  
V. F. Radionov
Keyword(s):  
Sharp Increase ◽  
Total Ozone ◽  
Early Spring ◽  
Ozone Hole ◽  
Dynamical Processes ◽  
Ozone Depleting Substance ◽  
Concentration Changes ◽  
N 93 ◽  
Ozone Variations

The results of observations of total ozone content (TOC) at the Russian Antarctic stations Mirny (66° 34′ N, 93° 01′ E), Novolazarevskaya (70° 46′ S, 11° 50′ E) and Vostok (78° 38′ S, 106° 52′ E) from 1975 to 2017 are presented. Measurements were carried out by filters ozonemeters M-83/M-124. Throughout this period, there have been steady decreases in TOC in spring time. Early 1990s, the average TOC in September and October at Mirny decreased by 70–75 % of its average values for 1975–1980. The effect of the ozone hole and its intensity depend on ozone-depleting substance (ODS) levels, the dynamical processes and variations of temperature in the stratosphere. Considering the slow rate of decrease ODSs concentration, changes in size and depth of ozone hole have been mainly controlled by variations in temperature and dynamical processes. The destruction of the stratospheric circumpolar vortex early spring of 1988 was the reason that the spring negative anomaly of the TOC was not formed at all. A sharp increase of temperature in the stratosphere in the spring of 2002 was accompanied by an increase in the TOC. It led to reduction in the size of the “ozone hole” and even its dividing into two parts at the end of September. Since the early 2000s, there has been a tendency to return the TOC to the values observed in 1970s and to increase its interannual variability in comparison to 1990s.

scholarly journals ANTARCTIC OZONE HOLE AS A NATURAL GEOPHYSICAL OBJECT

2019 ◽  
Vol 75 ◽  
pp. 02008
Author(s):  
Alexander V. Dergunov ◽  
Valentin B. Kashkin ◽  
Тatyana V. Rubleva ◽  
Alexey A. Romanov ◽  
Roman V. Odintsov
Keyword(s):  
Total Ozone ◽  
Polar Region ◽  
Total Content ◽  
Early Spring ◽  
Ozone Hole ◽  
Polar Regions ◽  
Middle Latitudes ◽  
Antarctic Ozone ◽  
The Antarctic ◽  
Antarctic Ozone Hole

Satellite data on total ozone content for 1985-2015 have been used. Methods of evaluating ozone deficit in the polar region and its excess in middle latitudes of the Southern Hemisphere have been developed. In early spring the ozone molecules outflow and the ozone anomaly forms. Ozone inflows the middle latitudes, its total content increases and a ring with elevated TO forms. In October-November the dynamic process reverses, from the ring the ozone molecules transfer to the polar latitudes. The amount of ozone leaving the ring into the polar regions and filling the ozone anomaly is virtually the same. The results produces indicate that the Antarctic ozone hole is a natural geophysical formation.

scholarly journals Decreases in wintertime total column ozone over the Tibetan Plateau during 1979–2017

2019 ◽  
Author(s):  
Yajuan Li ◽  
Martyn P. Chipperfield ◽  
Wuhu Feng ◽  
Sandip S. Dhomse ◽  
Richard J. Pope ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Regression Models ◽  
Total Ozone ◽  
The Tibetan Plateau ◽  
Total Column Ozone ◽  
Enso Events ◽  
Column Ozone ◽  
Total Column ◽  
Ozone Variations

Abstract. We use the ozone dataset from the Copernicus Climate Change Service (C3S) during 1979–2017 to investigate the long-term variations of the total column ozone (TCO) and the relative total ozone low (TOL) over the Tibetan Plateau (TP) during different seasons. Based on various regression models, the wintertime TCO over the TP decreases overall during 1979–2017 with ongoing decreases since 1997. We perform multivariate regression analysis to quantify the influence of dynamical and chemical processes responsible for the long-term TCO variability over the TP. We use both piecewise linear trend (PWLT) and equivalent effective stratospheric chlorine loading (EESC)-based regression models that include explanatory variables such as the 11-year solar cycle, quasi-biennial oscillation (QBO) at 30 hPa and 10 hPa and the geopotential height (GH) at 150 hPa. The 150 hPa GH is found to be a major dynamical contributor to the total ozone variability (8 %) over the TP in wintertime. We also find strong correlation between TCO in DJF and the following JJA, indicating that negative/positive anomalies in the wintertime build up persist into summer. We also use the TOMCAT/SLIMCAT 3-D chemical transport model to investigate the contributions of different factors to the ozone variations over the TP. Using identical regression model on simulated TCO time series, we obtain consistent results with C3S-based data. We perform two sensitivity experiments with repeating dynamics of 2004 and 2008 to further study the role that the GH at 150 hPa plays in the ozone variations over the TP. The GH differences between the two years show an obvious, negative centre near 150 hPa over the TP in DJF. Composite analysis show that GH fluctuations associated with Inter Tropical Convergence Zone, ENSO events or Walker circulation play a key role in controlling TCO variability in the lower stratosphere.

scholarly journals Assessment of the zonal asymmetry trend in Antarctic total ozonecolumn using TOMS measurements and CCMVal-2 models

2020 ◽  
pp. 50-58
Author(s):  
J. Siddaway ◽  
◽  
A. Klekociuk ◽  
S.P. Alexander ◽  
A. Grytsai ◽  
...  
Keyword(s):  
Greenhouse Gases ◽  
Ozone Depletion ◽  
Total Ozone ◽  
Stationary Wave ◽  
Phase Shifts ◽  
Ozone Hole ◽  
Seasonal Trends ◽  
Zonal Asymmetry ◽  
Spectrometer Data

In the paper the seasonal trends in the zonal asymmetry in the quasi-stationary wave pattern of total ozone column (TOC) at southern polar latitudes have been investigated. We evaluated and compared seasonal trends in the zonal TOC asymmetry from modern era satellite measurements using the Total Ozone Mapping Spectrometer data and the second Chemistry Climate Model Validation (CCMVal-2) assessment. The model longitude phase shifts in asymmetry are in general consistent with the eastward phase shifts observed in historical period 1979–2005, however, there are underestimated values in individual seasons. Future trends in zonal asymmetry from the eleven CCMVal-2 models up to 2100 are presented. They demonstrate the appearance of reverse (westward) future phase shifts, mainly in austral summer. The results are in agreement with previous study and highlight that the general eastward/westward phase shift is caused by both greenhouse gases changes and ozone depletion/recovery. The greenhouse gases change drives a basic long-term eastward shift, which is enhanced (decelerates or reverses) in austral spring and summer by ozone depletion (recovery). The trends in the TOC asymmetry are forced by a general strengthening of the stratospheric zonal flow, which is interacting with the asymmetry of the Antarctic continent to displace the quasi-stationary wave-1 pattern and thus influences the TOC distribution. The results will be useful in prediction of seasonal anomalies in ozone hole and long-term changes in the local TOC trends, in ultraviolet radiation influence on the Southern Ocean biological productivity and in regional surface climate affected by the zonally asymmetric ozone hole.

scholarly journals On the use of satellite observations to fill gaps in the Halley station total ozone record

2021 ◽  
Vol 21 (12) ◽  
pp. 9829-9838
Author(s):  
Lily N. Zhang ◽  
Susan Solomon ◽  
Kane A. Stone ◽  
Jonathan D. Shanklin ◽  
Joshua D. Eveson ◽  
...  
Keyword(s):  
Total Ozone ◽  
Ozone Hole ◽  
Research Station ◽  
Ice Shelf ◽  
Total Column Ozone ◽  
Antarctic Ozone ◽  
Historic Record ◽  
Column Ozone ◽  
The Antarctic

Abstract. Measurements by the Dobson ozone spectrophotometer at the British Antarctic Survey's (BAS) Halley research station form a record of Antarctic total column ozone that dates back to 1956. Due to its location, length, and completeness, the record has been, and continues to be, uniquely important for studies of long-term changes in Antarctic ozone. However, a crack in the ice shelf on which it resides forced the station to abruptly close in February of 2017, leading to a gap of two ozone hole seasons in its historic record. We develop and test a method for filling in the record of Halley total ozone by combining and adjusting overpass data from a range of different satellite instruments. Comparisons to the Dobson suggest that our method reproduces monthly ground-based total ozone values with an average difference of 1.1 ± 6.2 DU for the satellites used to fill in the 2017–2018 gap. We show that our approach more closely reproduces the Dobson measurements than simply using the raw satellite average or data from a single satellite instrument. The method also provides a check on the consistency of the provisional data from the automated Dobson used at Halley after 2018 with earlier manual Dobson data and suggests that there were likely inconsistencies between the two. The filled Halley dataset provides further support that the Antarctic ozone hole is healing, not only during September but also in January.

Long-Term Copper Toxicity on Scenedesmus quadricauda and Complexing Polypeptides

1995 ◽  
Vol 30 (2) ◽  
pp. 265-276 ◽  
Author(s):  
Denis Bussières ◽  
Raynald Côté ◽  
Clément Richard ◽  
Édith St-Pierre
Keyword(s):  
Heavy Metal ◽  
Sharp Increase ◽  
Copper Ions ◽  
Copper Toxicity ◽  
Scenedesmus Quadricauda ◽  
Continuous Exposure ◽  
Exponential Curve ◽  
Negative Exponential

Abstract Long-term copper toxicity has been demonstrated in Scenedesmus quadricauda. Upon continuous exposure to copper ions at 250 μg/L, the algae responded by a sharp increase in the synthesis of complexing polypeptides to chelate Cu. Complexing polypeptides gradually decreased, as observed by six sampling tests over 732 h, resembling to a negative exponential curve. This gradual diminution is considered to be a prime mechanism of acclimation or of adaptation to a heavy metal contaminated environment.

scholarly journals Variability of the total ozone trend over Europe for the period 1950–2004 derived from reconstructed data

2008 ◽  
Vol 8 (11) ◽  
pp. 2847-2857 ◽  
Author(s):  
J. W. Krzyścin ◽  
J. L. Borkowski
Keyword(s):  
Total Ozone ◽  
A Priori ◽  
Smooth Curve ◽  
Ozone Level ◽  
Svalbard Archipelago ◽  
Small Areas ◽  
Ozone Data ◽  
Curve Fit ◽  
Long Term Changes

Abstract. The total ozone data over Europe are available for only few ground-based stations in the pre-satellite era disallowing examination of the spatial trend variability over the whole continent. A need of having gridded ozone data for a trend analysis and input to radiative transfer models stimulated a reconstruction of the daily ozone values since January 1950. Description of the reconstruction model and its validation were a subject of our previous paper. The data base used was built within the objectives of the COST action 726 "Long-term changes and climatology of UV radiation over Europe". Here we focus on trend analyses. The long-term variability of total ozone is discussed using results of a flexible trend model applied to the reconstructed total ozone data for the period 1950–2004. The trend pattern, which comprises both anthropogenic and "natural" component, is not a priori assumed but it comes from a smooth curve fit to the zonal monthly means and monthly grid values. The ozone long-term changes are calculated separately for cold (October–next year April) and warm (May–September) seasons. The confidence intervals for the estimated ozone changes are derived by the block bootstrapping. The statistically significant negative trends are found almost over the whole Europe only in the period 1985–1994. Negative trends up to −3% per decade appeared over small areas in earlier periods when the anthropogenic forcing on the ozone layer was weak . The statistically positive trends are found only during warm seasons 1995–2004 over Svalbard archipelago. The reduction of ozone level in 2004 relative to that before the satellite era is not dramatic, i.e., up to ~−5% and ~−3.5% in the cold and warm subperiod, respectively. Present ozone level is still depleted over many popular resorts in southern Europe and northern Africa. For high latitude regions the trend overturning could be inferred in last decade (1995–2004) as the ozone depleted areas are not found there in 2004 in spite of substantial ozone depletion in the period 1985–1994.

Insights into associative long-term potentiation from computational models of NMDA receptor-mediated calcium influx and intracellular calcium concentration changes

1990 ◽  
Vol 63 (5) ◽  
pp. 1148-1168 ◽  
Author(s):  
W. R. Holmes ◽  
W. B. Levy
Keyword(s):  
Experimental Data ◽  
Nmda Receptor ◽  
Nmda Receptors ◽  
Dendritic Spine ◽  
Long Term Potentiation ◽  
Input Frequency ◽  
Spine Head ◽  
Term Potentiation ◽  
Concentration Changes

1. Because induction of associative long-term potentiation (LTP) in the dentate gyrus is thought to depend on Ca2+ influx through channels controlled by N-methyl-D-aspartate (NMDA) receptors, quantitative modeling was performed of synaptically mediated Ca2+ influx as a function of synaptic coactivation. The goal was to determine whether Ca2+ influx through NMDA-receptor channels was, by itself, sufficient to explain associative LTP, including control experiments and the temporal requirements of LTP. 2. Ca2+ influx through NMDA-receptor channels was modeled at a synapse on a dendritic spine of a reconstructed hippocampal dentate granule cell when 1-115 synapses on spines at different dendritic locations were activated eight times at frequencies of 10-800 Hz. The resulting change in [Ca2+] in the spine head was estimated from the Ca2+ influx with the use of a model of a dendritic spine that included Ca2+ buffers, pumps, and diffusion. 3. To use a compelling model of synaptic activation, we developed quantitative descriptions of the NMDA and non-NMDA receptor-mediated conductances consistent with available experimental data. The experimental data reported for NMDA and non-NMDA receptor-channel properties and data from other non-LTP experiments that separated the NMDA and non-NMDA receptor-mediated components of synaptic events proved to be limiting for particular synaptic variables. Relative to the non-NMDA glutamate-type receptors, 1) the unbinding of transmitter from NMDA receptors had to be slow, 2) the transition from the bound NMDA receptor-transmitter complex to the open channel state had to be even slower, and 3) the average number of NMDA-receptor channels at a single activated synapse on a single spine head that were open and conducting at a given moment in time had to be very small (usually less than 1). 4. With the use of these quantitative synaptic conductance descriptions. Ca2+ influx through NMDA-receptor channels at a synapse was computed for a variety of conditions. For a constant number of pulses, Ca2+ influx was calculated as a function of input frequency and the number of coactivated synapses. When few synapses were coactivated, Ca2+ influx was small, even for high-frequency activation. However, with larger numbers of coactivated synapses, there was a steep increase in Ca2+ influx with increasing input frequency because of the voltage-dependent nature of the NMDA receptor-mediated conductance. Nevertheless, total Ca2+ influx was never increased more than fourfold by increasing input frequency or the number of coactivated synapses.(ABSTRACT TRUNCATED AT 400 WORDS)

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