Occurrence of discontinuities in the ozone concentration data from three reanalyses

2020 ◽  
Author(s):  
Peter Krizan
Keyword(s):  
Vertical Distribution ◽  
Data Quality ◽  
Ozone Concentration ◽  
Frequent Occurrence ◽  
Homogeneity Test ◽  
Concentration Data ◽  
Trend Analyses ◽  
Ozone Data ◽  
Before And After ◽  
The Vertical Distribution

<p>The aim of this presentation is to compare the occurrence of discontinuities in the ozone concentration data from the MERRA-2, ERA-5 and JRA-55 reanalyse, with the help of the Pettitt homogeneity test. We distinguish between the significant and insignificant discontinuities, according to the relation between the dispersion and the average ozone values before and after the discontinuity.    This occurrence is important for trend analyses, because the presence of discontinuities influences the values of trends and their significance. Discontinuities arise from the changing in the assimilation procedure, introducing new observation to the reanalyse, and changing of data quality. We search for their spatial, temporal and geographical occurrence. There are differences among these reanalyses. In the case of the MERRA-2 data, the transition from SBUV to EOS Aura data in 2004 has great impact on discontinuity behaviour. The frequent occurrence of discontinuities is seen in the uppermost model layers. The uppermost MERRA-2 layer is 0.1 hPa, while for ERA-5 this layer is 1 hPa. So there are differences in the vertical distribution of discontinuities among the reanalyses. The ozone data with the strong occurrence of the significant discontinuities is not suitable for trend analyses.   </p>

Occurrence of discontinuities in the ozone concentration data from three reanalyses

2020 ◽  
Author(s):  
Peter Krizan ◽  
Michal Kozubek ◽  
Jan Lastovicka
Keyword(s):  
Time Evolution ◽  
Southern Hemisphere ◽  
Ozone Concentration ◽  
Temporal Structure ◽  
The Other ◽  
Trace Gas ◽  
Homogeneity Test ◽  
Concentration Data ◽  
Ozone Data ◽  
Ozone Trend

Abstract. Ozone is a very important trace gas in the stratosphere and thus we need to know its time evolution over the globe. The ground based measurements are rare, especially in the Southern Hemisphere. Satellite ozone data have broader coverage, but they are not available from everywhere. On the other hand, the reanalyse data have regular spatial and temporal structure, which is very good for trend analyses. But there are discontinuities in these data.These discontinuities may influence the result of trend studies. The aim of this paper is to detect the discontinuity occurrence (DO) in the following reanalyses: MERRA-2, ERA-5 and JRA-55 with the help of the Pettitt homogeneity test at all common layers above 500 hPa. The discontinuities are sorted according to their size to the significant and the insignificant ones; the former can affect the ozone trend studies. It was shown that DO for the significant discontinuities is the smallest in JRA-55. In the upper model layers, the discontinuity occurrence is the highest. The other area of high DO is the troposphere.

scholarly journals Discontinuities in the Ozone Concentration Time Series from MERRA 2 Reanalysis

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 812 ◽  
Author(s):  
Peter Krizan ◽  
Michal Kozubek ◽  
Jan Lastovicka
Keyword(s):  
Time Series ◽  
Trend Analysis ◽  
Ozone Concentration ◽  
Homogeneity Test ◽  
Concentration Data ◽  
Trend Analyses ◽  
Earth Observing System ◽  
Concentration Time ◽  
Concentration Time Series ◽  
Modern Era

Artificial discontinuities in time series are a great problem for trend analysis because they influence the values of the trend and its significance. The aim of this paper is to investigate their occurrence in the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA 2) ozone concentration data. It is the first step toward the utilization of the MERRA 2 ozone data for trend analysis. We use the Pettitt homogeneity test to search for discontinuities in the ozone time series. We showed the data above 4 hPa are not suitable for trend analyses due to the unrealistic patterns in an average ozone concentration and due to the frequent occurrence of significant discontinuities. Below this layer in the stratosphere, their number is much smaller, and mostly, they are insignificant, and the patterns of the average ozone concentration are explainable. In the troposphere, the number of discontinuities increases, but they are insignificant. The transition from Solar Backscatter Ultraviolet Radiometer (SBUV) to Earth Observing System (EOS) Aura data in 2004 is visible only above 1 hPa, where the data are not suitable for trend analyses due to other reasons. We can conclude the MERRA 2 ozone concentration data can be used in trend analysis with caution only below 4 hPa.

Travelling disturbances in the ionosphere

1950 ◽  
Vol 202 (1069) ◽  
pp. 208-223 ◽  
Keyword(s):  
Seasonal Variation ◽  
Vertical Distribution ◽  
Sudden Change ◽  
Frequent Occurrence ◽  
Vertical Movements ◽  
Short Period ◽  
The Mean ◽  
The Vertical Distribution

Methods have been developed for the examination of the horizontal and vertical movements of short-period disturbances in the ionosphere. It has been found that quasi-periodic travelling disturbances with periods of from 10 to 60 min. are of frequent occurrence in the F region by day. They appear as temporary variations in the vertical distribution of ionization which show a horizontal progression and a vertical progression downwards. The horizontal directions of travel have a well-defined mean direction on most days. The mean direction shows a marked seasonal variation with a sudden change at each equinox. The horizontal rate of travel is usually between 5 and 10 km./min., and the rate of vertical progression downwards is approximately half the horizontal rate. The disturbances are considered to be variations of a compressional type in the atmosphere resulting in changes in the distribution of ionization.

scholarly journals Past changes in the vertical distribution of ozone – Part 3: Analysis and interpretation of trends

2015 ◽  
Vol 15 (6) ◽  
pp. 8565-8608 ◽  
Author(s):  
N. R. P. Harris ◽  
B. Hassler ◽  
F. Tummon ◽  
G. E. Bodeker ◽  
D. Hubert ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Lower Stratosphere ◽  
Positive Trend ◽  
Data Merging ◽  
Before And After ◽  
Rigorous Treatment ◽  
The Tropics ◽  
Merging Techniques ◽  
The Vertical Distribution ◽  
Observational Record

Abstract. Trends in the vertical distribution of ozone are reported and compared for a number of new and recently revised datasets. The amount of ozone-depleting compounds in the stratosphere (as measured by Equivalent Effective Stratospheric Chlorine – EESC) maximised in the second half of the 1990s. We therefore examine the trends in the periods before and after that peak to see if any change in trend is discernible in the ozone record. Prior to 1998, trends in the upper stratosphere (~ 45 km, 4 hPa) are found to be −5 to −10% per decade at mid-latitudes and closer to −5% per decade in the tropics. No trends are found in the mid-stratosphere (28 km, 30 hPa). Negative trends are seen in the lower stratosphere at mid-latitudes in both hemispheres and in the deep tropics. However it is hard to be categorical about the trends in the lower stratosphere for three reasons: (i) there are fewer measurements, (ii) the data quality is poorer, and (iii) the measurements in the 1990s are perturbed by aerosols from the Mt. Pinatubo eruption in 1991. These findings are similar to those reported previously even though the measurements for the two main satellite instruments (SBUV and SAGE II) and the ground-based Umkehr and ozonesonde stations have been revised. There is no sign of a continued negative trend in the upper stratosphere since 1998: instead there is a hint of an average positive trend of ~ 2% per decade in mid-latitudes and ~ 3% per decade in the tropics. The significance of these upward trends is investigated using different assumptions of the independence of the trend estimates found from different datasets. The averaged upward trends are significant if the trends derived from various datasets are assumed to be independent, but are generally not significant if the trends are not independent. This arises because many of the underlying measurement records are used in more than one merged dataset. At this point it is not possible to say which assumption is best. Including an estimate of the drift of the overall ozone observing system decreases the significance of the trends. The significance will become clearer as (i) more years are added to the observational record, (ii) further improvements are made to the historic ozone record (e.g. through algorithm development), and (iii) the data merging techniques are refined, particularly through a more rigorous treatment of uncertainties.

scholarly journals Technical Note: Continuity of MIPAS-ENVISAT operational ozone data quality from full- to reduced-spectral-resolution operation mode

2008 ◽  
Vol 8 (8) ◽  
pp. 2201-2212 ◽  
Author(s):  
S. Ceccherini ◽  
U. Cortesi ◽  
P. T. Verronen ◽  
E. Kyrölä
Keyword(s):  
Data Quality ◽  
Spectral Resolution ◽  
Michelson Interferometer ◽  
Technical Note ◽  
Relative Bias ◽  
Measurement Time ◽  
Full Resolution ◽  
Ozone Data ◽  
Before And After

Abstract. MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is operating on the ENVIronmental SATellite (ENVISAT) since March 2002. After two years of nearly continuous limb scanning measurements, at the end of March 2004, the instrument was stopped due to problems with the mirror drive of the interferometer. Operations with reduced maximum path difference, corresponding to both a reduced-spectral-resolution and a shorter measurement time, were resumed on January 2005. In order to exploit the reduction in measurement time, the measurement scenario was changed adopting a finer vertical limb scanning. The change of spectral resolution and of measurement scenario entailed an update of the data processing strategy. The aim of this paper is the assessment of the differences in the quality of the MIPAS ozone data acquired before and after the stop of the operations. Two sets of MIPAS ozone profiles acquired in 2003–2004 (full-resolution measurements) and in 2005–2006 (reduced-resolution measurements) are compared with collocated ozone profiles obtained by GOMOS (Global Ozone Monitoring by Occultation of Stars), itself also onboard ENVISAT. The continuity of the GOMOS data quality allows to assess a possible discontinuity of the MIPAS performances. The relative bias and precision of MIPAS ozone profiles with respect to the GOMOS ones have been compared for the measurements acquired before and after the stop of the MIPAS operations. The results of the comparison show that, in general, the quality of the MIPAS ozone profiles retrieved from reduced-resolution measurements is comparable or better than that obtained from the full-resolution dataset. The only significant change in MIPAS performances is observed at pressures around 2 hPa, where the relative bias of the instruments increases by a factor of 2 from the 2003–2004 to 2005–2006 measurements.

scholarly journals Past changes in the vertical distribution of ozone – Part 3: Analysis and interpretation of trends

2015 ◽  
Vol 15 (17) ◽  
pp. 9965-9982 ◽  
Author(s):  
N. R. P. Harris ◽  
B. Hassler ◽  
F. Tummon ◽  
G. E. Bodeker ◽  
D. Hubert ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Lower Stratosphere ◽  
Data Sets ◽  
Positive Trend ◽  
Data Set ◽  
Data Merging ◽  
Before And After ◽  
Rigorous Treatment ◽  
The Tropics ◽  
The Vertical Distribution

Abstract. Trends in the vertical distribution of ozone are reported and compared for a number of new and recently revised data sets. The amount of ozone-depleting compounds in the stratosphere (as measured by equivalent effective stratospheric chlorine – EESC) was maximised in the second half of the 1990s. We examine the periods before and after the peak to see if any change in trend is discernible in the ozone record that might be attributable to a change in the EESC trend, though no attribution is attempted. Prior to 1998, trends in the upper stratosphere (~ 45 km, 4 hPa) are found to be −5 to −10 % per decade at mid-latitudes and closer to −5 % per decade in the tropics. No trends are found in the mid-stratosphere (28 km, 30 hPa). Negative trends are seen in the lower stratosphere at mid-latitudes in both hemispheres and in the deep tropics. However, it is hard to be categorical about the trends in the lower stratosphere for three reasons: (i) there are fewer measurements, (ii) the data quality is poorer, and (iii) the measurements in the 1990s are perturbed by aerosols from the Mt Pinatubo eruption in 1991. These findings are similar to those reported previously even though the measurements for the main satellite and ground-based records have been revised. There is no sign of a continued negative trend in the upper stratosphere since 1998: instead there is a hint of an average positive trend of ~ 2 % per decade in mid-latitudes and ~ 3 % per decade in the tropics. The significance of these upward trends is investigated using different assumptions of the independence of the trend estimates found from different data sets. The averaged upward trends are significant if the trends derived from various data sets are assumed to be independent (as in Pawson et al., 2014) but are generally not significant if the trends are not independent. This occurs because many of the underlying measurement records are used in more than one merged data set. At this point it is not possible to say which assumption is best. Including an estimate of the drift of the overall ozone observing system decreases the significance of the trends. The significance will become clearer as (i) more years are added to the observational record, (ii) further improvements are made to the historic ozone record (e.g. through algorithm development), and (iii) the data merging techniques are refined, particularly through a more rigorous treatment of uncertainties.

scholarly journals Technical Note: Continuity of MIPAS-ENVISAT ozone data quality from full- to reduced-spectral-resolution operation mode

2008 ◽  
Vol 8 (1) ◽  
pp. 797-825
Author(s):  
S. Ceccherini ◽  
U. Cortesi ◽  
P.T. Verronen ◽  
E. Kyrölä
Keyword(s):  
Data Quality ◽  
Spectral Resolution ◽  
Michelson Interferometer ◽  
Technical Note ◽  
Relative Bias ◽  
Measurement Time ◽  
Full Resolution ◽  
Ozone Data ◽  
Before And After

Abstract. MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is operating on the ENVIronmental SATellite (ENVISAT) since March 2002. After two years of nearly continuous limb scanning measurements, at the end of March 2004, the instrument was stopped due to problems with the mirror drive of the interferometer. Operations with reduced maximum path difference, corresponding to both a reduced-spectral-resolution and a shorter measurement time, were resumed on January 2005. In order to exploit the reduction in measurement time, the measurement scenario was changed adopting a finer vertical limb scanning. The change of spectral resolution and of measurement scenario entailed an update of the data processing strategy. The aim of this paper is the assessment of the differences in the quality of the MIPAS ozone data acquired before and after the stop of the operations. Two sets of MIPAS ozone profiles acquired in 2003–2004 (full-resolution measurements) and in 2005–2006 (reduced-resolution measurements) are compared with collocated ozone profiles obtained by GOMOS (Global Ozone Monitoring by Occultation of Stars), itself also onboard ENVISAT. The continuity of the GOMOS data quality allows to assess a possible discontinuity of the MIPAS performances. The relative bias and precision of MIPAS ozone profiles with respect to the GOMOS ones have been compared for the measurements acquired before and after the stop of the MIPAS operations. The results of the comparison show that, in general, the quality of the MIPAS ozone profiles retrieved from reduced-resolution measurements is comparable or better than that obtained from the full-resolution dataset. The only significant change in MIPAS performances is observed at pressures around 2 hPa, where the relative bias of the instruments increases by a factor of 2 from the 2003–2004 to 2005–2006 measurements.

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