Long-term changes (1980–2003) in total ozone time series over Northern Hemisphere midlatitudes

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.

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Flexible approach for quantifying average long-term changes and seasonal cycles of tropospheric trace species

10.5194/amt-2019-38 ◽

2019 ◽

Author(s):

David D. Parrish ◽

Richard G. Derwent ◽

Simon O'Doherty ◽

Peter G. Simmonds

Keyword(s):

Time Series ◽

Seasonal Cycle ◽

Linear Trend ◽

Power Series Expansion ◽

Mathematical Representation ◽

Seasonal Cycles ◽

Data Sets ◽

Significant Information ◽

Long Term Changes

Abstract. We present an approach to derive a systematic mathematical representation of the statistically significant features of the average long-term changes and seasonal cycle of concentrations of trace tropospheric species. The results for two illustrative data sets (time series of baseline concentrations of ozone and N2O at Mace Head, Ireland) indicate that a limited set of seven or eight parameter values provides this mathematical representation for both example species. This method utilizes a power series expansion to extract more information regarding the long-term changes than can be provided by oft-employed linear trend analyses. In contrast, the quantification of average seasonal cycles utilizes a Fourier series analysis that provides less detailed seasonal cycles than are sometimes represented as twelve monthly means; including that many parameters in the seasonal cycle representation is not usually statistically justified, and thereby adds unnecessary noise to the representation and prevents a clear analysis of the statistical uncertainty of the results. The approach presented here is intended to maximize the statistically significant information extracted from analyses of time series of concentrations of tropospheric species regarding their mean long-term changes and seasonal cycles, including non-linear aspects of the long-term trends. Additional implications, advantages and limitations of this approach are discussed.

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Optimal dates for assessing long-term changes in tree-cover in the semi-arid biomes of South Africa using MODIS NDVI time series (2001–2018)

International Journal of Applied Earth Observation and Geoinformation ◽

10.1016/j.jag.2019.05.014 ◽

2019 ◽

Vol 81 ◽

pp. 27-36

Author(s):

Moses Azong Cho ◽

Abel Ramoelo

Keyword(s):

South Africa ◽

Time Series ◽

Tree Cover ◽

Modis Ndvi ◽

Long Term Changes ◽

Ndvi Time Series ◽

Semi Arid

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Regional features of long-term changes in cloud cover in Siberian sector of Northern hemisphere for the last 45 years (1969–2013)

Atmospheric and Oceanic Optics ◽

10.1134/s1024856015020050 ◽

2015 ◽

Vol 28 (2) ◽

pp. 175-179 ◽

Cited By ~ 2

Author(s):

V. S. Komarov ◽

G. G. Matvienko ◽

S. N. Il’in ◽

N. Ya. Lomakina

Keyword(s):

Northern Hemisphere ◽

Cloud Cover ◽

Regional Features ◽

Long Term Changes

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Spectral UV measurements in Austria from 1994 to 2006: investigations of short- and long-term changes

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-7033-2008 ◽

2008 ◽

Vol 8 (23) ◽

pp. 7033-7043 ◽

Cited By ~ 13

Author(s):

S. Simic ◽

P. Weihs ◽

A. Vacek ◽

H. Kromp-Kolb ◽

M. Fitzka

Keyword(s):

Confidence Level ◽

Total Ozone ◽

Sunshine Duration ◽

Trend Test ◽

Total Column Ozone ◽

Clear Sky ◽

Uv Irradiance ◽

Long Term Changes ◽

Short And Long Term

Abstract. The influence of variability of atmospheric parameters on short- and long-term changes of spectral UV irradiance measured at the Sonnblick observatory (47.03° N, 12.57° E, 3106 m) during the period from 1994 to 2006 is studied. Measurements were performed with the Brewer #093 single-monochromator spectrophotometer and with a Bentham DM 150 spectroradiometer (double-monochromator). The influence of ozone, albedo, snowline and clouds on UV variability is evaluated for each parameter separately using 10-year climatology. It is found that the effect of total ozone on short-term variability of UV irradiance at 305 nm can be more than 200% and on average more than 50%. Clouds can cause variability of 150% or more and on average 35%. Variability caused by albedo reaches a maximum of 32% in April (6% on average). In summer and autumn, total ozone and clouds strongly influence the variability of UV radiation, whereas in winter and spring ozone has the more pronounced effect. A decrease in snowline height from 3000 m to 800 m a.s.l. enhances the UV irradiance by a factor of 1.24 for clear sky conditions and by a factor of 1.7 for 8/8 cloud cover. Long-term trends are investigated for the time period from 1994 to 2006 based on clear-sky measurements, using the non-parametric Mann-Kendall trend test. Significant downward trends (99% confidence level) are found for solar zenith angle 55° at wavelengths from 305 nm to 324 nm and erythemally weighted irradiance according to CIE, which are caused by an increase in sunshine duration during periods of high total column ozone. Significant trends (90% confidence level) were also found for other combinations of wavelength and SZA.

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