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Compared to recent years, the development of the Antarctic ozone hole in 2002 showed very unusual dynamical features. The midwinter polar vortex was one of the smallest observed during the past decade. Driven by planetary waves, the vortex showed a strong asymmetry in early spring. A large air mass separated in late September, leaving what was previously a small vortex even smaller. Furthermore, stratospheric temperatures exceeded the polar stratospheric cloud (PSC) threshold earlier than in previous years, leading to a decrease in halogen activation by heterogeneous surface reactions. Ground-based observation of stratospheric trace gases in austral spring of 2001 and 2002 using passive Differential Optical Absorption Spectroscopy (DOAS) observations of zenith-scattered sunlight in the UV and visible wavelength region (320-650 nm) are presented. Using DOAS measurements of ozone, N[O.sub.2], BrO, and OCIO at two different Antarctic sites, Neumayer Station (70[degrees]S, 8[degrees]W) and Arrival Heights (78[degrees]S, 167[degrees]E), the chemical composition of the stratosphere is investigated under the unusual conditions of the 2002 ozone hole period and compared to the more typical observations of the previous year (2001).

Microwave bandpass filters for wireless communication systems are optimized through large-area and double-sided pulsed laser deposition of YBa2Cu3O7-x thin films on LaAlO3 cylinder substrates and 3-in diameter sapphire wafers. Reproducible and homogeneous thin film deposition may be achieved through the technique. Films made through the process exhibited an inductively measured critical current densities of 3x10(super 6) to 5x10(super 6)A/cm2 at 77 K.

Aerosol observations above the Southern Ocean and Antarctic sea ice are scarce. Measurements of aerosols and atmospheric composition were made in East Antarctic pack ice on board the Australian icebreaker Aurora Australis during the spring of 2012. One particle formation event was observed during the 32 days of observations. This event occurred on the only day to exhibit extended periods of global irradiance in excess of 600 W m-2. Within the single air mass influencing the measurements, number concentrations of particles larger than 3 nm (CN3) reached almost 7700 cm-3 within a few hours of clouds clearing, and grew at rates of 5.6 nm h-1. Formation rates of 3 nm particles were in the range of those measured at other Antarctic locations at 0.2-1:1±0.1 cm-3 s-1. Our investigations into the nucleation chemistry found that there were insufficient precursor concentrations for known halogen or organic chemistry to explain the nucleation event. Modelling studies utilising known sulfuric acid nucleation schemes could not simultaneously reproduce both particle formation or growth rates. Surprising correlations with total gaseous mercury (TGM) were found that, together with other data, suggest a mercurydriven photochemical nucleation mechanism may be responsible for aerosol nucleation. Given the very low vapour pressures of the mercury species involved, this nucleation chemistry is likely only possible where pre-existing aerosol concentrations are low and both TGM concentrations and solar radiation levels are relatively high (~1.5 ng m-3 and ≤ 600W m-2, respectively), such as those observed in the Antarctic sea ice boundary layer in this study or in the global free troposphere, particularly in the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

Detection of climate change requires a network of stable ground-based long-term measurements. Building upon earlier work, we first explore requirements of such measurements (such as maximum random uncertainty and sampling frequency) to ensure a minimum random uncertainty in monthly mean temperatures and to ensure effective detection of trends. In agreement with previous work we find that only for individual measurement random uncertainties >0.2K does the measurement random uncertainty start to contribute significantly to the random uncertainty in the monthly mean. For trend analysis, we find that the quality of the trend determination is only compromised when the measurement random uncertainty exceeds 2K and measurements are made just once or twice a month. In the second part of the study we provide guidance on how to most effectively design a measurement network. To this end we developed a method to objectively identify the optimal location of sites for detecting projected trends in upper-air temperatures and total column ozone in the shortest possible time. This is done by first estimating the spatial distribution of the minimum length of time during which measurements have to be made in order to detect projected trends in temperature and ozone. This quantity is calculated from the unforced variance in the signal and the degree of autocorrelation, both estimated from historical data sets and assumed not to change in the future, and the projected trends as estimated from chemistry-climate models. The optimal site locations are then selected by an iterative procedure based on the minimum time required to detect a trend and a minimal distance between different measurement sites. While the optimal sites identified here result from our use of only one of a wide range of objective strategies, these results provide additional incentives for initiating measurement programmes at these sites or, if already in operation, to continue to be supported. [ABSTRACT FROM AUTHOR]

The trend in stratospheric NO2 column at the NDACC (Network for the Detection of Atmospheric Composition Change) station of Jungfraujoch (46.5° N, 8.0° E) is assessed using ground-based FTIR and zenith-scattered visible sunlight SAOZ measurements over the period 1990 to 2009 as well as a composite satellite nadir data set constructed from ERS-2/GOME, ENVISAT/SCIAMACHY, METOP-A/GOME-2 observations over the 1996-2009 period. To calculate the trends, a linear least squares regression model including explanatory variables for a linear trend, the mean annual cycle, the quasi-biennial oscillation (QBO), solar activity, stratospheric aerosol loading is used. For the 1990-2009 period, statistically indistinguishable trends of -3.7 ± 1.1% decade-1, -3.6 ± decade-11 are derived for the SAOZ and FTIR NO2 column time series, respectively. SAOZ, FTIR, satellite nadir data sets show a similar decrease over the 1996-2009 period, with trends of -2.4 ± 1.1% decade-11, -4.3 ± 1.4% decade-11, and -3.6 ± 2.2% decade-1, respectively. The fact that these declines are opposite in sign to the globally observed +2.5% decade-11 trend in N2O, suggests that factors other than N2O are driving the evolution of stratospheric NO2 at northern mid-latitudes. Possible causes of the decrease in stratospheric NO2 columns have been investigated. The most likely cause is a change in the NO2/NO partitioning in favor of NO, due to a possible stratospheric cooling and a decrease in stratospheric chlorine content, the latter being further confirmed by the negative trend in the ClONO2 column derived from FTIR observations at Jungfraujoch. Decreasing ClO concentrations slows the NO + ClO -> NO2 + Cl reaction and a stratospheric cooling slows the NO + O3 NO2 + O2 reaction, leaving more NOx in the form of NO. The slightly positive trends in ozone estimated from ground- and satellite-based data sets are also consistent with the decrease of NO2 through the NO2 + O3 -> NO3 + O2 reaction. Finally, we cannot rule out the possibility that a strengthening of the Dobson-Brewer circulation, which reduces the time available for N2O photolysis in the stratosphere, could also contribute to the observed decline in stratospheric NO2 above Jungfraujoch. [ABSTRACT FROM AUTHOR]

The trend in stratospheric NO2 column at the NDACC (Network for the Detection of Atmospheric Composition Change) station of Jungfraujoch (46.5° N, 8.0° E) is assessed using ground-based FTIR and zenith-scattered visible sunlight SAOZ measurements over the period 1990 to 2009 as well as a composite satellite nadir data set constructed from ERS-2/GOME, ENVISAT/SCIAMACHY, and METOP-A/GOME-2 observations over the 1996--2009 period. To calculate the trends, a linear least squares regression model including explanatory variables for a linear trend, the mean annual cycle, the quasi-biennial oscillation (QBO), solar activity, and stratospheric aerosol loading is used. For the 1990--2009 period, statistically indistinguishable trends of -3.7±1.1 %/decade and -3.6±0.9 %/decade are derived for the SAOZ and FTIR NO2 column time series, respectively. SAOZ, FTIR, and satellite nadir data sets show a similar decrease over the 1996--2009 period, with trends of -2.4±1.1 %/decade, -4.3±1.4 %/decade, and -3.6±2.2 %/decade, respectively. The fact that these declines are opposite in sign to the globally observed +2.5%/decade trend in N2O, suggests that factors other than N2O are driving the evolution of stratospheric NO2 at northern mid-latitudes. Possible causes of the decrease in stratospheric NO2 columns have been investigated. The most likely cause is a change in the NO2/NO partitioning in favor of NO, due to a possible stratospheric cooling and a decrease in stratospheric chlorine content, the latter being further confirmed by the negative trend in the ClONO2 column derived from FTIR observations at Jungfraujoch. Decreasing ClO concentrations slows the NO+ClO ! NO2 +Cl reaction and a stratospheric cooling slows the NO+O3→NO2 +O2 reaction, leaving more NOx in the form of NO. The slightly positive trends in ozone estimated from ground- and satellite-based data sets are also consistent with the decrease of NO2 through the NO2 +O3→NO3 +O2 reaction. Finally, we cannot rule out the possibility that a strengthening of the Dobson-Brewer circulation, which reduces the time available for N2O photolysis in the stratosphere, could also contribute to the observed decline in stratospheric NO2 above Jungfraujoch. [ABSTRACT FROM AUTHOR]

We have used a three-dimensional (3-D) off-line chemical transport model (CTM) to investigate long-term changes in stratospheric NO2. The basic model was integrated from 1977 to 2001 using ECMWF (European Centre for Medium-Range Weather Forcasts) ERA-40 reanalyses. Additional model runs were performed which assimilated HALOE observations of long-lived tracers to constrain the model trace gas distributions. Assimilation of a single long-lived species (CH4) improves not only the distribution of all other long-lived species, via tracer-tracer correlations, but also shorter lived radical and reservoir species. Assimilation of the long-lived species corrects for errors in the model, due to horizontal transport from the ERA-40 reanalyses, and allows a more direct test of the model's chemistry. The basic model significantly underestimates the observed column NO2 from midlatitude ground-based sites in the mid-late 1990s. The mean underestimate is ∼26% for summertime values between 1992 and 1998. Moreover, as the model agreement is better in the early 1990s, it underestimates the increasing trend throughout the decade. However, when the model assimilates HALOE CH4 data both comparisons are greatly improved. The mean model-observation difference reduces to 8% for summertime values and the trend improves. This indicates that given realistic wind fields to constrain the tracer transport, the model chemistry and aerosol schemes are able to reproduce the observed trends in NO2. Implications of this for using analysed wind fields to determine dynamical ozone trends are discussed. Ozone trends derived directly from transport models forced by analysed winds are likely subject to similar errors. [ABSTRACT FROM AUTHOR]

Compared to recent years, the development of the Antarctic ozone hole in 2002 showed very unusual dynamical features. The midwinter polar vortex was one of the smallest observed during the past decade. Driven by planetary waves, the vortex showed a strong asymmetry in early spring. A large air mass separated in late September, leaving what was previously a small vortex even smaller. Furthermore, stratospheric temperatures exceeded the polar stratospheric cloud (PSC) threshold earlier than in previous years, leading to a decrease in halogen activation by heterogeneous surface reactions. Ground-based observation of stratospheric trace gases in austral spring of 2001 and 2002 using passive Differential Optical Absorption Spectroscopy (DOAS) observations of zenith-scattered sunlight in the UV and visible wavelength region (320–650 nm) are presented. Using DOAS measurements of ozone, NO2, BrO, and OClO at two different Antarctic sites, Neumayer Station (70°S, 8°W) and Arrival Heights (78°S, 167°E), the chemical composition of the stratosphere is investigated under the unusual conditions of the 2002 ozone hole period and compared to the more typical observations of the previous year (2001). [ABSTRACT FROM AUTHOR]

Emission of bromine from sea-salt aerosol, frost flowers, ice leads, and snow results in the nearly complete removal of surface ozone during Arctic spring. Regions of enhanced total column BrO observed by satellites have traditionally been associated with these emissions. However, airborne measurements of BrO and O3 within the convective boundary layer (CBL) during the ARCTAS and ARCPAC field campaigns at times bear little relation to enhanced column BrO. We show that the locations of numerous satellite BrO “hotspots” during Arctic spring are consistent with observations of total column ozone and tropopause height, suggesting a stratospheric origin to these regions of elevated BrO. Tropospheric enhancements of BrO large enough to affect the column abundance are also observed, with important contributions originating from above the CBL. Closure of the budget for total column BrO, albeit with significant uncertainty, is achieved by summing observed tropospheric partial columns with calculated stratospheric partial columns provided that natural, short-lived biogenic bromocarbons supply between 5 and 10 ppt of bromine to the Arctic lowermost stratosphere. Proper understanding of bromine and its effects on atmospheric composition requires accurate treatment of geographic variations in column BrO originating from both the stratosphere and troposphere., Engineering and Applied Sciences

Examines the pulsed laser deposition of YBa[sub 2]Cu[sub 3]O[sub 7-x] thin films on sapphire wafers. Formation of microwave C-band strip-line filters; Measurement of the critical current densities; Application of planar high-temperature superconducting strip line filters.

For several years NO2 and OClO, two species important to understanding ozone destruction in the Antarctic stratosphere, have been measured at Arrival Heights, Antarctica by two groups: New Zealand's National Institute of Water and Atmospheric Research (NIWA) and the NOAA Aeronomy Laboratory in Boulder, Colorado. Using data independently collected by these two groups during the Austral spring of 1996, it is shown that the two data sets are in extremely close agreement. Besides offering validation of the instrumentation and analysis techniques of both groups, this result provides confidence in the more complete history of these species gained by combining the two data sets. [ABSTRACT FROM AUTHOR]