Northern Hemisphere, stratospheric

The Northern Hemisphere Stratosphere in the 2002/3 Winter, European Ozone Research Coordinating Unit, University of Cambridge (2003). 

On the other hand, sediments from the Ob and Yenisey Rivers show the presence of weapons-grade Pu originating from nuclear fuel reprocessing. The data are distinctly different from those of northern-hemisphere stratospheric fallout (see references in Haque and Nakanishi 1999). 

CFCs released to the atmosphere evenmally find their way up to the stratosphere where they destroy the ozone layer which protects the Earth s surface from harmful ultra-violet radiation. During the last decades, the ozone layer has been severely depleted, both over the Antarctic region where the ozone hole now appears annually, but also over the northern hemisphere. Ozone depletion up to 40% has been recorded in each of the last three years over Northern Europe. 

Wilson, J. C M. R. Stolzenburg, W. E. Clark, M. Loewenstein, G. V. Ferry, K. R. Chan, and K. K. Kelly, Stratospheric Sulfate Aerosol in and near the Northern Hemisphere Polar Vortex The Morphology of the Sulfate Layer, Multimodal Size Distributions, and the Effect of Denitrification, J. Geophys. Res., 97, 7997-8013 (1992). 

In this study we will present aspects of STE in relation with the budget and concentrations of ozone in the troposphere, specifically in the Northern Hemisphere. Firstly, we present ozone observations in the tropopause region from the measurement campaign MOZAIC, and discuss their correlation with potential vorticity. The results have been used to improve the parameterization of stratospheric ozone in a coupled tropospheric chemistry - general circulation model. We will show examples of the performance of the model regarding the simulation of ozone in the tropopause region, and present the simulated seasonality of cross-tropopause ozone transport in relation to other tropospheric ozone sources and sinks. Finally, we will examine and compare the influence of cross-tropopause transports to surface ozone concentrations for simulations with contemporary, pre-industrial, and future emission scenarios. 

Consequently, HjO in the troposphere affect 03 differently, depending on the tropospheric NO, levels (Thompson et al., 1989 Fuglestvedt et al., 1994), which are generally higher in the upper troposphere due to transport from the stratosphere and near the surface of the continents due to surface emissions. Note that anthropogenic NO, surface emission is concentrated mainly in the Northern Hemisphere. 

Long term observations indicate that UV-B radiation reaching the earth s surface may have decreased by 5-18% since the industrial revolution in the industrialised midlatitudes of the Northern Hemisphere (NH). However, on a global basis, this may have been offset by the stratospheric ozone layer reduction. It is not possible to estimate the net effect from both, attenuation and increase, because of the limited amount of spatial and temporal coverage of measurements (Liu et al., 1991). In an attempt to present calculated and modelled effects of aerosol on UV flux the authors used the Discrete Ordinate Radiative Transfer Model (DISORT Stammes et al. 1988) for different visual ranges and boundary layer depths (Figure 1). The decrease at 310 nm is 18% and 12 % for a 2km and 1km PBL respectively. 

In more recent times, there have been discoveries of ozone depletion in the Arctic that occur by similar mechanisms as the ones described here (see Figure 28). The Arctic equivalent does not tend to be as dramatic owing to the fact the Artie stratosphere does not get as cold as the Antarctic, mainly owing to a less well-formed vortex, largely owing to northern hemisphere topography. 

The measurements of H2 mixing ratios in the atmosphere, the troposphere, and the lower stratosphere were carried out by Schmidt in 1974. A constant mixing ratio of 0.548 ppmv was found in the southern troposphere and in the lower stratosphere ofthe northern hemisphere. Higher levels of 0.558 and 0.585 ppmv were obtained in the northern hemisphere in the upper troposphere and in surface air, respectively. The data do not indicate any change in the H2 mixing ratio of the lower stratosphere up to 4 km above the tropopause. The almost constant H2 mixing ratio in the tropopause region indicates that the flux of H2 between the troposphere and the stratosphere is very small. 

One of the most dramatic examples of concrete progress in the field of stratospheric chemistry has come from the work of de Zafra, Solomon, Parrish and coworkers, who adopted radio astronomy techniques to the detection of stratospheric free radicals. Three key reactive constituents have been examined CIO emissions at both 204 and 278 GHz from a number of sites in the northern hemisphere, with a rapidly growing seasonal coverage and sufficient time resolution to examine the exceedingly important diurnal behavior of the stratospheric column HO2 at 266 GHz from the Mauna Kea, Hawaii Observatory and H2O2 at 270 GHz, [Pg.356]

The concentration of atmospheric radionuclides has a special distribution which depends on latitudes and altitudes. Cosmogenic radionuclides have higher production rates in the stratosphere than in the troposphere, because of a higher intensity of cosmic rays in the stratosphere. Fallout nuclides have higher concentrations in mid-latitude of the Northern Hemisphere, because most atmospheric nuclear explosion experiments were made there. 

Most of the test sites for atmospheric nuclear testing were located in the northern hemisphere. The tests of France in the Pacific and of the United Kingdom in Australia were, with few exceptions, the only ones conducted in the southern hemisphere. Several tests of the United States were at or very near the equator, and from that location the injection of debris occurred to both hemispheres. The hemispheric partitioning of fission yields is shown in Table 10.5 140 Mt was injected into the atmosphere of the northern hemisphere, mostly into the stratosphere, and 18 Mt was injected into the atmosphere of the southern hemisphere. 

Kodera, K., 1994. Influence of volcanic eruptions on the troposphere through stratospheric dynamical processes in the Northern Hemisphere winter. Journal of Geophysical Research, 99, 1273-1282. 

Perlwitz, J., Graf, H. E, 1995. The statistical connection between tropospheric and stratospheric circulation of the northern hemisphere in winter. Journal of Climate, 8, 2281-2295. 

Ozone loss over the Arctic has been less dramatic than that over the Antarctic, mainly because the different distribution of land and sea in the Northern Hemisphere allows for only a weak vortex over the Arctic. There is more mixing of air with that from lower latitudes and temperatures do not become low enough for routine formation of polar stratospheric clouds. In years when the Arctic has been cold enough for cloud formation similar ozone destruction has been observed, but for less prolonged periods than over Antarctica. Trends in ozone over the rest of the globe have been small compared to those of the Antarctic, or even Arctic, and are quantified in section 2.4.1. 

Based on measurements of the total column ozone content of the atmosphere from the ground as well as from satellites, a consistent picture of the current loss of stratospheric ozone can be derived. The most recent results are discussed in ref. [3]. Relative to the values in the 1970 s, the ozone loss at the end of the 1990 s is estimated to be about 50% in the Antarctic spring, where the ozone hole appears every year, and about 15% in the Arctic spring. In the mid-latitudes of the Southern hemisphere the loss is about 5% all the year round, while in the Northern hemisphere it is about 6% in winter/spring and about 3% in sum-mer/fall. No significant trend in ozone has been found in the Equatorial regions. In the second half of the 1990 s relatively little change in ozone has been observed in the mid-latitudes of both hemispheres. 

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