Natural Synergy

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The North and South Poles are the best areas on earth for the evaluation of global effects and the study of climatic change. The majority of developed countries have established their scientific bases in one of these areas to perform their research because the local atmospheric circulation highlights modifications to planetary background values. Moreover, the Poles are privileged zones for studying solar electromagnetic flux that reaches the ground, e.g. within the ultraviolet region, because due to the ozone hole event, it is possible to investigate the large variability of the UV radiation, particularly during the spring season.

Ultraviolet radiation is defined as the portion of the electromagnetic spectrum between X-rays and visible light, which is between wavelengths of 40 nm and 400 nm (energy comprised between 30 eV and 3 eV). The UV spectrum can be divided into broad bands: vacuum UV (40 nm -190 nm), far UV (190 nm - 220 nm), UV-C (220 nm - 290 nm), UV-B (290 nm - 320 nm), and UV-A (320 nm - 400 nm) (Zeman, 2008). Solar UV-C, UV-B, and UV-A enter the earth's atmosphere, but only UV-B and UV-A reach the ground because UV-C is blocked in the stratosphere by the ozone layer (Chapman, 1930). Thus, the discovery of stratospheric ozone (O3) depletion due to disposal of CFCs in the atmosphere (Molina and Rowland, 1973; Farman et al., 1985; Bojkov et al., 1995) is very evident in the polar regions, and the consequent rise of UV levels in the troposphere has underlined two of the most important effects of human activity on the environment (Solomon, 1999) and on global change (IPCC, 2007). Additionally, increased UV due to a decline in O3 has affected the biosphere with implications for human health, as well as for fauna and flora (Caldwell et al., 1986; Worrest et al., 1989; Bigelow et al., 1998; Chaney and Sliney, 2005; UNEP, 2002). Additionally, UV radiation interacts with the DNA chain, which can produce cellular changes. This hazard can be responsible for the development of skin cancers and eye disease in humans (Slaper et al., 1996; WHO, 1999; 2006).

Ozone depletion was so evident that, shortly after its discovery, an international agreement, the "Vienna Convention for the Protection of the Ozone Layer", was signed in 1985 in an attempt to preserve the ozone layer. Two years later, the well-known "Montreal Protocol on Substances that Deplete the Ozone Layer," with its subsequent adjustments and amendments, was also designed. Thus, "Ozone Hole Protection" became a flag for environmental protection.

A strong widening of the ozone hole in the austral hemisphere, and a less intense ozone hole developing in the northern hemisphere, were recently observed (Bojkov et al., 1998; Uchino et al., 1999). In the Arctic, the consequences of depletion phenomena can be more serious due to the high density of human presence subjected to increased UV radiation. In September 2003, the surface of the austral polar vortex reached a new maximum (an extension of more than 12% compared with the previous maximum in 2000). Inside the ozone hole, the region with a very low O3 concentration also grew. Furthermore, on Sept. 27, 2002, the vortex split into two parts (Fig. 4.1, Orsolini et al., 2005). These could be signs of an evolution in the dynamics of the polar vortex and consequently, of the ozone hole (Alvarez-Madrigal and Perez-Peraza, 2005).

CP TCMS Vmbft I TcrtiJ Onn. V. Sop " 1. MW CPTCMS YnfUfcrt 1 Tnttx) :]. I M to) '.rv HU

CP TCMS Vmbft I TcrtiJ Onn. V. Sop " 1. MW CPTCMS YnfUfcrt 1 Tnttx) :]. I M to) '.rv HU

Figure 4.1 Ozone hole during splitting event in September 2002

The development of numerous measurement sites and long-term monitoring programs is necessary to understand these processes, to model the trends, and to study the ground effects. To this end, the international community is forming collaborations for monitoring minor atmospheric gases, particularly the ozone levels at ground level (Roscoe et al., 2005a), using data taken by airborne instruments (Giovanelli et al., 2005) and from satellites (Banks et al., 1978; Russell HI et al., 1993; Krueger, 2001; Schoeberl et al., 2006; Waters et al., 2006). After more than 25 years of application, these studies allow for an evaluation of the effects of environmental protection treaties.

Polar vortices develop a confining action for chemical substances that exist at those latitudes, and the low temperatures promote Polar Stratospheric Cloud (PSC) development. During the polar night, photolysis processes do not occur. During the following spring, UV solar radiation activates the catalytic cycles of Cl and Br on the PSC surface, and the destruction of ozone begins. Therefore, studies on the precursors of depletion in the high atmosphere during the polar nights (Orsolini and Jackson, 2008) are necessary to understand the chemistry that generates ozone reduction (Strawa et al., 2002; Voigt et al., 2003; Tilmes et al., 2004).

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