ИСТИНА

There are a lot of evidences of vitamin D deficiency all over the globe (Palacios, Gonzalez, 2014). Most Vitamin D in the human body is produced in the skin due to exposure to sunlight. In Northern Eurasia, vitamin D synthesis via skin is impossible throughout the whole year. There are different approaches for the definition of vitamin D UV threshold (for example,(Fioletov et al., 2010, CIE, 2014)). For vitamin D UV threshold, we use the relation between vitamin D production and Minimal Erythemal Dose suggested in (Holick, 2004). We take into account such parameter as open exposed body fraction as function of effective air temperature, which is important for vitamin D production. This methodology is in detail described in (Chubarova, Zhdanova, 2013) and implemented in an interactive UV-tool, which is available via www.momsu.ru/uv. The aim of this study is to determine peculiarities of spatial and temporal variations of UV deficiency over Northern Eurasia (40.5°N- 80.5°N, 25.5°W-180°E). We determined conditions with no vitamin D production during the whole day as 100-% UV deficiency, with no vitamin D production during the noon hour as noon UV deficiency. Conditions, when it is possible to receive vitamin D during the noon hour and it is not possible to receive erythema, have been called UV optimum. Using RT modeling and developed databases of main geophysical parameters influencing on UV (Chubarova, Zhdanova, 2013) we estimate UV deficiency distributions for different skin types and months. For example, we reveal that noon UV deficiency at the sea level is not observed over the whole Northern Eurasia only in May andsummer months in clear sky conditions. We compare UV deficiency distributions in clear and cloudy sky conditions. We also investigate an altitude effect on spatial features of UV-resources taking into account dependencies of molecular air density, aerosol optical depth, total aerosol content, surface albedo from surface elevation.