Browsing by Subject "vegetation land-cover"

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  • Safdari, Pezhman (Helsingin yliopisto, 2015)
    Surface albedo, which is the fraction of reflected radiant energy by earth’s surface to incoming solar energy, plays an important role in earth energy budget and energy equilibrium. Different features of the earth’s surface have different reflectivity rates which affect albedo. Vegetation land-covers covering vast areas of earth’s surface such as agricultural land, forest, grassland and so on, have great impact on land surface albedo. The species composition, geographical distribution, and seasonal phenology of different vegetation land-covers have an impact on surface albedo and earth’s energy budget and, consequently, on climate change. The boreal zone covering latitudes between 60º – 70º N is one of the largest vegetation biomes on earth and has a significant impact on surface albedo. The boreal region is mostly covered by coniferous forests which are optically very dark and absorb most of the incoming solar energy. This low reflectivity is very influential during the times that earth’s surface is snow covered by masking the high reflectivity of the snow covered land surface. This has caused most studies to focus on the boreal vegetation land-cover albedo during the snow covered periods of the year. In this study, the effects of five different vegetation classes (agricultural, deciduous, coniferous, mixed forest and shrubland), three different latitudinal gradients (northern, middle and southern Finland), and the vegetation phenology during the growing season on surface albedo of vegetated areas of Finland for the year 2009 has been investigated. The results of the study showed that there is a significant difference between the albedo of different vegetation land-cover classes. The albedo of agricultural lands tends to be systematically the highest in all conditions while coniferous are the lowest. The vegetation land-cover albedo is generally lower in northern Finland compared to middle and south. There is a gradual increase in vegetation albedo until mid-July and after reaching a maximum level it starts to decrease towards the end of the growing season. The peak in albedo is reached about two weeks earlier in the north compared to the south possibly due to and longer days during its shorter growing season.
  • Safdari, Pezhman (Helsingfors universitet, 2015)
    Surface albedo, which is the fraction of reflected radiant energy by earth’s surface to incoming solar energy, plays an important role in earth energy budget and energy equilibrium. Different features of the earth’s surface have different reflectivity rates which affect the albedo. Vegetation land-covers covering vast areas of earth’s surface as agricultural lands, forests, grass lands and so on, have great impact on land surface albedo. The Species composition, geographical distribution and seasonal phenology of different vegetation land-covers have an impact on surface albedo and consequently on earth’s energy budget and consequently, on climate change. Boreal zone covering latitudes between 60o – 70o N is one of the largest vegetation biomes on earth and which has a significant impact on surface albedo. The boreal region is mostly covered by coniferous forests which are optically very dark and absorb most of the incoming solar energy. This low reflectivity is very influential during the times that earth’s surface is snow covered by masking the high reflectivity of the snow covered land surface. This has caused most of the studies to focus on the boreal vegetation land-cover albedo during the snow covered periods of the year. In this study, the effect of five different vegetation classes (agriculture, broad leaves, coniferous, mixed forest and shrub lands) and the latitudinal gradient (northern, middle and southern Finland) and the vegetation phenology during the growing season on surface albedo of vegetated areas of Finland for the year 2009 has been investigated. The results of the study showed that there is a significant difference between the albedo of different vegetation land-cover classes. The albedo of agricultural lands tends to be systematically the highest in all conditions while conifers were the lowest. The vegetation land-cover albedo is generally lower in northern Finland compared to middle and south. There is a gradual increase in vegetation albedo until mid-July and after reaching a maximum level it starts to decrease towards the end of the growing season. The peak in albedo is reached about two weeks earlier in north compared to south possibly due to its shorter growing season and longer day during the growing season.