Abstract:Evaporation from a willow short-rotation forest was analysed using a modified version of the Shuttleworth-Wallace model. The main modification consisted of a two-layer soil module, which enabled soil surface resistance to be calculated as a function of the wetness of the top soil. Introduction of the threshold value of the leaf area index when scaling up from the leaf to the canopy resistance resulted in improvement to the simulated evaporation. The analysis was concentrated mainly on the 1988 season (May-October) when total evaporation was measured by the energy balance/Bowen ratio method throughout the growing season, covering all stages of canopy development. At the beginning of the 1994 season, soil evaporation were also measured with a ventilated chamber system. The general seasonal dynamics of the evaporation were fairly well simulated with the model. The largest deviation between measured and simulated evaporation occurred in June, when the model underestimated evaporation by about 1 mm day 1 . The model underestimated also in May but not as much as in June. In September and October the performance of the model was very good. For 130 days of the period May-October the cumulated measured evaporation was 364 mm and the simulated evaporation for the same days was 362 mm. It should be pointed out that this result was obtained without calibrating the model against the measured evaporation. The total simulated evaporation for the season was 450 mm with transpiration constituting 298 mm (66%), soil evaporation 102 mm (23%) and interception evaporation 50 mm (11%). The sensitivity analysis showed, in general, that simulated evaporation was most sensitive to changes in resistances when the leaf area index was smallest, i.e. under non-closed canopy conditions. Changes in stomatal resistance, which is one of the most sensitive parameters, with associated changes in canopy transpiration, resulted in a negative feedback effect on soil evaporation. This reduced the total evaporation's sensitivity to stomatal resistance. This type of interaction between canopy and soil or undergrowth fluxes has been observed in other studies as well.
Serious disruptions and exceptional circumstances for society, that the society tries to prepare for and act in them are at the center of security of supply. Current examples are the COVID pandemic and the ongoing energy crisis for which Finland's security of supply has also been strongly highlighted. Disturbances can also be caused by weather phenomena: in Finland, such examples are windstorms, severe thunderstorms, floods, and droughts, which can, at least in principle, paralyze the society. It is possible to prepare for the impacts of weather phenomena, but the ongoing rapid climate change makes it more complicated. Some of the weather phenomena that cause impacts are fast and violent (e.g. intense thunderstorms) and some occur more slowly (e.g. long heat waves), and climate change affects the phenomena in different ways. In this work, the estimated impacts of climate change on Finland's security of supply were investigated. The starting point was to gain an understanding of which weather phenomena and weather situations are central to security of supply and which sectors of security of supply are the most vulnerable. The work constituted of workshops and expert interviews organized with the National Emergency Supply Agency. In addition to the interviews, the work covered past significant weather situations in Finland that are known to have had significant societal impacts. Information was also extracted from recent literature, especially regarding the vulnerabilities and adaptability of different sectors in Finland. Estimates of the climate change impacts on the identified phenomena were combined with the collected information, resulting in a first understanding of how climate change affects Finland's security of supply. Based on the results, it can be concluded that the impacts of climate change on security of supply are quite complex, especially due to the wide spectrum of weather phenomena and their different impact mechanisms. In addition, the matter becomes more complicated by the fact that there is no clear distinction of what weather phenomenon actually is critical to security of supply and what is not. For example, could the increasing adverse impacts on health care due to the increasingly common heat conditions reach a serious societal disturbance situation at some point, if it is not sufficiently prepared in advance? Another key result is that in terms of security of supply, the direct effects of climate change are very small in Finland compared to many other countries. Although the climate in Finland has already changed considerably and will continue to change in the future, the biggest impacts to security of supply seem to be reflected from elsewhere: the experts of the National Emergency Supply Agency consider the worst situation to be a lack of food, water and habitable living environment in the world, which would also be reflected to Finland. Among the sectors, food/water and energy supply and logistics are perceived as the most vulnerable. The work mainly focused on the direct effects of climate change, i.e. the effects of climate change on the occurrence of various weather phenomena. However, the work also considers to some extent indirect effects, i.e. those reflected from other parts of the world, and transitional effects that result from climate change mitigation measures, especially from the rapid energy transition.
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