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Polar amplification is a prominent feature of recent and projected climate change. The Arctic region shows some of the strongest signs of climate change, including sea-ice retreat and temperatures increasing at twice the rate averaged over the northern hemisphere. A major concern for humanity is the sea-level rise associated with the melting of the ice-sheets and glaciers due to climate change. The atmospheric circulation transports an amount of energy into to the Arctic equivalent that received by the Arctic from the Sun. Thus, the atmospheric energy transport is an important subject to study in the light of Arctic climate change. The atmospheric energy transport may be decomposed into contributions by planetary-scale waves such as Rossby waves and small-scale waves such as cyclones. The energy transport contributions by the different length-scale separated systems are shown to affect the Arctic differently. The meridional energy transport is separated into length-scale contributions using a Fourier-series-based approach. Here we evaluate this approach by comparing it to a novel wavelet-based length-scale decomposition, developed as a part of this project. Further a machine-learning-based length-scale decomposition approximator is developed. The approximator may be applied to climate model output to investigate future changes in the length-scale decomposed energy transport. From the comparisons it is apparent that both the Fourier and wavelet-based length-scale decompositions are skilled approaches, which produce physically meaningful decompositions. Additionally, the Fourier-based decomposition is further developed to yield a length-scale decomposition on a latitude-longitude grid. Once evaluated the Fourier and wavelet-based decompositions are applied to investigate the effects of recent climate change on the atmospheric energy transport, and how these changes affect the Arctic and the Greenland ice-sheet. Through these studies it is conspicuous that shifts of energy transport between length-scale components has occurred during the last decades, and that these shifts have contributed to Greenland ice-sheet melt and Arctic warming.

Recently a new method, based on a Fourier decomposition in the zonal direction, for studying the atmospheric energy transport contribution by planetary and cyclone scale waves has been proposed. Recent studies based on this show that planetary waves contribute more than cyclone scale waves to the atmospheric energy transport into the Arctic. The planetary waves contribute to the Arctic amplification through latent heat transport, even when the total atmospheric energy transport is decreasing in model projections. However, the performance of the energy split method to capture transports by cyclone and planetary scale waves has not yet been evaluated. Here an attempt to evaluate the performance of the energy split method is presented. The energy split method is applied on synthetic data, where the wave structure and energy transport are known. This leads to a potential error in the energy split methods resolution of transport associated with synthetic isolated cyclones, transport is contributed to planetary waves in the Fourier spectra. When applied on atmospheric reanalysis data where only isolated cyclones are present in atmospheric state it is evident that more than 80% (70%) of the transport of dry static energy (latent heat) is contributed by planetary waves. From inspections of the vertically integrated energy transport field it is evident that the latent heat transport of cyclones is large compared to the climatology, which implies that there is a problem with the energy split method when the atmospheric state is characterized by an isolated cyclone scale wave, and that the error is especially important to consider for the latent heat transport into the Arctic. Further investigations are proposed to estimate the upper bound of the error introduced in the energy split method.

Restless legs syndrome is neurological disorder that causes unpleasant sensations in the limbs, usually legs. These sensations can cause an irresistible urge to move the legs. Moving the affected limb can relieve the symptoms. The urge to move the legs can make falling asleep or staying asleep difficult. Restless legs syndrome (RLS) can be treated with drugs that bring relief to the symptoms. There are also non-pharmacological treatments. For example, pneumatic compression devices (PCD) can be used to treat RLS. In this thesis work, a PCD is designed and built. Treating RLS with PCDs is based on a compression to the legs. These devices use air to produce compression to stimulate the leg and affect the peripheral blood circulation. The devices consist of a controlling unit, and a wearable part that wraps around the leg. The wearable part includes one or more air bladders that can be inflated and deflated. This thesis focuses on the design and build process of the prototype device. A working prototype device is the result of this thesis work. The device being built is similar to existing pneumatic compression devices. There are differences in the basic design and the functionality compared to the existing devices.