In 1619, Johannes Kepler published his magnum opus Harmonices mundi in which the astronomer derived distinct pitches and scales for each known planet in the solar system from calculations of various aspects of their orbital motions. This was the first theoretical realization of the ancient tradition of musica universalis (also called musica mundana), or music of the celestial bodies. It was not until the Estonian composer Urmas Sisask (b. 1960) began his compositional career by deriving his own “planetary scale,” however, that the theoretical musica universalis came into audible existence. Sisask’s work represents a distinctive musical voice among today’s choral composers, and although he is steadily gaining attention for his unique compositional style, only limited information exists about the specifics of his background, his interest in astronomy and shamanism, and the subsequent influence these interests have had on his choral music. At once traditional and modern, he bridges the gap between ancient Estonian folk song and the present. Through an application of exotic techniques including extreme repetition, ritualistically driving rhythms and sudden changes in timbre and texture; coupled with his own peculiarly crafted “planetary scale,” Urmas Sisask has created a completely unique body of work which is examined in this study by looking at representative works from his choral oeuvre including Gloria Patri…24 hymns for mixed choir, Magnificat, Ave Sol, and Benedictio.

<div> <div> <div> <p>Rapid melting of sea ice and an increased warming have been observed over the Arctic since 1990s and is expected to continue in future climate projections. Possible linkage between the Arctic sea ice and the Northern Hemisphere mid-latitude circulation has been studied previously but is not yet fully understood. This dissertation investigates the influence of the Arctic on the mid-latitudes and the underlying dynamical mechanisms. Specifically, we hypothesize that the stratosphere and its coupling with the troposphere play an important role in amplifying and extending the mid-latitude circulation response to arctic warming. </p><p><br></p> <p>First, we assess the robustness of the stratospheric pathway in linking the sea ice variability, specifically over the Barents-Kara Sea (BKS), in late autumn and early winter to the mid-latitude circulation in the subsequent winter using an ensemble of global climate model simulations. We analyze two groups of models from the Coupled Model Intercomparison Project phase 5 (CMIP5) archive, one with a well-resolved stratosphere (high-top models) and the other with a poorly-resolved stratosphere (low-top models) to distinguish the role of the stratospheric pathway. It has been found that, collectively, high-top models are able to capture the persistent mid-latitude circulation response in the subsequent winter. The response in low-top models is, however, weaker and not as long-lasting most likely due to lack of stratospheric variability. Diagnosis of eddy heat flux reveals that stronger vertical wave propagation leads to a stronger response in stratospheric polar vortex in high- top models. The results robustly demonstrate that multi-model ensemble of CMIP5 high-top models are able to capture the prolonged impact of sea ice variability on the mid-latitude circulation and outperforms the low-top models in this regard.</p><p><br></p></div></div></div><div><div><div> <p>We further explore the dynamical linkage between the BKS sea ice loss and the Siberian cold anomalies using a comprehensive Atmospheric General Circulation Model (AGCM), with a well-resolved stratosphere, with prescribed sea ice loss over BKS region. Decomposition of dynamic and thermodynamic components suggests a dynamically induced warm Arctic cold Siberia pattern in the winter following sea ice loss over the BKS in late autumn. Specifically, the results show that the meridional component of the horizontal temperature advection, from the Arctic into the Siberia, dominates in driving a cold temperature anomaly. Additionally, we conduct targeted experiments in order to quantitatively measure the role of the stratospheric pathway. We find that the stratosphere plays a critical role in the tropospheric circulation anomaly characterized by an intensified ridge-trough pattern that is attributable for the enhanced meridional temperature advection from the Arctic into the Siberia. </p><p><br></p> <p>Next, we extend our study to investigate the sensitivity to geographical location of Arctic sea ice loss and associated warming in modulating the atmospheric circulation. In particular, we assess the linear additivity of the regional Arctic sea ice loss and Arctic Amplification (AA), using a simplified dry dynamical core model. We find that the responses to regional AA over three key regions of the Arctic, i.e. Barents- Kara Sea, East Siberia-Chukchi sea and Baffin Bay-Labrador Sea, separately, show similar equatorward shift of the tropospheric jet but differences in the stratospheric polar vortex. In addition, responses to regional Arctic Amplification are not linearly additive and the residual resembles a positive Northern Annular Mode-like structure. Additional targeted experiments further diagnose the role of the stratosphere in the non-linearity. It is found that the stratosphere-troposphere coupling plays an important role in driving the non-linear circulation response to regional AA. </p><p><br></p> <p>The findings of our research leads to a systematic understanding of the role of the stratospheric pathway in modulating the mid-latitude circulation response to Arctic sea ice loss and accompanied surface warming. Our study suggests that the representation of the stratosphere in climate models plays an important role in correctly simulating the mid-latitude circulation response and could be accountable for the some of the discrepancies among recent studies. Additionally, the result indicates that studying the regional sea ice loss might not provide the full picture of pan-Arctic sea ice melting and caution the use of regional sea ice to explain the recent trend.</p></div></div></div>

In this study, theorem-based, generally applicable stochastic parameterisation schemes are developed and applied to a quasi-geostrophic model of extratropical atmospheric low-frequency variability (LFV). Hasselmann’s method is developed from limiting theorems for slow-fast systems of ordinary differential equations (ODEs) and applied to this high-dimensional model of intermediate complexity comprised of partial differential equations (PDEs) with complicated boundary conditions. Seamless, efficient algorithms for integrating the parameterised models are developed, which require only minimal changes to the full model algorithm. These algorithms may be readily adapted to a range of climate models of greater complexity in parameterising the effects of fast, sub-grid scale processes on the resolved scales. For comparison, the Majda-Timofeyev-Vanden-Eijnden (MTV) parameterisation method is applied to this model. The seamless algorithms are first adapted to probe the multiple regime behaviour that characterises the full model LFV. In contrast to the conclusions of a previous study, it is found that the multiple regime behaviour is not the result of a nonlinear interaction between the leading two planetary-scale modes, but rather is the result of interactions among these two modes and the leading synoptic-scale mode. The low-dimensional Hasselmann stochastic models perform well in simulating the statistics of the planetary-scale modes. In particular, a model with only one resolved (planetary-scale) mode captures the multiple regime behaviour of the full model. Although a fast-evolving synoptic-scale mode is of primary importance to the multiple regime behaviour, deterministic averaged forcing and not multiplicative noise is responsible for the regime behaviour in this model. The MTV models generate non-Gaussian statistics, but generally do not perform as well in capturing the climate statistics.