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An objective global climatology of polar lows based on reanalysis data
No full textHere an objective global climatology of polar lows has been developed. In order to obtain objective detection criteria the efficacy of several parameters for separating polar lows from other cyclones has been investigated. This parameter efficacy has been compared for polar lows subjectively identified by experts and for all kind of extra-tropical cyclones. The comparison is based on the ERA-Interim reanalysis from 1979 - 2016 and the higher resolution Arctic System Reanalysis from 2000 - 2012. The parameters found to be the most effective at separating polar lows from all other kinds of synoptic and meso-scale cyclones were the difference between the mean sea-level pressure of the low and its surroundings, the difference in the potential temperature between the sea surface and the 500 hPa level, and the tropopause wind poleward of the system. Other parameters often used for distinguishing, such as the 10m wind speed and the temperature difference between the sea surface and the 700 hPa level were found to be less effective. Investigation of the climatologies reveals that PLs occur in all maritime basins at high latitudes, but with high density in the vicinity of the sea-ice edge and coastal zones. The regions showing the highest degree of polar-low activity are the Denmark Strait and the Nordic Seas. Especially the most intense polar lows occur in these two regions. In the North Atlantic and Pacific the main polar-low season ranges from November to March. In the Southern Hemisphere polar lows are mainly detected between 50 - 65'S from April to October, indicating that this hemisphere compared to its northern counterpart has a two months longer, but less intense, polar-low season. No significant hemispheric long-term trends are observed, although some regions, such as the Denmark Strait and the Nordic Sea experience significant downward and upward trends in polar lows, respectively, over the last decades. For intense polar lows a significant decaying trend has been observed for the northern hemisphere
LeTourneau modified tank-tree crusher with R.G. LeTourneau and unidentified man.
No full textPhotograph of a Tree Crusher Tender built in Vicksburg, Mississippi and intended for use at the Tournata complex in Liberia, according to author Eric Orlemann. Shown with the tank are R.G. LeTourneau, left, and an unidentified man. The tank was never actually shipped to Tournata
On the linkage between atmospheric circulation changes and Arctic climate change
No full textPolar 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
Longview manufacturing plant under construction, LT21 Misc Photos Archive 062.
No full textPhotograph of the Longview manufacturing plant of R.G. LeTourneau, Inc. The plant's construction began in 1945 and completed in 1946. At the time, according to Otis Hays, author of R.G. LeTourneau: Move of Men and Mountains, at the time it was the world's largest welding and manufacturing plant under one roof, covering more than 100 acres
The Big Plow with 6-Foot Disc, J5G, Photo 35, L-8312
No full textPhotograph of R.G. LeTourneau's Series H (Model 6-16) Disc Plow, designed for land-clearing operations. It was powered by a front longitudinally mounted diesel, according to author Eric Orlemann
Large LeTourneau tree crusher, LT20
No full textPhotograph of aLeTourneau tree crusher with three unidentified men. This is likely the Series G-50 Tree Crusher, judging from a similar photo in author Eric Orlemann's book on R.G. LeTourneau's earthmoving equipment
The Added Value of Enterprise Architecture
No full textApplying architecture implies that it provides added value across an enterprise. Although widely adopted, this claim has only been scarcely investigated, not to mention quantified. This document describes the results of a case study to quantify the effects of applying Enterprise Architecture within a financial institution called FinCom. For confidential information reasons, the name of this company is fictive. The thesis attempts to capture several factors at project level with respect to the application of Enterprise Architecture and its subsequent financial benefits. The study analyzed 40 projects, with regard to time and budget overrun. In order to collect these data, a total of 35 business, enterprise and domain architects were interviewed on their experience with these projects. Among factors taken into account were architecture type, project compliance to architecture and experience of the architect. Consequently, these factors are recorded in hypotheses that relate to the budget and time figures of the project. These hypotheses are incorporated in the 'Architecture Effectiveness Model' and statistically tested with the acquired data. This led to more than 12.000 calculations to show the subsequent benefits of Enterprise Architecture.Information ArchitectureComputer ScienceElectrical Engineering, Mathematics and Computer Scienc
Side-Dump Train, built by R.G. LeTourneau, Inc.
No full textPhotograph of the LeTourneau Side-Dump Train designed as a bulk-material hauler. According to author Eric Orlemann, this model consisted of a 6-wheel tractor and two 6-wheel trailers. Only one example was ever built
Warm winds from the Pacific caused extensive Arctic sea-ice melt in summer 2007
No full textDuring summer 2007 the Arctic sea-ice shrank to the lowest extent ever observed. The role of the atmospheric energy transport in this extreme melt event is explored using the state-of-the-art ERA-Interim reanalysis data. We find that in summer 2007 there was an anomalous atmospheric flow of warm and humid air into the region that suffered severe melt. This anomaly was larger than during any other year in the data (1989–2008). Convergence of the atmospheric energy transport over this area led to positive anomalies of the downward longwave radiation and turbulent fluxes. In the region that experienced unusual ice melt, the net anomaly of the surface fluxes provided enough extra energy to melt roughly one meter of ice during the melting season. When the ocean successively became ice-free, the surface-albedo decreased causing additional absorption of shortwave radiation, despite the fact that the downwelling solar radiation was smaller than average. We argue that the positive anomalies of net downward longwave radiation and turbulent fluxes played a key role in initiating the 2007 extreme ice melt, whereas the shortwave-radiation changes acted as an amplifying feedback mechanism in response to the melt
On sea-ice forecasting
No full textAccurate sea-ice prediction is essential for safe operations in the Arctic and potentially also for weather forecast at high-latitudes. The increasing number of sea-ice related satellite observations in the Arctic can be used to improve the model predictions through data assimilation. For sea ice, sea-ice concentration (SIC) observations have been available for many years. Observational information of SIC can be used to constrain the sea-ice extent in models. In addition to SIC, other sea-ice related observations such as sea-ice thickness (SIT) and snow depth have recently become available. The assimilation of these observations is expected to have a substantial impact on the sea-ice forecast.
In this thesis, the main goal is to enhance the sea-ice model forecast accuracy by improving the initial model state on which the forecast is based. Primarily, the assimilation of sea-ice-related observations that are previously little used in sea-ice data assimilation is investigated. This includes the assimilation of SIT, snow depth and high-resolution SIC observations. A secondary objective of this thesis is to reduce the computational cost of both sea-ice assimilation and modelling. A new direct and computationally cheap method for data assimilation, the Multi-variate nudging (MVN) method, is proposed as an alternative to more complex assimilation methods for sea-ice. In addition, to reduce the computational cost of the sea-ice prediction, two machine-learning methods were applied for sea-ice forecasting, a fully convolutional network and a k nearest neighbours.
It is found that the assimilation of observations other than SIC has the potential to enhance the accuracy of sea-ice models and improve predictions. The proposed new assimilation method, the MVN, proves to be a valid assimilation alternative to the Ensemble Kalman Filter when few observation types are available, and the computational resources are limited. The machine-learning forecasts are found to improve upon persistence and show comparable skills to the dynamical model. Hence there is a potential for machine-learning methods for sea-ice predictions which should be developed further
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