Workshop AI for Data Science 2023, PoF IV Subtopic 2.4

The Workshop is part of a yearly series within the AI/ML-Cluster in Subtopic 2.4 of the research program PoF IV: Changing Earth - Sustaining our Future

Der Einfluss der Oberflaechenabhaengigkeit der Windschubspannung auf die Dynamik des Suedlichen Ozeans: Die Nah-Inertiale und die Sub-Inertiale Antwort

This thesis examines the consequences of the ocean-surface-velocity dependence of the wind stress (SVD) for the dynamics of the Southern Ocean. It does so by comparing the output from eddying ocean-model experiments that only differ in the way the wind stress is parameterized. The thesis consists of three separate research papers. The first paper assesses the influence of SVD on the near-inertial variability. It is shown that SVD leads to a substantial reduction of horizontally averaged near-inertial energy (NIE) and of horizontally averaged wind power input (WPI) into the near-inertial frequency band. The observed reduction of NIE and near-inertial WPI is explained by the fact that SVD, to leading order, adds a linear damping term to the momentum equation governing near-inertial oscillations in the mixed-layer. This damping term is inversely proportional to the mixed-layer depth and hence the effect of SVD on near-inertial oscillations is found to be largest if the mixed-layer is shallow. The second paper assesses the influence of SVD on sub-inertial time scales. It is found that SVD also substantially reduces sub-inertial WPI and mesoscale eddy kinetic energy (EKE). The largest effect of SVD on sub-inertial WPI and EKE is found along the path of the Antarctic Circumpolar Current (ACC). SVD is found to generally damp the amplitude of monthly to inter-annual variability in the model, without affecting the time-dependence of the wind stress, of WPI, and of the strength of the ACC. SVD is, however, found to have only a minor impact on the path and strength of the ACC. The third paper connects to the first one by focussing on the spatial and temporal distribution of NIE and near-inertial WPI in the Southern Ocean. The modelled near-inertial WPI is found to be mainly governed by the variability of the wind-stress at the local inertial frequency (IWSV). This relationship is used to indirectly examine the temporal evolution of near-inertial WPI on time scales much longer than those which can be directly examined with the model. It is found that from 1979 to 2011 IWSV over the Southern Ocean has increased substantially. Furthermore, the inter-annual variability of IWSV in the Southern Ocean is shown to be largely governed by the Southern Annular Mode.Die vorliegende Arbeit untersucht die Auswirkung einer Windstress-Parameterisierung, die von der Oberflaechengeschwindigkeit des Ozeans abhaengt (SVD), auf die Dynamik des Suedlichen Ozeans. Dazu wird die Ausgabe von Ozeanmodellexperimenten verglichen, die sich nur in der Art der Windstress-Parameterisierung unterscheiden. Die Arbeit besteht aus drei separaten Forschungsartikeln. Der erste Artikel untersucht den Einfluss der SVD auf die zeitliche Veraenderlichkeit bei Frequenzen nahe der Coriolis-Frequenz. Es wird gezeigt, dass die SVD zu einer deutlichen Verringerung der horizontal gemittelten kinetischen Energie von Inertialschwingungen (NIE) und der horizontalen Windarbeit (WPI) in das entsprechende Frequenzband fuehrt. Diese Verringerung wird dadurch erklaert, dass die SVD in fuehrender Ordnung einen linearen Daempfungsterm zur Impulsgleichung der Inertialschwingungen hinzufuegt. Dieser Daempfungsterm ist umgekehrt proportional zur Tiefe der Deckschicht. Daher sind die Auswirkungen der SVD dort besonders gross , wo die Deckschicht flach ist. Der zweite Artikel befasst sich mit dem Einfluss der SVD auf Zeitskalen l\"anger als die durch die Coriolis-Frequenz Bestimmten. Es wird gezeigt, dass die SVD auch auf diesen Zeitskalen die WPI und die kinetische Wirbelenergie (EKE) verringert. Der groesste Effekt der SVD findet sich entlang des Pfades des Antarktischen Zirkumpolarstromes (ACC). SVD daempft die Amplitude der zeitlichen Veraenderlichkeit im Modell auf monatlichen und auf zwischenjaehrlichen Zeitskalen ohne jedoch die normierte Zeitabhaengigkeit des Windstress, der WPI und der Staerke des ACC zu beeinflussen. Desweiteren ist der Einfluss der SVD auf den Pfad und die Staerke des ACC nur sehr gering. Der dritte Artikel schliesst sich thematisch an den Ersten an und konzentriert sich auf die raeumliche und zeitliche Verteilung der NIE und der nah-inertialen WPI im Suedlichen Ozean. Die nah-inertiale WPI im Modell ist vorrangig durch die Veraenderlichkeit des Windstress nahe der Coriolis-Frequenz (IWSV) bestimmt. Diese Beziehung wird ausgenutzt, um indirekt auch die zeitliche Entwicklung der nah-inertialen WPI auf Zeitskalen zu untersuchen, die viel laenger sind, als die mit dem Ozeanmodell behandelbaren Zeitraeume. Es wird gezeigt, dass sich die IWSV im Suedlichen Ozean von 1979 bis 2011 deutlich erhoeht hat. Desweiteren wird gezeigt, dass die zwischenjaehrlichen Schwankungen der IWSV zum grossen Teil durch die Southern Annular Mode bestimmt sind

The influence of ocean-surface-velocity-dependent wind stress on the dynamics of the Southern Ocean: The near-inertial and the sub-inertial response

This thesis examines the consequences of the ocean-surface-velocity dependence of the wind stress (SVD) for the dynamics of the Southern Ocean. It does so by comparing the output from eddying ocean-model experiments that only differ in the way the wind stress is parameterized. The thesis consists of three separate research papers. The first paper assesses the influence of SVD on the near-inertial variability. It is shown that SVD leads to a substantial reduction of horizontally averaged near-inertial energy (NIE) and of horizontally averaged wind power input (WPI) into the near-inertial frequency band. The observed reduction of NIE and near-inertial WPI is explained by the fact that SVD, to leading order, adds a linear damping term to the momentum equation governing near-inertial oscillations in the mixed-layer. This damping term is inversely proportional to the mixed-layer depth and hence the effect of SVD on near-inertial oscillations is found to be largest if the mixed-layer is shallow. The second paper assesses the influence of SVD on sub-inertial time scales. It is found that SVD also substantially reduces sub-inertial WPI and mesoscale eddy kinetic energy (EKE). The largest effect of SVD on sub-inertial WPI and EKE is found along the path of the Antarctic Circumpolar Current (ACC). SVD is found to generally damp the amplitude of monthly to inter-annual variability in the model, without affecting the time-dependence of the wind stress, of WPI, and of the strength of the ACC. SVD is, however, found to have only a minor impact on the path and strength of the ACC. The third paper connects to the first one by focussing on the spatial and temporal distribution of NIE and near-inertial WPI in the Southern Ocean. The modelled near-inertial WPI is found to be mainly governed by the variability of the wind-stress at the local inertial frequency (IWSV). This relationship is used to indirectly examine the temporal evolution of near-inertial WPI on time scales much longer than those which can be directly examined with the model. It is found that from 1979 to 2011 IWSV over the Southern Ocean has increased substantially. Furthermore, the inter-annual variability of IWSV in the Southern Ocean is shown to be largely governed by the Southern Annular Mode

AI for Earth System Science - Ocean & Cryosphere in Climate, Workshop

The Workshop within the Research Program "Changing Earth - Sustain our Future" focuses on Artificial Intelligence topics and projects within the Data Science sub-cluster in Subtopic 2.4. Common directions and posible collaborations are discussed in four thematic sessions: AI Classification, Explainable AI, AI for Parameterization, and AI Enablement

Reduction of Near-Inertial energy through the dependence of wind stress on the Ocean-Surface velocity

A realistic primitive-equation model of the Southern Ocean at eddying spatial resolution is used to examine the effect of ocean-surface-velocity dependence of the wind stress on the strength of near-inertial oscillations. Accounting for the ocean-surface-velocity dependence of the wind stress leads to a large reduction of wind-induced near-inertial energy of approximately 40 percent and of wind power input into the near-inertial frequency band of approximately 20 percent. A large part of this reduction can be explained by the leading-order modification to the wind stress if the ocean-surface velocity is included. The strength of the reduction is shown to be modulated by the inverse of the ocean-surface-mixed-layer depth. We conclude that the effect of surface-velocity dependence of the wind stress should be taken into account when estimating the wind-power input into the near-inertial frequency band and when estimating near-inertial energy levels in the ocean due to wind forcing

Towards Automated Metamorphic Test Identification for Ocean System Models

Metamorphic testing seeks to verify software in the absence of test oracles. Our application domain is ocean system modeling, where test oracles rarely exist, but where symmetries of the simulated physical systems are known. The input data set is large owing to the requirements of the application domain. This paper presents work in progress for the automated generation of metamorphic test scenarios using machine learning. We extended our previously proposed method [1] to identify metamorphic relations with reduced computational complexity. Initially, we represent metamorphic relations as identity maps. We construct a cost function that minimizes for identifying a metamorphic relation orthogonal to previously found metamorphic relations and penalize for the identity map. A machine learning algorithm is used to identify all possible metamorphic relations minimizing the defined cost function. We propose applying dimensionality reduction techniques to identify attributes in the input which have high variance among the identified metamorphic relations. We apply mutation on these selected attributes to identify distinct metamorphic relations with reduced computational complexity. For experimental evaluation, we subject the two implementations of an ocean-modeling application to the proposed method to present the use of metamorphic relations to test the two implementations of this application.Comment: 5 Pages, 1 Figur

The Influence of Various Factors on the Progress in Training of International Learners of the Preparatory Department (on the Example of the Course "Computer Science")

The task of research different factors affecting on the progress in training of students is actual. Two main factors as training the course in native language and knowledge of the language in which the course is studied were considered to solve this problem. The research is aimed at learners of the Preparatory Department studying in a non-native language (Russian) and takes into account the characteristics of such contingent of students. The study was made in the course "Computer science" with the help of methods of mathematical statistics. This research was conducted to improve the methods and to change the approaches in teaching the pre-university programs

Joint observation-model mixed-layer heat and salt budgets in the eastern tropical Atlantic

In this study, we use a joint observation-model approach to investigate the mixed-layer heat and salt annual mean and seasonal budgets in the eastern tropical Atlantic. The regional PREFCLIM observational climatology provides the budget terms with a relatively low spatial and temporal resolution compared to the online NEMO model, and this later is then re-sampled as in PREFCLIM climatology. In addition, advection terms are recomputed offline from the model as PREFCLIM gridded advection computation. In Senegal, Angola and Benguela regions, the seasonal cycle of mixed-layer temperature is mainly governed by surface heat fluxes; however, it is essentially driven by vertical heat diffusion in Equatorial region. The seasonal cycle of mixed-layer salinity is largely controlled by freshwater flux in Senegal and Benguela regions; however, it follows the variability of zonal and meridional salt advection in Equatorial and Angola regions respectively. Our results show that the time-averaged spatial distribution of NEMO offline heat/salt advection terms compares much better to PREFCLIM horizontal advection terms than the online heat/salt advection terms. However, the seasonal cycle of horizontal advection in selected regions shows that NEMO offline terms do not always compare well with PREFCLIM, sometimes less than online terms. Despite this difference, these results suggest the important role of small scale variability in mixed-layer heat and salt budgets.</p