Recent Comprehensive Model Research Articles

Exploring Mechanisms for Model‐Dependency of the Stratospheric Response to Arctic Warming

AbstractThe Arctic is estimated to have warmed up to four times faster than the rest of the globe since the 1980s. There is significant interest in understanding the mechanisms by which such warming may impact weather and climate at lower latitudes. One such mechanism is the “stratospheric pathway”; Arctic warming is proposed to induce a wave‐driven weakening of the stratospheric polar vortex, which may subsequently impact large‐scale tropospheric circulation. However, recent comprehensive model studies have found systematic differences in both the magnitude and sign of the stratospheric response to Arctic warming. Using a series of idealized model simulations, we show that this response is sensitive to characteristics of the warming and mean polar vortex strength. In all simulations, imposed polar warming amplifies upward wave propagation from the troposphere, consistent with comprehensive models. However, as polar warming strength and depth increases, the region through which waves can propagate is narrowed, inducing wave breaking and deceleration of the flow in the lower stratosphere. Thus, the mid‐stratosphere is less affected, with reduced sudden stratospheric warming frequency for stronger and deeper warming compared to weaker and shallower warming. We also find that the sign of the stratospheric response depends on the mean strength of the vortex, and that the stratospheric response in turn plays a role in the magnitude of the tropospheric jet response. Our results help explain the spread across multimodel ensembles of comprehensive climate models.

Australians' perceptions about health risks associated with climate change: Exploring the role of media in a comprehensive climate change risk perception model

We advance a recent comprehensive model of climate change risk perceptions by investigating the role of media in shaping individuals’ health risk perceptions. Results from a national survey in Australia (n = 1023) show that perceived health risks associated with climate change are related but distinct from perceived harm to self and society as measured in previous risk perception studies. Moreover, the full model explains 47% variance in health risks and 74% in perceived harm; While experiential processes (21%) account for about half of the variance in health risks, cognitive factors explain the largest share of variance in perceived harm (32%). Media processes explain a 10% variance in health risks and a 14% variance in perceived harm. News interest and media exposure to extreme weather events are significant to understand public health risks and harm perceptions, even after accounting for several other socio-demographic, cognitive, experiential, and socio-cultural factors. Findings support a conditional media effects model. Media can, directly and indirectly, affect public health risk perceptions by providing vicarious experience opportunities and information that Australians are looking for in the media about climate change.

Stationary Waves Weaken and Delay the Near-Surface Response to Stratospheric Ozone Depletion

Abstract An intermediate-complexity moist general circulation model is used to investigate the factors controlling the magnitude of the surface impact from Southern Hemisphere springtime ozone depletion. In contrast to previous idealized studies, a model with full radiation is used; furthermore, the model can be run with a varied representation of the surface, from a zonally uniform aquaplanet to a configuration with realistic stationary waves. The model captures the observed summertime positive Southern Annular Mode response to stratospheric ozone depletion. While synoptic waves dominate the long-term poleward jet shift, the initial response includes changes in planetary waves that simultaneously moderate the polar cap cooling (i.e., a negative feedback) and also constitute nearly one-half of the initial momentum flux response that shifts the jet poleward. The net effect is that stationary waves weaken the circulation response to ozone depletion in both the stratosphere and troposphere and also delay the response until summer rather than spring when ozone depletion peaks. It is also found that Antarctic surface cooling in response to ozone depletion helps to strengthen the poleward shift; however, shortwave surface effects of ozone are not critical. These surface temperature and stationary wave feedbacks are strong enough to overwhelm the previously recognized jet latitude/persistence feedback, potentially explaining why some recent comprehensive models do not exhibit a clear relationship between jet latitude/persistence and the magnitude of the response to ozone. The jet response is shown to be linear with respect to the magnitude of the imposed stratospheric perturbation, demonstrating the usefulness of interannual variability in ozone depletion for subseasonal forecasting.

The Signature of Geomagnetic Field External Drivers in Virtual Observatory 30‐day Means Derived From Swarm Data

AbstractThe separation of contributions from different sources in the magnetic field signal measured at satellite altitude is an open challenge. An approach to this problem, using Principal Component Analysis, is here applied to geomagnetic external field series at Virtual Observatories (VOs). These series are computed from an enlarged data set of Swarm data covering all local times and all geomagnetic activity levels between January 2014 and December 2019. For each 30‐day time window, the Equivalent Source Dipole technique is used to reduce all measurements inside a cylinder to one single “observation” at its axis and 500 km altitude. Our results reveal a first principal mode with dipolar geometry and time variation following very closely the RC‐index of geomagnetic activity. They display a resolved second principal mode with annual periodicity and of approximately zonal quadrupolar radial pattern, reminiscent of results in a previous study using VO series from a filtered satellite data set and with lower time resolution. We resort to the recent comprehensive model CM6 to identify a possible source for this second mode. We propose that the dipolar mode is the expression of the magnetospheric ring current dynamics, at 30‐day time resolution, and the quadrupolar mode is the expression of the annual asymmetry between local summer and winter Sq current vortices. Two fainter modes could be related to the equinoctial amplification of Sq vortices and the ionospheric dynamo modulation by nonmigrating tides. We show that a more uniform local time sampling could contribute to better resolve ionospheric structures.

Can the comprehensive model phase 4 (CM4) predict the geomagnetic diurnal field for days away from quiet time?

Abstract. The most recent comprehensive model (CM4) of the geomagnetic field (Sabaka et al., 2004) has been used in conjunction with geomagnetic ground observatory station data to analyse and study the geomagnetic diurnal variation field for days away from quiet time and the CM4 prediction for these times. Even though much has been learnt about many components of the geomagnetic field, the diurnal variation field behaviour for days away from quiet time (moderately disturbed time) has not been intensively studied. Consequently, we analyse these, and the predictive ability of the CM4 for ground variations, and whether the CM4 prediction of the diurnal variation (whether at quiet time or away from quiet time) is valid outside the period of reference that from which the data were used in modelling. In carrying out the study, we compared the observatory station data and the CM4 prediction directly. Using the CM4 code, well-characterised internal and magnetospheric components were subtracted from the data, plots and global maps of the residual field generated and then compared with the CM4 to see how well the model performed in predicting the data at moderately disturbed time (Kp ≤ 5). The results show that the CM4 is valid and produces useful predictions outside the period covering the timespan of the model and during moderately disturbed time, despite the lack of active data in the original model dataset. The model predictability of the data increases as we move to higher spherical harmonic degree truncation, as the model–data misfit is reduced, but with increased roughness as a result of small-scale features incorporated. The observed results show that this relationship between the increase in spherical harmonic degree truncation and reduction in misfit can be restricted by data quality or quantity and global coverage or spread.

Value priorities and preferences for a relationship partner

Despite extensive research into preferences for a romantic partner, previous work has not addressed the role of individual values in informing desires for a partner. The present study employed a recent comprehensive model of values [Schwartz, S. H. (1994). Beyond individualism-collectivism: new cultural dimensions of values. In U. Kim, H. C. Triandis, C. Kagitcibasi, S-C. Choi, & G. Yoon (Eds.), Individualism and collectivism: theory, method and application (pp. 81–119). Newbury Park, CA: Sage] to examine the role of values and sex, age and education in partner preferences. One hundred general population respondents from two British towns completed the Schwartz Value Survey and rated the desirability of 13 partner characteristics. Correlational analyses confirmed 12 of the 17 expected relationships between value scores and partner preferences whilst regressions conducted on three preference factors underlined the importance of the sex and education of the respondent in their rating of some partner ideals. We conclude by considering the need for future studies of partner preferences to combine the study of values with a range of demographic factors studied across a number of cultural settings.

Triple-loop model of path control by head direction and place cells.

Arthropods as well as mammals are able to return straight home after a random search excursion under conditions that are designed to exclude all external cues. After a brief clarification of the terminology, two principal systems of information processing that can achieve this performance are introduced and analysed: Polar versus Cartesian path integration. The different demands and achievements of the two systems are confronted with neurophysiological findings on the functioning of the hippocampus, and with a recent comprehensive model of how the hippocampal place cells perform path integration. To connect the neurophysiological findings with the behavior of the animal, a new model is developed. It achieves three functionally diverse performances: maintenance and control of a compass direction, navigation by path integration, and formation of goals by connecting non-spatial features with their location. This is done by three interconnected feedback loops, set by a common reference variable. Their information-processing structure enables the animal not only to home but also to go straight from any stored goal to any other, without explicit representation of the distance between them, and without a topological arrangement of the store. The model explains behaviors not yet understood and predicts still undiscovered performances. Because it allows the isolation of orienting from storing functions yet also shows how they can be connected, the model may help to reconcile conflicting views on the function of the hippocampus.

The large scale structure of the Galactic magnetic field

We explore the possibility of refining the description for the large-scale magnetic field in our galaxy using the rotation measures (RM) of pulsars. A major new input in our analysis is the recent comprehensive model of the electron density distribution ( Taylor & Cordes, 1993) that explicitly accounts for the electron density variations due to the spiral structure in our galaxy. We examine various models to assess the possibility that the magnetic field strength and the electron density may have correlated variations. Our analysis shows that in most of the regions the `net' field is stronger in the interarm regions rather than in the spiral arms, and the model in which the large-scale magnetic field is positively correlated with the electron density can be rejected with a high degree of confidence based on the pulsar RM data.

On the Hellenic subduction zone and the geodynamic evolution of Crete since the late Middle Miocene

In recent syntheses of the geodynamic evolution of the Aegean area the Hellenic subduction zone and in particular its initiation, plays a central role. Two basic aspects of the recent comprehensive model put forward by Le Pichon, Angelier and co-workers, are: (a) initiation of subduction along the Hellenic arc is inferred to have taken place approximately 13 Ma ago. whereas several others have suggested approximately 5 Ma, and (b) migration of the trench system to the south-southwest, giving rise to an extensional regime in the back-arc region, which led to general subsidence and formation of the present-day Aegean Sea. New data on the structure of the Upper Mantle underneath the Aegean area indicate that the former aspect requires modification. The seismic velocity structure indicating a northward dipping slab down to a depth of at least 600 km and the depth distribution of earthquake hypocenters can not be reconciled with straightforward initiation of subduction approximately 13 Ma ago. Estimates of about 5 Ma for the time of initiation of the present subduction zone are even more difficult to reconcile. Assuming 400 km as an upper bound for the effect of stretching of the Aegean Sea and of other processes contributing to the separation of Crete from the Eurasian mainland we arrive at an age for the Hellenic subduction zone of at least 26 Ma. As to aspect (b): geological data of Crete lend strong support to the idea that (on Crete) compressional tectonics is of much greater importance than current models imply. Combining geophysical and geological data we propose a modification of the tectonic evolution for the Cretan segment of the Hellenic arc. Whereas the basic process of extension caused by a migrating trench system (roll-back) in a land-locked basin remains a very useful and sound concept, the tectonics of the margins of a region subject to stretching (in this case Crete) may be more complicated than hitherto thought. In our model the documented fragmentation of Crete into several basins which started about 12 Ma ago is not attributed to initiation of subduction but to inception of the roll-back process. Compressional tectonics on Crete is taken to be associated with deformation of the crust resulting from the overall tensional stress regime.

14th-order harmonics in the geopotential from analysis of satellite orbits at resonance

The Earth's gravitational potential is usually expressed as a double series of tesseral harmonics of degree l and order m, and values of coefficients for l and m up to 36 or more are determined in recent models. The individual harmonic coefficients of a particular order m can most accurately be evaluated by analysing the perturbations on satellites which experience mth-order resonance (i.e. repeat their ground track after m revolutions). Here we use results from analyses of 15 satellite orbits at 14th-order resonance to evaluate 7 pairs of individual coefficients of 14th order and odd degree ( l = 15, 17,… 27), and 6 pairs of coefficients of even degree ( l = 14, 16,… 24). The five most accurate pairs of values, for l = 14, 15, 16, 17 and 19, have a mean standard deviation corresponding to an accuracy of 0.9 cm in geoid height. These values are used as a test of the accuracy of three recent comprehensive models of the geopotential : the agreement is generally satisfactory, the differences being consistent with the expected errors (about 3 × 10 −9) in the models. We also obtain values for the pair of coefficients of order 28 and degree 28, again with standard deviation equivalent to 0.9 cm in geoid height.