Because continuous meteorological observations across Antarctica did not start until the middle of the twentieth century, little is known about the full spatial pattern of pressure variability across ...the extratropical Southern Hemisphere (SH) in the early twentieth century, defined here as the period from 1905 to 1956. To fill this gap, this study analyzes pressure observations across the SH in conjunction with seasonal pressure reconstructions across Antarctica, which are based on observed station-to-station statistical relationships between pressure over Antarctica and the southern midlatitudes. Using this newly generated dataset, it is found that the early twentieth century is characterized by synchronous but opposite-signed pressure relationships between Antarctica and the SH midlatitudes, especially in austral summer and autumn. The synchronous pressure relationships are consistent with the southern annular mode, extending its well-known influence on SH extratropical pressure since 1957 into the early twentieth century. Apart from connections with the southern annular mode, regional and shorter-duration pressure trends are found to be associated with influences from tropical variability and potentially the zonal wavenumber 3 pattern. Although the reduced network of SH observations and Antarctic reconstruction captures the southern annular mode in the early twentieth century, reanalysis products show varying skill in reproducing trends and variability, especially over the oceans and high southern latitudes prior to 1957, which stresses the importance of continual efforts of historical data rescue in data-sparse regions to improve their quality.
Transcranial direct current stimulation (tDCS) may be a viable tool to improve motor and cognitive function in advanced age. However, although a number of studies have demonstrated improved cognitive ...performance in older adults, other studies have failed to show restorative effects. The neural effects of beneficial stimulation response in both age groups is lacking. In the current study, tDCS was administered during simultaneous fMRI in 42 healthy young and older participants. Semantic word generation and motor speech baseline tasks were used to investigate behavioral and neural effects of uni- and bihemispheric motor cortex tDCS in a three-way, crossover, sham tDCS controlled design. Independent components analysis assessed differences in task-related activity between the two age groups and tDCS effects at the network level. We also explored whether laterality of language network organization was effected by tDCS. Behaviorally, both active tDCS conditions significantly improved semantic word retrieval performance in young and older adults and were comparable between groups and stimulation conditions. Network-level tDCS effects were identified in the ventral and dorsal anterior cingulate networks in the combined sample during semantic fluency and motor speech tasks. In addition, a shift toward enhanced left laterality was identified in the older adults for both active stimulation conditions. Thus, tDCS results in common network-level modulations and behavioral improvements for both age groups, with an additional effect of increasing left laterality in older adults.
Energetics of the major atmospheric teleconnection patterns of the Northern Hemisphere winter are examined to investigate the role of baroclinic and barotropic energy conversions in their growth. ...Based on characteristics of the energetics and the horizontal structures, the patterns are classified into three general types: meridional dipole (D-type), wave (W-type), and hybrid (H-type). The primary energy conversion term that differentiates these patterns is the baroclinic energy conversion of the available potential energy from the climatology to the eddy field associated with the teleconnections. For this conversion term, D-type patterns exhibit the comparable conversion of potential energy via the eddy heat flux across the climatological thermal gradient in both the zonal and meridional directions. In contrast, baroclinic conversion for W-type patterns occurs primarily in the meridional direction, while H-type patterns exhibit a structure that combines the characteristics of the other two pattern types.An important secondary factor is barotropic conversion from the climatology to the eddy field, which takes place mainly in the regions where the climatological shear is strong. For the D-type patterns, conversion occurs on the flank of the climatological jet exit, while it occurs at the center of the jet exit for the W-type patterns. Last, for all the patterns, synoptic-time-scale eddies make a negative contribution via the baroclinic process, but a positive contribution via the barotropic process. Damping by diabatic heating weakens the temperature anomalies associated with the patterns.
CALYPSO Mahadevan, Amala; Pascual, Ananda; Rudnick, Daniel L. ...
Bulletin of the American Meteorological Society,
06/2021, Volume:
102, Issue:
6
Journal Article
Using Process Studies to Improve Climate Modeling Sprintall, Janet; Coles, Victoria J.; Reed, Kevin A. ...
Bulletin of the American Meteorological Society,
06/2021, Volume:
102, Issue:
6
Journal Article
Year of Polar Prediction Bromwich, David H.; Werner, Kirstin; Casati, Barbara ...
Bulletin of the American Meteorological Society,
06/2021, Volume:
102, Issue:
6
Journal Article
Global models comprising the sixth-generation Coupled Climate Model Intercomparison Project (CMIP6) are downscaled using a very high-resolution but simplified coupled atmosphere–ocean tropical ...cyclone model, as a means of estimating the response of global tropical cyclone activity to increasing greenhouse gases. As with a previous downscaling of CMIP5 models, the results show an increase in both the frequency and severity of tropical cyclones, robust across the models downscaled, in response to increasing greenhouse gases. The increase is strongly weighted to the Northern Hemisphere, and especially noteworthy is a large increase in the higher latitudes of the North Atlantic. Changes are insignificant in the South Pacific across metrics. Although the largest increases in track density are far from land, substantial increases in global landfalling power dissipation are indicated. The incidence of rapid intensification increases rapidly with warming, as predicted by existing theory. Measures of robustness across downscaled climate models are presented, and comparisons to tropical cyclones explicitly simulated in climate models are discussed.
STUDY QUALITY IN SLA Plonsky, Luke
Studies in second language acquisition,
12/2013, Volume:
35, Issue:
4
Journal Article
Peer reviewed
This study assesses research and reporting practices in quantitative second language (L2) research. A sample of 606 primary studies, published from 1990 to 2010 in Language Learning and Studies in ...Second Language Acquisition, was collected and coded for designs, statistical analyses, reporting practices, and outcomes (i.e., effect sizes). The results point to several systematic strengths as well as many flaws, such as a lack of control in experimental designs, incomplete and inconsistent reporting practices, and low statistical power. I discuss these trends, strengths, and weaknesses in comparison with methodological reviews of L2 research (e.g., Plonsky & Gass, 2011) as well as reviews from other fields (e.g., education, Skidmore & Thompson, 2010). On the basis of the findings, I also make a number of suggestions for methodological reforms in applied linguistics.
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