Two dominant global-scale teleconnections in the Northern Hemisphere (NH) extratropics during boreal summer season (June–August) have been identified: the western North Pacific–North America (WPNA) ...and circumglobal teleconnection (CGT) patterns. These teleconnection patterns are of critical importance for the NH summer seasonal climate prediction. Here, how these teleconnections will change under anthropogenic global warming is investigated using representative concentration pathway 4.5 (RCP4.5) experiments by 20 coupled models that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5). The six best models are selected based on their performance in simulation of the two teleconnection patterns and climatological means and variances of atmospheric circulation, precipitation, and sea surface temperature. The selected models capture the CGT and its relationship with the Indian summer monsoon (ISM) reasonably well. The models can also capture the WPNA circulation pattern but with striking deficiencies in reproducing its associated rainfall anomalies due to poor simulation of the western North Pacific summer monsoon rainfall. The following changes are anticipated in the latter half of twenty-first century under the RCP4.5 scenario: 1) significant weakening of year-to-year variability of the upper-level circulation due to increased atmospheric stability, although the moderate increase in convective heating over the tropics may act to strengthen the variability; 2) intensification of the WPNA pattern and major spectral peaks, particularly over the eastern Pacific–North America and North Atlantic–Europe sectors, which is attributed to the strengthening of its relationship with the preceding mature phase of El Niño–Southern Oscillation (ENSO); and 3) weakening of the CGT due to atmospheric stabilization and decreasing relationship with ISM as well as weakening of the ISM–ENSO relationship.
Mass exchanges in the upper ocean between the equatorial and off‐equatorial Pacific Ocean associated with the El Niño/Southern Oscillation (ENSO) are investigated using the National Centers for ...Environmental Prediction (NCEP) ocean assimilation data. The data show that ENSO‐related meridional mass transport in the Northern Hemisphere (NH) is larger than that in the Southern Hemisphere (SH). We found that the antisymmetric characteristics are mainly due to a southward shift of the maximum zonal wind stress anomaly during the ENSO mature phase. The Ekman and geostrophic transports associated with ENSO are separated into symmetric and antisymmetric components. For the symmetric part, the mass divergence over the equatorial Pacific by the geostrophic transport is generally larger than the convergence by the Ekman transport during the El Niño mature phase. Therefore mass is transported from the equator to off the equator at this time. As for the antisymmetric part, the Ekman transport due to antisymmetric wind stress dominates the geostrophic transport so that the mass is transported from the SH to the NH during the El Niño mature phase. The net mass transport in the NH is larger than that in the SH. A theoretical interpretation and intermediate model experiments support these arguments.
In this study, a statistical prediction model has been developed to forecast monthly Sea Surface Temperature (SST) in the Indian Ocean. It is a linear regression model based on a lagged relationship ...between the Indian Ocean SST and the NINO3 SST. A new approach to the statistical modeling has been tried out, in which the model predictors are obtained from not only observed NINO3 SST but also predicted results produced by a dynamical El Niño model. The forecast skill of the present model is better than that of persistence prediction. In particular, the present model has a significantly improved predictive skill during the spring and summer seasons when the boreal summer Indian monsoon is affected by the Indian Ocean SST.
The asymmetric nature of El Niño and La Niña sea surface temperature (SST) anomalies is investigated by the use of National Centers for Environmental Prediction reanalysis data and various ocean and ...atmosphere models. It is demonstrated that the relatively weak SST anomalies during La Niña compared with those of El Niño are related to the westward shift of wind stress anomalies by 10°–15°. The asymmetric characteristics of atmospheric responses are confirmed by the general circulation model experiments with the two different SST anomalies, which have equal amplitude but are of opposite sign from each other. The experiments with an intermediate ocean model and a hybrid coupled model clearly show that the SST anomalies over the equatorial Pacific become weaker as the zonal wind stress shifts to the west. Not only the amplitude but also the oscillation timescale of the SST anomaly is shown to be sensitive to the location of wind stress anomalies. The duration of La Niña, which is rather shorter than that of El Niño, is also related to the longitudinal displacement of the wind stress anomaly.
A near‐annual coupled ocean‐atmosphere mode in the equatorial Pacific is studied using the NCEP ocean assimilation data set. This fast mode of tropical Pacific climate variability is superimposed on ...the slow 3–5 year El Niño‐Southern Oscillation (ENSO) phenomenon. Anomalous zonal advection plays a crucial role in generating this fast mode. It is suggested that this fast mode can be understood in terms of a coupled Pacific basin mode. It is responsible for the occurrence of some minor El Niño and La Niña events and has implications for the prediction of ENSO events.
An El‐Nino prediction model is developed based on an intermediate ocean model similar to the Cane and Zebiak (CZ) and a statistical atmosphere model. The present ocean model differs from CZ in the ...parameterization of sub‐surface temperature and the basic state. The predictability skill of the present model is better than that of CZ. The better performance is particularly distinctive for early stage of the prediction everywhere in the domain and in the central Pacific for all period of prediction. It is suggested that the better performance for the early stage is due to the use of SST anomalies in the initialization, and the better performance in the central Pacific results from a better representation of subsurface temperature in the present model.
The El Niño–La Niña asymmetry was estimated in the 10 different models participating in the Coupled Model Intercomparison Project (CMIP). Large differences in the “asymmetricity” (a variance-weighted ...skewness) of SST anomalies are found between models and observations. Most of the coupled models underestimate the nonlinearity and only a few exhibit the positively skewed SST anomalies over the tropical eastern Pacific as seen in the observation. A significant association between the nonlinear dynamical heating (NDH) and asymmetricity in the model–ENSO indices is found, inferring that asymmetricity is caused mainly by NDH. Among the 10 models, one coupled GCM simulates the asymmetricity of the tropical SST realistically, and its simulation manifests a strong relationship between the intensity and the propagating feature of ENSO—the strong ENSO events moving eastward and the weak ENSO events moving westward—which is consistent with the observation. Interestingly, the coupled general circulation models, of which the ocean model is based on the one used by Bryan and Cox, commonly showed the reasonably positive skewed ENSO.
The decadal changes in the skewness, variance, and NDH of the model-simulated ENSO are also observed. These three quantities over the tropical eastern Pacific are significantly correlated to each other, indicating that the decadal change in ENSO variability is closely related to the nonlinear process of ENSO. It is also found that these decadal changes in ENSO variability are related to the decadal variation in the tropical Pacific SST, implying that the decadal change in the El Niño–La Niña asymmetry could manifest itself as a rectified change in the background state.
Human dental pulp-derived stem cells (hDPSCs) have been considered alternative sources of adult stem cells because of their potential to differentiate into multiple cell lineages. This study ...investigated the possible role of gangliosides in the neural differentiation of hDPSCs. When hDPSCs were cultured under neural differentiation conditions, expression of neural cell marker genes such as
Nestin,
MAP-2, and
NeuN was detected. Immunostaining and high-performance thin-layer chromatography analysis showed that an increase in ganglioside biosynthesis was associated with neural differentiation of hDPSCs. Specifically, a significant increase in GD3 and GD1a expression was observed during neural differentiation. To confirm the role of gangliosides in neural differentiation, ganglioside biosynthesis was inhibited in hDPSCs by knockdown of UDP-glucose ceramide glucosyltransferase (
Ugcg), which prevented differentiation into neural cells. These results suggest that gangliosides may play a role in the neural differentiation process of hDPSCs.
We present a study that suggests greening in the circumpolar high-latitude regions amplifies surface warming in the growing season (May–September) under enhanced greenhouse conditions. The ...investigation used a series of climate simulations with the Community Atmospheric Model version 3—which incorporates a coupled, dynamic global vegetation model—with and without vegetation feedback, under both present and doubled CO
2
concentrations. Results indicate that climate warming and associated changes promote circumpolar greening with northward expansion and enhanced greenness of both the Arctic tundra and boreal forest regions. This leads to additional surface warming in the high-latitudes in the growing season, primarily through more absorption of incoming solar radiation. The resulting surface and tropospheric warming in the high-latitude and Arctic regions weakens prevailing tropospheric westerlies over 45–70N, leading to the formation of anticyclonic pressure anomalies in the Arctic regions. These pressure anomalies resemble the anomalous circulation pattern during the negative phase of winter Arctic Oscillation. It is suggested that these circulation anomalies reinforce the high-latitude and Arctic warming in the growing season.
BiFeO3 (BFO) nanopowders were synthesized at low temperatures via a hydrothermal process with the aid of triethanolamine (TEA) and their structural, optical, and photocatalytic properties were ...investigated. As a result of a strong reaction between TEA and Fe ions, pure BFO nanopowders without any secondary phases could be synthesized at temperatures as low as 130°C. BFO nanopowders exhibited a strong absorption in the visible‐light regime, which resulted in the efficient photocatalytic activity for decomposition of organic compounds.
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