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In this study the role of an Indian Ocean heating dipole anomaly in the transition of the North Atlantic–European (NAE) circulation response to El Niño–Southern Oscillation (ENSO) from early to late winter is analyzed using a twentieth-century reanalysis and simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). It is shown that in early winter a warm (cold) ENSO event is connected through an atmospheric bridge with positive (negative) rainfall anomalies in the western Indian Ocean and negative (positive) anomalies in the eastern Indian Ocean. The early winter heating dipole, forced by a warm (cold) ENSO event, can set up a wave train emanating from the subtropical South Asian jet region that reaches the North Atlantic and leads to a response that spatially projects onto the positive (negative) phase of the North Atlantic Oscillation. The Indian Ocean heating dipole is partly forced as an atmospheric teleconnection by ENSO, but can also exist independently and is not strongly related to local Indian Ocean sea surface temperature (SST) forcing. The Indian Ocean heating dipole response to ENSO is much weaker in late winter (i.e., February and March) and not able to force significant signals in the North Atlantic region. CMIP5 multimodel ensemble reproduces the early winter Indian Ocean heating dipole response to ENSO and its transition in the North Atlantic region to some extent, but with weaker amplitude. Generally, models that have a strong early winter ENSO response in the subtropical South Asian jet region along with tropical Indian Ocean heating dipole also reproduce the North Atlantic response.

Change in hot extremes is one of the accepted evidence and also a global indicator of an anthropogenic climate change, which has serious environmental and economic impacts. In the present study, the India Meteorological Department gridded temperature data is used to characterize hot extremes over India in terms of frequency and intensity. Results provide compelling evidence that large parts of India, except the Indo-Gangetic plains, have experienced more occurrences of hot days (upsurge by 24.7%) having higher temperatures in the recent period (1976–2018), compared to the past (1951–1975), which suggests a shift in climate. Strong positive geopotential height anomalies at 500 hPa over the northern parts of India, which dynamically produces subsidence and clear sky conditions along with reduced precipitable water and depleted soil moisture are identified to be the crucial factors responsible for an increase of hot extremes in recent decades. Furthermore, the preceding December-February Niño-3.4 sea surface temperature (SST) anomalies are strongly connected with hot days frequency and the mechanism for the lag of several months is related to 3–4 months delayed response of Indian Ocean SSTs to El Niño/Southern Oscillation. Thus, post-Niño hot extremes over India can be potentially anticipated in advance and this will help society to prepare for such extremes.

The present study evaluates the fidelity of 32 models from the fifth Coupled Model Intercomparison Project (CMIP5) in simulating the observed teleconnection of Interdecadal Pacific Oscillation (IPO) with Indian summer monsoon rainfall (ISMR). Approximately two-thirds of the models show well-defined spatial pattern of IPO over the Pacific basin and most amongst these capture the IPO-ISMR teleconnection. In general, the models that fail to reproduce the IPO-ISMR teleconnection are the ones that are also showing a poor spatial pattern of IPO, irrespective of the extent to which they reproduce the precipitation climatology and seasonal cycle. The results reveal a strong relationship between the quality of reproducing the IPO pattern and the IPO-ISMR teleconnection in the models, in particular with respect to the tropical–extratropical as well as the equatorial Pacific-Indian Ocean sea surface temperature gradients during IPO phases. Furthermore, the CMIP5 models that are capable of reproducing the IPO-ISMR teleconnection also reasonably simulate the atmospheric circulation as well as the convergence/divergence patterns associated with the IPO. Thus, for the better understanding of decadal-to-multidecadal variability and to improve decadal prediction of rainfall over India it is therefore vital that models should simulate the IPO skillfully.

This study provides a pertinent ground for acquiring deeper insight about the low-frequency variability of precipitation and its extremes over India and its homogeneous monsoon regions under the combined interplay of both the Atlantic multidecadal oscillation (AMO) and the interdecadal Pacific oscillation (IPO). The percent of variance in the total/heavy rainfall on decadal-to-multidecadal timescales that can be attributed to these oceanic indices is 88.3/76.7 % for west central and 84.4/72.6 % for northeast regions, which implies that the recent changes in rainfall and it extremes over respective regions is mainly caused by internal natural variability. The opposite phases of AMO and IPO together modulates the total/moderate rainfall over west central and northeast regions in an asymmetric manner; whereas their warm phase stimulates the heavy rainfall over west central region, while their opposite phases together influences the precipitation extremes over northeast region. Based on the projected conditions of these oceanic indices the outlook for west central/northeast regions is fairly good/bad and these regions will experience above-/below-normal precipitation in the upcoming decade or two. The rainfall over northwest region is mainly influenced by the IPO and this region will also likely to receive above-normal precipitation in the upcoming decade or so due to the present cold phase of IPO. Wind circulation pattern divulges that during the warm phase of AMO the southwesterlies over Indian region are strengthened by the equatorial Atlantic winds coming through the equatorial Africa, while in the cold phase of IPO it gets strengthen by the easterlies from the equatorial Pacific.

The present study aims to provide a relevant ground for attaining deeper perception about the teleconnection between the Atlantic multidecadal oscillation (AMO) and the Indian summer monsoon rainfall (ISMR) in observations as well as in 30 models from the World Climate Research Programme (WCRP) Coupled Model Intercomparison Project Phase 5 (CMIP5). Approximately 73% of models reproduce the internal natural variability allied with AMO, but mostly all underestimate the variance. Amongst these, very few replicate the explicit comma-shaped AMO sea surface temperature (SST) pattern, whereas rest illustrates warm SSTs over the sub-polar region and very weak or non-existent AMO’s signature over the sub-tropical North Atlantic. However, only 53% of models emulate the observed AMO–ISMR relationship. The observational analysis bestows the compelling evidence that the AMO influences ISMR through two physical processes: firstly by modulating the El Niño related anomalous Walker and regional Hadley circulations asymmetrically and secondly through the tropospheric response allied with the Rossby wave train. The models that fail to reproduce the AMO–ISMR teleconnection are incompetent in capturing the first physical mechanism correctly, whereas in general all models show limitations in simulating the second physical mechanism. The results divulge a moderate relationship between the quality of reproducing the AMO pattern and the AMO–ISMR teleconnection in models, particularly with respect to the tropical–extratropical Pacific SST gradients during AMO phases. The models, which do show the observed rainfall response over India, also simulate the large-scale features allied with AMO like the cross-equatorial flow, the tropical easterly jets, the anomalous divergence/convergence over the Indian sub-continent at upper/lower levels, the Webster and Yang Monsoon index, and the Monsoon Hadley Circulation index.

Conducting polymer – metal oxide based hybrid nanocomposites are a fascinating class of materials for miniaturized and flexible gas sensor devices. They exhibit enhanced physiochemical properties such as sensitivity, selectivity towards various volatile and hazardous chemical and bioanalytes. Our study focuses on conducting polyaniline (PANI) and WO3 nanocomposites, where different weight percentages (wt.%) of WO3 nanoparticles are embedded within the conducting PANI matrix using an in-situ oxidation polymerization synthesis technique. The surface morphology analysis indicated that the WO3 nanoparticles with an average grain size of ~200 nm are homogeneously distributed within the PANI nanofibers. The Fourier Transform Infra-Red (FTIR) spectrum analysis showed that the absorption peaks at 1111,1291, 1385, 1474, and 1560 cm−1 are typical of the conducting PANI emeraldine phase. We attribute the additional broad peak ranging between 840 to 720 cm−1 in the spectrum to WO3 phase, wherein, the intensity of the peak increases with WO3 content in case of hybrid composites. Current-voltage (I-V) characteristics for all our samples showed linear behaviour up to 1.2 volts. Temperature-dependent DC electrical conductivity (σ) studies measured from room temperature to 120°C for pure PANI, and PANI-WO3 composites showed an enhanced electrical conductivity of values up to 0.12 S/cm for PANI as compared to WO3 with σ ~ 1.4 x 10−3 S/cm. Pure PANI exhibits semiconducting behavior with an increase in electrical conductivity with temperature due to the charge carrier delocalization within the dispersed PANI backbone. The addition of higher concentrations of WO3 in composites leads to a metallic-like behavior, characterized by a decrease in electrical conductivity with temperature. These observations are attributed to the field-assisted band bending effects at the interfaces of PANI and WO3. Our composites show desired electrical characteristics suitable for gas sensing applications.

Studies in different animal model systems have revealed the impact of odors on immune cells; however, any understanding on why and how odors control cellular immunity remained unclear. We find that Drosophila employ an olfactory-immune cross-talk to tune a specific cell type, the lamellocytes, from hematopoietic-progenitor cells. We show that neuronally released GABA derived upon olfactory stimulation is utilized by blood-progenitor cells as a metabolite and through its catabolism, these cells stabilize Sima/HIFα protein. Sima capacitates blood-progenitor cells with the ability to initiate lamellocyte differentiation. This systemic axis becomes relevant for larvae dwelling in wasp-infested environments where chances of infection are high. By co-opting the olfactory route, the preconditioned animals elevate their systemic GABA levels leading to the upregulation of blood-progenitor cell Sima expression. This elevates their immune-potential and primes them to respond rapidly when infected with parasitic wasps. The present work highlights the importance of the olfaction in immunity and shows how odor detection during animal development is utilized to establish a long-range axis in the control of blood-progenitor competency and immune-priming.

The spectral analysis of gridded rainfall data obtained from 1384 rain gauge stations by India Meteorological Department demonstrates not much change in low‐frequency components of decadal spectra of all India and its four subregions, namely, southwest, southeast, central, and northwest, during the last 10 decades. However, the dominant as well as the significant cycles lying between the periods 10–20 days, 20–30 days, 30–40 days, and 40–50 days are highly variable on an interdecadal basis. On close inspection, it can be inferred that the 40–50 day oscillations that corresponds to Madden‐Julian Oscillations is mainly associated with the southern Indian region, namely southwest and southeast, and the 30–40 day oscillation of southeast region is gradually increasing on a decadal scale during the last 4 decades. The physical context of interdecadal variability of rainfall in India can be linked with the warm phase of Atlantic multidecadal oscillations and the cold phase of interdecadal Pacific oscillations. The correlogram analysis shows the presence of 15, (17, 19), and 17 year cycles for the southwest, central, and northwest regions, respectively. No significant trend is discernable during the last 10 decades, when the linear least squares fitting method and Mann‐Kendall statistic to identify the trend and the normalized test statistic and statistical probability to quantify the significance of the trend are applied, on the annual rainfall data for all India and its subregions.

Humans receive around 50% of natural radiation dose due to 222 Rn (radon), 220 Rn (thoron) and their decay products. Several field campaigns measuring these gases and the decay products in different regions of India have been conducted in the recent past. Some of these studies measured indoor activity concentration and/or dose due to these gases and the associated decay products. This work compares the fraction of 222 Rn and decay products and 220 Rn and decay products in inhalation dose for 10 studies conducted in Uttarakhand state. It is seen that AEDT (annual effective dose due to 220 Rn and decay products) for these regions varies between 21 and 48% and it is significantly higher than the averaged worldwide reference value of 6%. Based on elaborative measurements performed in the Bageshwar district (present work), Almora and Nainital districts (our previous campaigns); the reasons for this high value have been explored. It was observed that a higher source term for mud houses could be the main reason for the high AEDT range. Interestingly, preliminary analysis revealed that the fraction is higher for the dwellings situated at higher altitudes thus indicating the role of the unavailability of modern building construction materials at remote locations. The study highlights the significant contribution of thoron in the Indian Himalayas.

Regional averages of radon, thoron, and associated decay product concentration are reported to be higher than their respective global averages in recent studies conducted in Indian Himalayan belt. The present study explores another region in Indian Himalayan belt by conducting measurements of radon, thoron, and decay product’s activity concentration in 92 dwellings of Bageshwar district. The year-long measurements were performed in all 3 seasons distinguishing dwellings as per their construction material. The average radon and thoron concentration for the study region was measured as 57 Bq/m 3 and 66 Bq/m 3 , respectively. Analysis of the measured data in terms of seasonal effects and construction material led to well established inferences, i.e., higher concentration for mud houses and for winter season. In addition, the present study focuses on lesser probed statistical inferences. One of them is related to the appropriateness of frequency distribution function for the measured data and other dwells upon the correlation analysis of inter-related factors for high concentration cases. Three distribution functions (Lognormal, Weibull, and Gamma) were found to be following the trend of frequency distribution curve of the measured data. For mud houses in winter season, variations of radon/thoron concentration were attempted to correlate with mass/surface exhalation rate, emanation rate, and source term content. More than 80% of the dwellings of the study region were found to have gas and decay product’s concentration levels, higher than the respective global average values. However, these values were mostly within the reference levels for residential environments. Nevertheless, this region requires further studies to pinpoint the causes for elevated levels and suggest simple remedial modifications if required.