On the Epochal Strengthening in the Relationship between Rainfall of East Africa and IOD

Abstract Variability of the equatorial East Africa "short rains" (EASR) has intensified significantly since the turn of the twentieth century. This increase toward more extreme rainfall events has not been gradual but is strongly characterized by epochs. The rain gauge–based Global Precipitation Climatology Centre (GPCC) monthly precipitation dataset for the period 1901–2009 is used to demonstrate that the epochal changes were dictated by shifts in the Indian Ocean dipole (IOD) mode. These shifts occurred during 1961 and 1997. In the pre-1961 period, there was virtually no significant linear link between the IOD and the EASR. But a relatively strong coupling between the two occurred abruptly in 1961 and was generally maintained at that level until 1997, when another sudden shift to even a greater level occurred. The first principal component (PC1) extracted from the EASR spatial domain initially merely explained about 50% of the rainfall variability before 1961, and then catapulted to about 73% for the period from 1961 to 1997, before eventually shifting to exceed 82% after 1997. The PC1 for each successive epoch also displayed loadings with notably improved spatial coherence. This systematic pattern of increase was accompanied by both a sharp increase in the frequency of rainfall extremes and spatial coherence of the rainfall events over the region. Therefore, it is most likely that the 1961 and 1997 IOD shifts are responsible for the epochal modulation of the EASR in both the spatial and temporal domain

Role of Antarctic Circumpolar Current in decadal climate variability over southern Africa

第6回極域科学シンポジウム分野横断セッション：[IG] 全球環境変動を駆動する南大洋・南極氷床11月17日（火）　国立極地研究所 2階 大会議

Sensitivity of Indian summer monsoon simulation to physical parameterization schemes in the WRF model

A set of 17 experiments, using various combinations of physical parameterization schemes in the Weather Research and Forecasting (WRF) model, were carried out to choose a combination suitable for simulating the Indian summer monsoon. The model experiments, forced with the ERA-Interim reanalysis data, were at 30 km horizontal resolution. The WRF model experiments were initialized on 1 May of each year and integrated until 30 September to cover the entire monsoon season for the years 1982 to 2013. The results indicate that the simulated Indian summer monsoon precipitation and 2 m air temperature are sensitive to the physical parameterization schemes in the WRF model and that choosing the correct combination of physical parameterization schemes is essential for simulating the Indian summer monsoon realistically. Our analysis shows that a model setup with the Kain-Fritsch cumulus scheme, a radiation package with the Dudhia shortwave and Rapid Radiative Transfer Model longwave schemes, the Yonsei State University planetary boundary layer scheme, the WRF Single-Moment 3-class microphysics scheme, the revised MM5 Monin-Obukhov surface layer scheme, and the Unified Noah land surface model is suitable for simulating the precipitation realistically. The model setup with a combination of these physical parameterization schemes was found to have smaller biases and root mean square errors in the simulated precipitation, along with a realistic simulation of intraseasonal and interannual variability of precipitation. The results of this study will be useful to researchers and forecasters using the WRF model to improve the Indian summer monsoon simulations/forecasts over the Indian region

Validation of the WRF regional climate model over the subregions of Southeast Asia: climatology and interannual variability

This study investigates the capability of a regional climate model in simulating the climate variability over Southeast Asia (SE Asia). The present-day climate, covering the period 1991 to 2015, was dynamically downscaled using the Weather Research and Forecasting (WRF) model with a horizontal resolution of 27 km. The initial and boundary conditions for the WRF model is provided with the European Centre for medium-range weather forecasting (ECMWF) reanalysis (ERA-Interim) data. The model reproduced the mean precipitation climatology as well as the annual cycle. Nevertheless, the model overestimated the boreal summer precipitation over the SE Asian mainland, and underestimated the boreal winter precipitation over the Indonesian region. Model biases are associated with the bias in simulating the vertically integrated moisture fluxes. At an interannual scale, the model shows good performance over the SE Asian mainland and the Philippines in all seasons except for the boreal summer. The influence of El Niño/Southern Oscillation (ENSO) on rainfall over mainland SE Asia and the Philippines during JJA is weak, and the model successfully simulated the weak relationship realistically. In contrast, model interannual variability over the Indonesia region is good only in boreal summer and autumn seasons. This is because the model successfully simulated the significant negative correlation between rainfall and ENSO. The influence of the Indian Ocean Dipole (IOD) is seen only in the boreal autumn over the Indonesian region, and the model reproduced it reasonably well. The improvement in the representation of precipitation anomaly associated with ENSO/IOD is due to reasonably accurate simulation of large-scale circulation over SE Asia

Role of Weddell Sea ice in South Atlantic atmospheric variability

We investigated the role of Weddell Sea ice in atmospheric variability over the South Atlantic by conducting observational data analysis and coupled general circulation model (CGCM) experiments. Weddell Sea ice exhibits a pronounced interannual variability in early austral summer (November-January). Low sea-ice concentration (SIC) anomalies in the Weddell Sea are strongly associated with anticyclonic atmospheric circulation anomalies in the South Atlantic. Composite analysis reveals that the low SIC anomalies in the Weddell Sea may be attributed to increased solar radiation and northwesterly wind anomalies. The low SIC anomalies, in turn, contribute to warmer skin temperature in the band of 60-70°S and enhance the near-surface atmospheric stability north of this band, implying favorable conditions for sustaining the anticyclonic circulation anomalies in the South Atlantic. This intriguing association between the SIC and atmospheric circulation anomalies is also simulated in CGCM experiments, e.g. when the interannual sea surface temperature variability in the tropics and mid-latitudes is suppressed. These results suggest that Weddell Sea ice, which may undergo interannual variation via air-sea-ice interactions in the high latitudes, influences atmospheric variability over the South Atlantic

ENSO’s far reaching connection to Indian cold waves

During boreal winters, cold waves over India are primarily due to transport of cold air from higher latitudes. However, the processes associated with these cold waves are not yet clearly understood. Here by diagnosing a suite of datasets, we explore the mechanisms leading to the development and maintenance of these cold waves. Two types of cold waves are identified based on observed minimum surface temperature and statistical analysis. The first type (TYPE1), also the dominant one, depicts colder than normal temperatures covering most parts of the country while the second type (TYPE2) is more regional, with significant cold temperatures only noticeable over northwest India. Quite interestingly the first (second) type is associated with La Niña (El Niño) like conditions, suggesting that both phases of ENSO provide a favorable background for the occurrence of cold waves over India. During TYPE1 cold wave events, a low-level cyclonic anomaly generated over the Indian region as an atmospheric response to the equatorial convective anomalies is seen advecting cold temperatures into India and maintaining the cold waves. In TYPE2 cold waves, a cyclonic anomaly generated over west India anomalously brings cold winds to northwest India causing cold waves only in those parts

Metallic Glasses: A Revolution in Material Science

Metallic glasses represent one kind of advanced material, very popular in recent decades. These materials are very adaptable like plastics for their manufacturability in very complex shapes. TPF (Thermoplastic forming) based processes seem very good method to process them. These materials can compete with plastics but have metallic properties. They behave as magnetic materials with less hysteresis loss and less eddy current loss making them suitable for transformer and MEMS (Micro-Electromechanical System) applications. These materials exhibit good corrosion resistance, hardness and toughness. Based on the property and application, metallic glasses are good rivals to plastics, metals and ceramics. Chemical composition and kinetics of supercooling of these materials are the areas where young researchers can focus attention with a view to their improvement

Abating coastal pollution for protecting environment in ecologically sensitive area of Astaranga, Puri district, Odisha

Pir Jahania, the famous shrine situated in the shore of Bay of Bengal and its scenic beach attract many tourists for their religious sentiment and as a beautiful picnic spot. The green cover of casuarinas, good mangrove vegetation and the mass nesting site of Olive ridley (Lepidochelys olivacea) turtles are the specialty of this place. In spite of constant efforts by the forest department of Puri, continuous human interference deteriorates the environment with plastic pollution and other non-biodegradable materials like stray foam, thermocol, glass bottles turning the protection of the same as a major concern for the environmentalists. Puri Field Centre of ICAR-CMFRI along with forest department of Puri thus decided to make an awareness programme on plastic pollution in this tourist place