4D-variational assimilation over the Bay of Bengal using the Adjoint of a Variable Resolution Global Ocean Model

Summary The adjoint technique has been widely used over the last two decades in applications involving the dynamics of the Atmosphere and Ocean. This present study applies this technique in the assimilation of oceanic parameters such as temperature and net-surface heat flux, in a variable resolution Ocean General Circulation Model (OGCM). The National Center for Environmental Prediction (NCEP) 1999 July–August global data (sea-surface temperature and derived surface heat flux) and vertical temperature profiles collected from ORV Sagar Kanya and INS Sagardhwani during the Bay of Bengal Monsoon Experiment (BOBMEX 1999) are used for assimilation over the Bay of Bengal. The net-surface heat flux and temperature obtained after assimilation show good agreement with their respective seasonal patterns over the whole Indian Ocean, though there are some differences in the numerical values of heat fluxes. The vertical profiles of temperature after assimilation over the Bay of Bengal show strong resemblance with the corresponding ship observations, emphasizing the importance of the adjoint technique in ocean data assimilation.     

Impact of assimilation of INSAT-3D retrieved atmospheric motion vectors on short-range forecast of summer monsoon 2014 over the South Asian region

The Weather Research and Forecasting (WRF) model and its three-dimensional variational data assimilation system are used in this study to assimilate the INSAT-3D, a recently launched Indian geostationary meteorological satellite derived from atmospheric motion vectors (AMVs) over the South Asian region during peak Indian summer monsoon month (i.e., July 2014). A total of four experiments were performed daily with and without assimilation of INSAT-3D-derived AMVs and the other AMVs available through Global Telecommunication System (GTS) for the entire month of July 2014. Before assimilating these newly derived INSAT-3D AMVs in the numerical model, a preliminary evaluation of these AMVs is performed with National Centers for Environmental Prediction (NCEP) final model analyses. The preliminary validation results show that root-mean-square vector difference (RMSVD) for INSAT-3D AMVs is ～3.95, 6.66, and 5.65 ms^?1 at low, mid, and high levels, respectively, and slightly more RMSVDs are noticed in GTS AMVs (～4.0, 8.01, and 6.43 ms^?1 at low, mid, and high levels, respectively). The assimilation of AMVs has improved the WRF model of produced wind speed, temperature, and moisture analyses as well as subsequent model forecasts over the Indian Ocean, Arabian Sea, Australia, and South Africa. Slightly more improvements are noticed in the experiment where only the INSAT-3D AMVs are assimilated compared to the experiment where only GTS AMVs are assimilated. The results also show improvement in rainfall predictions over the Indian region after AMV assimilation. Overall, the assimilation of INSAT-3D AMVs improved the WRF model short-range predictions over the South Asian region as compared to control experiments.     

Comparison of Kalpana-1 atmospheric motion vectors with other observations

The operational derivation of atmospheric motion vectors (AMVs) using infrared (10.5–12.5 μm) and water vapor (6.3–7.1 μm) channels of successive geostationary satellite images started in the 1980s. Subsequently, AMVs have become an important component for operational numerical weather prediction throughout the globe for the last decade or so. In India, at the Space Applications Centre, Indian Space Research Organisation, the operational derivation of AMVs (infrared winds and water vapor winds) from the Indian geostationary satellite Kalpana-1 has been initiated a few years back. Recently, an L-band radar lower atmosphere wind profiler (LAWP) has been installed at the National Atmospheric Research Laboratory, Gadanki located at (13.58°N, 79.28°E) for continuous high-resolution wind measurements in the lower atmosphere. In this study, a comparison of Kalpana-1 AMVs with wind measurements from LAWP and radiosonde has been carried out for a period of one and a half years. The performances of Kalpana-1 AMVs are also assessed by a separate comparison of Meteosat-7 AMVs, derived at the European Organisation for the Exploitation of Meteorological Satellites, with wind measurements from LAWP and radiosonde. Both sets of comparison show that AMVs from Kalpana-1 and Meteosat-7 are comparable over the Indian Ocean region.     

Metal Impregnated Silica‐Carbon Materials from Rice Husk: A Versatile Sorbent for Toxic Organics and Inorganics in Water and Air

Carbon bearing materials derived from rice husk (RH) have long been recognized as sorbents for diverse chemicals – both organic and inorganic. This work presents an overview of studies demonstrating a single step process of carbonization of chemically pretreated RH to produce metal impregnated silica‐carbon char designated as silicarbon materials that can be utilized in sorbing out water‐borne organic and inorganic hazardous substances (such as phenol, hexavalent chromium, fluoride, and arsenic) and air‐borne volatile organic chemicals (such as acetone, chloroform, benzene, and pyridine). The metal‐impregnated silicarbon solids derived from RH appear to constitute renewable, low‐cost, user‐friendly, and efficient materials for control systems for indoor air contamination and for industrial as well as non‐industrial hazardous aqueous pollution.     

Evaluation of rainfall–runoff model performance under non-stationary hydroclimatic conditions

ABSTRACT

Understanding of rainfall–runoff model performance under non-stationary hydroclimatic conditions is limited. This study compared lumped (IHACRES), semi-distributed (HEC-HMS) and fully-distributed (SWATgrid) hydrological models to determine which most realistically simulates runoff in catchments where non-stationarity in rainfall–runoff relationships exists. The models were calibrated and validated under different hydroclimatic conditions (Average, Wet and Dry) for two heterogeneous catchments in southeast Australia (SEA). SWATgrid realistically simulates runoff in the smaller catchment under most hydroclimatic conditions but fails when the model is calibrated in Dry conditions and validated in Wet. All three models perform poorly in the larger catchment irrespective of hydroclimatic conditions. This highlights the need for more research aimed at improving the ability of hydrological models to realistically incorporate the physical processes causing non-stationarity in rainfall–runoff relationships. Although the study is focussed on SEA, the insights gained are useful for all regions which experience large hydroclimatic variability and multi-year/decadal droughts.     

Changes in daily maximum temperature extremes across India over 1951–2014 and their relation with cereal crop productivity

This study used gridded daily maximum temperature data (1°?×?1°) for 1951–2014 period to analyze the trend in monthly extreme warm days (ExWD) and changes in its probability distribution in each grid. It also analyzed the trend in spatial spread of annual ExWD over the study period at four exceedance levels and further related the number of ExWDs with cereal crop productivity of India. Extreme warm days have increased throughout India but were statistically significant in 42% grids. The increase was consistent over all the months in north-eastern region, southern plateau and both the coastal plains. It also increased significantly over north-western and central India during April to June summer period. The probability distribution of ExWD also changed significantly in many grids, especially in southern plateau and both the coastal plains. The changes indicated increased frequency in the existing levels of extremes and new occurrences of higher frequency of extremes. The analysis of land area affected by different levels of extremes indicated significant increase, with the rate being highest for higher extremes. In terms of extreme warm day temperatures, the study identified southern plateau, east and west coast plains, and north-eastern India as highly vulnerable. Using copula probability model, study showed that increase in ExWD from 20 to 60% may increase the probability of 5% or more yield loss from 17 to 53% for Kharif cereals, 11 to 43% for Rabi cereals and 19 to 63% for wheat crop. The results may be used for devising zone specific adaptation strategies.     

Propagation of plane relativistic shock waves

Similarity solutions for propagation of plane shock waves in a relativistic gas, where the nucleon number density varies linearly as distance from its edge at near vacuum is obtained. The shock front moves with constant speed and the solutions are applicable only to an isothermal medium or cold gas.     

Planar and nonplanar ion acoustic shock waves with nonthermal electrons and positrons

The nonlinear propagation of ion acoustic shock waves (IASWs) are studied in an unmagnetized plasma consisting of nonthermal electrons, nonthermal positrons, and singly charged adiabatically hot positive ions, whose dynamics is governed by the two dimensional nonplanar Kadomstev-Petviashvili-Burgers (KPB) equation. The shock solution of the KPB equations is obtained numerically. The effects of several parameters and ion kinematic viscosities on the properties of ion acoustic shock waves are discussed in planar and nonplanar geometry. It is shown that the ion acoustic shock wave propagating in cylindrical/spherical geometry with transverse perturbation will be deformed as time goes on. Also, it is seen that the strength and the steepness of the IASWs increases with increasing β, the nonthermal parameter.     

Post-Cyclone Sidr nutritional status of women and children in coastal Bangladesh: an empirical study

Cyclone Sidr, a Category 4 storm, struck the southwestern coast of Bangladesh on November 15, 2007, causing 3,406 deaths, 2.51 million acres of crop damage, and aggregated damage of US$1.7 billion. It significantly damaged household food availability and increased post-cyclone nutritional insecurity. This study assesses the nutritional status of household and explores influences of various socioeconomic variables on nutritional security. More specifically, it explores the impact of the cyclone on short-term nutritional status of women of reproductive age and children under 5?years. For this study, 331 households living in three villages devastated by Cyclone Sidr were selected. The nutritional status of women of reproductive age was measured based on body mass index, and that of children aged 6?C59?months was measured based on weight-for-height (wasting), height-for-age (stunting), and weight-for-age (underweight). This study found that the nutritional status, along with other household characteristics, of the study groups was not remarkably different across the three selected villages. Findings of this study further suggest that the nutritional security situation was not much changed in the post-cyclone period compared with the pre-cyclone period primarily because of rapid and effective distribution of essential food items among cyclone survivors by the government of Bangladesh along with donor and other organizations. However, nutritional insecurity was more prevalent in the island village relative to inland and coastline villages. Similarly, fishermen were found to be the most vulnerable to nutritional insecurity in the post-cyclone period. Several recommendations are made to improve food aid distribution in the aftermath of a cyclone.