On the numerical evaluation of theH-functions of transfer problems in multiplying media

Extensive tables of the values ofH-functionsH ⁰(z, ) andH ₁ ⁰ (z, ) appropriate for the problems of radiative transfer in multiplying media characterized by >1, have been constructed correctly to the sixth decimal place for values of in the range 1.05–10. This accuracy has been attained with the aid of a 32-point Gaussian quadrature.     

Evaluation of climate reanalysis and space-borne precipitation products over Bangladesh

ABSTRACT

This study aims to quantify the spatial distribution of errors in two climate reanalysis (ERA5 and CFSR) and two satellite (TMPA-RT and TMPA-V7) precipitation products over Bangladesh. The datasets are assessed against ground-based rain gauge observations to capture the extreme rainfall accumulations at daily temporal scale over a 5-year period (January 2010–December 2014). The bias ratio scores indicate that CFSR and TMPA-RT seriously overestimate the rainfall values over much of the study area. Whilst TMPA-V7 performs better than the other precipitation products, all datasets lose their detection skills substantially for higher quantile thresholds (i.e. above 50th and 75th percentiles). With respect to rainfall detection metrics – probability of detection (POD) and volumetric hit index (VHI) – both ERA5 and CFSR show superior performance (in the range 0.9–1.0 for all the analysis grid boxes). All rainfall datasets are equally good in terms of false alarm ratio (FAR) and volumetric FAR (VFAR), even though the lowest values are associated with ERA5 for higher quantiles. All products demonstrate a decrease in skill to capture the amount of rainfall but show satisfactory results to detect the rainfall events when using higher quantile thresholds (i.e. rainfall above the 50th and 75th percentiles) to sample the data before computing product skill.     

Drought adaptation measures and their effectiveness at Barind Tract in northwest Bangladesh: a perception study

Natural Hazards - Drought is a natural calamity frequently occurs at Barind Tract in northwest Bangladesh and affects both the human and natural life. An initiative has been taken...     

Seasonal ensemble generator for radar rainfall using copula and autoregressive model

Uncertainty analysis of radar rainfall enables stakeholders and users have a clear knowledge of the possible uncertainty associated with the rainfall products. Long-term empirical modeling of the relationship between radar and gauge measurements is an efficient and practical method to describe the radar rainfall uncertainty. However, complicated variation of synoptic conditions makes the radar-rainfall uncertainty model based on historical data hard to extend in the future state. A promising solution is to integrate synoptic regimes with the empirical model and explore the impact of individual synoptic regimes on radar rainfall uncertainty. This study is an attempt to introduce season, one of the most important synoptic factor, into the radar rainfall uncertainty model and proposes a seasonal ensemble generator for radar rainfall using copula and autoregressive model. We firstly analyze the histograms of rainfall-weighted temperature, the radar-gauge relationships, and Box and Whisker plots in different seasons and conclude that the radar rainfall uncertainty has strong seasonal dependence. Then a seasonal ensemble generator is designed and implemented in a UK catchment under a temperate maritime climate, which can fully model marginal distribution, spatial dependence, temporal dependence and seasonal dependence of radar rainfall uncertainty. To test its performance, 12 typical rainfall events (4 for each season) are chosen to generate ensemble rainfall values. In each time step, 500 ensemble members are produced and the values of 5th to 95th percentiles are used to derive the uncertainty bands. Except several outliers, the uncertainty bands encompass the observed gauge rainfall quite well. The parameters of the ensemble generator vary considerably for each season, indicating the seasonal ensemble generator reflects the impact of seasons on radar rainfall uncertainty. This study is an attempt to simultaneously consider four key features of radar rainfall uncertainty and future study will investigate their impacts on the outputs of hydrological models with radar rainfall as input or initial conditions.     

Impact assessment due to rural electrification in hill tract of Bangladesh for sustainable development

Environmental impact assessment (EIA) of any project is essential for understanding the sustainability of the project. For sustainable development of hill tracts, electricity is inseparable. Like other parts of Bangladesh hill tracts districts felt increasing demand of electricity. In this paper an attempt has been taken to present the existing environmental condition and analysis the future environmental condition after implementation of project. Electrification will extend the length of the active day. Electrification will improve security (people’s perception of safety and security) at the region. The elements of the project identified as components for analysis are chosen based on DOE’s guideline. The study showed that 87% people say that they feel safer at night since being electrified. Impacts are classified on the basis of EPA’s scaling and DOE, university’s teachers, NGOs expert’s opinions. Value more than 10 is classified significantly affected element of the project. In this paper advantages and disadvantages of the Electrification Project has been presented.     

Paleozoic glaciation in NE Africa: field and remote sensing-based evidence from the South Eastern Desert of Egypt

ABSTRACT

Exhumed Paleozoic glacial deposits and landforms of the North Gondwana are reported here for the first time from the South Eastern Desert (SED) of Egypt. Using field observations and remote sensing datasets (Advanced Land Observing Satellite [ALOS], Phased Array L-band Synthetic Aperture Radar [PALSAR] radar, multispectral Landsat TM datasets, and digital elevation models [DEMs]), we mapped the distribution of Paleozoic glacial features (i.e. deposits and landforms) in the SED. Two main glaciogenic facies were identified in three locations in the SED: (1) massive, poorly sorted, matrix supported, boulder-rich diamictites in Wadi El-Naam and Korbiai, and (2) moderately-sorted, occasionally bedded outwash deposits in Betan area. Inspection of radar, DEMs, and Landsat Operational Land Imager (OLI) images revealed previously unrecognized ENE-WSW trending glacial megalineations (MLs) over the peneplained Neoproterozoic basement rocks in the central sections of the SED, whose trends align along their projected extension with those of glacial features (tunnel valleys and striation trends) reported from Saudi Arabia. The glaciogenic features in the SED are believed to be largely eroded during the uplift associated with the Red Sea opening, except for those preserved as basal units beneath the Nubia Sandstone Formation or as remnant isolated deposits within paleo-depressions within the basement complex. The apparent spatial correlation of the SED glacial features with well-defined Late Ordovician deposits in North Africa and in Saudi Arabia, and the reported thermochronometric analyses and fossil records are consistent with a Late Ordovician age for the SED glaciogenic features and support models that call on the continuation of the Late Ordovician (Hirnantian) ice sheet from the Sahara into Arabia through the SED of Egypt.     

Characteristics of the internal and external sources of the Mediterranean synoptic cyclones for the period 1956–2013

This paper investigates the main sources and features of the Mediterranean synoptic cyclones affecting the basin, using the cyclone tracks. The cyclones’ tracks are identified using sea level pressure (SLP) from the NCEP/NCAR reanalysis data for the period 1956–2013. The identified cyclones are classified into two categories: basin affected and basin non-affected. Most of the basin-affected (non-affected) cyclones are internal (external), i.e., generated inside (outside) the Mediterranean basin. This study reveals four (five) main sources of internal (external) cyclones. These four (five) main sources generated about 63.76% (57.25%) of the internal (external) cyclones. Seasonal analysis shows that most of the basin-affected internal (external) cyclones were generated in the winter (spring) season. The lowest number of cyclones were found in the summer. Moreover, the synoptic study of the atmospheric systems accompanied the highest- and lowest-generated years demonstrates that the deepening of the north Europe cyclones and the relative positions of Azores- and Siberian-high systems represent the important factors that influence the number of internal cyclones. Essential factors influencing the external cyclones are the strength of the maximum upper wind, Azores high, Siberian high, and orientations of their ridges.     

Envelope solitons and their modulational instability in dusty plasmas with two-temperature superthermal electrons

The modified ion-acoustic envelope solitons and their modulational instability in a multi-component unmagnetized plasma (consisting of negatively charged immobile dusts, inertial ions and superthermal electrons of two distinct temperatures) are theoretically investigated. A multiple scale (in space and time) perturbation technique is used to derive the cubic nonlinear Schrödinger equation (which describes the evolution of a slowly varying wave envelope with space and time). It is observed that the plasma system under consideration supports two types (bright and dark) envelope solitons. It is also found that the dark (bright) envelope solitons are modulationally stable (unstable). The variation of the growth rate of the unstable bright envelope solitons with various plasma parameters (e.g. wave number, temperature of superthermal electrons, etc.) are found to be significant. The modulational instability criterions of the modified ion-acoustic envelope solitons are also seen to be influenced due to the variation of the intrinsic plasma parameters. The implications of the results of this theoretical investigations in some space plasma systems (viz. Saturn’s magnetosphere) are briefly mentioned.     

Evaluation of TRMM rainfall for soil moisture prediction in a subtropical climate

The Tropical Rainfall Measuring Mission (TRMM) is a joint space mission between NASA and the Japan Aerospace Exploration Agency (JAXA) designed to monitor and study tropical rainfall. In this study, the daily rainfall from TRMM has been utilized to simulate the soil moisture content up to 30 cm vertical soil profile of at an interval depth of 15 cm by using the HYDRUS 1D numerical model for the three plots. The simulated soil moisture content using ground-based rainfall and TRMM-derived rainfall measurements indicate an agreeable goodness of fit between the both. The Nash–Sutcliffe efficiency using ground-based and TRMM-derived rainfall was found in the range of 0.90–0.68 and 0.70–0.40, respectively. The input data sensitivity analysis of precipitation combined with different irrigation treatment indicates a high dependency of soil moisture content with rainfall input. The overall analysis reveals that TRMM rainfall is promising for soil moisture prediction in absence of ground-based measurements of soil moisture.     

Assessment of arsenic health risk and source apportionment of groundwater pollutants using multivariate statistical techniques in Chapai-Nawabganj district,Bangladesh

This study assessed arsenic health risk to the local residents through oral and dermal exposure pathways of drinking water and to investigate source apportionment of groundwater pollutants using multivariate statistical techniques in the Chapai-Nawabganj district, Bangladesh. Groundwater samples collected from shallow tube well and dug well at the depth ranges (15-60 m) were analyzed for physio-chemical parameters and trace elements. Most of the studied physio-chemical parameters were found within their respective permissible limits. However, total As, Fe and Mn concentrations exceeded Bangladesh and WHO guideline values. The assessment of arsenic health risk reveals that children as compared to adults are found at a higher risk as the values of hazard quotients (HQ) >1 in the most of the groundwater samples. This level of arsenic contamination should have medium to high chronic risk and medium carcinogenic risk when compared with US EPA guidelines which can cause serious health hazard. The results of principal component analysis (PCA) and factor analysis (CA) indicate that geogenic (interaction of water and basement rock) and anthropogenic (agrochemicals, agricultural fertilizer and domestic sewage) sources are responsible for variation in arsenic and other physio-chemical parameters in the groundwater aquifer of the study area. Furthermore,the inter-correlation of arsenic with metals and ions were also calculated by correlation matrix and linear regression analysis. The outcomes of this study will help to meet the challenge of sustainable groundwater quality management in Bangladesh and enhancing better vision of potential health risk of local inhabitants in the study area.