Dynamical downscaling approach for wintertime seasonal-scale simulation over the Western Himalayas

The performance of RegCM4 for seasonal-scale simulation of winter circulation and associated precipitation over the Western Himalayas (WH) is examined. The model simulates the circulation features and precipitation in three distinct precipitation years reasonably well. It is found that the RMSE decreases and correlation coefficient increases in the precipitation simulations with the increase of model horizontal resolutions. The ETS and POD for the simulated precipitation also indicate that the performance of model is better at 30 km resolution than at 60 and 90 km resolutions. This improvement comes due to better representation of orography in the high-resolution model in which sharp orography gradient in the domain plays an important role in wintertime precipitation processes. A comparison of model-simulated precipitation with observed precipitation at 17 station locations has been carried out. Overall, the results suggest that 30 km model produced better skill in simulating the precipitation over the WH and this model is a useful tool for further regional downscaling studies.     

Environmental Geochemistry of Iron and Manganese in Six Himalayan Lakes

The distribution and abundance of iron and manganese, the two important mobile metals, in an aquatic environment have been presented. These metals play an important role in the binding of nutrients and toxic elements by virtue of their high specific area in the oxide form. The concentration of Fe ranged from 1.08 to 5.2 mg/g and that of Mn from 0.27 to 2.17 mg/g. The Dal lake sediments were rich in Fe and those of the Wular lake had the lowest mean concentration of Fe. It was observed that the smaller particle size fractions had a higher metal content in comparison to large size fractions. Data on the selective extraction of Fe and Mn and their accumulation in humus material have also been given.     

Drought forecasting through statistical models using standardised precipitation index: a systematic review and meta-regression analysis

Quality and reliable drought prediction is essential for mitigation strategies and planning in disaster-stricken regions globally. Prediction models such as empirical or data-driven models play a fundamental role in forecasting drought. However, selecting a suitable prediction model remains a challenge because of the lack of succinct information available on model performance. Therefore, this review evaluated the best model for drought forecasting and determined which differences if any were present in model performance using standardised precipitation index (SPI). In addition, the most effective combination of the SPI with its respective timescale and lead time was investigated. The effectiveness of data-driven models was analysed using meta-regression analysis by applying a linear mixed model to the coefficient of determination and the root mean square error of the validated model results. Wavelet-transformed neural networks had superior performance with the highest correlation and minimum error. Preprocessing data to eliminate non-stationarity performed substantially better than did the regular artificial neural network (ANN) model. Additionally, the best timescale to calculate the SPI was 24 and 12 months and a lead time of 1–3 months provided the most accurate forecasts. Studies from China and Sicily had the most variation based on geographical location as a random effect; while studies from India rendered consistent results overall. Variation in the result can be attributed to geographical differences, seasonal influence, incorporation of climate indices and author bias. Conclusively, this review recommends use of the wavelet-based ANN (WANN) model to forecast drought indices.

     

Polycyclic aromatic hydrocarbons in sediments,mussels and crustacea around a former gasworks site in Shoreham-by-Sea,UK

Concentrations of polycyclic aromatic hydrocarbons have been determined in sediments, mussels and crustacea in the vicinity of a former gasworks site by Shoreham Harbour, UK. Very high concentrations of PAH were found in the substrate, an ash-like material deposited on the former gasworks site, which exhibited a profile consistent with the major source of contamination being coal or coke tar produced during the period of gas production at the site. Elevated PAH concentrations were also found in mussels both from the beach below the former gasworks site, and from sites further to the east in Portslade and Hove. The significance of these concentrations were assessed using an approach which involved the calculation of benzo[a]pyrene equivalent conoentrations (BaPEs), summing concentrations of individual PAH on the basis of their comparative potency as carcinogens. BaPE ranged from values of, or close to, zero for crustacea, to 336 microg kg(-1) wet weight in mussels from Southwick Beach. The contaminated mussels are not exploited commercially but may be taken by casual gatherers, and notices have been posted to warn potential consumers.     

Evaporation of perennial semi‐arid woodland in southeastern Australia is adapted for irregular but common dry periods

Measurements of water vapour flux from semi‐arid perennial woodland (mallee) were made for 3 years using eddy covariance instrumentation. There have been no previous long‐term, detailed measures of water use in this ecosystem. Latent energy flux (LE) on a half hourly basis was the measure of the combined soil and plant evaporation, ‘evapotranspiration’ (E_LE) of the site. Aggregation over 3 years of the site measured rain (1136 mm) and the estimated evaporation (794 mm) suggests that 342 mm or 30% of rain had moved into or past the root zone of the vegetation. Above average rainfall during 2011 and the first quarter of 2012 (633 mm, 15 months) would likely have been the period during which significant groundwater recharge occurred. At times immediately after rainfall, E_LE rates were the same or exceeded estimates of potential E calculated from a suitably parameterized Penman–Monteith (E_PMo) equation. Apparent free water E from plant interception and soil evaporation was about 2.3 mm and lasted for 1.3 days following rainfall in summer, while in autumn, E was 5.1 mm that lasted over 5.4 days. The leaf area index (LAI) needed to adjust a wind function calibrated Penman equation (E_PMe) to match the E_LE values could be back calculated to generate seasonal change in LAI from 0.12 to 0.46 and compared well with normalized difference vegetation index; r = 0.38 and p = 0.0213* and LAI calculated from digital cover photography. The apparently conservative response of perennial vegetation evaporation to available water in these semi‐arid environments reinforces the conclusion that these ecosystems use this mechanism to survive the reasonably common dry periods. Plant response to soil water availability is primarily through gradual changes in leaf area. Copyright © 2015 John Wiley & Sons, Ltd.     

Solar models with strong turbulence

A series of evolutionary models for the Sun were constructed using the strong turbulence model of the variable mixing-length theory (AMLT) of Canuto (1990). The present values of the solar model were obtained by an initial compositionX = 0.754,Z = 0.019, and(x) = 1.1. The physical variables which were obtained by applying the strong turbulence case of AMLT were similar to those of weak turbulence model (Kzlolu and Civelek, 1992) if we focused on the fitting of present solar radius and luminosity.