Direct and indirect radiative effects of sea-salt aerosols over Arabian Sea

Estimation of the indirect radiative effect of aerosols requires an understanding of the role of aerosols in influencing cloud properties. Several investigations have focused on the determination of the indirect effect, but most of them were confined to the anthropogenic (manmade) sulphate aerosols. Studies on the indirect effect of natural aerosols (such as sea salt) are rather few. In this article, a simple approach has been used to determine the indirect effect of sea-salt aerosols over the Arabian Sea for different seasons using long-term data available from ship-borne and island-based observations in the past. We demonstrate that the indirect radiative effect of sea-salt (natural) aerosols (at the top of the atmosphere) is as large as –7 ± 4 Wm–2 when compared to the direct radiative effect of –2 ± 1 Wm–2, and hence cannot be ignored. These values are larger than the anthropogenic aerosol forcing (~ 5.0 ± 2.5 Wm–2) reported over this region. The high variability in indirect effect from – 4 Wm–2 to around –18 Wm–2 brings out the importance of natural aerosols in this region. The study also demonstrates the important role of wind speed on aerosol characteristics and hence its impact on direct and indirect radiative effects. The magnitude of indirect radiative effect (and uncertainty) is severalfold more than the direct radiative effect of sea-salt aerosols

Biosorption of metals from contaminated water using seaweed

Heavy metals are major pollutants in marine, lake and groundwaters as well as in industrial and even treated effluents. Biosorption, an inexpensive and reliable method to remove cadmium and lead ions from solution using dry seaweed biomass as adsorbents, was investigated. Sargassum wightii exhibited maximum metal uptake at pH 4–5 and the value ranged from 18% to 29% of dry biomass. The kinetics of metal adsorption was fast with 70–80% taking place within 30 min. Based on these results, a biobattery involving perforated columns packed with pulverized dry biomass of S. wightii was designed, which could remove metals in the range of 50–97% from a multi-metal ion solution within two and a half hours. The mechanism of metal sorption by seaweeds and the advantages of the present design of seaweed columns are discussed in the light of ecofriendly and cost-effective approach for effluent treatment

Aerosol characteristics at a remote island: minicoy in southern Arabian sea

Extensive measurements of aerosol optical and microphysical properties made at a remote island, Minicoy in southern Arabian Sea for the period (February 2006-March 2007) are used to characterize their temporal variability and Black Carbon (BC) mass mixing ratio. Large decrease in aerosol BC (from ~800 ng m-3 to ~100 ng m-3) was observed associated with change in airmass characteristics and monsoon rains. The total aerosol mass varied between ~80 and 20 μg m-3. Though the total mass fell drastically, a slight increase in super micron mass was observed during the June-August period associated with high winds. The mass fraction of Black Carbon aerosols during the prevalence of continental airmass is found to be ~1.2% of the composite aerosols, which is much lower than the values reported earlier for this region

Multisoliton solutions and integrability aspects of coupled nonlinear Schrodinger equations

Using Painleve singularity structure analysis, we show that coupled higher-order nonlinear Schrodinger (CHNLS) equations admit Painleve property. Using the results of Painleve analysis, we succeed in Hirota bilinearizing the CHNLS equations, one soliton and two soliton solutions are explictly obtained. Lax pairs are explictly constructed.Comment: Eight pages and six figures. Physical Review E (to be appear

Modeling regional aerosol variability over California and its sensitivity to emissions and long-range transport during the 2010 CalNex and CARES campaigns

Abstract. The performance of the Weather Research and Forecasting regional model with chemistry (WRF-Chem) in simulating the spatial and temporal variations in aerosol mass, composition, and size over California is quantified using measurements collected during the California Nexus of Air Quality and Climate Experiment (CalNex) and the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted during May and June of 2010. The extensive meteorological, trace gas, and aerosol measurements collected at surface sites and along aircraft and ship transects during CalNex and CARES were combined with operational monitoring network measurements to create a single dataset that was used to evaluate the one configuration of the model. Simulations were performed that examined the sensitivity of regional variations in aerosol concentrations to anthropogenic emissions and to long-range transport of aerosols into the domain obtained from a global model. The configuration of WRF-Chem used in this study is shown to reproduce the overall synoptic conditions, thermally-driven circulations, and boundary layer structure observed in region that controls the transport and mixing of trace gases and aerosols. However, sub-grid scale variability in the meteorology and emissions as well as uncertainties in the treatment of secondary organic aerosol chemistry likely contribute to errors at a primary surface sampling site located at the edge of the Los Angeles basin. Differences among the sensitivity simulations demonstrate that the aerosol layers over the central valley detected by lidar measurements likely resulted from lofting and recirculation of local anthropogenic emissions along the Sierra Nevada. Reducing the default emissions inventory by 50% led to an overall improvement in many simulated trace gases and black carbon aerosol at most sites and along most aircraft flight paths; however, simulated organic aerosol was closer to observed when there were no adjustments to the primary organic aerosol emissions. The model performance for some aerosol species was not uniform over the region, and we found that sulfate was better simulated over northern California whereas nitrate was better simulated over southern California. While the overall spatial and temporal variability of aerosols and their precursors were simulated reasonably well, we show cases where the local transport of some aerosol plumes were either too slow or too fast, which adversely affects the statistics regarding the differences between observed and simulated quantities. Comparisons with lidar and in-situ measurements indicate that long-range transport of aerosols from the global model was likely too high in the free troposphere even though their concentrations were relatively low. This bias led to an over-prediction in aerosol optical depth by as much as a factor of two that offset the under-predictions of boundary-layer extinction resulting primarily from local emissions. Lowering the boundary conditions of aerosol concentrations by 50% greatly reduced the bias in simulated aerosol optical depth for all regions of California. This study shows that quantifying regional-scale variations in aerosol radiative forcing and determining the relative role of emissions from local and distant sources is challenging during "clean" conditions and that a wide array of measurements are needed to ensure model predictions are correct for the right reasons. In this regard, the combined CalNex and CARES datasets are an ideal testbed that can be used to evaluate aerosol models in great detail and develop improved treatments for aerosol processes

Detection and attribution of human influence on regional precipitation

Understanding how human influence on climate is affecting precipitation around the world is immensely important for defining mitigation policies, and for adaptation planning. Yet despite increasing evidence for the influence of climate change on global patterns of precipitation, and expectations that significant changes in regional precipitation should have already occurred as a result of human influence on climate, compelling evidence of anthropogenic fingerprints on regional precipitation is obscured by observational and modelling uncertainties and is likely to remain so using current methods for years to come. This is in spite of substantial ongoing improvements in models, new reanalyses and a satellite record that spans over thirty years. If we are to quantify how human-induced climate change is affecting the regional water cycle, we need to consider novel ways of identifying the effects of natural and anthropogenic influences on precipitation that take full advantage of our physical expectations