Long-range persistence in sea surface temperature off the coast of central California

We estimate long-range persistence in ocean surface temperature off the coast of central California, a region where similar observations have not been made. The database consists of 20-year records of daily sea surface temperature from three locations: Pacific Grove and Granite Canyon along the coast, and Southeast Farallon Island located 40 km off the coast and slightly further north. Long-range persistence is important for a number of reasons: on the negative side, it can have serious detrimental effects for statistical inference and on the positive side, it provides access to the ocean’s memory which can lead to a greater understanding of the processes involved and thus to better prediction. Long-range persistence also provides important insights into the relationship between the scaling that is obtained and the time scales employed. The first step in the analysis was to remove the annual cycle from the data at each location because of its detrimental effect on estimating long-range persistence. Then detrended fluctuation analysis was used to calculate long-range persistence where a single scaling exponent is obtained that relates the magnitudes of the fluctuations in the data to the time scales involved. Similar scaling exponents were obtained for Granite Canyon and Pacific Grove with values of 1.04 and 1.05, respectively. At Southeast Farallon Island, a value of 1.16 was obtained. The increase in the scaling exponent at Southeast Farallon Island is consistent with observations made elsewhere and model results, which indicate that as coastal influence decreases further offshore, the scaling exponents for sea surface temperature tend to increase. Because Southeast Farallon Island is exposed to subarctic waters offshore, whereas Pacific Grove and Granite Canyon are exposed to warmer waters from the California Undercurrent along the coast, these exposures to different water masses may contribute to the observed change in scaling behavior.

Selection of sustainable technologies for reducing emission of volatile organic compounds and greenhouse gases

Selection of sustainable and environmental friendly technologies is very important in meeting strict environmental regulations on industrial emissions of volatile organic compounds and greenhouse gases. Many of the industrial volatile organic compounds are toxic and carcinogenic, and they are regulated under Clean Air Act for hazardous air pollutants. Similarly, global environmental agreements such as European Union’s 2015 Paris Agreement and Kyoto Protocol restrict carbon emission, which is responsible for global warming, sea-level rise, flooding, and ecological imbalance. It is essential that industries choose suitable technologies that reduce not only toxic volatile organic compounds in the air but also greenhouse gas emissions. In this communication, biotechnological methods are discussed and compared with conventional processes, which are used for control of volatile organic compounds. The readers may find this article useful in the selection of an appropriate technology for their application while minimizing the greenhouse gas emissions.

Spatial and seasonal variations in atmospheric aerosols over Nigeria: Assessment of influence of intertropical discontinuity movement

This study examines the influence of intertropical discontinuity movement on seasonality and distribution of atmospheric aerosols over Nigeria, using remote sensing approach. The Moderate Resolution Imaging Spectroradiometer (MODIS) Terra aerosol optical depth, wind speed and precipitation/intertropical discontinuity (ITD) dataset were used. Geospatial interpolation model was used to analyse the aerosol seasonal distribution. Correlations analysis was used to evaluate the degree of influence of wind and ITD on the monthly distribution of aerosol. The results show significant variations in monthly mean distributions of aerosol, but the variation is much more extraordinary during Harmattan season than Wet and Dry seasons, with 0.29 ⩽ aerosol optical depth ⩾ 0.46. In other ecological zones, the highest mean aerosol optical depth values were observed in the months of December, January and February with 0.30 ⩽ aerosol optical depth ⩾ 0.60, with highest value in Sahel ecological zone. Generally, the results further show a strong relationship between aerosol optical depth distribution and migration of ITD with correlation r2 ⩾ 0.60 @ p = 0.05 mostly during Dry and Harmattan seasons but relatively low correlation r2 ⩽ 0.40 @ p = 0.05 during Wet season. The major findings of this study are that seasonal shifts in the location of the ITD considerably affect not only rainfall distribution, resulting in the Wet and Dry seasons in the study area, but also have significant impacts on atmospheric aerosol distributions. Although not all aerosols presented in this study are dust originated from Sahara desert, since biomass-burning activities frequently occur in the study area, the study concludes that satellite-based aerosol optical depth datasets continue to be advantageous to understand atmospheric aerosols distribution in a region where there is fewer ground aerosols data.

Past and possible future influence of the Atlantic Meridional Overturning Circulation on the climate responsible for concentration of geopolitical power and wealth in the North Atlantic region

Previous research has shown that nations that controlled global-scale empires over the most recent centuries and presently possess great per-capita wealth are in Earth’s two largest regions of regular moderate rainfall. That rainfall regime is the pattern of atmospheric precipitation most supportive of agriculture and water-wheel-powered industry, both of which presumably contributed to those nations’ advancement. Those regions of regular moderate rainfall ring the North Atlantic, and this article reviews the evidence that the Gulf Stream delivers warm vapor-releasing water in the upper limb of the Atlantic Meridional Overturning Circulation, generating the distinctive climate of western Europe and eastern North America. Ocean circulation’s control on continental climate has thus contributed significantly to the Euro-American concentration of wealth and geopolitical power that has dominated the last few centuries of human history. However, comparison of the present apparent weakening or failure of the Atlantic Meridional Overturning Circulation with both the early Holocene 8.2 ka event and modeling of the Atlantic Meridional Overturning Circulation’s diminished generation of water vapor suggests that Europe and eastern North America may lose their beneficent climate pattern as rainfall there lessens.

Experimental validation of lift and drag forces on an asymmetrical hydrofoil for seafloor anchoring applications

Tidal power can be described as harnessing the kinetic energy of the in and out flows known as tides created by the changing gravitational pull of the moon and the sun on the oceans of the world. As the relative positions of the sun and moon can be accurately predicted, so can the resultant tidal movements, making tidal energy such a valuable resource and an attractive option for renewable power generation. However, the high costs and difficulties associated with the deployment of underwater turbines, which includes anchoring, are prohibitive factors in the widespread utilisation of tidal power technology. Existing turbine fixation methods are primarily based on the use of large gravity anchors or monopole structures to secure the turbine to the seabed. In an effort to reduce size, environmental impact on the seafloor and installation cost, a hydrofoil-based anchor could be considered. The objective of this study is to experimentally test the lift and drag force behaviour of a finite-span hydrofoil with endplates, whose profile was selected based on simplified two-dimensional (2D) numerical simulations using the vortex panel method. A customised lift and drag force measurement system for this prototype hydrofoil was designed, fabricated and calibrated, and subsequently installed and tested in the Dutch Tidal Testing Centre (TTC) in Den Oever, the Netherlands. A series of tests with force and flow velocity measurements are described for different angles-of-attack under realistic tidal flow conditions. Results for the lift and drag coefficients as a function of angle-of-attack are compared to numerical simulation data and revealed that the real-world lift force is predicted well, whereas the drag force is underpredicted by the numerical predictions. These findings provide useful information for the design of anchoring systems based of hydrofoil profiles.

WAM and WAVEWATCH-III intercomparison studies in the North Indian Ocean using Oceansat-2 Scatterometer winds

This paper presents the intercomparison of wave hindcasts using the third-generation models WAM and WAVEWATCH-III for the North Indian Ocean over 1° × 1° (latitude × longitude) grid resolutions, which reveals the first assessment of their relative performance through intercomparison of the model results. Hindcast wave parameters such as significant wave height, mean wave period, and swell wave height obtained from the simulations using Oceansat-2 scatterometer winds are analyzed to understand the quality and variability associated with the individual model outputs in the Indian Ocean. WAM and WAVEWATCH-III intercomparison studies are carried out for four different cases (January and June 2010, and January and June 2011). A comparative study of the relative performances of these two models is evaluated through extensive and robust statistical error analysis. Based on both qualitative and quantitative assessment of the model results, this study clearly indicates that both WAM and WAVEWATCH-III performed well in the common model domain using Oceansat-2 scatterometer winds, and they can be confidently used for long-term hindcasting in the North Indian Ocean, which will be very useful for most of the user community dealing with various coastal/offshore activities. The study also suggests that it would be preferable to consider available long-term wave measurements both in deep and coastal waters of the North Indian Ocean to validate and intercompare WAM and WAVEWATCH-III further.