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Alternative climate products, such as gauge-based gridded data, ground-based weather radar, satellite precipitation and climate reanalysis products, are being increasingly applied for hydrological modelling. This review aims to summarize the studies that have evaluated alternative climate products within Soil and Water Assessment Tool (SWAT) applications and to propose future research directions, primarily for modelers who wish to study limited gauge, ungauged or transnational river basins. A total of 126 articles have been identified since 2004, the majority of which have been published within the last five years. About 58% of the studies were conducted in Asia, mostly in China and India, while another 14% were reported for United States studies. CFSR and TRMM are the most popular applied products in SWAT modelling, followed by PERSIANN, CMADS, APHRODITE, CHIRPS and NEXRAD. Generally, the performance of climate products is region-dependent; e.g., CFSR typically performs well in the United States and South America, but performs more poorly for Asia, Africa and mountainous basin conditions, as compared to other products. In contrast, the CMADS, TRMM, APRHODITE and NEXRAD have shown the strongest capability for supporting SWAT modelling in these regions. However, most of the evaluated products contain only precipitation input; therefore, merging reliable precipitation with CFSR-temperature is recommended for hydro-climatic modelling. Future research directions include: (1) examination of optimal combinations; e.g. CHIRPS-precipitation and CFSR-temperature, for simulating streamflow in different types of river basins; (2) development of a standardized validation scheme which incorporates the commonly accepted products, statistical approaches and temperature variables; (3) further evaluation of existing climate data products to accurately capture extreme events, pattern and indices as well as WGEN statistics; (4) improvement of climate data in terms of averaging approach, bias correction and additional factors or indices integration; and (5) bias correction of CMIP6 climate projections using the optimal climate data combinations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The radiative budget, cloud properties, and precipitation over tropical Africa are influenced by solar absorption by biomass-burning aerosols (BBA) from Central Africa. Recent field campaigns, reinforced by new remote-sensing and aerosol climatology datasets, have highlighted the absorbing nature of the elevated BBA layers over the South-East Atlantic (SEA), indicating that the absorption could be stronger than previously thought. We show that most of the latest generation of general circulation models (GCMs) from the sixth phase of the Coupled Model Intercomparison Project 6 (CMIP6) underestimates the absorption of BBA over the SEA. This underlines why many (~75%) CMIP6 models do not fully capture the intense positive (warming) direct radiative forcing at the top of the atmosphere observed over this region. In addition, underestimating the magnitude of the BBA-induced solar heating could lead to misrepresentations of the low-level cloud responses and fast precipitation feedbacks that are induced by BBA in tropical regions.

Photoacoustic spectroscopy (PAS) is a sensitive technique for the detection of trace gases and aerosols and measurements of their absorption coefficients. The accuracy of such measurements is often governed by the fidelity of the PAS instrument calibration. Gas samples laden with O3 of a known or independently measured absorption coefficient are a convenient and commonplace route to calibration of PAS instruments operating at visible wavelengths (λ), yet the accuracy of such calibrations remains unclear. Importantly, the photoacoustic detection of O3 in the Chappuis band (λ ∼ 400-700 nm) depends strongly on the timescales for energy transfer from the nascent photoproducts O(3P) and O2(X, v > 0) to translational motion of bath gas species. Significant uncertainties remain concerning the dependence of these timescales on both the sample pressure and the bath gas composition. Here, we demonstrate accurate characterisation of microphone response function dependencies on pressure using a speaker transducer to excite resonant acoustic modes of our photoacoustic cells. These corrections enable measurements of photoacoustic response amplitudes (also referred to as PAS sensitivities) and phase shifts with variation in static pressure and bath gas composition, at discrete visible wavelengths spanning the Chappuis band. We develop and fit a photochemical relaxation model to these measurements to retrieve the associated variations in the aforementioned relaxation timescales for O(3P) and O2(X, v > 0). These timescales enable a full assessment of the accuracy of PAS calibrations using O3-laden gas samples, dependent on the sample pressure, bath gas composition and PAS laser modulation frequency.

Aerosols interact with radiation and clouds. Substantial progress made over the past 40 years in observing, understanding, and modeling these processes helped quantify the imbalance in the Earth's radiation budget caused by anthropogenic aerosols, called aerosol radiative forcing, but uncertainties remain large. This review provides a new range of aerosol radiative forcing over the industrial era based on multiple, traceable, and arguable lines of evidence, including modeling approaches, theoretical considerations, and observations. Improved understanding of aerosol absorption and the causes of trends in surface radiative fluxes constrain the forcing from aerosol-radiation interactions. A robust theoretical foundation and convincing evidence constrain the forcing caused by aerosol-driven increases in liquid cloud droplet number concentration. However, the influence of anthropogenic aerosols on cloud liquid water content and cloud fraction is less clear, and the influence on mixed-phase and ice clouds remains poorly constrained. Observed changes in surface temperature and radiative fluxes provide additional constraints. These multiple lines of evidence lead to a 68% confidence interval for the total aerosol effective radiative forcing of -1.6 to -0.6 W m -2 , or -2.0 to -0.4 W m -2 with a 90% likelihood. Those intervals are of similar width to the last Intergovernmental Panel on Climate Change assessment but shifted toward more negative values. The uncertainty will narrow in the future by continuing to critically combine multiple lines of evidence, especially those addressing industrial-era changes in aerosol sources and aerosol effects on liquid cloud amount and on ice clouds., (©2019. The Authors.)

Solar geoengineering refers to a range of proposed methods for counteracting global warming by artificially reducing sunlight at Earth's surface. The most widely known solar geoengineering proposal is stratospheric aerosol injection (SAI), which has impacts analogous to those from volcanic eruptions. Observations following major volcanic eruptions indicate that aerosol enhancements confined to a single hemisphere effectively modulate North Atlantic tropical cyclone (TC) activity in the following years. Here we investigate the effects of both single-hemisphere and global SAI scenarios on North Atlantic TC activity using the HadGEM2-ES general circulation model and various TC identification methods. We show that a robust result from all of the methods is that SAI applied to the southern hemisphere would enhance TC frequency relative to a global SAI application, and vice versa for SAI in the northern hemisphere. Our results reemphasise concerns regarding regional geoengineering and should motivate policymakers to regulate large-scale unilateral geoengineering deployments.

This corrects the article DOI: 10.1038/nature22974.

Aerosols have a potentially large effect on climate, particularly through their interactions with clouds, but the magnitude of this effect is highly uncertain. Large volcanic eruptions produce sulfur dioxide, which in turn produces aerosols; these eruptions thus represent a natural experiment through which to quantify aerosol-cloud interactions. Here we show that the massive 2014-2015 fissure eruption in Holuhraun, Iceland, reduced the size of liquid cloud droplets-consistent with expectations-but had no discernible effect on other cloud properties. The reduction in droplet size led to cloud brightening and global-mean radiative forcing of around -0.2 watts per square metre for September to October 2014. Changes in cloud amount or cloud liquid water path, however, were undetectable, indicating that these indirect effects, and cloud systems in general, are well buffered against aerosol changes. This result will reduce uncertainties in future climate projections, because we are now able to reject results from climate models with an excessive liquid-water-path response.

This work describes the preparation of a selenium-modified TiO(2) photocatalyst and a preliminary evaluation of its photocatalytic activity. Se-TiO(2) displayed greater visible absorption than undoped TiO(2) and was still capable of degrading quinoline at a slightly faster rate than undoped TiO(2) under UV light. Se-TiO(2) was also able to degrade organic molecules under purely visible light by a single electron transfer pathway. Irradiation with >435 nm light showed no evidence of efficient production of HO•-like species. Se-TiO(2) was also examined under hypoxic conditions, where the Se atoms were capable of trapping photogenerated electrons as evidenced by XPS.

Larvae of the black cutworm, Agrotis ipsilon Hufnagel, were more susceptible to infection by A. ipsilon multiple nucleopolyhedrovirus (AgipMNPV: Baculoviridae) after feeding on Herculex I, a transgenic corn hybrid expressing the Bacillus thuringiensis (Bt)-derived toxin Cry1Fa2 compared to larvae fed on isoline corn. We investigated the physiological basis for increased susceptibility to virus infection following exposure to Herculex I by analyzing the midgut pH, gut protease activity and peritrophic matrix structure which are important factors for both Bt toxin action and baculovirus infection. No significant treatment differences were found in the pH of anterior midgut, central midgut or posterior midgut in larvae fed Herculex I or isoline diets. Analysis of soluble and membrane-associated gut proteinase activities from larvae fed Herculex I or isoline diets indicated that membrane-associated aminopeptidase activity and soluble chymotrypsin-like proteinase activity were significantly lower in Herculex I -fed larvae compared to isoline-fed larvae. The number and relative molecular masses of soluble chymotrypsin-like proteinases did not differ. Baculoviruses were not susceptible to in vitro degradation by bovine chymotrypsin, suggesting that chymotrypsin degradation of baculovirus occlusion-derived virus did not result in reduced infection of larvae fed on isoline diet. Scanning electron micrographs of the peritrophic matrices of Herculex I -fed larvae and isoline-fed larvae indicated that Herculex I did not result in damage to the peritrophic matrix that could facilitate subsequent baculovirus infection. Additional research is required to further delineate the physiological basis for enhanced baculovirus infection following exposure to sublethal doses of Bt toxins.

Tropospheric aerosols affect the radiative forcing of Earth's climate, but their variable concentrations complicate an understanding of their global influence. Model-based estimates of aerosol distributions helped reveal spatial patterns indicative of the presence of tropospheric aerosols in the satellite-observed clear-sky solar radiation budget over the world's oceans. The results show that, although geographical signatures due to both natural and anthropogenic aerosols are manifest in the satellite observations, the naturally occurring sea-salt is the leading aerosol contributor to the global-mean clear-sky radiation balance over oceans.

Research at the University of Central Florida has determined that the injection of hydrogen peroxide (H 2 O 2 ) into a simulated flue gas stream effectively oxidizes NO to NO 2 , and NO 2 to HNO 2 and HNO 3 . These oxides of nitrogen are much more soluble in water than NO, and therefore may be more easily scrubbed from the flue gas in a typical wet scrubber. Oxidation and NO x removal efficiencies of greater than 90% were demonstrated in the laboratory. An economic comparison between the H 2 O 2 injection-wet scrubbing method and the selective catalytic reduction (SCR) method of NO x removal was conducted for a design base case and a variety of alternative cases. This study illustrates the trade-off between capital and operating costs for the two alternatives. The single largest factor in determining whether the total cost of the H 2 O 2 injection-wet scrubbing method compares favorably with the total cost of the SCR method is the H 2 O 2 :NO x molar ratio. At the H 2 O 2 :NO x molar ratio demonstrated in the laboratory (1.92:1.0), the H 2 O 2 injection-wet scrubbing method of NO x removal was shown to be uneconomical. However, the molar ratio in a full-size coal-fired power plant could be lower than that found in the laboratory. Based on all the cost assumptions stated in this article, at a molar ratio of 1.37:1.0, the hydrogen peroxide injection method was calculated to be an economically feasible alternative to the SCR method for NO x control.

A set of X-ray test objects has been developed for quality control in digital subtraction fluorography (DSF). Factors which can be assessed include dynamic range, highlight overload and signal-to-noise ratio, low contrast sensitivity, unsharpness, and systematic misregistration. These test objects complement, both in design and calibration, those previously developed to evaluate the imaging performance of television fluoroscopy and small-format fluorography systems. In this article, the first of two, we describe the Leeds DSF test objects, paying particular attention to the reasoning behind their design.

In the previous article we introduced a set of test objects for quality control of digital subtraction fluorography (DSF) systems. These test objects have been evaluated using several commercial DSF systems in their clinical environment. In this second article we present test images and results obtained during these trails and explain how the test objects can be used to analyse the imaging performance of DSF systems.