The Moderate Resolution Imaging Spectroradiometer(MODIS) sensor onboard NASA's Aqua satellite has been collecting valuable data about the Earth system for more than 14 years, and one of the benefits of this is that it has made it possible to detect the long-term variation in aerosol loading across the globe. However, the long-term aerosol optical depth(AOD)trends derived from MODIS need careful validation and assessment, especially over land. Using AOD products with at least 70 months' worth of measurements collected during 2002–15 at 53 Aerosol Robotic Network(AERONET) sites over land,Mann–Kendall(MK) trends in AOD were derived and taken as the ground truth data for evaluating the corresponding results from MODIS onboard Aqua. The results showed that the AERONET AOD trends over all sites in Europe and North America, as well as most sites in Africa and Asia, can be reproduced by MODIS/Aqua. However, disagreement in AOD trends between MODIS and AERONET was found at a few sites in Australia and South America. The AOD trends calculated from AERONET instantaneous data at the MODIS overpass times were consistent with those from AERONET daily data, which suggests that the AOD trends derived from satellite measurements of 1–2 overpasses may be representative of those from daily measurements. 相似文献
ABSTRACTIt has been frequently observed that there are surface cold patches (SCPs) in the Yellow Sea in summer. Although previous studies based on monthly mean temperature distribution found that these SCPs are a result of tidal mixing and tide-induced upwelling, tidal mixing and upwelling alone cannot explain all the occurrences. In our study we found that the three typical patches, namely, the Shandong SCP, the Subei SCP, and the Mokpo SCP, have different temporal patterns over a spring–neap tidal cycle; hence, they have different generating mechanisms. Based on a multiple-year simulation, the latter two show conspicuous spring–neap variations. The highest temperature occurs during the neap tide phase (about two days after a quarter moon). Because of weak upwelling and mixing, strong stratification is established and the SCPs are suppressed or even disappear. The opposite holds for the spring tide phase (about two days after a new or full moon). This is quite different from the Shandong SCP, which does not display a distinct difference between spring and neap tides. Buoy observations and composite analyses with data from the Moderate Resolution Imaging Spectroradiometer (MODIS) further support this conclusion. 相似文献
Brazil's nationally determined contribution (NDC) pledged under the Paris Agreement has marked a new stage in its climate policy towards strengthening low-carbon economic development beyond the recent drastic cuts in emissions from deforestation. Brazil especially means to limit oil consumption driven by future economic growth and to increase energy efficiency and biofuel use in the transport sector. On the other hand, Brazil still aspires to become a major petroleum province given its huge reserves of ‘pre-salt’ oil. This article aims to clarify under what conditions low-carbon economic development and oil exploration can possibly be combined in Brazil and what would be the energy system, environmental and macroeconomic implications of enabling policies for doing so. To address these questions, an energy–economy computable general equilibrium (CGE) model of the Brazilian economy is used to simulate alternative scenarios up to 2030. The results first show that implementing the most recent energy plans, which take into account the new economic reality in Brazil, should lead to over 20% lower domestic CO2 emissions in 2030 than the indicative NDC target, and to the export of the bulk of newfound crude oil. Second, with the same level of oil production, deeper domestic decarbonization, triggered by additional carbon pricing and sustainable efficiency measures, appears achievable with very small gross domestic product (GDP) loss and maximum oil exports, while being aligned with a 2°C emission pathway. However, (i) extra oil exports may induce net additional emissions outside Brazil and be seen as a perverse incentive and (ii) the economic growth strategy based on high oil exports may hinder the necessary diversification of the Brazilian economy.
Key policy insights
Low-carbon development goals will strongly interact with oil policy in Brazil.
The 2030 NDC target should be easy to achieve considering the new economic reality in Brazil.
Deeper domestic decarbonization is achievable with very limited GDP loss and significant oil exports, while being aligned with a 2°C emission pathway.
A broad strategic vision is needed to reconcile climate policy, energy policy and other economic development objectives.
This article shows the potential impact on global GHG emissions in 2030, if all countries were to implement sectoral climate policies similar to successful examples already implemented elsewhere. This assessment was represented in the IMAGE and GLOBIOM/G4M models by replicating the impact of successful national policies at the sector level in all world regions. The first step was to select successful policies in nine policy areas. In the second step, the impact on the energy and land-use systems or GHG emissions was identified and translated into model parameters, assuming that it would be possible to translate the impacts of the policies to other countries. As a result, projected annual GHG emission levels would be about 50 GtCO2e by 2030 (2% above 2010 levels), compared to the 60 GtCO2e in the ‘current policies’ scenario. Most reductions are achieved in the electricity sector through expanding renewable energy, followed by the reduction of fluorinated gases, reducing venting and flaring in oil and gas production, and improving industry efficiency. Materializing the calculated mitigation potential might not be as straightforward given different country priorities, policy preferences and circumstances.
Key policy insights
Considerable emissions reductions globally would be possible, if a selection of successful policies were replicated and implemented in all countries worldwide.
This would significantly reduce, but not close, the emissions gap with a 2°C pathway.
From the selection of successful policies evaluated in this study, those implemented in the sector ‘electricity supply’ have the highest impact on global emissions compared to the ‘current policies’ scenario.
Replicating the impact of these policies worldwide could lead to emission and energy trends in the renewable electricity, passenger transport, industry (including fluorinated gases) and buildings sector, that are close to those in a 2°C scenario.
Using successful policies and translating these to policy impact per sector is a more reality-based alternative to most mitigation pathways, which need to make theoretical assumptions on policy cost-effectiveness.
A 3873-km2 large rectangular area of the Precambrian basement in south-western Sweden has been investigated regarding gross morphology of palaeosurfaces. GIS and digital elevation data were used to construct maps of relative and absolute relief and E–W trending height profiles. Three different palaeosurfaces were recognised and delimited; the very even sub-Cambrian peneplain in the east at an intermediate altitudinal position, an uplifted and broken part of the sub-Cambrian peneplain in the centre at the highest present elevation, and in the western coastal areas a joint-aligned valley landscape with high relative relief, probably an exhumed Mesozoic etch-surface. Phanerozoic faulting has dissected the different palaeosurfaces into tectonic blocks, which are shown from trend surface analysis to be tilted in different directions and to different degrees, characteristic and decisive for the morphological development. 相似文献
The capability of RADARSAT synthetic aperture radar (SAR) for the purpose of snow-line/accumulation area mapping for a temperate alpine glacier is examined. In agreement with other orbital C-band SAR studies, RADARSAT can discriminate between firn and bare ice facies. Limited observations are reported with respect to the electromagnetic variability of the ice facies in the ablation area, but they are inconclusive. Operational considerations are discussed with respect to reconciling the uncertainties of late-summer weather and their possible impact on the dielectric and scattering properties of the glacier surface. Vagaries associated with other glacier settings, mass balance states and their associated facies configurations are discussed including the difficulty of using the transient snow-line to define the equilibrium line and the lower extent of the accumulation area for glaciers where superimposed ice may form. The radar remote-sensing reconnaissance of equilibrium line altitude (ELA) and accumulation area ratio (AAR) for estimating glacier mass balance requires serious consideration in those instances where traditional ground measurements used in the direct glaciological method are absent. However, with respect to the ELA, such estimates can vary depending on the accuracy of the reference digital elevation information. Moreover, for many glacier configurations, where mass balance variations due to altitude are influenced or in some cases completely masked by local balance variations, defining the ELA may be an irreconcilable problem. Using the AAR may be more robust in this regard. It is further determined that the total error inherent in the reconnaissance method would have serious implications for the confident estimation of mass balance normals and climate-related trends if the method were to be utilized over the longer term. 相似文献