气象卫星云图的多分辨小波分解及人工神经网络降水估计研究

采用多分辨小波分析对卫星图象进行预处理 ,在保留其特征信息的同时 ,减小了数据量 ,改善了神经网络训练过程的收敛性能 ,提高了处理速度。采用这一方法根据 GOES- 8的红外亮温图象和气象雷达资料对巴西圣保罗州中部的降水量估计进行了试验 ,取得了良好的效果。     

Revisiting wintertime cold air intrusions at the east of the Andes: propagating features from subtropical Argentina to Peruvian Amazon and relationship with large-scale circulation patterns

This study investigates the spatial and temporal characteristics of cold surges that propagates northward along the eastern flank of the Andes from subtropical to tropical South America analysing wintertime in situ daily minimum temperature observations from Argentina, Bolivia and Peru and ERA-40 reanalysis over the 1975–2001 period. Cold surges usually last 2 or 3 days but are generally less persistent in the southern La Plata basin compared to tropical regions. On average, three to four cold surges are reported each year. Our analysis reveals that 52 % of cold episodes registered in the south of La Plata basin propagate northward to the northern Peruvian Amazon at a speed of around 20 m s^?1. In comparison to cold surges that do not reach the tropical region, we demonstrate that these cold surges are characterized, before they reach the tropical region, by a higher occurrence of a specific circulation pattern associated to southern low-level winds progression toward low latitudes combined with subsidence and dry condition in the middle and low troposphere that reinforce the cold episode through a radiative effect. Finally, the relationship between cold surges and atmosphere dynamics is illustrated for the two most severe cold intrusions that reached the Peruvian and Bolivian Amazon in the last 20 years.     

Soluble organic compounds in fog and cloud droplets: what have we learned over the past few years?

We have recently set up a new procedure for characterising the water soluble organic compounds (WSOC) in fog water, for which information is still rather limited. Fog samples collected during the 1998–1999 fall–winter season in the Po Valley (Italy) were analysed following this procedure, which allows a quantitative determination of three main classes of organic compounds (neutral species, mono- and di-carboxylic acids, polycarboxylic acids), together accounting for ca. 85% of the total WSOC. This procedure also provides information on the main chemical characteristics of these three classes of compounds (functional groups, aliphatic vs. aromatic character, etc.). The enhanced chemical knowledge on fog/cloud chemical composition opens new scenarios as far as chemical and microphysical processes in clouds and fogs are concerned.     

Accounting for uncertainties and time preference in economic analysis of tackling climate change through forestry and selected policy implications for Scotland and Ukraine

The paper discusses the development of economic techniques for dealing with uncertainties in economic analysis of planting trees to mitigate climatic change. In consideration of uncertainty, time preference and intergenerational equity, the traditional cost-benefit analysis framework is challenged with regard to the discounting/non-discounting of carbon uptake benefits, and because it usually uses a constant and positive discount rate. We investigate the influence of various discounting protocols on the outputs of economic analysis. The idea of using the declining discount rate is also considered. Several numerical examples dealing with the analysis of afforestation for carbon sequestration in Scotland and Ukraine are provided. We show that the choice of discounting protocols have a considerable influence on the results of economic analysis, and therefore, on the decision-making processes related to climate change mitigation strategies. The paper concludes with some innovative insights on accounting for uncertainties and time preference in tackling climate change through forestry, several climate policy implications of dealing with uncertainties, and a brief discussion of what the use of different discounting protocols might imply for decision making.     

Cross-national patterns of governance mechanisms in nationally determined contributions (NDCs) under the Paris Agreement

ABSTRACT

The continuous submission and scaling-up of Nationally Determined Contributions (NDCs) constitutes a key feature of the Paris Agreement. In their NDCs, states propose governance mechanisms for implementation of climate action, in turn distinguishing appropriate roles for the state in climate governance. Clarity on Parties’ suggested roles for the state makes explicit assumptions on the premise of climate policy, in turn contributing to enhanced transparency in negotiations on the scaling-up of NDCs. This also speaks to ongoing debates on roles for the state in climate governance literature. This article identifies the governance mechanisms proposed by states in their NDCs and the roles for the state envisioned by those governance mechanisms, and also examines how cross-national patterns of roles for the state break or converge with conventional patterns of international politics. The analysis shows that states propose a plurality of roles, which to different extents may be complementary or conflictual. We conclude that income, region, and the Annexes under the United Nations Framework Convention on Climate Change (UNFCCC) are important for understanding suggested roles for the state, but that there are nuances to be further explored. We argue that this paper has three key findings: i) a majority of states rely on market mechanisms to implement their NDCs while rules on implementation and assessment of market mechanisms are still an outstanding issue in the negotiations, meaning that resolving this issue will be essential; ii) the process for evaluating and assessing qualitative governance mechanisms needs to be specified; and iii) increased awareness of differing views on the state’s roles makes explicit different perspectives on what constitutes an ambitious and legitimate contribution to combating climate change.

Key policy insights

• A majority of states (> 75%) envision the state as regulator (creating and strengthening legislation), market facilitator (creating and maintaining market structures), or facilitator (creating more favourable material conditions for climate-friendly behaviour).

• Greater awareness of differing views on roles for the state can increase understanding of different perspectives on ambition and legitimacy of contributions, in turn facilitating trust in negotiations.

• A distinction between substantive and procedural qualitative governance mechanisms and their function and interaction would facilitate the stocktaking dialogues.

     

Land tenure and REDD+: The good,the bad and the ugly

A number of international donors, national governments and project proponents have begun to lay the groundwork for REDD+, but tenure insecurity – including the potential risks of land grabbing by outsiders and loss of local user rights to forests and forest land – is one of the main reasons that many indigenous and other local peoples have publicly opposed it. Under what conditions is REDD+ a threat to local rights, and under what conditions does it present an opportunity? This article explores these issues based on available data from a global comparative study on REDD+, led by the Center for International Forestry Research, which is studying national policies and processes in 12 countries and 23 REDD+ projects in 6 countries. The article analyses how tenure concerns are being addressed at both national and project level in emerging REDD+ programs. The findings suggest that in most cases REDD+ has clearly provided some new opportunities for securing local tenure rights, but that piecemeal interventions by project proponents at the local level are insufficient in the absence of broader, national programs for land tenure reform. The potential for substantial changes in the status quo appear unlikely, though Brazil – the only one with such a national land tenure reform program – offers useful insights. Land tenure reform – the recognition of customary rights in particular – and a serious commitment to REDD+ both challenge the deep-rooted economic and political interests of ‘business as usual’.     

Geostrophic Adjustment Problems in a Polar Basin

The geostrophic adjustment of a homogeneous fluid in a circular basin with idealized topography is addressed using a numerical ocean circulation model and analytical process models. When the basin is rotating uniformly, the adjustment takes place via excitation of boundary propagating waves and when topography is present, via topographic Rossby waves. In the numerically derived solution, the waves are damped because of bottom friction, and a quasi-steady geostrophically balanced state emerges that subsequently spins-down on a long time scale. On the f-plane, numerical quasi-steady state solutions are attained well before the system's mechanical energy is entirely dissipated by friction. It is demonstrated that the adjusted states emerging in a circular basin with a step escarpment or a top hat ridge, centred on a line of symmetry, are equivalent to that in a uniform depth semicircular basin, for a given initial condition. These quasi-steady solutions agree well with linear analytical solutions for the latter case in the inviscid limit.

On the polar plane, the high latitude equivalent to the β-plane, no quasi-steady adjusted state emerges from the adjustment process. At intermediate time scales, after the fast Poincaré and Kelvin waves are damped by friction, the solutions take the form of steady-state adjusted solutions on the f-plane. At longer time scales, planetary waves control the flow evolution. An interesting property of planetary waves on a polar plane is a nearly zero eastward group velocity for the waves with a radial mode higher than two and the resulting formation of eddy-like small-scale barotropic structures that remain trapped near the western side of topographic features.

RÉSUMÉ?Traduit par la rédaction] Nous étudions l'ajustement géostrophique d'un fluide homogène dans un bassin circulaire ayant une topographie idéalisée à l'aide d'un modèle numérique de circulation océanique et de modèles analytiques de processus. Quand le bassin est en rotation uniforme, l'ajustement se fait par l'excitation d'ondes de propagation aux limites, et en présence de topographie, par des ondes de Rossby topographiques. Dans la solution numériquement dérivée, les ondes sont amorties à cause frottement contre le fond, et un état quasi-stable géostrophiquement équilibré s’établit pour ensuite décélérer sur une longue période de temps. Sur le plan f, les solutions numériques d’états quasi-stables sont atteintes bien avant que l’énergie du système mécanique soit entièrement dissipée par le frottement. Nous démontrons que les états ajustés apparaissant dans un bassin circulaire avec un accore en forme de marche ou une crête en forme de merlon, centrés sur une ligne de symétrie, sont équivalents à ceux d'un bassin semi-circulaire de profondeur uniforme pour une condition initiale donnée. Les solutions quasi-stables s'accordent bien avec les solutions analytiques linéaires pour le dernier cas dans la limite de la non-viscosité.

Sur le plan polaire, la haute latitude équivalente au plan β, le processus d'ajustement n'aboutit à aucun état ajusté quasi-stable. Aux échelles de temps intermédiaires, après l'amortissement des ondes rapides de Poincaré et Kelvin par le frottement, les solutions prennent la forme de solutions ajustées d’états stables sur le plan f. Aux échelles de temps plus longues, les ondes planétaires déterminent l’évolution de l’écoulement. Une propriété intéressante des ondes planétaires sur un plan polaire est une vitesse de groupe presque nulle vers l'est pour les ondes ayant un mode radial plus grand que deux et la formation résultante de structures barotropiques de petite échelle de type remous qui demeurent emprisonnées près du bord ouest des caractéristiques topographiques.     

Enhancing the relevance of Shared Socioeconomic Pathways for climate change impacts,adaptation and vulnerability research

This paper discusses the role and relevance of the shared socioeconomic pathways (SSPs) and the new scenarios that combine SSPs with representative concentration pathways (RCPs) for climate change impacts, adaptation, and vulnerability (IAV) research. It first provides an overview of uses of social–environmental scenarios in IAV studies and identifies the main shortcomings of earlier such scenarios. Second, the paper elaborates on two aspects of the SSPs and new scenarios that would improve their usefulness for IAV studies compared to earlier scenario sets: (i) enhancing their applicability while retaining coherence across spatial scales, and (ii) adding indicators of importance for projecting vulnerability. The paper therefore presents an agenda for future research, recommending that SSPs incorporate not only the standard variables of population and gross domestic product, but also indicators such as income distribution, spatial population, human health and governance.     

Getting Lost in Cities: Spatial Patterns of Phonetically Confusing Street Names

A large street network is likely to contain duplicated or similar sounding street names. These conflicts can cause confusion in communication between people or in machine‐human interaction. Municipal authorities have begun to see the importance of uncovering these existing street name conflicts and mitigating future ones, for improved record keeping, emergency response, etc. However the commonly used Soundex phonetic algorithm is generally considered to produce poor similarity results in terms of uncovering street name conflicts. This study reports on a new fusion algorithm that combines phonetic methods and approximate string matching for street names, weighted by street type suffix (Avenue, Boulevard, Court, etc.), to quantitatively measure the collision/confusion potential presented by a pair of streets. This algorithm is then applied to the entire street network in Greater Melbourne, Australia, and the pattern of collisions at various spatial scales, and within municipalities, is mapped. The goal of this work is to produce better tools that can aid policy makers, administrators and industries dealing with location‐based services to make better decisions when assigning and disambiguating street names.     

Real-time cycle slip detection in triple-frequency GNSS

The modernization of the global positioning system and the advent of the European project Galileo will lead to a multifrequency global navigation satellite system (GNSS). The presence of new frequencies introduces more degrees of freedom in the GNSS data combination. We define linear combinations of GNSS observations with the aim to detect and correct cycle slips in real time. In particular, the detection is based on five geometry-free linear combinations used in three cascading steps. Most of the jumps are detected in the first step using three minimum-noise combinations of phase and code observations. The remaining jumps with very small amplitude are detected in the other two steps by means of two-tailored linear combinations of phase observations. Once the epoch of the slip has been detected, its amplitude is estimated using other linear combinations of phase observations. These combinations are defined with the aim of discriminating between the possible combinations of jump amplitudes in the three carriers. The method has been tested on simulated data and 1-second triple-frequency undifferenced GPS data coming from a friendly multipath environment. Results show that the proposed method is able to detect and repair all combinations of cycle slips in the three carriers.