Aviation is and remains one of the key infrastructures of our modern world, and recently aviation vulnerability with regards to natural hazards was demonstrated. The scientific studies presented in this special issue should support the capabilities to respond to disasters effectively and efficiently, minimizing system downtimes and thus economic damage while enhancing the safety of millions of passengers. In particular, this special issue focuses on the aviation hazard category that is referred to as “airborne hazards” (environmental emergency scenarios), including, for example, volcanic eruptions, nuclear accidents, forest fires, and desert dust events.

The augmented use of numerical prediction models and their combination with observational products from ground and satellite platforms allows a holistic representation of the state of the environment and also improvement of useful and efficient early-warning information in case of an emergency and predictions of the hazardous event and its impact. Papers should focus on the tailoring of relevant Earth observations in the frame of early-warning systems and assimilation and evaluation of Earth observations with dispersion models.

The special issue is mainly based on but not limited to the developments and advancements made under the EUNADICS-AV H2020 project.

Extreme hydro-meteorological events (e.g., storms, storm surges, floods, extreme waves, marine heatwaves) have caused serious damage to society and infrastructures at coastal areas during the past decades. The continued growth in commerce, infrastructure, and population and the impacts of climate change on coastal hazards are all contributing to an increase in the risk associated with living and working at the coast. These extreme events are caused by interactions of large- and small-scale forcing mechanisms, sequences of weather anomalies, and non-linear combined atmosphere-wave-circulation-hydrologic-morphologic responses. They can cause tremendous economic losses at coastal areas, leading to substantial damage to infrastructure and ecosystems. It is, thus, important to gain improved scientific understanding on the physical drivers controlling such extreme events, their occurrence and frequency, and the resulting impact on coastal hazards. This gain in knowledge will allow the improvement of predictive skills at daily to decadal timescales. However, state-of-the-art numerical predictions and projections are not skilful enough yet for stakeholders, water managers, and policy makers. The full capabilities of hindcasting and predicting weather-driven extremes have not been realized yet due to systematic errors in the simulation of feedbacks between atmosphere, terrestrial, and oceanic systems, particularly for coastal areas, with enhanced difficulties in representing multiscale processes and discrepancies in the modelled physics.

This special issue deals with coastal hazards and hydro-meteorological extremes, tackling coastal impacts on a broad range of environmental and economic systems. The focus will be on physical hazard drivers and hydro-meteorological extreme events, identifying the key physical processes and/or model resolutions for resolving their interactions, as well as examining their predictability at multiple timescales. Considered topics include, but are not limited to, estuarine/deltaic dynamics, hydrologic controls on sediment supply and salinity intrusion, ecosystem responses and morphologic evolution under natural and anthropogenic changes, cascading/compounding effects of extremes, and resulting coastal impacts. Papers on modelling improvements for simulating and predicting extreme events and coastal hazards and assessing their socioeconomic impact are also encouraged.

Droughts are among the most damaging and least understood of all so-called natural hazards. Droughts often lead to long-lasting and cascading impacts on different sectors across multiple spatial scales. Because the impacts of drought are less direct and immediately visible than the impacts of events such as floods or storms, drought has, for a long time, received less attention in disaster research and risk reduction. The likelihood of such impacts, understood as drought risk, is caused by the combination of drought hazard, exposure, and a broad range of underlying vulnerability factors. To support the identification and planning of drought risk reduction, risk transfer, and adaptation options, information on the drivers, patterns, and dynamics of current and future drought risk is needed in all dimensions of drought hazard, exposure, and system vulnerability. We aim at soliciting contributions (commentaries, review articles, original research articles) for a special issue on drought vulnerability, risk, and impact assessments that aim to inform drought risk management, risk transfer, and adaptation policy and action in the context of global environmental change and societal transformation.

Papers may consider the following topics:

• drought vulnerability, risk, or impact assessments (qualitative, quantitative, or mixed-method approaches) for different sectors (e.g. agriculture, energy production, transportation, tourism) and systems (e.g. ecosystems), at different spatial (local to global) and/or temporal scales (past trends, current patterns, future scenarios);
• assessment and communication of uncertainties in drought risk assessments (and risk components);
• validation strategies of the outcomes of drought risk assessments (e.g. through loss and damage information or expert-based);
• validation of the utility of drought vulnerability, risk, and impact assessments for climate action, resilience-building, and (inter)national climate policy;
• emergent risks associated with droughts (including in the focus of compound hazards), the multiple interconnections that influence systemic drought risks, and the cascading effects of droughts;
• studies that aim to bridge the ``science to policy-action'' gap by providing science-based solutions to the international community, nations, and communities on how to build resilience.

A series of contributions will be drawn from the EGU2020: Sharing Geoscience Online session ``Drought risk, vulnerability and impact assessment: achievements and future directions'' held on 8 May 2020; however, unsolicited contributions are also highly encouraged. The guest editors aim for diversity and balance in contributions and authors. We especially encourage researchers from developing countries, women, and underrepresented minorities to contribute to this special issue.

Coastal cities are hotspots of risks related to natural hazards. Already today, many of these cities face high economic and non-economic losses from disasters and creeping environmental changes. However, risks in coastal cities are expected to rise even further, fuelled by the interplay of two global mega-trends: climate change and continued coastal urbanization. The question of how to adapt cities to the hazards of the future is therefore of great concern – not only for scientists, but also for policy makers and risk practitioners. The relevance of this question even increases when considering the central role of coastal cities in economies and societies at the global scale, for instance, in terms of trade, transport, and culture.

However, a number of important scientific knowledge gaps persist with regards to risk assessment and adaptation analysis in coastal cities. While the assessment of future risk trends in these cities is predominantly focused on scenarios of future hazards (sea level rise, floods, typhoons, etc.), scenarios of socio-economic changes and hence future trends in exposure and vulnerability are typically not part of the picture due to a lack either of awareness or adequate methods and data. This lack is significant and leads to potentially flawed and imprecise assessments of future risk trends and eventually adaptation needs. Secondly, knowledge on the feasibility of different – often competing – adaptation options remains thin. It is too often based on a reductionist set of evaluation criteria, e.g. economic costs and benefits, and a view towards singular adaptation measures, e.g. hard coastal protection. Integrative and comparative assessments that evaluate different adaptation options (e.g. retreat vs. flood accommodation) against a wider set of criteria such as social acceptance or political feasibility are still poorly developed. Thirdly, scientific engagement with coastal urban risk too often remains within siloes of different disciplines (engineering, sociology, economics, planning, etc.). This hampers interdisciplinary assessments and leads to significant blind spots, e.g. with respect to private sector adaptation or collective action for adaptation across different groups of actors.

The special issue aims at making a significant contribution towards closing these knowledge gaps. It is open to theoretical, methodological, and empirical contributions and will combine a mixture of research articles, review articles, and brief communications. Submissions for all these manuscript types are therefore welcome. Both local case studies from across the globe as well as regional- or and global-level perspectives are invited. The special issue is particularly interested in contributions that draw on combined perspectives from different disciplines. A particular focus will be on coastal cities with high growth dynamics and adaptation pressure, as can be observed in many transition economies of Asia and Africa.

The Hydrological cycle in the Mediterranean Experiment (HyMeX, https://www.hymex.org/) programme is a 10-year concerted effort at the international level started in 2010 with aims to advance the understanding of the water cycle, and with emphases on the predictability and evolution of high-impact weather events, as well as on evaluating social vulnerability to these extreme events. The special issue is jointly organized between the Atmospheric Chemistry and Physics, Hydrology and Earth System Sciences, Ocean Science, Natural Hazards and Earth System Sciences, Atmospheric Measurement Techniques, and Geoscientific Model Development journals. It aims at gathering contributions to the areas of understanding, modelling, and predicting at various timescales and spatial scales of the Mediterranean water cycle and its related extreme events, including cyclones, heavy precipitation, flash floods and impacts, drought and water resources, strong winds, and dense water formation. The special issue is not limited to studies conducted within HyMeX: any multiscale or multidisciplinary approaches related to the Mediterranean water cycle are encouraged.

Climate change impacts on the water cycle have become more evident during the last decade with several parts of the hydrological cycle affected. Consequently, the increase in natural hazards, especially droughts and floods, directly affect society, e.g. by water stress, urban floods, limitations in irrigation and many more. In order to cope with these impacts, the associated risks need to be analysed and prioritized. Based on the risk assessment, measures can be derived to mitigate the impact of climate and hydrological change on society. Therefore, this special issue aims at research following the modelling and analysis chain climate–hydrology–risks–measures. The research topics should also address their direct applicability to stakeholders in order to provide established transferability links of research results to practical implementation. Six hotspot regions in Europe have been chosen, which are prone to a large variety of natural hazards due to climate change, such as droughts and floods: (1) Bergen, Norway; (2) Cyprus; (3) Tagus River basin, Portugal; (4) Wupper River basin, Germany; (5) the Veluwe, the Netherlands; (6) and Barcelona and nearby coastal cities, Spain.

The purpose of the special issue is to present recent advances and future challenges in drought and water scarcity monitoring, modelling, and prediction capabilities to improve risk management, adaptation strategies, and resilience to such adverse events.
This special issue welcomes, but is not limited to, the most innovative contributions to EGU 2019 session HS4.1.1/NH1.31, mainly addressing the following topics:
drought monitoring tools able to merge multiple information sources, including satellite-based data describing vegetation status and evapotranspiration;
land surface hydrologic models driven by remote-sensing data, reanalysis datasets, or climate forecasts to investigate current or future drought impacts on water resources;
influence of internal ocean-atmosphere variability on the occurrence and magnitude of drought phenomena;
role of climate models in investigating the spatio-temporal evolution of drought under climate change conditions;
statistical approaches for drought characterization coupled with uncertainty analysis.

Remote sensing and Earth observations (EOs) are used increasingly in different phases of risk management and in development cooperation, due to the challenges posed by contemporary issues such as climate change, population pressure, and increasingly complex social interactions. EO-based applications have a number of advantages over traditional fieldwork expeditions including safety, the provision a synoptic view of the region of interest, the availability of data extending back several years, and, in many cases, cost savings. Fortunately, the advent of new, more powerful sensors and more finely tuned detection algorithms provides the opportunity to image, assess, and quantify natural hazards, their consequences, and vulnerable regions more comprehensively than ever before.

For these reasons, civil protection organizations, development agencies, and space agencies now permanently use applications of EO data to risk management. During the preparedness and prevention phase, EO has proven invaluable, especially in data-scarce environments, for hazard, vulnerability, and risk mapping. EO data are applicable during both the forecasting and early emergency response phases, thanks to the possibility of rapid mapping and interpretation. EO data are also increasingly being used for planning operations during the recovery phase. This special issue is dedicated to multidisciplinary contributions in particular focused on the demonstration of the benefit of the use of EO for risk management. The research presented might focus on

• addressed value of EO data in risk/hazard forecasting models (observation of possible precursory events and evaluation of potential predictive capabilities);
• innovative applications of EO data for rapid mapping;
• innovative applications of EO data for hazard, vulnerability, and risk mapping;
• innovative applications of EO data for the post-disaster recovery phase;
• innovative applications in support of disaster risk reduction strategies (e.g. landscape planning);
• development of tools and platforms for assessment and validation of hazard/risk models.

The use of different types of remote sensing observations (e.g. thermal, visual, radar, laser, and/or the fusion of these) might be considered, with an evaluation of their respective pros and cons. Evaluation of current sensors, data capabilities, and algorithms will be welcomed, as will suggestions for future sensor considerations, algorithm developments, and opportunities for emergency management agency buy-in. Authors are discouraged from submitting solely engineering papers that do not also deal with remote applications for natural hazard studies.

A note: in 2017, a special issue on the use of remotely piloted aircraft systems (RPAS) in monitoring applications and management of natural hazards was published in NHESS (https://www.nat-hazards-earth-syst-sci.net/special_issue859.html). The authors should be aware that this is not a special issue again on RPAS; the number of papers on this technique will be limited while focusing more on other types of platforms.

Fire is an essential feature of terrestrial ecosystems and plays an important role in the Earth system. Fires are regulated by climate, vegetation characteristics, and human activity and also feedback to them in multiple ways. For example, fires can shape vegetation composition and structure; adjust land carbon, nutrient, water, and energy cycles; change atmospheric composition, chemistry, and physics; and affect air quality and human health. Elevated fire activity in 2019 across the arctic, Amazon, and other regions underscores the urgency of a quantitative understanding of fire as an Earth system process that interacts with vegetation, climate, and humans. The EGU2020 B3.17 session on the role of fire in the Earth system received the most abstracts in the Biogeosciences division this year and was highly attended during the live chat. The abstracts cover several aspects of interactions between fire and the biosphere, atmosphere, and humans across various temporal and spatial scales using modelling, field and laboratory observations, and remote sensing. Given that the topic is highly interdisciplinary and overarching, we propose an inter-journal (ESD/BG/ACP/GMD/NHESS) special issue for this session with ESD as the lead journal, and we also encourage the submission of topic-related studies outside the EGU fire session. The special issue will bring together new advances in understanding the feedbacks and interactions between fire and other components of the Earth system at all temporal and spatial scales using various methods, including (1) impacts of fire on weather, climate, and atmospheric chemistry; (2) interactions between fire, the biogeochemical cycle, vegetation composition and structure, and land water and energy budgets; (3) influence of humans on fire and vice versa; (4) fire characteristics (e.g., fire duration, emission factor, emission height, smoke transport); (5) spatial and temporal changes of fires in the past, present, and future; (6) fire products and models, their validation, and error/bias assessment; and (7) analytical tools designed to enhance situational awareness among fire practitioners and early warning systems, addressing specific needs of operational fire behaviour modelling.

Compound weather and climate events refer to combinations of multiple weather and climate drivers and/or hazards that lead to potentially large impacts. Compound events encompass a highly diverse set of events including concurrent climate extremes but also an array of nonstandard high-impact events. Consequently, research on compound events requires expertise from a variety of disciplines such as climate science, hydrology, impact modelling, engineering, and statistics, among others. The European COST Action DAMOCLES (http://damocles.compoundevents.org) provides a platform for compound event research and for generating synergies between the different research domains. This inter-journal special issue will serve as an outlet for the work within DAMOCLES and aims to advance our understanding of different aspects of compound events, including present-day and future risk assessments of such events, modelling of individual compound events, bottom-up approaches to identify new types of compound events, and novel model evaluation techniques. It is open for all submissions within its scope.

The city of Venice and its lagoon represent great historic, ecologic, and economic interest. The most known and debated symptom of the frailty of the Venetian lagoon system are the periodic flooding events that afflict Venice, locally referred to as “acqua alta”. An increased impact of storm surges on Venice has been observed in recent decades, and the future rise of sea level as a consequence of global warming may lead to dramatic impacts on both the historical centre and the surrounding ecosystem. Local changes such as subsidence must also be considered. A large amount of scientific literature has been devoted at understanding the dynamics leading to the flooding of Venice, predicting the timing and intensity of the events and describing changes in their frequency and intensity under future global warming scenarios.

This special issue aims to critically discuss the current understanding of the Venice flooding phenomenon. It is structured with a focus on “its meteorological and climatic precursors, its prediction, and its historical and expected future variations under a globally changing climate”. The synthesis is oriented toward clarifying consolidated knowledge, highlighting gaps of knowledge as well as identifying major opportunities for progress. This special issue is composed of three review papers, addressing three different and complementary aspects of the hazards causing the flood of Venice. Review paper 1 describes the tools that have been developed and are currently used for the prediction of the sea level events, which are used for warning the population and will be needed for managing the movable barriers to prevent future floods. Review paper 2 describes the factors leading to extreme events, their past evolution, and expected future levels under a climate change perspective. Review paper 3 considers the evolution of the mean relative sea level, whose past increase and future expected positive rate are the major causes of the increasing flood hazard level. The editorial provides an introduction to the three reviews, where the critical issues posed by the floods of Venice are summarized and the basic meteorological and oceanographic processes and factors involved (that are common to the three reviews) are introduced.

Coastal cities are hotspots of risks related to natural hazards. Already today, many of these cities face high economic and non-economic losses from disasters and creeping environmental changes. However, risks in coastal cities are expected to rise even further, fuelled by the interplay of two global mega-trends: climate change and continued coastal urbanization. The question of how to adapt cities to the hazards of the future is therefore of great concern – not only for scientists, but also for policy makers and risk practitioners. The relevance of this question even increases when considering the central role of coastal cities in economies and societies at the global scale, for instance, in terms of trade, transport, and culture.

However, a number of important scientific knowledge gaps persist with regards to risk assessment and adaptation analysis in coastal cities. While the assessment of future risk trends in these cities is predominantly focused on scenarios of future hazards (sea level rise, floods, typhoons, etc.), scenarios of socio-economic changes and hence future trends in exposure and vulnerability are typically not part of the picture due to a lack either of awareness or adequate methods and data. This lack is significant and leads to potentially flawed and imprecise assessments of future risk trends and eventually adaptation needs. Secondly, knowledge on the feasibility of different – often competing – adaptation options remains thin. It is too often based on a reductionist set of evaluation criteria, e.g. economic costs and benefits, and a view towards singular adaptation measures, e.g. hard coastal protection. Integrative and comparative assessments that evaluate different adaptation options (e.g. retreat vs. flood accommodation) against a wider set of criteria such as social acceptance or political feasibility are still poorly developed. Thirdly, scientific engagement with coastal urban risk too often remains within siloes of different disciplines (engineering, sociology, economics, planning, etc.). This hampers interdisciplinary assessments and leads to significant blind spots, e.g. with respect to private sector adaptation or collective action for adaptation across different groups of actors.

The special issue aims at making a significant contribution towards closing these knowledge gaps. It is open to theoretical, methodological, and empirical contributions and will combine a mixture of research articles, review articles, and brief communications. Submissions for all these manuscript types are therefore welcome. Both local case studies from across the globe as well as regional- or and global-level perspectives are invited. The special issue is particularly interested in contributions that draw on combined perspectives from different disciplines. A particular focus will be on coastal cities with high growth dynamics and adaptation pressure, as can be observed in many transition economies of Asia and Africa.

Extreme hydro-meteorological events (e.g., storms, storm surges, floods, extreme waves, marine heatwaves) have caused serious damage to society and infrastructures at coastal areas during the past decades. The continued growth in commerce, infrastructure, and population and the impacts of climate change on coastal hazards are all contributing to an increase in the risk associated with living and working at the coast. These extreme events are caused by interactions of large- and small-scale forcing mechanisms, sequences of weather anomalies, and non-linear combined atmosphere-wave-circulation-hydrologic-morphologic responses. They can cause tremendous economic losses at coastal areas, leading to substantial damage to infrastructure and ecosystems. It is, thus, important to gain improved scientific understanding on the physical drivers controlling such extreme events, their occurrence and frequency, and the resulting impact on coastal hazards. This gain in knowledge will allow the improvement of predictive skills at daily to decadal timescales. However, state-of-the-art numerical predictions and projections are not skilful enough yet for stakeholders, water managers, and policy makers. The full capabilities of hindcasting and predicting weather-driven extremes have not been realized yet due to systematic errors in the simulation of feedbacks between atmosphere, terrestrial, and oceanic systems, particularly for coastal areas, with enhanced difficulties in representing multiscale processes and discrepancies in the modelled physics.

This special issue deals with coastal hazards and hydro-meteorological extremes, tackling coastal impacts on a broad range of environmental and economic systems. The focus will be on physical hazard drivers and hydro-meteorological extreme events, identifying the key physical processes and/or model resolutions for resolving their interactions, as well as examining their predictability at multiple timescales. Considered topics include, but are not limited to, estuarine/deltaic dynamics, hydrologic controls on sediment supply and salinity intrusion, ecosystem responses and morphologic evolution under natural and anthropogenic changes, cascading/compounding effects of extremes, and resulting coastal impacts. Papers on modelling improvements for simulating and predicting extreme events and coastal hazards and assessing their socioeconomic impact are also encouraged.

The city of Venice and its lagoon represent great historic, ecologic, and economic interest. The most known and debated symptom of the frailty of the Venetian lagoon system are the periodic flooding events that afflict Venice, locally referred to as “acqua alta”. An increased impact of storm surges on Venice has been observed in recent decades, and the future rise of sea level as a consequence of global warming may lead to dramatic impacts on both the historical centre and the surrounding ecosystem. Local changes such as subsidence must also be considered. A large amount of scientific literature has been devoted at understanding the dynamics leading to the flooding of Venice, predicting the timing and intensity of the events and describing changes in their frequency and intensity under future global warming scenarios.

This special issue aims to critically discuss the current understanding of the Venice flooding phenomenon. It is structured with a focus on “its meteorological and climatic precursors, its prediction, and its historical and expected future variations under a globally changing climate”. The synthesis is oriented toward clarifying consolidated knowledge, highlighting gaps of knowledge as well as identifying major opportunities for progress. This special issue is composed of three review papers, addressing three different and complementary aspects of the hazards causing the flood of Venice. Review paper 1 describes the tools that have been developed and are currently used for the prediction of the sea level events, which are used for warning the population and will be needed for managing the movable barriers to prevent future floods. Review paper 2 describes the factors leading to extreme events, their past evolution, and expected future levels under a climate change perspective. Review paper 3 considers the evolution of the mean relative sea level, whose past increase and future expected positive rate are the major causes of the increasing flood hazard level. The editorial provides an introduction to the three reviews, where the critical issues posed by the floods of Venice are summarized and the basic meteorological and oceanographic processes and factors involved (that are common to the three reviews) are introduced.

Droughts are among the most damaging and least understood of all so-called natural hazards. Droughts often lead to long-lasting and cascading impacts on different sectors across multiple spatial scales. Because the impacts of drought are less direct and immediately visible than the impacts of events such as floods or storms, drought has, for a long time, received less attention in disaster research and risk reduction. The likelihood of such impacts, understood as drought risk, is caused by the combination of drought hazard, exposure, and a broad range of underlying vulnerability factors. To support the identification and planning of drought risk reduction, risk transfer, and adaptation options, information on the drivers, patterns, and dynamics of current and future drought risk is needed in all dimensions of drought hazard, exposure, and system vulnerability. We aim at soliciting contributions (commentaries, review articles, original research articles) for a special issue on drought vulnerability, risk, and impact assessments that aim to inform drought risk management, risk transfer, and adaptation policy and action in the context of global environmental change and societal transformation.

Papers may consider the following topics:

• drought vulnerability, risk, or impact assessments (qualitative, quantitative, or mixed-method approaches) for different sectors (e.g. agriculture, energy production, transportation, tourism) and systems (e.g. ecosystems), at different spatial (local to global) and/or temporal scales (past trends, current patterns, future scenarios);
• assessment and communication of uncertainties in drought risk assessments (and risk components);
• validation strategies of the outcomes of drought risk assessments (e.g. through loss and damage information or expert-based);
• validation of the utility of drought vulnerability, risk, and impact assessments for climate action, resilience-building, and (inter)national climate policy;
• emergent risks associated with droughts (including in the focus of compound hazards), the multiple interconnections that influence systemic drought risks, and the cascading effects of droughts;
• studies that aim to bridge the ``science to policy-action'' gap by providing science-based solutions to the international community, nations, and communities on how to build resilience.

A series of contributions will be drawn from the EGU2020: Sharing Geoscience Online session ``Drought risk, vulnerability and impact assessment: achievements and future directions'' held on 8 May 2020; however, unsolicited contributions are also highly encouraged. The guest editors aim for diversity and balance in contributions and authors. We especially encourage researchers from developing countries, women, and underrepresented minorities to contribute to this special issue.

Fire is an essential feature of terrestrial ecosystems and plays an important role in the Earth system. Fires are regulated by climate, vegetation characteristics, and human activity and also feedback to them in multiple ways. For example, fires can shape vegetation composition and structure; adjust land carbon, nutrient, water, and energy cycles; change atmospheric composition, chemistry, and physics; and affect air quality and human health. Elevated fire activity in 2019 across the arctic, Amazon, and other regions underscores the urgency of a quantitative understanding of fire as an Earth system process that interacts with vegetation, climate, and humans. The EGU2020 B3.17 session on the role of fire in the Earth system received the most abstracts in the Biogeosciences division this year and was highly attended during the live chat. The abstracts cover several aspects of interactions between fire and the biosphere, atmosphere, and humans across various temporal and spatial scales using modelling, field and laboratory observations, and remote sensing. Given that the topic is highly interdisciplinary and overarching, we propose an inter-journal (ESD/BG/ACP/GMD/NHESS) special issue for this session with ESD as the lead journal, and we also encourage the submission of topic-related studies outside the EGU fire session. The special issue will bring together new advances in understanding the feedbacks and interactions between fire and other components of the Earth system at all temporal and spatial scales using various methods, including (1) impacts of fire on weather, climate, and atmospheric chemistry; (2) interactions between fire, the biogeochemical cycle, vegetation composition and structure, and land water and energy budgets; (3) influence of humans on fire and vice versa; (4) fire characteristics (e.g., fire duration, emission factor, emission height, smoke transport); (5) spatial and temporal changes of fires in the past, present, and future; (6) fire products and models, their validation, and error/bias assessment; and (7) analytical tools designed to enhance situational awareness among fire practitioners and early warning systems, addressing specific needs of operational fire behaviour modelling.

Compound weather and climate events refer to combinations of multiple weather and climate drivers and/or hazards that lead to potentially large impacts. Compound events encompass a highly diverse set of events including concurrent climate extremes but also an array of nonstandard high-impact events. Consequently, research on compound events requires expertise from a variety of disciplines such as climate science, hydrology, impact modelling, engineering, and statistics, among others. The European COST Action DAMOCLES (http://damocles.compoundevents.org) provides a platform for compound event research and for generating synergies between the different research domains. This inter-journal special issue will serve as an outlet for the work within DAMOCLES and aims to advance our understanding of different aspects of compound events, including present-day and future risk assessments of such events, modelling of individual compound events, bottom-up approaches to identify new types of compound events, and novel model evaluation techniques. It is open for all submissions within its scope.

Remote sensing and Earth observations (EOs) are used increasingly in different phases of risk management and in development cooperation, due to the challenges posed by contemporary issues such as climate change, population pressure, and increasingly complex social interactions. EO-based applications have a number of advantages over traditional fieldwork expeditions including safety, the provision a synoptic view of the region of interest, the availability of data extending back several years, and, in many cases, cost savings. Fortunately, the advent of new, more powerful sensors and more finely tuned detection algorithms provides the opportunity to image, assess, and quantify natural hazards, their consequences, and vulnerable regions more comprehensively than ever before.

For these reasons, civil protection organizations, development agencies, and space agencies now permanently use applications of EO data to risk management. During the preparedness and prevention phase, EO has proven invaluable, especially in data-scarce environments, for hazard, vulnerability, and risk mapping. EO data are applicable during both the forecasting and early emergency response phases, thanks to the possibility of rapid mapping and interpretation. EO data are also increasingly being used for planning operations during the recovery phase. This special issue is dedicated to multidisciplinary contributions in particular focused on the demonstration of the benefit of the use of EO for risk management. The research presented might focus on

• addressed value of EO data in risk/hazard forecasting models (observation of possible precursory events and evaluation of potential predictive capabilities);
• innovative applications of EO data for rapid mapping;
• innovative applications of EO data for hazard, vulnerability, and risk mapping;
• innovative applications of EO data for the post-disaster recovery phase;
• innovative applications in support of disaster risk reduction strategies (e.g. landscape planning);
• development of tools and platforms for assessment and validation of hazard/risk models.

The use of different types of remote sensing observations (e.g. thermal, visual, radar, laser, and/or the fusion of these) might be considered, with an evaluation of their respective pros and cons. Evaluation of current sensors, data capabilities, and algorithms will be welcomed, as will suggestions for future sensor considerations, algorithm developments, and opportunities for emergency management agency buy-in. Authors are discouraged from submitting solely engineering papers that do not also deal with remote applications for natural hazard studies.

A note: in 2017, a special issue on the use of remotely piloted aircraft systems (RPAS) in monitoring applications and management of natural hazards was published in NHESS (https://www.nat-hazards-earth-syst-sci.net/special_issue859.html). The authors should be aware that this is not a special issue again on RPAS; the number of papers on this technique will be limited while focusing more on other types of platforms.

Climate change impacts on the water cycle have become more evident during the last decade with several parts of the hydrological cycle affected. Consequently, the increase in natural hazards, especially droughts and floods, directly affect society, e.g. by water stress, urban floods, limitations in irrigation and many more. In order to cope with these impacts, the associated risks need to be analysed and prioritized. Based on the risk assessment, measures can be derived to mitigate the impact of climate and hydrological change on society. Therefore, this special issue aims at research following the modelling and analysis chain climate–hydrology–risks–measures. The research topics should also address their direct applicability to stakeholders in order to provide established transferability links of research results to practical implementation. Six hotspot regions in Europe have been chosen, which are prone to a large variety of natural hazards due to climate change, such as droughts and floods: (1) Bergen, Norway; (2) Cyprus; (3) Tagus River basin, Portugal; (4) Wupper River basin, Germany; (5) the Veluwe, the Netherlands; (6) and Barcelona and nearby coastal cities, Spain.

The purpose of the special issue is to present recent advances and future challenges in drought and water scarcity monitoring, modelling, and prediction capabilities to improve risk management, adaptation strategies, and resilience to such adverse events.
This special issue welcomes, but is not limited to, the most innovative contributions to EGU 2019 session HS4.1.1/NH1.31, mainly addressing the following topics:
drought monitoring tools able to merge multiple information sources, including satellite-based data describing vegetation status and evapotranspiration;
land surface hydrologic models driven by remote-sensing data, reanalysis datasets, or climate forecasts to investigate current or future drought impacts on water resources;
influence of internal ocean-atmosphere variability on the occurrence and magnitude of drought phenomena;
role of climate models in investigating the spatio-temporal evolution of drought under climate change conditions;
statistical approaches for drought characterization coupled with uncertainty analysis.

Aviation is and remains one of the key infrastructures of our modern world, and recently aviation vulnerability with regards to natural hazards was demonstrated. The scientific studies presented in this special issue should support the capabilities to respond to disasters effectively and efficiently, minimizing system downtimes and thus economic damage while enhancing the safety of millions of passengers. In particular, this special issue focuses on the aviation hazard category that is referred to as “airborne hazards” (environmental emergency scenarios), including, for example, volcanic eruptions, nuclear accidents, forest fires, and desert dust events.

The augmented use of numerical prediction models and their combination with observational products from ground and satellite platforms allows a holistic representation of the state of the environment and also improvement of useful and efficient early-warning information in case of an emergency and predictions of the hazardous event and its impact. Papers should focus on the tailoring of relevant Earth observations in the frame of early-warning systems and assimilation and evaluation of Earth observations with dispersion models.

The special issue is mainly based on but not limited to the developments and advancements made under the EUNADICS-AV H2020 project.

The Hydrological cycle in the Mediterranean Experiment (HyMeX, https://www.hymex.org/) programme is a 10-year concerted effort at the international level started in 2010 with aims to advance the understanding of the water cycle, and with emphases on the predictability and evolution of high-impact weather events, as well as on evaluating social vulnerability to these extreme events. The special issue is jointly organized between the Atmospheric Chemistry and Physics, Hydrology and Earth System Sciences, Ocean Science, Natural Hazards and Earth System Sciences, Atmospheric Measurement Techniques, and Geoscientific Model Development journals. It aims at gathering contributions to the areas of understanding, modelling, and predicting at various timescales and spatial scales of the Mediterranean water cycle and its related extreme events, including cyclones, heavy precipitation, flash floods and impacts, drought and water resources, strong winds, and dense water formation. The special issue is not limited to studies conducted within HyMeX: any multiscale or multidisciplinary approaches related to the Mediterranean water cycle are encouraged.