Flood forecasting and early warning have long played an important role in disaster risk reduction. Accurate flood forecasting, effective early warning, and proper responses enabled by actionable risk information are key to reducing potential flood damages and disruptions to properties, assets, the natural environment, and the normal functioning of the society. Over the past decades, significant advances have been made in these areas, owing to the increased availability of data, computational resources, and digital technology. However, challenges remain in many aspects.

This special issue aims to solicit contributions from different disciplines in the broad field of flood forecasting, early warning, and risk communication to exchange new knowledge, recent advances, and best practices from the perspectives of researchers, industry, and government organizations. Specific topics of this special issue will cover, but are not limited to

• new and emerging flood forecasting methods and techniques for fluvial, pluvial, coastal, and groundwater flooding at various scales;
• uncertainties in flood forecasting and mitigating methods;
• flood forecasting and early warning under deep uncertainties;
• forecasting and warning of flood-related perils such as landslides and debris flow;
• advances in flood warning and risk communication;
• new methods, tools, and techniques for communicating flood risks;
• advances in risk evaluation;
• flood warning based on strategic and operational responses.

Theoretical, methodological, and applied research in the field is encouraged. Submissions for all manuscript types such as commentaries, review articles, and research papers are welcome.

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.

The special issue will collect contributions from the scientific abstracts submitted to vEGU 2021 in the NH4.1 session "Earthquake-induced hazards: ground motion amplification and ground failures". Nevertheless, it is open to other submissions that are consistent with the topic of the EGU session. Generally, the main concern of the occurrence of an earthquake is ground shaking, although past events worldwide demonstrated that damage and death toll depend on both the strong ground motion and the ground effects. The variability of earthquake ground motion is caused by local geological conditions beneath a given site, due to the stratigraphic or topographic setting, that can give rise to amplification and resonances. Earthquake-induced ground effects are mainly landslides, soil liquefaction, surface faulting, and ground subsidence. They can affect an area with damage related to the full collapse or loss in functionality of facilities, roads, pipelines, and other lifelines.

One of the main interesting points of the special issue is that the topic of earthquake-induced hazards is observed with a multidisciplinary point of view, including different processes that are frequently analysed independently, although they are all tightly linked together. Moreover, the special issue will offer the opportunity to join scientific communities that rarely share their knowledge and results.

Specific topics of the special issue are

• subsoil investigation and characterization for seismic microzonation mapping,
• evaluation of seismic site response (1D, 2D, 3D),
• case histories of earthquake-triggered landslides analysed at either the local or regional scale,
• slope stability analyses and runout modelling of seismically/volcanically induced landslides, and
• studies on soil liquefaction and earthquake-induced subsidence.

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.

This special issue looks at perspectives from organizations on challenges and step changes for addressing natural hazards. In this special issue, we ask representatives of national and international organizations to identify, from the point of view of the organization, (i) what the most pressing scientific challenge(s) with respect to natural hazards is and (ii) what broad step change(s) should or could be achieved by the scientific natural hazard community to address natural hazards.

The format will be one- to two-page invited perspectives (not including any references cited).

This special issue will be published as part of the 20th anniversary of the journal Natural Hazards and Earth System Sciences (NHESS). We invite any representatives of national or international organizations involved with natural hazards to write to the guest editors (NHESS executive editors) for inclusion in this special issue.

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.

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.

The special issue will collect contributions from the scientific abstracts submitted to vEGU 2021 in the NH4.1 session "Earthquake-induced hazards: ground motion amplification and ground failures". Nevertheless, it is open to other submissions that are consistent with the topic of the EGU session. Generally, the main concern of the occurrence of an earthquake is ground shaking, although past events worldwide demonstrated that damage and death toll depend on both the strong ground motion and the ground effects. The variability of earthquake ground motion is caused by local geological conditions beneath a given site, due to the stratigraphic or topographic setting, that can give rise to amplification and resonances. Earthquake-induced ground effects are mainly landslides, soil liquefaction, surface faulting, and ground subsidence. They can affect an area with damage related to the full collapse or loss in functionality of facilities, roads, pipelines, and other lifelines.

One of the main interesting points of the special issue is that the topic of earthquake-induced hazards is observed with a multidisciplinary point of view, including different processes that are frequently analysed independently, although they are all tightly linked together. Moreover, the special issue will offer the opportunity to join scientific communities that rarely share their knowledge and results.

Specific topics of the special issue are

• subsoil investigation and characterization for seismic microzonation mapping,
• evaluation of seismic site response (1D, 2D, 3D),
• case histories of earthquake-triggered landslides analysed at either the local or regional scale,
• slope stability analyses and runout modelling of seismically/volcanically induced landslides, and
• studies on soil liquefaction and earthquake-induced subsidence.

Flood forecasting and early warning have long played an important role in disaster risk reduction. Accurate flood forecasting, effective early warning, and proper responses enabled by actionable risk information are key to reducing potential flood damages and disruptions to properties, assets, the natural environment, and the normal functioning of the society. Over the past decades, significant advances have been made in these areas, owing to the increased availability of data, computational resources, and digital technology. However, challenges remain in many aspects.

This special issue aims to solicit contributions from different disciplines in the broad field of flood forecasting, early warning, and risk communication to exchange new knowledge, recent advances, and best practices from the perspectives of researchers, industry, and government organizations. Specific topics of this special issue will cover, but are not limited to

• new and emerging flood forecasting methods and techniques for fluvial, pluvial, coastal, and groundwater flooding at various scales;
• uncertainties in flood forecasting and mitigating methods;
• flood forecasting and early warning under deep uncertainties;
• forecasting and warning of flood-related perils such as landslides and debris flow;
• advances in flood warning and risk communication;
• new methods, tools, and techniques for communicating flood risks;
• advances in risk evaluation;
• flood warning based on strategic and operational responses.

Theoretical, methodological, and applied research in the field is encouraged. Submissions for all manuscript types such as commentaries, review articles, and research papers are welcome.

This special issue looks at perspectives from organizations on challenges and step changes for addressing natural hazards. In this special issue, we ask representatives of national and international organizations to identify, from the point of view of the organization, (i) what the most pressing scientific challenge(s) with respect to natural hazards is and (ii) what broad step change(s) should or could be achieved by the scientific natural hazard community to address natural hazards.

The format will be one- to two-page invited perspectives (not including any references cited).

This special issue will be published as part of the 20th anniversary of the journal Natural Hazards and Earth System Sciences (NHESS). We invite any representatives of national or international organizations involved with natural hazards to write to the guest editors (NHESS executive editors) for inclusion in 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.

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.

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.

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.