The radiation budget of the Earth is a key determinant for the genesis and evolution of climate on our planet and provides the primary energy source for life. Anthropogenic interference with climate occurs first of all through a perturbation of the Earth radiation balance. We invite observational and modelling papers on all aspects of radiation in the climate system. A specific aim of this session is to bring together newly available information on the spatial and temporal variation of radiative and energy fluxes at the surface, within the atmosphere and at the top of atmosphere. This information may be obtained from direct measurements, satellite-derived products, climate modelling as well as process studies. Scales considered may range from local radiation and energy balance studies to continental and global scales. In addition, related studies on the spatial and temporal variation of cloud properties, albedo, water vapour and aerosols, which are essential for our understanding of radiative forcings and their relation to climate change, are encouraged. Studies focusing on the impact of radiative forcings on the various components of the climate system, such as on the hydrological cycle, on the cryosphere or on the biosphere and related carbon cycle, are also much appreciated. This session will include dedicated sections on the contribution of far-infrared radiation and surface temperature to the Earth radiation budget and climate.

The North Atlantic exhibits a high level of natural variability from interannual to centennial time scales, making it difficult to extract trends from observational time series. Climate models, however, predict major changes in this region, which in turn will influence sea level and climate, especially in western Europe and North America. In the last years, several projects have been focused on the Atlantic circulation changes, for instance OVIDE, RACE, OSNAP, and ACSIS. Another important issue is the interaction between the atmosphere and the ocean as well as the cryosphere with the ocean, and how this affects the climate.
We welcome contributions from observers and modelers on the following topics:

-- climate relevant processes in the North Atlantic region in the atmosphere, ocean, and cryosphere
-- response of the atmosphere to changes in the North Atlantic
-- atmosphere - ocean coupling in the North Atlantic realm on time scales from years to centuries (observations, theory and coupled GCMs)
-- interpretation of observed variability in the atmosphere and the ocean in the North Atlantic sector
-- Comparison of observed and simulated climate variability in the North Atlantic sector and Europe
-- Dynamics of the Atlantic meridional overturning circulation
-- variability in the ocean and the atmosphere in the North Atlantic sector on a broad range of time scales
-- changes in adjacent seas related to changes in the North Atlantic
-- role of water mass transformation and circulation changes on anthropogenic carbon and other parameters
-- linkage between the observational records and proxies from the recent past

Invited Speakers: Professor Ric Williams, University of Liverpool, UK
Dr. Arnaud Czaja, Imperial College, London, UK

The rapid decline of Arctic sea ice in the last decade is a dramatic indicator of climate change.  The last 12 years have seen lower Arctic summer sea ice extents than in the previous 29 years of satellite records. The Arctic sea ice cover is now thinner, weaker and drifts faster. The ocean is also changing, the volume of freshwater stored in the Arctic and has increased as have the inputs of coastal runoff from Siberia and Greenland. Concurrently inflows from the Atlantic and Pacific Oceans have warmed. As the global surface temperature rises, the Arctic Ocean is speculated to become seasonally ice-free in the 21st century, which prompts us to revisit our perceptions of the Arctic system as a whole. What could the Arctic look like in the future? How are the present changes in the Arctic going to affect the lower latitudes? What aspects of the changing Arctic should future observations and modelling programs address? The scientific community is investing considerable effort in organising our current knowledge of the physical and biogeochemical properties of the Arctic, exploring poorly understood coupled atmosphere-sea-ice-ocean processes to improve prediction of future changes in the Arctic.
 
In this session, we invite contributions on a variety of aspects of past, present and future climates of the Arctic. We encourage submissions addressing interaction between ocean, atmosphere and sea ice and on studies linking changes in the Arctic to the global ocean. Submissions with a focus on emerging cryospheric, oceanic and biogeochemical processes and their implications are particularly welcome. The session promotes results from current Arctic programmes and discussions on future plans for Arctic Ocean modelling and measurement strategies. This session is cosponsored by the CLIVAR /CliC Northern Ocean Regional Panel (NORP) that aims to facilitate progress and identify scientific opportunities in (sub)Arctic ocean-sea-ice-atmosphere research.

The Southern Ocean, which stretches from Antarctic ice-shelf cavities to the northern fringe of the Antarctic Circumpolar Current, is a key region for water mass formation and for the uptake, storage and lateral exchanges of heat, carbon and nutrients. At present, the Southern Ocean acts as a sink of anthropogenic carbon and heat and as a source of natural carbon, but its role in future climate conditions remains uncertain. Processes on the Antarctic continental shelf also need to be better understood in order to assess the ocean’s role in Antarctic ice loss and the resulting meltwater impact on sea level. To reduce these uncertainties, it is critical to investigate the mechanisms underlying Southern Ocean's internal variability and its response to external forcing. Recent advances in observational technology, data coverage, circulation theories, and numerical models are providing a deeper insight into the three-dimensional patterns of Southern Ocean change. This session will discuss the current state of knowledge and novel findings concerning Southern Ocean circulation, water mass formation and pathways, mixing and mesoscale dynamics, ocean-ice-atmosphere interactions, sea ice changes, inflow of warm water to ice shelf cavities, and biological productivity, as well as the heat, nutrient and carbon budgets. This includes work on all spatial scales (from local to basin-scale to circumpolar) and temporal scales (past, present and future). We particularly invite cross-disciplinary topics involving physical and biological oceanography, glaciology, or biogeochemistry.

The climate state of the Atlantic Ocean is known to exert a huge control and hence a decisive role on the surface climate over the neighbouring continents as well as that of the Arctic Ocean. Heat in the South Atlantic converges from both the Pacific and Indian Oceans and is carried northward to higher latitudes along the dynamically-rich oceanic current systems to key deep water formation regions where the atmosphere is in direct contact with the deep ocean. Understanding what drives the variability of the Atlantic Ocean on multiple time scales and long-term trends is thus imperative for more confident predictions of the climate in the future decades.

This session will offer the opportunity to focus on the dynamics, variability and trends along the key climatic current systems from the South Atlantic to the North Atlantic and into Arctic Ocean and how they are influenced by local-, large- or global-scale processes or teleconnections. We aim to bring together researchers using observations, ocean models and state-of-the-art climate models.

We welcome presentations addressing:

- Sources, dynamics, pathways and meridional connectivity of heat and freshwater anomalies from lower to higher latitudes
- Impact of large- and global-scale atmospheric modes on Atlantic Ocean circulation
- Variations and long-term trends in Atlantic overturning circulation and relationship to sea-level and sea-ice change

Invited speaker: Penny Holliday, National Oceanography Centre, UK

The WMO World Weather Research Programme (WWRP)–World Climate Research Programme (WCRP) Sub-seasonal to Seasonal (S2S) Prediction Project has the goal of improving forecast skill of the 2 week to 2 month lead time range and now provides research communities with unprecedented access to a comprehensive database of forecasts and hindcasts from a large number of forecasting centres from across the globe.

This session invites contributions that span all aspects of S2S meteorological, hydrological and oceanographic prediction, including impacts studies that may or may not make use of the S2S databases.

Specifically we welcome contributions that focus on phenomena such as

- The Madden Julian Oscillation (MJO)
- Tropical/extra-Tropical waves
- Stratospheric variability and stratosphere -troposphere coupling
- Predictability and skill of atmospheric or surface variables
- Transition of weather regimes
- Case studies of extreme weather events on the S2S scale

Contributions regarding impacts studies at the S2S time-range are also highly welcome, including the areas of water management (e.g floods, drought), health (vector-borne diseases, heat waves, air quality) and security (fires), agriculture and energy. These can include modelling studies of the impacts through to presentations of how S2S-derived information can be integrated into decision support systems at the local, regional and country level.

*********** UPDATE ********************

Solicited talks:

Dr Andrea Manrique-Suñén from Barcelona Supercomputer Centre (BSC) will talk about the S2S4E project which aims to bring sub-seasonal to seasonal climate predictions to the renewable energy sector. To illustrate the potential benefits of S2S predictions the S2S4E projects have analysed several case studies, i.e. periods pointed out by the energy companies as having an unusual climate behavior that affected the energy market. Two of these case studies show how the climate predictions of each event would have helped stakeholders to take precautionary actions several weeks ahead.

Dr Andrew Robertson from Columbia University will give a review of the status of the S2S project, and show some examples of the sub-seasonal forecast products which have been developed at IRI

Papers are solicited related to the understanding and prediction of weather, climate and geophysical extremes, from both an applied sciences and theoretical viewpoint.

In this session we propose to group together the traditional geophysical sciences and more mathematical/statistical approaches to the study of extremes. We aim to highlight the complementary nature of these two viewpoints, with the aim of gaining a deeper understanding of extreme events.

Potential topics of interest include but are not limited to the following:

· How extremes have varied or are likely to vary under climate change;
· How well climate models capture extreme events;
· Attribution of extreme events;
· Emergent constraints on extremes;
· Linking dynamical systems extremes to geophysical extremes;
· Geophysical flows as a dynamical system: classification of large-scale flows and metastable states;
· Advances in diagnosing local and mean properties of the climate system as a dynamical system (e.g. maximum entropy production principles);
· Extremes in dynamical systems;
· Dynamical systems metrics as indicators of climate change;
· Dynamical downscaling of weather and climate extremes.

Confirmed Invited Speakers are:
-David Barriopedro (Complutense University of Madrid, Spain)
-Pascale Braconnot (IPSL, France)
-Nikki Vercauteren (Freie Universitaet Berlin, Germany)

The occurrence of extremes such as droughts, flash floods, hailstorms, storm surges and tropical storms can have significant and sometimes catastrophic consequences to society. However, not all low probability weather/climate events will lead to “high impacts” on human or natural systems or infrastructure. Rather, the severity of such events depend also intrinsically on the exposure, vulnerability and/or resilience to such hazards of affected systems, including emergency management procedures. Similarly, high impact events may be compounded by the interaction of several, e.g., in their own right less severe hydro-meteorological incidents, sometimes separated in time and space. Or they may similarly result from the joint failures of multiple human or natural systems. Consequently, it is a deep transdisciplinary challenge to learn from past high impact events, understand the mechanisms behind them and ultimately to project how they may potentially change in a future climate.

The ECRA (European Climate Research Alliance) Collaborative Programme on “High Impact Events and Climate Change” aims to promote research on the mechanisms behind high impact events and climate extremes, simulation of high impact events under present and future climatic conditions, and on how relevant information for climate risk analysis, vulnerability and adaptation may be co-created with users, e.g., in terms of tailored climate services. For this aim, this Interdisciplinary and Transdisciplinary Session invites contributions that will serve to (i) better understand the mechanisms behind high impact events from a transdisciplinary and interdisciplinary perspective, e.g. case studies and the assessment of past high impact events, including detection and attribution; (ii) project changes to high impact events through, e.g. high resolution climate and impacts modelling (including economic modelling); (iii) produce climate information at the relevant scales (downscaling); and co-create climate services with users to help deal with the risk and/or impacts of high-impact events, e.g. risk analysis and climate adaptation. Abstracts that highlight recent advances from a transdisciplinary perspective for example through the innovation of climate services will be particularly encouraged. Authors and contributors to this session will be offered to present their work in a Special Issue of the journal “Sustainability”.

The assessment of precipitation variability and uncertainty is crucial in a variety of applications, such as flood risk forecasting, water resource assessments, evaluation of the hydrological impacts of climate change, determination of design floods, and hydrological modelling in general. Within this framework, this session aims to gather contributions on research, advanced applications, and future needs in the understanding and modelling of precipitation variability, and its sources of uncertainty.
Specifically, contributions focusing on one or more of the following issues are particularly welcome:
- Novel studies aimed at the assessment and representation of different sources of uncertainty versus natural variability of precipitation.
- Methods to account for different accuracy in precipitation time series, e.g. due to change and improvement of observation networks.
- Uncertainty and variability in spatially and temporally heterogeneous multi-source precipitation products.
- Estimation of precipitation variability and uncertainty at ungauged sites.
- Precipitation data assimilation.
- Process conceptualization and modelling approaches at different spatial and temporal scales, including model parameter identification and calibration, and sensitivity analyses to parameterization and scales of process representation.
- Modelling approaches based on ensemble simulations and methods for synthetic representation of precipitation variability and uncertainty.
- Scaling and scale invariance properties of precipitation fields in space and/or in time.
- Physically and statistically based approaches to downscale information from meteorological and climate models to spatial and temporal scales useful for hydrological modelling and applications.

ENSO is the dominant source of interannual climate variability in the tropics and across the globe. Understanding ENSO's dynamics, predicting El Niño and La Niña, and anticipating changes in ENSO's characteristics and impacts are thus of vital importance for society. This session invites contributions regarding the dynamics of ENSO, including multi-scale interactions; low frequency, decadal and paleo ENSO variability; ENSO theory; ENSO diversity; ENSO impacts on climate, society and ecosystems; ENSO teleconnections; seasonal forecasting of ENSO; and climate change projections of ENSO. Studies aimed at understanding ENSO in models of a range of complexity are especially welcomed, including analysis of CMIP model intercomparisons.

Process understanding is key to assessing the sensitivity of glacier systems to changing climate. Comprehensive glacier monitoring provides the base for large-scale assessment of glacier change. Glaciers are monitored on different spatio-temporal scales, from extensive seasonal mass balance studies at selected glaciers to multi-decadal repeat inventories at the scale of entire mountain ranges. Internationally coordinated glacier monitoring aims at combining in-situ measurement with remotely sensed data, and local process understanding with global coverage. This session invites studies from a variety of disciplines, from tropical to polar glaciers, addressing both in-situ and remotely sensed monitoring of glaciers, as well as uncertainty assessments.
Keynotes:
Laura Thomson & David Burgess (Canada): The role and response of Canada's Arctic glaciers: Lessons learned from >50 years of mass balance observations
Bryn Hubbard (UK): 3D structure of Khumbu Glacier, Nepal, from borehole experiments.

Understanding the impacts of climate change on ice sheets and glaciers requires accurate surface mass balance. The interaction of ice sheets and glaciers with the atmosphere means that coupled atmosphere-ocean modes and large-scale weather patterns, meso-scale circulations over mountains, and local-scale energy and mass exchanges in the near-surface boundary layer can control the surface mass balance. Surface processes including melt-albedo feedbacks and firn densification introduce further complexity in determining surface mass balance. The Ice Sheets Model Intercomparison Project (ISMIP6), part of the Climate Model Intercomparison Project (CMIP6), aims to constrain the total mass balance contribution of ice sheets and glaciers to sea level rise. In this context, accurate estimates of surface mass balance from both models and observations are crucial, and so intercomparisons of models are currently underway.

This session focuses on (i) novel field- and remotely-sensed advances in measuring the surface energy balance and surface mass balance and (ii) process-based modelling that improves our understanding of glacier and ice sheet surface mass balance and atmospheric interaction. We invite contributions from a broad range of theoretical, numerical or observational studies that explore historic, recent and projected changes to glacier and ice sheet surface mass balance and atmospheric interaction. The range of topics includes but is not limited to: surface energy balance; improvements to satellite SMB retrievals; firn densification; future atmospheric circulation impacts; changes in cloudiness; and the impact of impurities upon albedo. We particularly welcome contributions which focus on improvements to process understanding that will lead to better SMB estimates in the future.

Snow cover characteristics (e.g. spatial distribution, surface and internal physical properties) are continuously evolving over a wide range of scales due to meteorological conditions, such as precipitation, wind and radiation.
Most processes occurring in the snow cover depend on the vertical and horizontal distribution of its physical properties, which are primarily controlled by the microstructure of snow (e.g. density, specific surface area). In turn, snow metamorphism changes the microstructure, leading to feedback loops that affect the snow cover on coarser scales. This can have far-reaching implications for a wide range of applications, including snow hydrology, weather forecasting, climate modelling, and avalanche hazard forecasting or remote sensing of snow. The characterization of snow thus demands synergetic investigations of the hierarchy of processes across the scales ranging from explicit microstructure-based studies to sub-grid parameterizations for unresolved processes in large-scale phenomena (e.g. albedo, drifting snow).

This session is therefore devoted to modelling and measuring snow processes across scales. The aim is to gather researchers from various disciplines to share their expertise on snow processes in seasonal and perennial snowpacks. We invite contributions ranging from “small” scales, as encountered in microstructure studies, over “intermediate” scales typically relevant for 1D snowpack models, up to “coarse” scales, that typically emerge for spatially distributed modelling over mountainous or polar snow- and ice-covered terrain. Specifically, we welcome contributions reporting results from field, laboratory and numerical studies of the physical and chemical evolution of snowpacks, statistical or dynamic downscaling methods of atmospheric driving data, assimilation of in-situ and remotely sensed observations, representation of sub-grid processes in coarse-scale models, and evaluation of model performance and associated uncertainties.

This session is linked closely to the session HS2.1.2/CR3.11. While the focus of our session is on monitoring and modelling snow processes across scales, session HS2.1.2/CR3.11 addresses monitoring and modelling of snow for hydrologic applications.

Variations in stratospheric aerosol -- arising primarily from sporadic volcanic eruptions -- are an important contributor to climate variability. Major volcanic eruptions have led to pronounced decreases in global surface temperature over seasonal-to-decadal timescales.

The transition from the unusual 1998-2002 period of a “fully decayed to quiescence” stratospheric aerosol layer, into a more typical period of modest volcanic activity temporarily offset a substantial proportion of the subsequent decadal forcing from increased greenhouse gases.

Advancing our understanding of the influence of volcanoes on climate relies upon better knowledge of the radiative forcings of past eruptions and the microphysical, chemical and dynamical processes which affect the evolution of stratospheric aerosol properties. This can only be achieved by combining information from satellite and in-situ observations of recent eruptions, stratospheric aerosol modelling activities, and reconstructions of past volcanic histories from proxies.

This session seeks presentations from research aimed at better understanding the stratospheric aerosol layer and its volcanic perturbations through the post-industrial period (1750-present) and also those further back in the historical record.

This year contributions addressing volcanic influences on atmospheric composition, such as changes in stratospheric water vapour, ozone and other trace gases are also particularly encouraged.

The session also aims to highlight research on volcanoes and climate contributing to current international SPARC-SSiRC, CMIP6-VolMIP, CMIP6-PMIP, and PAGES-VICS co-ordinated activities.

Atmosphere and Cryosphere are closely linked and need to be investigated as an interdisciplinary subject. Most of the cryospheric areas have undergone severe changes in last decades while such areas have been more fragile and less adaptable to global climate changes. This AS-CR session invites model- and observational-based investigations on any aspects of linkages between atmospheric processes and snow and ice on local, regional and global scales. Emphasis is given on the Arctic, high latitudes and altitudes, mountains, sea ice, Antarctic regions. In particular, we encourage studies that address aerosols (such as Black Carbon, Organic Carbon, dust, volcanic ash, diatoms, bioaerosols, bacteria, etc.) and changes in the cryosphere, e.g., effects on snow/ice melt and albedo. The session also focus on dust transport, aeolian deposition, and volcanic dust, including health, environmental or climate impacts at high latitudes, high altitudes and cold Polar Regions. We emphasize contributions on biological and ecological sciences including dust-organisms interactions, cryoconites, bio-albedo, eco-physiological, biogeochemical and genomic studies. Related topics are light absorbing impurities, cold deserts, dust storms, long-range transport, glaciers darkening, polar ecology, and more. The scientific understanding of the AS-CR interaction needs to be addressed better and linked to the global climate predictions scenarios.

The regional climate change assessment reports for the Baltic (BACC I and II) and North Sea regions (NOSCCA) have recently estimated the extent and impact of climate change on the environments of the North and Baltic Sea regions. A major outcome of these reports is the finding that climate change is one of multiple drivers, which have a continuing impact on terrestrial, aquatic and socio-economic (resp. human) environments. These drivers interact with regional climate change in ways, which are not completely understood.
This session invites contributions, which focus on the connections and interrelations between climate change and other drivers of environmental change, be it natural or human-induced, in different regional seas and coastal regions. Observation and modelling studies are welcome, which describe processes and interrelations with climate change in the atmosphere, in marine and freshwater ecosystems and biogeochemistry, coastal and terrestrial ecosystems as well as human systems. In particular, studies on socio-economic factors like aerosols, land cover, fisheries, agriculture and forestry, urban areas, coastal management, offshore energy, air quality and recreation, and their relation to climate change, are welcome.
The aim of this session is to provide an overview over the current state of knowledge of this complicated interplay of different factors, in different coastal regions all over the world.

The energy of a closed system is steady. It is not lost but rather converted into other forms, such as when kinetic energy is transferred into thermal energy. However, this fundamental principle of natural science is often still a problem for climate research. For example, in case of the calculation of ocean currents and circulation, where small-scale vortices as well as diapycnal mixing and the deep convection processes they induce, need to be considered, to compute how heat content is redistributed along the entire water column and how such processes may change in the future. Similarly, in the atmosphere, the conversion of available potential energy into kinetic energy is the key driver of atmospheric dynamics at a variety of scales, from the zonal-mean general circulation to mesoscale convection. Local turbulent processes can drive larger movements and waves on a larger scale can disintegrate into small structures. All these processes are important for the Earth’s climate and determine its evolution in the future.

How exactly the energy transfers between waves, eddies, local turbulence and mixing in the ocean and the atmosphere works, often remains unclear. This session wants to discuss this by inviting contributions from oceanographers, meteorologists, climate modelers, and mathematicians. We are particularly interested in coupled atmosphere-ocean studies, we are also aiming at filling a knowledge gap on deep ocean processes, as well as novel subgrid-scale parameterizations, and studies of the energy budget of the complex Earth system, including the predictability of the global oceanic thermohaline circulation and thus climate variability.

Invited speakers:
Martin Wild, ETH, Zürich, Switzerland
Raffaele Ferrari, MIT, USA
Robert Weller, WHOI and OOI Research Infrastructures, USA

The atmospheric water cycle is a key component of the climate system,
and links across many scientific disciplines. Processes and dynamics at
different scales interact throughout the atmospheric life cycle of
water vapour from evaporation to precipitation. This session sets the
focus on processes, dynamics and characteristics at the evaporation
sources, during moisture transport, and at the precipitation sinks as
observed from in-situ and remote sensing, recorded by (paleo)climate
archives, and as simulated for past, present and future climates.

We invite studies

* focusing on extensive transient features of the atmospheric water
cycle, such as Atmospheric Rivers, Cold-Air Outbreaks, warm conveyor
belts, tropical moisture exports, precipitation extremes, and the
monsoon systems.

* investigating the large-scale drivers of the water cycle features’
variability and change by looking at observations, reanalyses or
global/regional climate simulations, in order to improve their
predictability

* involving and connecting results from field campaigns (YOPP, MOZAIC,
NAWDEX), reanalysis data, indicators of past hydroclimate from climate
proxies such as ice cores and stalagmites, and model predictions of the
future evolution of the atmospheric water cycle,

* applying methods such as stable isotopes as physical tracers in the
water cycle, tagged water tracers, and Lagrangian moisture source
diagnostics to identify source-sink relationships and to evaluate model
simulations of the water cycle,

* describing the global and regional state of the atmospheric cycle
with characteristics such as the recycling ratio, life time of water
vapour, and moisture transport distance

We particularly encourage contributions to link across neighbouring
disciplines, such as atmospheric science, climate, paleoclimate,
cryosphere, and hydrology.

Remote sensing techniques and earth system modelling have been widely used in earth science and environmental science. In particular, the world is suffering significant environmental changes such as hydro-climatic extremes, sea level rise, melting glaciers and ice caps and forest fires. The earth observations and earth system models provide valuable insight into climate variability and environmental change. Meanwhile, the question on how to derive and present uncertainties in earth observations and model simulations has gained enormous attention among communities in the earth sciences.

However, quantification of uncertainties in satellite-based data products and model simulations is still a challenging task. Various approaches have been proposed within the community to tackle the validation problem for satellite-based data products and model simulations. These progress include theory advancement, mathematics, methodologies, techniques, communication of uncertainty and traceability.

The aim of this session is to summarize current state-of-the-art in uncertainty quantification and utilization for satellite-based earth observations and earth system models.

Climate changes (CC) are expected affecting weather forcing regulating the triggering and reactivation of slope movements. The influence of CC on landslides can be different, according to the area, the time horizon of interest and the actual trends of socio-economic factors driving greenhouse gases concentration. However, even the simple identification of weather patterns regulating landslide occurrence represents a not trivial issue, also assuming steady conditions, due to crucial role played by geomorphological details.
In last years, such elements partly prevented the investigations aimed to assess how CC influence slope stability at different temporal and spatial scales.
In this regard, the Session has the main aim to gather test cases and investigations carried out in different geographical contexts in evaluation of ongoing and future landslide activity.
Researches may concern: (i) modeling of future slope stability conditions exploiting downscaled climate projections or (ii) analyses of historical records of landslides (using both historical research or paleo-evidences) and climate variables and their combinations.
Analysis at different detail from slope to regional scale to global scale, considering variations in landslide occurrence, frequency, susceptibility, hazard and risk result of interest. Nevertheless, studies considering the coupled effect of environmental (e.g., land use/cover) and climate changes will be taken into account.

As the most evident example of land use and land cover change, urban areas play a fundamental role in local to large-scale planetary processes, via modification of heat, moisture, and chemical budgets. With rapid urbanization ramping up globally it is essential to recognize the consequences of landscape conversion to the built environment. Given the capability of cities to serve as first responders to global change, considerable efforts are currently being dedicated across many cities to understand urban atmospheric dynamics and examine various adaptation and mitigation strategies aimed to offset impacts of rapidly expanding urban environments and influences of large-scale greenhouse gas emissions.

This session solicits submissions from both the observational and modelling communities examining urban atmospheric dynamics, processes and impacts owing to urban induced climate change, the efficacy of various strategies to reduce such impacts, and techniques highlighting how cities are already using novel science data and products that facilitate urban adaptation to and mitigation of the effects of climate change.

As discussed by EGU2017 DB2 and EGU 2018 TM16, there had been an impressive series of international agreements and development of large networks of cites that call for qualitative improvements of urban systems and their interactions with their environment. The main goal of this ITS is to mobilise geoscientists, highlight their present contributions and encourage holistic approaches beyond the traditional silos of urban meteorology/hydrology/climatology/ecology/resilience, as well as some other terms.

Public information:
See also Town Hall TM 19 "Cities and Interdisciplinary Geosciences"
to be held on Thursday 11 April in room 1.85 from 19:00 to 20:00.
https://meetingorganizer.copernicus.org/EGU2019/session/33913

Cities all over the world are facing rising population densities. This leads to increasing fractions of built-up and sealed areas, consequencing in a more and more altered and partly disrupted water balance - both in terms of water quantities and qualities. On top, climate change is altering precipitation regimes.

This session focuses on according urban ecohydrological problems and approaches to solve them spanning from technical to nature-based solutions in different time and spatial scales from the building to the whole city.

The originality of the session is to emphasize on the central position of human activities in environmental research (both terrestrial and atmospheric), as a driving factor and/or a response, by combining different spatio-temporal scales.
Continental environments (under various climatic conditions) experience profound societal and physical changes, which prompt scientists to investigate the complex interactions between environmental functioning and human activities.
The complexity originates from the multiplicity of factors involved and resulting spatial and temporal variabilities, of their multiple origins in time (historical integration) and/or legacy.
As a consequence, causal links in this societal-environmental relationship are difficult to establish but, it is fundamental to understand these causal links to adapt, conserve, protect, preserve and restore the functioning of the environment as well as human activities. From this point of view, the geographical approach highlights the relationships (or their absence) through the expression of the spatial and temporal trajectories of the processes studied by clarifying the observation of signals.
The ensuing issues on the relevance of indicators used in different supports of nowadays research (imagery, archives, models ...) are raised as a methodological open up.
In this context, oral and poster presentations dealing with any studies related to the following issue(s) are welcome:
- human forcing on the environments and environmental resilience
- response of socio-systems to environmental changes
- scenarios, prospective and retrospective models of the evolution of environments and human activities
- management modes (adaptive management) of anthropised continental environments, reciprocity, mutual benefits (ecosystem services), positive feedback

The session may include the following methodological aspects:
- in situ metrology,
- statistical and numerical modeling,
- spatio-temporal analysis,
- remote Sensing,
- surveys,
- landscape analysis,
- paleoenvironmental approach,
at various scales:
- spatial scales, from the station and site through watershed,
- time scales from the event to the Holocene.

Hydroclimatic variability is an emerging challenge with increasing implications on water resources management, planning, and the mitigation of water-related natural hazards. The above variability, along with the continuous development of water demands, and aging water supply system infrastructure make the sustainability of water use a high priority for modern society. In fact, the Global Risk 2015 Report of the World Economic Forum highlights global water crises as being the biggest threat facing the planet over the next decade.
To mitigate the above concerns we need to shed light on hydroclimatic variability and change. Several questions and mysteries are still unresolved regarding natural fluctuations of climate, anthropogenic climate change and associated variability, and changes in water resources. What is a hydroclimatic trend? What is a (long term) cycle? How can we distinguish between a trend and a cycle? Is such discrimination technically useful? How do human activities affect rainfall, hydrological change and water resources availability? How to set priorities and take action to ensure sustainability in light of variability and change?
The objective of this session is to explore hydrological and climatic temporal variability and their connections and feedbacks. More specifically, the session aims to:
1. investigate the hydrological cycle and climatic variability and change, both at regional and global scales;
2. explore the interplay between change and variability and its effect on sustainability of water uses;
3. advance our understanding of the hydrological cycle, benefiting from hydrological records and innovative techniques; and
4. improve the efficiency, simplicity, and accurate characterization of data-driven modeling techniques to quantify the impacts of past, present and future hydroclimatic change on human societies.
This session is sponsored by the International Association of Hydrological Sciences (IAHS) and the World Meteorological Organization – Commission for Hydrology (WMO CHy) and it is also related to the scientific decade 2013–2022 of IAHS, entitled “Panta Rhei - Everything Flows”.