The Open Session on atmosphere, land and ocean monitoring aims at presenting highlights of recent results obtained through observations and modelling as well as relevant reviews in these fields.

The session is intended as an open forum for interdisciplinary discussion between representatives of different fields. Thus, we welcome especially overarching presentations which may be interesting to a wider community.

Observations are one major link to get an overall picture of processes within the Earth environment during measurement campaigns. This includes application to derive atmospheric parameters, surface properties of vegetation, soil and minerals and dissolved or suspended matter in inland water and the ocean. Ground based systems and data sets from ships, aircraft and satellites are key information sources to complement the overall view. All of these systems have their pros and cons, but a comprehensive view of the observed system is generally best obtained by means of a combination of all of them.

The validation of operational satellite systems and applications is a topic that has come increasingly into focus with the European Copernicus program in recent years. The development of smaller state-of-the-art instruments, the combination of more and more complex sets of instruments simultaneously on one platform, with improved accuracy and high data acquisition speed together with high accuracy navigation and inertial measurements enables more complex campaign strategies even on smaller aircraft or unmanned aerial vehicles (UAV).

This session will bring together a multidisciplinary research community to present:

• Atmosphere-land-ocean (or inland water) system modelling and validation
• new instruments (Lidar, etc), platforms (UAV etc.), setups and use in multidisciplinary approaches
• Larger scale in-situ and remote sensing observation networks from various platforms (ground based, airborne, ship-borne, satellite)
• recent field campaigns and their outcomes
• (multi-) aircraft campaigns
• satellite calibration/validation campaigns
• sophisticated instrument setups and observations
• advanced instrument developments
• UAV applications

This session invites contributions on the latest developments and results in lidar remote sensing of the atmosphere, covering
• new lidar techniques as well as applications of lidar data for model verification and assimilation,
• ground-based, airborne, and space-borne lidar systems,
• unique research systems as well as networks of instruments,
• lidar observations of aerosols and clouds, thermodynamic parameters and wind, and trace-gases.
Atmospheric lidar technologies have shown significant progress in recent years. While, some years ago, there were only a few research systems, mostly quite complex and difficult to operate on a longer-term basis because a team of experts was continuously required for their operation, advancements in laser transmitter and receiver technologies have resulted in much more rugged systems nowadays, many of which are already operated routinely in networks and some even being automated and commercially available. Consequently, also more and more data sets with very high resolution in range and time are becoming available for atmospheric science, which makes it attractive to consider lidar data not only for case studies but also for extended model comparison statistics and data assimilation. Here, ceilometers provide not only information on the cloud bottom height but also profiles of aerosol and cloud backscatter signals. Scanning Doppler lidars extend the data to horizontal and vertical wind profiles. Raman lidars and high-spectral resolution lidars provide more details than ceilometers and measure particle extinction and backscatter coefficients at multiple wavelengths. Other Raman lidars measure water vapor mixing ratio and temperature profiles. Differential absorption lidars give profiles of absolute humidity or other trace gases (like ozone, NOx, SO2, CO2, methane etc.). Depolarization lidars provide information on the shapes of aerosol and cloud particles. In addition to instruments on the ground, lidars are operated from airborne platforms in different altitudes. Even the first space-borne missions are now in orbit while more are currently in preparation. All these aspects of lidar remote sensing in the atmosphere will be part of this session.

Instrumentation and measurement technologies are currently playing a key role in the monitoring, assessment and protection of environmental resources. Climate study related experiments and observational stations are getting bigger and the number of sensors and instruments involved is growing very fast. This session deals with measurement techniques and sensing methods for the observation of environmental systems, focusing on water systems and climate.
We welcome contributions about advancements on field measurement approaches, the development of new sensing techniques, as well as the deployment of sensor networks and measurement methods enabling crowdsourced data collection, including innovative low cost sensors. Remote sensing techniques for the monitoring of water resources and/or the related infrastructures are within the scope of this session and welcome.
Studies about signal and data processing techniques targeted to event detection and the integration between sensor networks and large data systems are also very encouraged. Water quantity and quality measurements alongside water characterization techniques are within the scope of this session. This session is also open for all works about an existing system, planning a completely new network, upgrading an existing system, improving streaming data management, and archiving data.
Contributions dealing with the integration of data from multiple sources are solicited, as well as about establishing, maintaining, and managing a fixed network of sensors for water systems and climate.

The Arctic is changing at a dramatic speed in response to the global warming. Management and planning of human activities in the Arctic, and in regions mostly affected by the Arctic climate change, depends on understanding of Arctic-particular physical, chemical, and biological processes that can only arise from systematic observations of key variables. However, the Arctic is difficult and expensive to access, and consequently in-situ observations are scarce and rarely sustained over long time. The international efforts to monitor components of the Arctic climate- and ecosystem from in-situ and remote sensing platforms are growing, but the observing systems including data management are largely uncoordinated. There are a number of international programmes and projects with focus on observing and documenting climate and environmental change, but in the Arctic, where the largest changes are found, there are huge gaps in the observing systems.

In this session, we invite presentations on the efforts done to catalogue and assess the existing Arctic observations, as well as the initiatives carried out to enhance the Arctic observational capacity and improve FAIR data access and reuse. The aim of the session is to foster the international collaboration among the actors playing a role in the Arctic observing systems (managers of infrastructures, manager of data, data collectors, data users) toward the optimization of the observing system. This effort is in line with the Road Map Task Force recently established by the Sustaining Arctic Observing Networks (SAON) and it served the needs of Arctic data users at the local, regional, and global level.

Snow plays an essential role in the climatic and environmental challenges of the 21st century. The snow cover represents a key source of global water supply and climate regulation, and has shown high sensitivity to a warming climate. The amount of collected snow information is also constantly increasing due to novel automated methods for cheaper and easier measurements, especially imagery. During the last decades, instrumentation and measurement techniques, especially remote sensing, have advanced fast, providing significant amount of new information about the extent and properties of snow (e.g. snow water equivalent, (SWE), albedo, reflectance, microstructure, and impurities). In addition, novel technologies such as unmanned aerial vehicles (UAVs) and webcams provide new opportunities and challenges. Optimization and agreement on sampling strategies are important to get spatially distributed data at different scales, and ensure broad use of the acquired data. Data management has become an important issue after general open data policy, where data sets should be available and usable for other users. A large variety of NWP and hydrological models or operational applications routinely make use of snow data to improve their performance. Forecasting snow related hazards in Europe is mostly performed at the country or regional level, and heavily relies on the concurrent meteorological factors and snowpack properties, which are usually acquired from point measurements or physical models. A big challenge is bridging information from microstructural scales of the snowpack up to the grid resolution in models and then to provide knowledge-based information on potential impacts to society, economy and safety (e.g. hydro-power, water availability, transportation, tourism, flooding and avalanches). In this session we would like discuss recent developments and progresses on (1) Snow data collection, curation, and management including harmonized observation techniques for several snow parameters and remote sensing snow observations by applying novel techniques, (2) Snow models, satellite-derived snow products, and data assimilation including improved snow modelling and prediction at different scales taking into account macro and microscale snow properties and (3) Monitoring snow-related hazards and extreme events including latest reanalysis and satellite data sets and models to predict and forecast extreme events and snow-related natural hazards.