The Workshop on Modelling Meltwater in Snow and Firn: Processes, Validation, Intercomparison and Model uses of Optical Remotely Sensed Data will be held at the Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K. it is the second workshop held as part of Danish Council for Independent Research (DFF) Natural Sciences program (FNU) project 4002-00234: Understanding and predicting non-linear change in the permeability of Greenland firn and has a special session co-sponsored by the ESA Scientific Exploitation of Operational Missions (SEOM) Sentinel-3 for Science, Land Study 1: SNOW.

The purpose of the workshop is to:

• to present and discuss results on modeling of meltwater retention processes in snow and firn on ice sheets and glaciers;
• to plan and coordinate meltwater retention model development;
• to emphasize optical remote sensing snow parameter data comparison and data assimilation;
• to formulate a protocol for a meltwater retention model intercomparison project (RetMIP)

List of Sessions:

Session 1: Snow model development

Welcomes, for example, model considerations of water availability vs. percolation rate vs. refreezing rate to explore the importance of heterogeneous percolation modelling in polar firn; fine-and-local scale/detailed modeling with possible suggestions to including bulk effects in larger-scale models; inclusion of piping (for instance, by "skipping layers" during percolation) in distributed or single-column models; inclusion of horizontal water motion in snow and firn, i.e. between grid cells.

Session 2: Meltwater retention model validation

Will focus on discussions of useful model validation metrics and aim to compile observational datasets that may be used to validate the above processes.

Session 3: Meltwater retention model intercomparison project (RetMIP)

Will discuss and formulate a protocol for a meltwater retention model intercomparison project.

Session 4: Optical remote sensing to improve snow models

Serves an ESA Sentinel-3 for Science Land Study: Snow "S-3-Snow" that includes an element to gather and prioritize snow modeller interest and requirements about optical remotely sensed snow parameters (snow extent, albedo, grain size, impurity content, etc.). The ESA study is to engage users of Sentinel-3 snow optical retrievals in 1.) model comparison and/or 2.) data assimilation.  The workshop session is to:

1. survey and prioritize remotely sensed snow parameter data users' requirements for global and regional snow information
2. discuss how to enhance methods for estimating snow parameters, either from remote sensing or from modeling, and to evaluate advantages and disadvantages of the different approaches
3. consult users about the utility/interest in other snow products suitable for studying climate-related issues.

The expected outcomes of the workshop are:

• a protocol for a retention model intercomparison project (RetMIP) including instructions and datasets for validation;
• a list of requirements and minimum accuracy levels for models using optical remotely sensed snow parameter data;
• a journal special issue like the 2016 special issue in Frontiers in Earth Science - Melt Water Retention Processes in Snow and Firn on Ice Sheets and Glaciers: Observations and Modeling, papers feeding into the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC)the Ocean and Cryosphere in a Changing Climate (SROCC).

Contributions are welcomed in the form of oral presentations and/or posters. Presentation duration will be 15-20 minutes, including discussion. One or more longer invited keynote presentations are planned. Those intending to attend the workshop should submit abstracts (maximum length 200 words) by email to Peter Langen (This email address is being protected from spambots. You need JavaScript enabled to view it.) no later than the registration deadline Friday 18 August 2017.  Abstracts should indicate whether an oral or poster presentation is preferred.

We have some financial support, but may ask a modest registration fee. We plan for the workshop to include lunch, morning and afternoon coffee breaks. We are working to raise some financial support for early-career scientists to participate in the workshop. Please indicate at registration whether you will request support.

For accommodation, a range of hotels and hostels exist near the workshop location. Public transport is very efficient, including bike rental. Booking these early is recommended due to high demand that may occur.