Session Questions

1) Applications (w/ focus on atmospheric microphysics and modeling)

Q1: What kind of measurements ensemble would be required to bridge the gap in models between ice clouds, precipitation, radiation and atmospheric moisture balance? In short range forecasting to long range climate scales? Can we define a strategy to meet these needs? Are we currently on the right track?

Q2: How should we deal with: prognostic 3D ice crystals fields in clouds (non-precipitating), falling crystal layers, and surface accumulation? How do we insure physical consistency between processes from measurements and theory?

Q3: Should we pay special attention to the cold-dry Arctic-Antarctic Regions with very extensive Thin Ice Clouds (TIC)?

Q4: What about the treatment of TIC near the tropopause in the upper ITCZ region? Does Cirrus virga need special attention for moisture flux and energy balance in the upper troposphere? What are the requirements for lab studies, model simulations, and satellite or campaign measurements?

Q5: Do we need to link aerosol/IFN chemical and physical nucleation properties to formation of TIC types? What's the current status? How do we progress?

Q6: How can we best improve the knowledge and the treatment of light precipitation initiation (versus scales) from measurements? What are the model requirements on light precipitation initiation?

Q7: Measurements of ice particle shape and number densities are crucial for optical properties and are also highly parameterized and uncertain in NWP and climate models. Is there some agreement between retrievals/measurements for those parameters?

Q8: Measurements of mixed-phase properties or glaciation of clouds are necessary to constrain, validate, or falsify ice nucleation assumptions in models. Ideas of how to measure the glaciation of clouds? Inside the clouds, of course!

Q9: Degree of riming or amount of supercooled liquid water is crucial for many reasons (e.g. to know whether we are dealing with snow or graupel) since it makes large differences for fall speeds, ice water content, etc. Can we trust the available IWC retrievals when riming/graupel is present?

2) Radiative Properties of Falling Snow

Q1: How do we determine which scattering models are the best? How can we integrate the various approaches to ice scattering?

Q2: How can realistic uncertainty bounds be established on optical properties?

Q3: How do we deal with cloud liquid water emission/absorption?

3) Global and Regional Detection and Estimation

Q1a: There are a growing number of snow scattering models in existence. Can we start thinking of ways to use field observations to identify the most appropriate ones, perhaps as a function of snowfall regime? (eg. through comparisons against radar/in situ observations)

Q1b: What additional field observations or experiments are of highest priority for testing scattering models, mass-dimension relationships, and fall-speed parameterizations? Are we missing particular snowfall regimes?

Q2: Similarly, a number of different snowfall retrieval approaches (both active and passive) have been developed in recent years. Are we finally in a position to conduct an initial Snowfall-retrieval Intercomparison Project? If not, what information are we missing?

Q3: Can we make use of the nearly 5 years of CloudSat/AMSU-B intersections to formally test passive microwave snowfall detection algorithms? And how can we best use this information be used to develop multi-sensor retrieval methodologies for the future?

Q4: How can we best use ground-based snowfall networks for climatological evaluation of satellite snowfall products (i.e. seasonal/watershed scales)? Is there a role for NWP models in such comparisons?

Q5: How can we make optimal use of the answers to these questions to make a case for future global snowfall missions and develop corresponding instrument requirements?

4) Missions and Concepts

Q1. What mission concepts and/or individual missions (prioritized) are needed and also ready to be implemented?

Q2. What type of instruments are planned or conceived so far? Which have not, but have complementary skills that we should explore more in depth?

Q3. What are the science requirements that we would like to impose? What are the resulting instrument requirements?

5) Validation

Measurement Needs:

Q1: What technology can be used to estimate snowfall rate? How can the errors in the measurements be quantified?

Q2: How do we determine the background radiometric emissivity of the snow pack?

Q3: Is there liquid in the cloud systems? Where is it?

Q4: How do we make quantitative use of ground-based dual polarization radar measurements in GV?

Q5: Considering the uncertainties in snowfall estimation, what, if any, role can network GV play in the estimation of snowfall from space?

Q6: How can we design experiments that can infer the density of the falling snow and the fallen snow? Over what scales is this necessary?

Q7: What tools (e.g. instrument simulators, models) can be used to allow GV measurements to be used effectively in integrated validation? What improvements are required?