General comments Need for new observations versus new parameterizations? Should explore what GCOS and others are doing Urgent need for concerted physical process study –in Antarctic »Field campaign: PBL, cloud, synergy/comparison with Satellites to assist in transfer of research satellites to operations. »Model intercomparison over period of field study »Build on RIME proposal –Arctic: e.g. use/acquire new obs like ASCOS –Real-time data availability important (e.g. example of concordiasi, SHEBA) Data mining Intercomparison of polar forecasts –New metrics required

Scientific challenges to advance forecast skill in polar regions Coupled modelling – snow - more realistic representation of (1) snow albedo (function of ageing and temperature, aerosols, black carbon), (2) snow fraction (hysteresis effect) and (3) snow thermal insulation, more generally fluxes -Limiting factor: Knowledge vs data - potential benefits from “tiling” -snow-vegetation interaction -Surface roughness (over ice ridges) -Mass balance? - issues for NWP: (1) initialization; (2) snow over sea-ice; (3) use of schemes developed for climate models -importance of blowing snow? Parameterization of sublimation -Cryosat may help? -Use of “A-train” for validation studies

Scientific challenges to advance forecast skill in polar regions Coupled modelling – sea-ice and ocean - climate perspective - potential predictability: - decadal scales: THC-SAT connection -  ocean memory - seasonal scales: - suggestion that thicker sea ice is more predictable -sensitivity to (1) ocean initial state; (2) near-ice-edge conditions - Need for enhanced operational analysis -Needs ice thickness and snow data, albedo, etc.. -To explore predictability on seasonal scales for sea ice forecasts?

Scientific challenges to advance forecast skill in polar regions Physical processes – PBL and clouds - the PBL problem: -(1) assumed mesoscale spectral gap not observed in Arctic; may be true more generally -(2) difficulties in modelling of stable boundary layer; -(3) conflict between PBL observations and model parametrizations (indicate revision of stability functions and underlying principles); -(4) need for enhanced vertical resolution - PBL schemes need to include clouds -solving polar clouds needs multiple directions (PBL, surface, microphysics, radiation) - cloud detection in polar regions remains a challenge -Need for new observational techniques, including aerosols. -Highlights need for comprehensive observational studies -How to include differences between N and S poles in NWP -Other projects may be able to contribute (OASIS, PolarCAT, AICI, aeronet)

Scientific challenges to advance forecast skill in polar regions Physical processes – free atmosphere - Arctic: -(1) PBL and microphysics impact mostly over ocean; -(2) clouds play role in many feedbacks; -(3) mixed-phase clouds and super-cooled water important; -(4) pollution / haze / cloud-aerosol interaction need to be taken into account (evidence of day-to-day variation) -Seasonal cycle of aerosols - Antarctica: -(1) long-wave absorption due to clouds most important effect; -(2) need new studies and measurements (not much done in past 10 years); -(3) water and mixed-phase clouds present despite cold temperature; -(4) urgent need for concerted cloud campaign? Not just clouds, PBL, etc needed as well.

Scientific challenges to advance forecast skill in polar regions Physical processes – orographic effects - large-scale flow response to Greenland and Antarctica - complex orography / effects: (1) blocking and gravity- wave drag; (2) katabatic winds, rotors, barrier jets, tip jets, coastal jets, orographic precipitation; (3) high resolution needed; (4) initial conditions important - But, sometimes 1km not enough… -Link between PBL and steep terrain -New high-resolution topographic dataset would be helpful - detailed model studies still required. -More observations required for initialization

Scientific challenges to advance forecast skill in polar regions Physical processes – sea-ice and ocean - importance of (1) polynyas; (2) tides; (3) sea-ice representation (roughness, melt ponds, extent, thickness) - importance of coupled atmosphere-ice-ocean interaction (fluxes) - need of (1) detailed process studies; (2) careful parametrizations; (3) support from observations - Data mining: MIZEX, IPY! IICWG - Ocean initialization a particular problem -WGOMD – CORE -Inclusion of ice shelves problematic. An up-to-date and accurate land sea mask important(with shelves)

Scientific challenges to advance forecast skill in polar regions Data assimilation (global) - improving models and data assimilation leads to greater improvements than increase in observations. - frontiers: -(1) improved quality control and data % used; -better use of observations already available -(2) new obs; -Potential for enhanced polar VOS -(3) novel diagnostics to assist DA tuning and observation network design (OSSE); -(4) use of ensemble forecasts; -(5) coupled initialization/data assimilation -Cryospheric data assimilation using multi-sensors - EC-PORS website: satellite task plan white paper: “satellite component of a comprehensive cryospheric and polar region observing system” -questions: - gap in AMVs QC plot around 60S - temporary reduction in Canadian radiosondes -6 month period. No wind direction and speed for of two measurements per day.

Scientific challenges to advance forecast skill in polar regions Coupled regional reanalyses - operation coupled analyses for polar regions -Using coupled models -Coupled data assimilation still far off, for now data assimilation using coupled models is focus - benefited from using - common grid - coastal anisotropic background error covariances (quasi flow dependent) - importance of flux coupling to be investigated

Scientific challenges to advance forecast skill in polar regions Polar observing system for regional operational NWP - NWP in polar regions depends on quality of (1) model, (2) boundary forcing and (3) initial conditions -Ocean models and ocean observations are a critical component to accurate polar NWP -Sustainability an issue -Polar obs system: (1) insufficient density of radiosondes and surface obs; (2) most satellite are free atmosphere; surface / lower troposphere info lacking; (3) use of satellite data harder over land and sea-ice than over ocean; (4) issues in use of microwave sounding data (sea-ice emissivity, penetration depth, realistic first guess of surface temperature) -UAV could be useful for operations as well -Targeted regions -What observations are most useful for polar NWP?