Formerly called: AtmosMainTopics.doc
Main groups / topics
Clouds (incl. Aerosols) prio: high
- Cloud phase partitioning and controls thereof
- Aerosols acting as CCN and IN - identifying sources, chem. composition, microphysical
properties & transport ways
Fraction of aerosols acting as CCN/IN, what are the properties of aerosols which make them
act as CCN/IN, particularly for IN? Key IN processes are unknown and modelling is
rudimentary, like Köhler theory parameterisation for IN and CCN concentrations and
processes.
Basic aerosol properties are missing, incl. CCN, IN, interstitial aerosol concentration, size
distributions, and their spatial and seasonal development in the inner Arctic.
Background versus polluted events.
Impacts on optical properties of clouds and microphysical processes, incl. precipitation.
Measurements around and within clouds are needed.
Identified within aerosol community, IPCC, AMAP Black Carbon in the Arctic
Links to instrumental developments, e.g. for in situ profiling
Linkages to Biology:
Biological activity DMS, VOC depending on sea ice seasonality changes
How is transport through the stable PBL
Influence of bio mass burning events?
Pathways of progress:
- seasonal & vertical PDFs of size distribution profiles, CCN activity
- Models should reproduce seasonal development of aerosol load, incl. chemical processing,
e.g. related to organic components , aging
- how could non-chemistry models include aerosol components
Precipitation
- precipitation over sea ice (phase, amount and spatial distribution and seasonal timing), both
during freezing and melting seasons;
- little knowledge about precip in the first place, so scope of the issue is hard to estimate
- NCAR NCEP reanalyses have a mismatch between moisture convergence and net
precipitation (60 % mismatch, Mark Serreze)
- precip over open ocean impacts freshening and stratificationing of upper ocean
- over sea ice impacts freezing, melting, snow accumulation, snow ice formation potentially
becoming more important in the Arctic.
Linkages to microphys. parameteri. Large scale dynamics, moisture budget,
Melt pond parameterisation
AMAP SWIPA report, Mark Serreze papers, IPCC,
Linkages / impacts:
Impact on sea ice, upper ocean stratification, surface energy budget, cloud formation
Thermodynamic of ice is influenced by snow layer depth, thereby amount of sea ice in the
system
Potentially the greatest uncertainty in atm. forcing for sea ice thermo dynamics is due to
precipitation uncertainty (Cheng papers).
Satellite techniques of snow thickness
C-Band radar
Melt ponds linked
Wind drift
Joint PDFs of snow thickness and sea ice thickness
Mass balance measurements over different types of ice, in the vicinity of drift station
- Evaporation: reason or effect of reduced sea ice; is increasing or decreasing?
Large scale circulation & advection
- Cyclones & storms
- Moisture transport from lower latitudes & oceans
- Storm events & pathways, cyclones providing warm air to the “new arctic”
- Mid level clouds advected? Large scale oscillations and how they might control individual
cyclones
- Arctic ocean generated cyclones <-> low latitude generated cyclones
- Beaufort high and its importance
How is it maintained, seasonal development
Link between BH, storm tracks, ice drift
- Heat transport in free troposphere
- Polar Lows? Will they occur further north when sea ice declines?
- MIZ during on / off ice flows
General:
local <-> transport
Boundary layer
- stable PBL, sea ice growth depending on PBL during winter
Ability / inability of models to reproduce
Formation mechanisms (summer <-> winter)
- entrainment
- cloud top radiative cooling etc.
Lack of understanding of
- Interaction between turbulence, waves, LR, clouds
- Threshold of decoupling (from slightly stable to very stable cond.)
- role of non local sources of turbulence (cloud driven, low level jets)
Problems are well identified and accepted to exist. Grachev,
Linkages to cloud radiative forcing, cond. Heat flux, turbulent heat flux, surface energy
budget, momentum transfer, stratification and vertical transport of atm. constituents
Impacts: to understand and interpret the evolution of the changing climate
Progress: more observations on vertical profiles of mean variables and fluxes,
More systematic model experiments needed,
System process diagnostics (joint PDF: near surface temp. gradient, wind normalized sensible
heat flux. heat transfer coeff., LW flux divergence
- interaction PBL and free atm. (turbulence, gravity waves, …) and links to storm (tracks)
question: are mid latitude approaches valuable or important in central arctic?
Interaction PBL – cyclones, synoptic scale processes
- momentum transfer
- Momentum flux for ice transport;
momentum transfer (spatial information needed)
Surface drag coefficients in the new arctic (old measurements might be off now)
Roughness variability and how does vary throughout the year.
- Wave generation in MIZ depending on jet structure
Atm. Constituents, short lived forcers
- Short lived <-> long lived forcers (GHG, CH4, O3 and precursors, black carbon and others
deposited)
change of albedo
Black carbon effects in atmosphere and after deposition
Surface energy budget
Over first year sea ice and its evolution over a year, observations are missing
Current parameterisations had been derived over thick ice.
Key deficiencies: annual cycle of surface energy budget over first year ice and multi year ice
Spatial variability. Cloud effects on radiative budget. Joint variability in time and space of
different components of the SEB.
- heat fluxes over leads & thin ice (might become more important as thin ice increases, the big
picture is missing: total effect of leads (distribution & connection to sea ice properties),
thin ice (frozen over leads) might become more important, the effect can be lasting over
months
- Evaporation: reason or effect of reduced sea ice; is increasing or decreasing?
- Heat content in the ocean mixed layer important for atmosphere, new measurements become
available (like long temperature sensor strings from water through ice to air). Could be
important for freezing processes.
Ocean temperature influenced by atm. Radiation transfer and ice coverage, thickness
Development of Surface energy budget, fluxes within the seasons, event driven (storms) vs.
long term effects ?
- Radiative fluxes, depending on cloud structures, variability specifically in the marginal ice
zone.
- Melt ponds
Forecasting issues and Arctic Basin atm. Structure
Forecasting possibilities: how does lower 1500 m look like? Vertical structure, RS profiles
and their impact on analyses and forecasting (for Arctic, globally)
Single station can have an effeft, but more than 1 or 2 soundings/day needed
Profiles needed up to 100 hPa (incl. tropopause)