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Overview
Objectives of GREENICE AGCM experiments
1. To better understand atmospheric impact of SST, sea ice, and snow cover
2. To assess the relative contributions of SST, sea ice, snow cover, and internal atmospheric dynamics in recent NH climate change
Models:
- Four models: CAM4/WACM, IFS, ECHAM5, IAP
- Low and high top, low and high-horizontal resolution
Experiments
Tier1
- AGCM with full sea ice and SST variations
- AGCM with full sea ice and climatological SST variations
- Period 1981 to present
- Number of ensemble: 20 member for each experiments to be determined by each group (e.g., different days in January 1981)
- Daily SST and sea ice variations will be used
Tier 2
- Case studies based on analysis of tier 1 experiments to better diagnose mechanisms
- Experiments to assess impact of snow cover variations
Boundary conditions and external forcing
- NOAA Optimum Interpolation 1/4 Degree Daily Sea Surface Temperature Analysis – version2, AVHRR-only product. This extends from September 2001 till present. The sea ice for 1981-2004 is from Cavalieri et al. [1997,2005]. The sea ice from 2005 to present is from Grumbine et al. [1998].
- Download from http://www.ncdc.noaa.gov/sst/index.php
- Reference for the data Reynolds et al. [2007].
- Transient forcing following CMIP5 protocol, RCP8.5 from 2006 onward
- Boundary conditions for the experiments with varying SIC and climatological SIC will follow Screen et al. [2013]: In any grid box north of 40N, if the daily mean SIC deviated from daily climatology by > 10%, the grid box was set to observed SIC and SST. Otherwise, climatological SIC and SST were used (this includes all grid boxes south of 40N). South of 40N and at grid boxes where the daily mean sea ice concentration was within 10% of the climatological daily mean, the climatological daily sea ice concentration and/or SST values were used.
Some specific issues to be addressed by groups
- Impact of daily versus monthly mean SST and SIC data in simulations at relatively high-horizontal resolution T255 (SMHI/DMI)
- Role of stratosphere-troposphere interaction at medium horizontal resolution ~1deg by comparing low versus high top simulations with daily SST and SIC data (UiB/NERSC)
Output variables
To be made available by each modeling group.
3D-fields (daily)
- temperature
- wind u, v
- humidity
- vertical velocity
- GPH
- liquid water cloud, ice water cloud (monthly means)
2D-fields (daily)
- SLP
- surface pressure
- all radiation components (both clear and all sky fluxes)
- evaporation
- daily max/min temperature
- surface temperature
- 10m wind
- cloud cover (total, low, medium, high)
- Cloud liquid water content
- cloud ice water content
- total column water
- total column water vapor
- soil temperature (several layers)
- soil wetness (several layers)
- runoff (surface and deep)
- snow cover
- snow depth and density or liquid water equivalent.
- Total precipitation
- T2m
2D fields at 3hrly frequency
- T2m
- Surface fluxes (latent, sensible, momentum)
- Precipitation (large scale, convective, snow)
Experiments to start by mid-November to be completed by the first year annual meeting
References
- Cavalieri D., C. Parkinson, P. Gloerson, and H.J. Zwally. 1997, updated 2005. Sea ice concentrations from Nimbus-7 SMMR and DMSP SSM/I passive microwave data, June to September 2001. Boulder, CO, USA (from http://nsidc.org/data/nsidc-0051.html)
- Grumbine, R. W., 1996: Automated passive microwave sea ice concentration analysis at NCEP, 13pp. Unpublished manuscript available from NCEP/NWS/NOAA, 5200 Auth Road, Camp Springs, MD, 20746, USA. (from http://polar.ncep.noaa.gov/seaice/)
- Reynolds, R. W., T. M. Smith, C. Liu, D. B. Chelton, K. S. Casey, and M. G. Schlax (2007), Daily high-resolution-blended analyses for sea surface temperature, J Climate, 20(22), 5473-5496
- Screen, J. A., I. Simmonds, C. Deser, and R. Tomas (2013), The Atmospheric Response to Three Decades of Observed Arctic Sea Ice Loss, J Climate, 26(4), 1230-1248, 10.1175/jcli-d-12-00063.1.
