1. Sea surface temperature and Sea ice coverage for the proposed sensitivity experiemnts

1.1 For control experiments

For control experiments: Climatological monthly mean SST & sea-ice concentrations derived from the HadISST observations for 1961-1990 when CO2 average concentration is ~332.32 ppmv at the HadAM3 grid have been prepared. SST are in C and sea ice coverage is either 1 or 0. The files are in netcdf format with values over land being 2.0E+20.

Download SST and sea ice coverage for control experiments

The model climatological biases relative to the HadISST are shown in figure 1

1.2 For perturbed experiments (2xCO2):

For perturbed experiments: Monthly mean SST anomalies are added to climatological fields used for control experiments. SST anomalies are derived from 1% pa CO2 CMIP-type integration with HadCM3 model. The anomalies are the difference between two 30 year means: a) mean for period with CO2 values near present day b) mean for period with CO2 values near 2 x present day CO2. The model annual and seasonal mean anomalies are shown in figure 2.

 
  For perturbed experiments: The monthly mean sea ice coverage is simply taken from the 30 year mean for period with CO2 values near 2 x present day CO2 of the HadCM3 1% CO2 integration. In addition, the gridpoints are taken as sea ice covered where SSTs are less than -1.8C when the model SST anomalies are added to the control SSTs. This is due to the cooling over the North Atlantic associated with the weakening of the THC when CO2 increases in the model. The validity of this approach will be explained in the following section.

Download SST and sea ice coverage for perturbation experiments

Download land sea mask

1.3 Greenhouse Gases

The Greenhouse gas concentrations for the control experiments are the mean concentrations for the period of 1961-1990. Only CO2 is changed for 2XCO2 experiments. The concentrations for the control and 2XCO2 experiments are listed in Table 1 and Table 2. Table 1 is for a model requires equivalent forcings. Table 2 breaks the Equivalent CFC-11 in Table 1 into specific concentrations and is for a model that requires specific concentrations.



Table 1: Radiative Greenhouse Gas concentrations

	Control experiments	2XCO2 experiments
CO2	332.32 (ppmv)	664.64 (ppmv)
CH4	1476.11 (ppbv)	1476.11 (ppbv)
N2O	299.61 (ppbv)	299.61 (ppbv)
CFC-12	233.43 (pptv)	233.43 (pptv)
Equivalent CFC-11	258.02 (pptv)	258.02 (pptv)





Table 2: Decomposition of Equivalent CFC-11 in Table 1

	Control experiments	2XCO2 experiments
CFC11	121.89 (pptv)	121.89 (pptv)
CFC113	19.18 (pptv)	19.18 (pptv)
HCFC22	32.67 (pptv)	32.67 (pptv)
HFC125	0.0 (pptv)	0.0 (pptv)
HFC134a	0.0 (pptv)	0.0 (pptv)





2. Sea ice coverage

The climatological seasonal cycle of sea ice coverage has been analysed. Shown in Figure 3 are the seasonal cycle of global, northern hemisphere, and southern hemisphere sea ice area (percentage) for those based on observations (1961-1990), and 2 periods of 30 year mean HadCM3 simulation. The sea ice cover for Reynolds data set is derived from SST. When SST in a gridpoint in Reynolds data set is below -1.8C, it is assumed that gridpoint is sea ice covered.
In general, the global seasonal cycle of sea ice coverage for present day based on HadCM3 simulation is very close to that based on HadISST. As it is expected, global sea ice coverage at time of 2XCO2 is reduced by 15%-25% relative to that at time of present day CO2, with a similar seasonal cycle as present day.
Model gneraly underestimates the north hemisphere sea ice coverage in summer and autumn, and sea ice coverage in southern hemisphere from September to November is overestimated. Despite of this deficiency, the spatial coverage of sea ice extent is simulated in a satisfactory manner. This is further illustrated by the geographical patern of sea ice coverage shown in figures 4-7. Given the satisfactory simulation of present day sea ice coverage, it is reasonable to use the model sea ice coverage at time 2XCO2 as the sea ice extent for the 2XCO2 experiment. In addition, the gridpoints are taken as sea ice covered where SSTs are less than -1.8C when the model SST anomalies are added to the control SSTs. This is due to the cooling over the North Atlantic associated with the weakening of the THC when CO2 increases in the model.
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7

 
 

3. Proposed diagnostics

For diagnostics, they are classcified as monthly mean 2-D fields, monthly 3-D fields, daily fields, 6 hourly fields, and extremes.




Monthly mean 2-D fields of radiation (M2DR)

Variable	Long Name	Standard Name	Unit
hfls	Surface Latent Heat Flux	surface_upward_latent_heat_flux	W m-2
hfss	Surface Sensible Heat Flux	surface_upward_sensible_heat_flux	W m-2
rlds	Surface Downwelling Longwave Radiation	surface_downwelling_longwave_flux_in_air	W m-2
rldscs	Downwelling Surface Clear-Sky Longwave	surface_downwelling_longwave_flux_clear_sky	W m-2
rlntp	Net Upward Longwave Flux at 200 hPa	net_upward_longwave_flux_in_air	W m-2
rlntpcs	Net Upward Clear-Sky Longwave Flux at 200 hPa	net_upward_longwave_flux_clear_sky	W m-2
rlus	Surface Upwelling Longwave Radiation	surface_upwelling_longwave_flux_in_air	W m-2
rlut	Outgoing Longwave Radiation	toa_outgoing_longwave_flux	W m-2
rlutcs	Outgoing Clear-Sky Longwave	toa_outgoing_longwave_flux_clear_sky	W m-2
rsds	Surface Downwelling Shortwave Radiation	surface_downwelling_shortwave_flux_in_air	W m-2
rsdscs	Incident Surface Clear-Sky Shortwave	surface_downwelling_shortwave_flux_clear_sky	W m-2
rsdt	TOA Incident Shortwave Radiation	toa_incoming_shortwave_flux	W m-2
rsntp	Net Downward Shortwave Flux at 200 hPa	net_downward_shortwave_flux_in_air	W m-2
rsntpcs	Net Downward Clear-Sky Shortwave Flux at 200 hPa	net_downward_shortwave_flux_clear_sky	W m-2
rsus	Surface Upwelling Shortwave Radiation	surface_upwelling_shortwave_flux_in_air	W m-2
rsuscs	Reflected Surface Clear-Sky Shortwave	surface_upwelling_shortwave_flux_clear_sky	W m-2
rsut	TOA Reflected Shortwave Radiation	toa_outgoing_shortwave_flux	W m-2
rsutcs	Reflected Clear-Sky Shortwave	toa_outgoing_shortwave_flux_clear_sky	W m-2
rtmt	Net Flux at Top of Model	net_downward_radiative_flux_at_top_of_atmos.	W m-2





Monthly mean 2-D fields of hydrology (M2DH)

Variable	Long Name	Standard Name	Unit
clivi	Column Integerated Cloud Ice Content	atmosphere_cloud_ice_content	kg m-2
clt	Total Cloud Fraction	cloud_area_fraction	%
clwvi	Column Integerated Cloud Water Content	atmosphere_cloud_condensed_water_content	kg m-2
huss	Surface Specific Humidity	specific_humidity	1 (i.e., dimensionless fraction)
mrfso	Soil Frozen Water Content	soil_frozen_water_content	kg m-2
mrro	Surface and Subsurface Runoff	runoff_flux	kg m-2s-1
mrros	Surface Runoff	surface_runoff_flux	kg m-2s-1
mrso	Total Soil Moisture Content	soil_moisture_content	kg m-2
mrsos	Moisture in Upper 0.1 m of Soil Column	moisture_content_of_soil_layer	kg m-2
pr	Precipitation	precipitation_flux	kg m-2s-1
prl	Large Scale Precipitation	large_scale_precipitation_flux	kg m-2s-1
prc	Convective Precipitation	convective_precipitation_flux	kg m-2s-1
prsn	Snowfall Flux	snowfall_flux	kg m-2s-1
prveg	Precipitation Intercepted by Vegetation Canopy	precipitation_flux_onto_canopy	kg m-2s-1
prw	Precipitable Water	atmosphere_water_vapor_content	kg m-2
snc	Snow Area Fraction	surface_snow_area_fraction_where_land	%
snd	Snow Depth	surface_snow_thickness	m
snm	Snow Melt	surface_snow_melt_flux_where_land	kg m-2s-1
snw	Snow Amount	surface_snow_amount_where_land	kg m-2
mrsol	Soil Moisture (profile on model levels)	soil_moisture_content_at_model_levels	kg m-2





Monthly mean 2-D fields of others (M2DO)

Variable	Long Name	Standard Name	Unit
orog	Surface Altitude	surface_altitude	m
sftgif	Fraction of Grid Cell Covered with Glacier	land_ice_area_fraction	%
sftlf	Land Area Fraction	land_area_fraction	%
mrsofc	Capacity of Soil to Store Water	soil_moisture_content_at_field_capacity	kg m-2
ps	Surface Pressure	surface_air_pressure	Pa
psl	Sea Level Pressure	air_pressure_at_sea_level	Pa
tas	Surface Air Temperature	air_temperature	K
tasmax	Daily Miximum Surface Air Temperature	air_temperature	K
tasmin	Daily Minimum Surface Air Temperature	air_temperature	K
tauu	Zonal Surface Wind Stress	surface_downward_eastward_stress	Pa
tauv	Meridional Surface Wind Stress	surface_downward_northward_stress	Pa
ts	Surface Skin Temperature	surface_temperature	K
uas	Zonal Surface Wind Speed	eastward_wind	m s-1
vas	Meridional Surface Wind Speed	northward_wind	m s-1
tsol	Soil Temperature (profile on model levels)	soil_temperature_at_model_levels	K





Monthly mean 3-D fields (Except for cloud area fraction, this data must be provided on pressure levels, including at least the following standard levels: 1000, 925, 850, 700, 600, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20, 10 hPa)

Variable	Long Name	Standard Name	Unit
ta	Temperature	air_temperature	K
ua	Zonal Wind Component	eastward_wind	m s-1
va	Meridional Wind Component	northward_wind	m s -1
zg	Geopotential Height	geopotential_height	m
wap	Omega (=dp/dt)	lagrangian_tendency_of_air_pressure	Pa s-1
hur	Relative Humidity	relative_humidity	%
hus	Specific Humidity	specific_humidity	1 (i.e.,dimensionless fraction)
cl	Cloud Fraction	cloud_area_fraction_in_atmosphere_layer	%





Daily mean fields

Variable	Long Name	Standard Name	Unit
hfls	Surface Latent Heat Flux	surface_upward_latent_heat_flux	W m-2
hfss	Surface Sensible Heat Flux	surface_upward_sensible_heat_flux	W m-2
hus	Specific Humidity at 250, 500, 850hPa	specific_humidity	1 (i.e.,dimensionless fraction)
pr	Precipitation	precipitation_flux	kg m-2s-1
psl	Sea Level Pressure	air_pressure_at_sea_level	Pa
rlds	Surface Downwelling Longwave Radiation	surface_downwelling_longwave_flux_in_air	W m-2
rlus	Surface Upwelling Longwave Radiation	surface_upwelling_longwave_flux_in_air	W m-2
rlut	Outgoing Longwave Radiation	toa_outgoing_longwave_flux	W m-2
rsds	Surface Downwelling Shortwave Radiation	surface_downwelling_shortwave_flux_in_air	W m-2
rsus	Surface Upwelling Shortwave Radiation	surface_upwelling_shortwave_flux_in_air	W m-2
ta	Temperature 250, 500, 850hPa	air_temperature	K
tas	Surface Air Temperature	air_temperature	K
tasmax	Maximum Daily Surface Air Temperature	air_temperature	K
tasmin	Minimum Daily Surface Air Temperature	air_temperature	K
ua	Zonal Wind Component 250, 500, 850hPa	eastward_wind	m s-1
va	Meridional Wind Component 250, 500, 850hPa	northward_wind	m s-1





6 hour instantaneous fields

Variable	Long Name	Standard Name	Unit
pr	Precipitation	precipitation_flux	kg m-2s-1
psl	Sea Level Pressure	air_pressure_at_sea_level	Pa
tas	Surface Air Temperature	air_temperature	K
ua	Zonal Surface Wind	eastward_wind	m s-1
va	Meridional Surface Wind	northward_wind	m s-1
ua	Zonal Wind Component at 250 hPa	eastward_wind	m s-1
va	Meridional Wind Component at 250 hPa	northward_wind	m s-1
va	Meridional Wind Component at 700 hPa	northward_wind	m s-1
ta	Temeprature at 700 hPa	air_temperature	K
zg	Geopotential Height at 500 hPa	geopotential_height	m





extremes

Variable	Long Name	Standard Name	Unit
cdd	Maximum Number of Consecutive Dry Days	N/A	days
etr	Intra-Annual Extreme Temperature Range	N/A	K
fd	Total Number of Frost Days in Year	N/A	days
gsl	Growing Season Length	N/A	days
hwdi	Heat Wave Duration Index	N/A	days
r10	Number of Days for which Precipitation Rate Exceeds 10 mm/day	N/A	days
r5d	Maximum 5-day Precipitation Total	N/A	kg m-2
r95t	Percent of Annual Total Precipitation due to Events Exceeding the 1961-1990 95th Percentile	N/A	%
sdii	Simple Daily Precipitation Index	N/A	kg m-2s-1
tn90	Percent of time Tmin > the 90th percentile value of daily minimum temperature	N/A	%