Description of the initial conditions and forcing data used for the SCM SHEBA runs. In most cases the data directories contain meta data files ITD initial conditions Data directory: /data/sheba/ghdata Source: JOSS, PI: Rothrock The ITD initial conditions are derived from the SCICEX cruise data. The data are provided as the average distribution for each of 34 tracks taken over 4 days from Sept 28 - Oct 1. I computed a single distribution from these by weighting each track's distribution by the number of scans taken on that track. The models begins on Oct 22, 1997, which is 22 days after the last SCICEX track. I assume no growth occured between the SCICEX cruise and Oct 22. The model calls a routine in ice_init.F that sets these values directly. -------------------------------------- Deformation forcing -- Opening and closing rates Data directory: /data/sheba/open_clos and /data/sheba/lindsay Source: Harry Stern and Ron Lindsay Harry gave me opening and closing rates on 28 Sept 2000. Harry says he generated the data for "4 sizes of square regions centered on the SHEBA site. Within each region there are a certain number of 5x5 km cells. The crude method I used is simply to look at the area changes of the cells within the region. For example, in the 50x50 km region there are normally 100 cells. Each cell has an initial area of 25 km^2, so the total area is 2500 km^2. Suppose 20 of the cells increase in area over the time interval between the SAR image observations, and suppose the total area increase of those 20 cells is 150 km^2. Then the opening is 150/2500 = 0.06 = 6% per time interval. If the images are 3 days apart, it's 2%/day." Also from Harry, "The method probably overestimates opening and closing because small errors in tracking the ice motion cause some cells to "open" and others to "close" erroneously. Also, because of the square geometry, a shear line running at an angle across the scene will cause some cells along the line to open and others to close, even if the actual motion across the shear line is pure sliding." I have two types of data files that can be used to force the column model. The first uses Harry's opening and closing data only. (Does not assume elliptical yield curve.) I had to fill in two parts of the timeseries to make it complete. (1) For Sep 15 to Nov 2, 1997, I used the mean for all data available for period between 15 Sep to Nov 15 from 1997 and 1998. (2) For Dec 23, 1997, to Jan 10, 1998, I used the mean for all data available for period between Dec 11 to Jan 25. Finally the data were linearly interpolated from the SAR data (considered as the value at the midpoint of the time between scans) to hourly intervals. Then the data were smoothed with a 12-hour running mean, which hardly changes them. The opening and closing rates are otherwise unmodified. file: open_clos_oct22.dat day since 12/31/96 opening closing [1/s] [1/s] The second option is derived from Harry's divergence and shear data, also estimated from SAR. This time I computed an opening rate by assuming an elliptical yield curve with e=2. Also I filled in data during the two "gaps" described in the previous paragraph with data from Ron Lindsay. Ron says he used SAR and buoy data, so I suppose during the gaps he just used buoy data. I used linear interpolation and 12 hour smoothing as above. My datafiles have four estimates of closing. First I have the closing from SAR as in the previous paragraph, except that I limited it to be no greater than the divergence (which occured because I filled in the closing with the mean and yet the divergence gaps were filled in with Ron's values). The next three estimates of the closing were computed from delta=sqrt(divergence.^2+0.25*shear.^2) closing=0.5000*(delta-abs(divergence))-min(divergence,0) closing=0.2500*(delta-abs(divergence))-min(divergence,0) and closing=0.1125*(delta-abs(divergence))-min(divergence,0) where the estimates have decreasing contribution from shearing motion. file: div_clos_oct22.dat day since 12/31/96 divergence closing1 closing2 closing3 closing4 [1/s] [1/s] [1/s] [1/s] [1/s] -------------------------- Zenith Angle Data directory /data/sheba/zenith Depends on ships position from SPO Moritz /data/sheba/ship_position The ccm ocean albedo parameterization has a strong zenith angle dependence for the direct beam component of the down solar. I wrote a utility program to input the ships position and time and call the CCM routines "shr_orb_params", "shr_orb_decl", and "shr_orb_cosz". I saved the output and use it as forcing in the ice_only model. file: zenith_oct22.dat The data set is in the following format: day since 12/31/96 cosine zenith angle -------------------------- Surface flux forcing data from Judy Curry flux_force.dat % starts on oct 10 simip2_forcing_data.txt % begins on oct 31 Took flux data from Judy Curry's single column model forcing datasets web site and the snowfall rate from the SIMIP2 web site. I needed snowfall rates for Oct 22-30 and the last couple of days of the datafile and so I used the mean from the first 2000 hours starting Oct 31. file: currydata_oct22.dat The data set is in the following format: ws10 airT10 qa10 lwrd swrd snofall [m/s] [K] [g/kg] [W/m^2] [W/m^2] [mm/day]