Radiation:
Infrared

All-wave      Incident     Reflected      Transmitted      Laboratory      Infrared

The surface temperature of the sea ice was recorded using a Kt-19 infrared photometer with an operational wavelength band of 8-14 microns. The instrument was operated in handheld mode from the ship’s rail at a nadir angle of approximately 45 degrees and the output was recorded on a handheld data logger (Polycorder®). To maintain proper calibration the instrument case was insulated with a foam jacket and an electric heater. As the air temperature decreased with the onset of freezup, a rail site was selected to take advantage of heat vented from the ship’s living quarters. The case temperature of the Kt-19 was thus kept above 0oC for all results shown maintaining the instrument calibration within manufacturers specifications. Calibrations were initially provided by repeated observations of melting drained ice, whose surface temperature was 0oC. During freezup, a calibration was provided by observing open leads in which the water in the boundary layer was well mixed and had a temperature close to –1.8oC.

Observations were carried out at the same time of day as the shortwave observations (near solar noon) to record the characteristics of the same ice types. Data were recorded selectively for each different ice type available on a given day by sighting in on different types of interest. This helped to remove the bias against infrequent surface types. Average values and their standard deviations are shown in the graph below for the various surface types. The sky temperature was also recorded by pointing the instrument upward at 45 degrees to provide distinct benchmarks in the observational record and to aid in the determination of the (small) reflected sky contribution to the observed signal. Because the instrument was located less than 10 m above the surface, the contribution from the air was negligible as verified by comparative measurements from the rail and on the ice at selected ice stations.



Tom and Jeremy making measurements with the KT-19 radiometers.

Summary of all ice infrared temperature results. Note the general downward trend.
 		 Summary of all infrared temperature measurements of the sky. The large differences are due to clear (cold) and cloudy (warm) conditions.
 
Date Time (UT) Latitude Longitude Comments
11-Aug-05  2400  76.232 -157.480   CO-SDNV, low clouds, fog, mist, visibility about 1 km
13-Aug-05  2130  77.461 -152.575   CO-SDV, light fog, visibility about 1 km
14-Aug-05  2330  78.230 -154.10   CO-SDV, fog is gone, ceiling about 3000 feet, variable clouds.
15-Aug-05  2415  78.183 -160.175   CO-SDV, fog is gone, ceiling about 800 feet, some light snow
16-Aug-05  2440  78.295 -172.554   SDCV, scattered fog, shadows
17-Aug-05  2310  78.294  -172.276  SDCV, low fog,  bits of blue sky
18-Aug-05  2330  78.186 -176.186   SDNV, low fog, total clouds
19-Aug-05  2315  78.566 -177.831   SDCV, foggy visibility a couple of km
21-Aug-05  2250  79.999 -170.990   SDCV, foggy visibility a couple of km
22-Aug-05  2330  81.086 -176.915   CO-SDNV, great visibility to the horizon, no fog at all
23-Aug-05  2320  82.047 -178.277   CO-SDNV, snowing hard
24-Aug-05  2300  83.198 -179.270   PO-SDCV, sun bright enough to cast shadows, some blue sky.
27-Aug-05  2458  84.108 -167.932   CO-SDNV, totally overcast with intermittent light precipitation
28-Aug-05  2345  84.209 -156.848   PC-SDCV, no fog, good visibility
29-Aug-05  2630  84.310 -149.072   CO-SDCV, can see sun, but no shadows
30-Aug-05  2420  83.955 -143.190   CO-SDCV, can see sun, but no shadows 
1-Sep-05  2340  84.602 -153.620   CO-SDV sun in and out
3-Sep-05  2430   86.129  -178.995   
4-Sep-05  2330  86.603 176.215   CO-SDNV, no fog, very windy 25 knots with 30 kt gusts
5-Sep-05  2215  86.656 155.205   CO-SDNV, no fog, low ceiling, still fairly windy
7-Sep-05  2235  87.692 153.140   CO-SDNV, no fog, low ceiling, blowing like crazy
8-Sep-05  2440  88.516 148.508  
9-Sep-05  2400  88.514 152.465   
12-Sep-05  2300  89.967 -69.947  
14-Sep-05  1410  88.815 70.202   CO-SDNV
15-Sep-05  1440  88.062 58.414   PC-SDCV, sun breaking through
16-Sep-05  1420  87.610 58.919  BC, some thin clouds on horizon
17-Sep-05  1440  87.270 57.179  
19-Sep-05  1240  86.341 50.364  
20-Sep-05  1300  85.639 47.059   CO-SDNV, low stratus present
21-Sep-05  1230  85.016 43.857   PC-SDBV, there is a definite bright glow to the south
22-Sep-05  1200  84.356 42.925  CO-SDNV
23-Sep-05  1800  81.849 33.551  CO-SDNV, dull glow to the south
24-Sep-05  1200  81.464 20.916  Sunny skies with some haze, diamond dust and low clouds
25-Sep-05  1145  80.688 11.001  CO-SDNV
26-Sep-05  1320  80.177 5.754  CO-SDNV

Codes: CO - complete overcast    PC - partly cloudy    BC - brillantly clear
           SDCV - solar disk clearly visible    SDV - solar disk visible    SDNV - solar disk not visible