SHEBA Hobo Measurements:

"Small Hobo-XT data loggers logger (Hobo XT manufactured by Onset Computer Corp.,"

"536 MacArthur Blvd., Pocasset, MA  02559-3450: 508-563-9000), were installed at 30 "
stakes near the SHEBA camp and at “Baltimore” to measure the variation in temperature 
"at the snow-ice interface.  Each HOBO logger had a thermistor placed at the interface, "
with the data logger in a Nalgene jar taped to the snow-ice depth stake. The instruments 
"were installed in late-October, over a period of several days. They recorded data "
"continuously until about April 25th, at which time their memory storage was full. On the "
"28th and 29th of April, the loggers were dumped and relaunched, leaving a data gap of "
about 4 days. They then ran until freeze-up. Table 1 indicates the location of each Hobo 
"by stake and site name, and the snow depth (n=3) on April 28-29th."



Measurement Uncertainties
Thermistors were capable of measuring temperatures between  -37° and +46°C with an 
accuracy stated by the manufacturer  to range between 0.5 and 1%.  This translates to 
"uncertainties of up to ±0.5°C for recorded temperatures. To be conservative,  we think the "
uncertainty  should be considered ±1°C.  Temperatures lower than -37°C are recorded as      
"-37°C, so periods of extreme cold are represented as ""flat"" spots in the temperature "
record. 

The data loggers recorded the time each datum was collected in Alaska Standard Time. A 
worst case timing  error due to data logger drift of about 45 minutes was calculated for 
the longest period of operation (6 months) based on the manufacturer's specifications. 
Logger times were reset to computer time during the site visit at which time uncertainties 
due drift were returned to zero. Examination indicated that all loggers were synchronous 
"to ±1.5 hours, and as this is less than the timing accuracy, all data are associated with a "
single set of time-date values. Care should be excercised in interpreting time delays 
between sites that are less than 4 hours. 

"Inidividual thermistors may have been alternately buried by snow, and excavated by the ",,,,,,
"wind, giving rise to large relative variations in temperature between thermistors. Once the ",,,,,,
"thermistors were exposed (Temp. > 0°C), temperatures may be unreliable (see data from ",,,,,,
"Late-May through July, 1998. ",,,,,,


Table 1: Location of Hobo data loggers,,,,,,

Hobo,Stake,Location,Depth1,Depth2,Depth3,Ave. Depth
2,81,Pittsburg,50,48,49,49
3,79,Pittsburg,20,21,20,20.33
4,41,"the ""Ridge""",44,46,43,44.33
5,31,"the ""Ridge""",88,83,89,86.67
6,75,Pittsburg,57,52,54,54.33
7,77,Pittsburg,14,14,14,14
8,55,"the ""Ridge""",58,55,49,54
9,47,"the ""Ridge""",25,25,32,27.33
10,58,"the ""Ridge""",6,6,6,6
11,26,"the ""Ridge""",74,74,73,73.67
12,70,"the ""Ridge""",36,38,36,36.67
13,73,"the ""Ridge""",48,49,31,42.67
14,21,"the ""Ridge""",41,41,43,41.67
15,57,"the ""Ridge""",61,63,63,62.33
16,133,Baltimore,44,45,45,44.67
17,29,Pittsburg,11,11,11,11
18,148,Baltimore,33,33,34,33.33
19,9,Pittsburg,35,34,37,35.33
20,32,"the ""Ridge""",71,58,70,66.33
21,142,Seattle,48,48,50,48.67
22,37,Baltimore,65,67,69,67
23,63,Baltimore,52,55,56,54.33
24,11,Baltimore,80,81,83,81.33
25,51,Baltimore,20,19,18,19
26,39,Seattle,39,39,39,39
27,44,Seattle,8,9,8,8.33
29,7,Seattle,43,43,43,43
30,34,Seattle,35,35,37,35.67