Instrument Description for Mobile Radiometric Platform (MRP) (see the on-line web documents for more information, including schematic and photograph): The MRP consists of the following sensors, provided by the NOAA Climate Modeling and Diagnostics Laboratory: _ Heimann KT19 infrared thermometer (3o field of view, 8 - 14 micrometer wavelength range); _ LI-COR Inc. LI-200SZ pyranometers (0.4 to 1.2 micrometer wavelength range); _ YSI 44031 Precision thermistor in a shielded tube. These instruments, data logger, and power supply were mounted onto a sled, and either towed by snow machine along transects, or positioned at the edge of leads, with the instrument package positioned over the lead. Three LI-COR pyranometers were used with the MRP; two in unmodified, hemispheric-viewing form and a third which was fitted inside a cone to effectively reduce its field of view to sample a spot on the surface approximately 60 cm in width from the platform¹s viewing height. Air and snow temperatures were measured using the YSI thermistor, either mounted on the MRP boom to sample air temperature, or removed from the boom and inserted into the snow surface to provide temperatures coincident with KT19 radiometric temperatures at fixed locations. The design of the housing shielding the thermistor allowed for accurate placement of the thermistor tip into the snow surface, and also acted as a shade to minimize solar heating of the thermistor. The KT19 optics were typically about 125 cm above the surface. The boom extends 120 cm from the side of the structure, with an additional 180 cm available as an attachable extension when the system is operated at a fixed location. The narrowed-view pyranometer could be mounted on the boom to provide a nadir view of the surface, or pointing rearward at 30o from nadir. As an alternative to the narrowed-view LI-COR sensor, a hemispheric-viewing LI-COR could be mounted in down-looking mode on a brace beneath the boom, about 35 cm above the surface and with 80 cm between the LI-COR and the sled edge. In addition, the hemispheric- view LI-CORs were used on a separate, portable mount to measure albedos. For albedo measurements, a single LI-COR was switched rapidly between level up-looking and down- looking directions, with the output voltages logged and averaged over time. The instrument package is controlled using Campbell Scientific CR10 data logger. A multiplexer activates a total of 18 channels, controlled by a switch array used to select which combinations of measurements are recorded. Two gel-cel batteries supply 24 volts to the logger and to the heating elements in the KT19 housing. The gel-cels were sufficient to power the system for about 6 hours at temperatures near - 20o C. At SHEBA, 12-volt marine batteries and solar panels were used to provide additional power for continuous monitoring over periods exceeding 24 hours. The logger and gel-cel batteries are packaged in an insulated box which can be removed to facilitate battery charging and downloading of data. The package can be carried in a small backpack, and was used with the KT19 separately from the sled configuration to acquire data over areas such as large ridges and re-freezing leads that could be sampled only on foot. File Format for Field Sample Runs (Level 1 Text Files) (Note: Format for KT-19 calibration sampling runs is slightly different, and is explained in a subsequent section). (Note: Level 0 files are available upon request. The only substantive difference between Level 0 and Level 1 is the conversion in Level 1 of the thermistor reading from resistance to temperature. This conversion was done using the manufacturer-supplied conversion table. Organization: 11 columns organized as a table, with one row per observation. Column Definition: (1) record type, (2) year, (3) Julian day, (4) hour of observation, (5) minute of observation, (6) second of observation, (7) data sampling mode (see below), (8) thermistor temperature (degrees Celsius), (9) KT-19 housing temperature (degrees Celsius), (10) KT-19 temperature (degrees Celsius), (11) LICOR pyranometer voltage (millivolts). Format (Fortran): (5(I4,1x),F5.2,I3,4(f12.4)) Time Sampling: The time sampling interval for transects was 1 second. Sampling interval for point measurements (for example, the observations obtained at lead edges) was 10 seconds. The time interval can be determined from the "Second of Observation" column (column 6) in the data files. Available Files: File Name Size # Rows Description (Mbytes) (records) --------- -------- --------- ----------- A_TRAN1.TXT 983262 11991 transects A_TRAN2.TXT 963582 11751 transects S0424B1C.TXT 48306 575 BRDF experiment S0428L1C.TXT 593628 7076 Lead monitoring S0430L1C.TXT 619416 7374 Lead monitoring S0503L1C.TXT 37884 451 Lead monitoring S0504L1C.TXT 208152 2478 Lead monitoring S0505L1C.TXT 858396 10219 Lead monitoring S0508L1C.TXT 1200192 14288 Lead monitoring SH_CAL2.TXT 684609 11508 KT-19 calibration Data Sampling Mode Definition: During operation of the MRP, a bank of four on/off switches could be set to send a data code value to the Campbell data logger. This code value appears within each data record in column 7 of the above files This code was used to identify the particular type of experiment being conducted at the time. The code definition is as follows: Code Value Experiment Mode ---------- --------------- 1 Standard operation along transects 3 KT-19 calibration; probe thermistor measuring air temperature 5 Probe thermistor at snow surface; KT-19 looking downward 7 KT-19 calibration; probe thermistor at snow surface 9 Standard operation for Bi-directional reflectance sampling 13 Probe thermistor at snow surface; KT-19 looking upward KT-19 Calibration: The supplied KT-19 temperatures in the above files can be calibrated according to field calibration measurements conducted in the field (see the available summary paper on MRP operation for a description of this calibration system). The latest available calibration equation for this conversion is: KT19(calibrated) = 0.797525 + 0.927807*KT19(raw) File Format for Calibration Files: These files consist of observations collected for calibration of the KT-19 radiometer. Organization: 14 columns organized as a table, with one row per observation. Column definition: (1) record type, (2) year, (3) Julian day, (4) hour of observation, (5) minute of observation, (6) second of observation, (7) data sampling mode, (8) thermistor temperature (degrees Celsius), (9) KT-19 housing temperature (degrees Celsius), (10) KT-19 temperature (degrees Celsius), (11) LICOR pyranometer voltage (millivolts), (12-14) thermistor temperatures of calibration source (three identical thermistors attached to the calibration source). Format (Fortran): (5(I4,1x),F5.2,I3,7(f12.4)) Quality Control and Data Cautions The files available via this page have been quality controlled to remove initial data-collection problems during data logging. Missing data values have been recoded as "99999." or "-99999." in these Level 1 data files. Possible data outliers have not been filtered from these files. Shadowing of the surface affected the observations along certain segments of the transects. "Spikes" were introduced into the KT-19 and LI-COR observations to mark particular points along transects. These spikes can be seen in the data sets, and can be used to delineate particular legs of transects. Users interested in these data are strongly encouraged to contact the investigators so that we can provide additional guidance and suggestions regarding data use. For example, field notes recorded likelihood of shadowing, and provides additional information on sky and surface conditions that are relevant to interpretations of the MRP data.