Downwelling Irradiance (Ed)

1. Upper and lower four byte portions of each averaged count for each wavelength.

   ocr504_412nm_counts_lower

   ocr504_412nm_counts_upper

   ocr504_443nm_counts_lower

   ocr504_443nm_counts_upper

   ocr504_490nm_counts_lower

   ocr504_490nm_counts_upper

   ocr504_555nm_counts_lower

   ocr504_555nm_counts_upper

   If the OCR507 is involved, then three additional wavelengths, 510, 665, and 670 are required.

2. Number of counts averaged for each observation, ocr504_num_samples_used.

3. Serial number for OCR instrument (obtained from a global attribute)

1. OCR calibration table for irradiance sensor.

OCRConvert.m

Downwelling irradiance for each wavelength in microwatts/cm^2/nm, Ed.

The data from any OCR sensor (either OCR507 or OCR504) is reported in raw digital counts, which have a baseline value of about 2147000000. As this number is too large for the Campbell data logger to handle, the datums for each of the wavelengths is split into two parts by first converting the average to a hexadecimal number, and then splitting the hex number into an upper and lower four byte portion. These hex portions are then converted back to integers and then output as two numbers (the upper and lower counts in the NetCDF file). Thus each wavelength of data will have two integer numbers that have to be reassembled to get the average digital count reading for that wavelength. Thus a seven wavelength sensor (OCR507) will have fourteen high resolution numbers, while a four wavelength sensor (OCR504) will have eight pieces of data. If not enough counts were used, then the irradiance value cannot be considered valid. Once the counts are fully formed, they are turned into irradiance using calibration coefficients for each wavelength. The calibration coefficients are particular for each individual sensor.