The Narrow Field of View (NFOV) radiometer was removed from service at SGP and sent to NASA GSFC for calibration using the AERONET facilities. Christine Chiu reports that recalibration of the 2-channel NFOV at NASA GSFC resulted in good agreement with a Cimel sunphotometer at 870 nm and 673 nm. (A 5% bias was observed for low radiances at 673 nm, but the bias disappeared at higher radiance values.)
The 2-channel NFOV radiometer was installed at Shouxian, China and Heselbach, Germany for the AMF deployments.
With the advent of the 2-channel NFOV, there no longer appears to be any interest in the 1- channel NFOV. Consequently it has been suggested that the 1-channel NFOV be retired.
The Narrow Field of View Zenith Radiometer (NFOV) is a ground-based radiometer that looks straight up. As implied by the name, the field of view of the instrument is narrow, thus permitting the measurement of the downwelling zenith radiance. The output of the instrument consists of a time series of 1-sec observations of the zenith spectral radiance. The radiance is measured at a wavelength of 869 nm. Data from the instrument have many uses; for example, the internal structure of clouds may be characterized by examining a time series of the radiance data.
* For more information see the NFOV Instrument web page.
Radiance flags overnight due to lack of incoming radiation; this is what the metrics typically look like.
The tests and bit numbers can vary between variables. Below is a list of many of the QC Tests specific for the AERI instrument. Explanations of the Mentor QC and Data Quality Office QC can be found at DQO QC Bits.
Detector Temp vs Time
Radiance (673nm and 870 nm) vs Time
Raw counts (673nm and 870nm) vs Time
Instrument is compared against SASZE
The NFOV is located at AMF1.
List of known issues for this instrument that MAY NOT need to be mentioned in your DQA's:
Data Clipping/Over ranging
After moving the NFOV2CH from the higher latitudes of Cape Cod, Massachusetts, to equatorial Brazil the radiance plots experience large spikes around solar noon. When the data falls outside of the top range (0.5 W/m^2/nm/sr) it "clips" and "overflows" to the lowest limit (-19 W/m^2/nm/sr). The issue is not an instrument failure, but it was not properly calibrated for the increase in incoming solar radiation from Massachusetts to Brazil.
List of past problems for this instrument that DO need to be mentioned in your DQA's:
Instrument noise problem
When the signals are very low, a regular feature can be seen in the data. It begins on the hour, and lasts for ~20 minutes. This feature is a rise in the signal of ~1/4 to ~1/3 count, or 0.25 to 0.33 mV. It is small even when compared with the NFOV's typically small signals. My initial hunch is the NFOV is located next to or nearby equipment that operates/broadcasts/etc beginning on the hour, and lasting for ~20 minutes. Looking (very closely) back at the previous deployment, this regular signal bump is also evident, so it seems the equipment contaminating the NFOV is part of the AMF1, and not unique to this deployment.
Noise from nearby objects