¶ Ka Band ARM Cloud Radar (KAZR)
¶ Background
The Ka-band ARM zenith radar (KAZR) remotely probes the extent and composition of clouds at millimeter wavelengths. The KAZR is a zenith-pointing Doppler radar that operates at a frequency of approximately 35 GHz. The main purpose of this radar is to determine the first three Doppler moments (reflectivity, vertical velocity, and spectral width) at a range resolution of approximately 30 meters from near-ground to nearly 20 km in altitude.
¶ Additional Information
The KAZR replaces the millimeter wavelength cloud radar (MMCR) and utilizes a new digital receiver that provides higher spatial and temporal resolution than the MMCR. In addition, spectral artifacts in the data are significantly reduced in the KAZR, providing researchers the ability to study cloud dynamics to a much higher degree than with the MMCR. After the MMCR was upgraded, it was decided that it should be named differently as there were only 2 components from the original MMCR that were in the KAZR.
For more information on radar, please see General Information on radar
For more information see KAZR.
¶ Expected Operations
¶ Metrics
The DQ Office provides all the QC flags for the KAZR. These can sometimes be off, so do not trust the flags completely. We keep revising the limits as best we can. The RH and various temps will flag at times. There is also the twta_status_state that is flagged constantly as well. After viewing the metrics for a prolonged period of time, and something does change, that may be cause for further investigation.
¶ Plots
Moderate Sensitivity Mode (MD)
This should have the same variables as the general mode, but is a little more sensitive.
High Sensitivity Mode (MD)
Depending on the location, this mode may only have the Co-Pol mode but will have the main variables listed above (Reflectivity, Doppler Velocity, Spectral Width, Signal-to-Noise Ratio).
Diagnostic Data
There are a lot of components in a radar and there are many sensors used to monitor the system, so the diagnostic plots have a lot of data in them. They mostly include, temperatures, powers, noise, gains, calibration constants and transmit powers, see Fig. 2 and Fig. 3.
- Figure 2A shows the outside air temperature as well as the local temperature and relative humidity inside the instrument. The local temp is relatively constant as is the local rh. The local RH looks like it is spiking, but the range of the data is only over 3%, so there is a little variability in the data.
- Figure 2B shows an array of temperatures from different components inside the instrument. These temperatures should be relatively constant, but does have oscillations throughout the day.
- Figure 2C shows temperature for the antenna and feedhorn as well as the antenna relative humidity. These sensor are attached to the antenna, so they should follow similar patterns for temp and rh throughout the day. The antenna can heat up causing it to indicate a higher temperature than the other temp variable.
- Figure 2D shows the different voltages from the power supplies. These will oscillate, but should be relatively constant.
- Figure 3A shows different status flags and alarms. These should always be 0 unless there is a problem or someone is remotely controlling it.
- Figure 3B shows the calibration constants. These should be constant unless the instrument mentor changes them. If they do change, it is worth noting in the DQA's.
- Figure 3C shows the noise signal and receiver gain for the horizontal and vertical channels. These should not vary much.
- Figure 3D shows the receiver noise, which also should not vary much.
- Figure 3E shows how much power is being transmitted. This should not change much. Note the axis limits on the plot are over 0.03 dBm which is why it looks like it is changing a lot
¶ Comparison Plots
Noise Floor Comparison
Through some special processing, we are able to pull out the noise floor that the KAZR is measuring. This is plotted up over 14 days, normally with other vertically pointing radars. The data should be somewhat steady, there will be fluctuations. If the data are abnormally fluctuating over time, bring it to our attention.
Radar Lidar Comparison
Most 2D profiling instruments are plotted up on the same plot at a site to compare. Drop size distributions from the disdrometers are also plotted at the bottom. The white overlay is the cloud base height from the vceil25k. Blue overlays of when surface precipitation instruments are reporting precip are at the top of each profile plot.
¶ Site-Specific Information
Instrument is located at all sites.
¶ Known Issues
¶ Known Behaviors
Known issues for this instrument that MAY NOT need to be mentioned in your DQA's can be documented here.
¶ Past Problems
Past problems for this instrument that DO need to be mentioned in your DQA's and possibly requiring a DQPR submittal:
Sometimes the transmitter will go out on the KAZR and the KAZR will not be able to detect clouds. The reflectivity will look like a clear day. The easiest way to determine this is by viewing the comparison plots. Please see DQR D110809.1
Channels Switched
The channels were switched so that the Cross-Pol reflectivity was higher than the Co-Poll reflectivity. This can be seen when there is meteorological echoes and also in the LDR. The LDR should be negative, but when this problem occurs, the LDR becomes positive. Please see DQR D130813.1
