¶ Laser Precipitation Monitor (LPM)
¶ Instrument Description
The LPM measures the amount, intensity, and type of precipitation and is better suited for cold climates. It is routinely deployed inside of a snow fence to help reduce the effect of blowing snow on the measurements.
* For more information see the LPM Instrument web page.
¶ Expected Operations
¶ Metrics
The LPM metrics are mainly of the different voltages and statuses reported and not the primary variables and should be all green. This is an a1 level and QC is generally not provided in this level. The limits for these variables are set in the DQ scripts and can be adjusted if needed.
¶ Plots
Drop Size Spectrum
2D plots of the drop distribution over time based on drop diameter (1st plot) and fall speed (2nd plot)
Precipitation Variables
A number of variables related to the precipitation measurement are plotted; 5 minute and total intensities, solid and liquid precipitation intensity, number of particles, accumulation, visibility, calculated radar reflectivity, etc... The last 2 plots are the air temperature measured by the LPM compared to that measured by the MET and the wind speed as measured by the MET.
Note: since the instruments are utilizing different types of sensors to measure the temperature, it is expected that there will be a slight difference.
Weather Code
Plot of the weather code reported by the LPM every 15 minutes(SYNOP 4677) along with a plot of a 2D profiling instrument (KAZR, MPL, etc) showing the clouds/precipitation over the site. Note, even if there are clouds, it will say clear. The sensor will indicate clear until it detects precipitation or fog/haze.
Diagnostic
Plots of the various temperatures, voltages, and currents. The corresponding status variables are also plotted and should be 0 unless there's a problem.
Site Camera
Note shown... This is a movie showing the precipitation measurement instruments at NSA and OLI. Along with the LPM, you will also see the SRS and the WB. It is mainly just there to give you an idea about the conditions onsite. In the past, we have seen snow pile up and bury the sensors.
¶ Comparison Plots
Precipitation Comparison
The LPM is included on the NSA and OLI precipitation comparison plots. This is used as a measure to make sure the instruments are recording precip at the same time. The accumulations will be different, sometimes drastically. This is all based on how each instrument measures precipitation and the fact that some are better than others for measuring solid precipitation. There is no need to mention problems that show up with instruments other than the LPM. I.e. if the PWD is spiking, you don't need to indicate anything in the LPM DQA. The analyst covering the PWD will handle that in the instrument specific DQA.
¶ Site-Specific Information
The LPM is located at NSA and AMF3.
¶ Known Issues
¶ Known Behaviors
List of known issues for this instrument that MAY NOT need to be mentioned in your DQA's:
Document some here
¶ Past Problems
List of past problems for this instrument that DO need to be mentioned in your DQA's:
Buried in Snow
The LPM along with the SRS and WB were all buried in snow at the OLI site during the 2018 winter. This was characterized by control_output_laser_status constantly flagging and all the variables being flatlined.
Heater Problem
The NSA LPM had a problem with the heater from the install and the metrics were consistently flagged accordingly.
