Intro:

    The weather station on the platform failed on 01dec20 when the platform collapsed. We purchased the same Orion weather station. It was  installed  on the roof of the lidar lab (about 1000 ft north of the previous site) on 13jan21.  The configuration was similar to the old weather station (15 second logging of data).

    After a few large rains, we noticed that the rainfall reported by the Orion station did not match the local manual measurement of the rainfall. The manual measurement used a tipping rain gauge that is measured each morning at 6:00 ast by the guards. Its dipping stick has a resolution of .02 inches (need to check).

    We also looked at the recorded rainfall  from  a nearby  usgs rain gauge 

• utuado, tanama station 4 miles south of AO (station # 50028000).  see map
• The marker is the station
• AO is the round circle in the upper middle part of the map

    As part of checking out the Orion station we did a tap test on the sensor using the eraser end of a pencil.

Tap Test

    On 9Feb21 we did a tap test on the Orion rain sensor.  This should generate rainfall in the sensor. Using the erase end of a pencil we :

• 14:19   30 taps in center of sensor. took about 20 seconds
• 14:21   30 taps moving around the sensor. took about 20 seconds
• 14:23   30 taps moving around the sensor.

Plot showing results of the tap test (.ps) (.pdf)

• You can see the 3 rainfall transitions for each set of the tap test.
• The expected value was .02 to .03 Inches of rain
• The last 2 sets showed this amount.
• the first set change by  almost twice the expected value. I wonder if i was tapping too hard, or that concentrating in the center gives a larger value.

Comparing with tanama site

    The usgs has  weather station located near utuado on the rio tanama river (same river that flows by AO).
 The station location:

• utuado, tanama station 4 miles south of AO (station # 50028000).  see map
• The marker is the station
• AO is the round circle in the upper middle part of the map

    I downloaded the 15 minute data from 13jan21 through 15Feb21 and compared it with the AO data. To keep the plot size smaller, i averaged the AO 15 second data to 1 minute samples.

The plot compares the two sets of rainfall data (.ps)   (.pdf)

• Black trace: the AO Orion weather station
• red : the usgs tanama values (the plot say 5 mile from  AO, after checking the map it's closer to 4 miles).
• I've removed the tap test data from the plots.
  
• Top: cumulative monthly rainfall
• Bottom:Daily rainfall for the time period
• During January there were multiple occasions when the usgs saw > .75 inches while AO saw  < .1 inches.
• In February there are two days when AO saw more than the usgs site.
• The rainfall around AO can be extremely  localized (it can rain at AO and be dry 1 mile away)...So this comparison may not be useful.

processing: x101/wst/test/pltaousgs.pro

Comparing aoTipper with Orion

    There is a manual tipping rainfall gauge at the AO gate. The guards read this every morning at 6:00 ast. The dip stick has a resolution of about .02 inches. It is located less than 1000 ft from the Orion station.
    The tipper data is  a single value. It contains data from 6:00 on a day to 6:00 on the following day.

The plot compares the Orion data with the AO tipper (.ps) (.pdf)

• The blue lines are the Orion rainfall data.
• It covers the 24 hours starting at the beginning of the AO tipper value
• The red line is the AO tipper value read at the end of each horizontal red line.
• The vertical dotted lines show each dataset of the AO tipper.
• If the two values matched, then  the blue line at the right edge of each set should match the red line.
• Every single tipper set  with appreciable rainfall (>.1 inches) surpasses the Orion data (except for 11-12Feb21).
• on 13-14 Feb21 the AO tipper aw 1.01 inches while the Orion station registered 0.

Comparing the AO tipper with the Orion weather station shows that the Orion weather station is not working correctly. The sensors are so close together that spatial variability can not account for this.
processing: x101/wst/test/pltaotip.pro

210510:Orion rain sensor & tipping bucket

• The mraintoday and mraintoday_2 were used for the comparison
• The plotted values is the value at the end of each day.
• Top: over plot the rain sensor and the tipping bucket by day.
• Black is the orion tipping bucket, red is the orion rain sensor.
• Middle: plot  Tipping bucket - rain sensor
• there are 4 days (out of 62) where the difference was greater than .1 inches.
• The largest difference was .4 " (where the bucket measured 1", the sensor .6").
  
• Bottom: plot the measured difference versus the average daily rainfall
• There is no linear relationship between the difference and the amplitude.

The 2nd  plot compares the orion sensor, bucket, and the ao tipping bucket (.ps) (.pdf)

•  The ao tipping bucket is located at the gate (< 1000 feet from the orion station)
• It  is read manually each morning at 6am and reported to usgs.
• I used the mrainthismonth and mrainthismonth_2 for the orion values
• the monthly data was taken at 6am (with the  monthly data 1 data before was subtracted).
• i also  checked for crossing a month boundary.
• The black is the orion tipping bucket
• the red is the orion rain sensor
• the  light blue is the ao  tipping bucket at the gate.
• The gate tipping bucket occasionally differs from the other 2.
• For  the days with large orion bucket - sensor readings
• the  gate value is much closer to the orion bucket value

processing: x101/wst/test/compare_sensors.pro, pltaotip_both.pro

Summary

• The tap test showed that the Orion sensor was responding to external events
• Comparing the Orion values with the close by usgs site was inconclusive
• the rainfall spatial variation makes 4 mile comparisons   inconclusive.
• Comparing different measurements:
• orion sensor vs orion tipping bucket (at the same location)
• 4 out of 62 days showed a difference of > .1 inches
• for these 4 days the ao gate tipping bucket was much closer to the orion tipping bucket.
• to  do:
• 210511:replaced orion rain sensor with the spare sensor to see if  it has better  agreement  with the orion tipping bucket.
  

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