Example Executive Summary- Climate Program Precip¶
How to use this example¶
This is an example of a 2 page summary of a much more complicated analysis. Providing an overview is always more helpful than you think.
This short document uses standard ReStructuredText (rst) format. It includes syntax for headings (chapter, section, sub-section, etc.) numberd lists, bullet points, hyperlinks, and probably a few others.
This section shows up first in the final documentation because it is listed first in index.rst.
Summary¶
Sheltertop and Stand Alone rain gauges at HJA benchmark climate stations (UPLO, CENT, VARA) use industrial tank gauges (analog level transmitters) to record precipitation. Both styles of rain gauge have a heated orifice that feeds into a smaller, heated, collection tank, amplifying the increase in the tank for a given amount of precipitation. The tank gauge measures the current tank depth, which is then processed through QA programs to identify accumulation of precipitation.
2 of the industrial tank gauges began to fail in WY2019. Any repalcement must fit in our installation and maintain the precision and accuracy of our dataset.
Sizes of orifice, tank, and instrument¶
The first step is to understand the current tank size and its relationship to orifice size.
The closest recreation of the coefficients currently applied at the stations relies on several assumptions, that contradict most of the formal documentation derived from FSDB and other sources posted on our website:
- SH orifice is 13.3”
- measured at UPLO
- consistent throughout documentation
- SA orifice is 19.75” at UPLO/CENT
- Implied in EDLOG program notes for VARA
- Contradicts all current docs , as well as older method documentation
- SH tank gague length is 53”
- Required for calculating coefficient
- Contradicts UPLO Establishment Report
- Taken from on-site instrument label
- SA tank gague length is 113”
- Taken from on-site instrument label at UPLO/VARA
- contradicts method documentation
- Assumed that the mounting distance was set at 5” and is subtracted from instruemnt range (in addition to 3” dead zone).
Tank gauge accuracy¶
Current instrument specifications, adjusted for conversion between orifice and well. Numbers represent potential errors in mm of precipitation:
- Stand alone: accurate +-0.2794 mm and repeatable within +- 0.0803 mm
- Shelter: accurate +-0.3810 mm and repeatable within +- 0.1120 mm
The worst case shelter measurement would be +- 0.4930 mm
Total measurment error observed within our record from 2015- 2020 was assessed by looking at average change during known dry periods when the true change should be 0. I suggest the mean can be interpreted as accuracy, the standard deviation as precision, and the that the two combined represent total measurement error. The observation perdiod had lower meaurment error than sensor specs.
- Stand alone: mean -0.0011 mm, StdDev 0.0861, total error 0.0872 mm
- Shelter: mean -0.0029, StdDev 0.1922, total error 0.1951 mm
A spot check of UPLO SA from 1996 - 2005 showed that the sensor has at least been within it’s manufacturing specs since instalation, though there was 4 - 5 x more error in this earlier period.
It was also found that the measurement error could be 5x smaller if we averaged our measurements; either repeating the sample multiple times, or taking a mean of 15 second samples at the 5 min record.
Replacement sensor¶
A tipping bucket is the most accurate and precise replacement sensor as well as the most affordable. In the shelters, it is trivial to position the tipping bucket beneath the hose coming from the orifice, and so that the tip empties into the tank. This would continue to allow a redundant monthly total to be calculated from the tank sight-gauge.
However there is no practical installation in the stand alone. For the stand alone, the only replacement that doesn’t reduce precision and accuracy is the MTS LPR, an upgrade of our current MTS tank gauge.