the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
A new reference-quality precipitation gauge wind shield
John Kochendorfer
Tilden P. Meyers
Mark E. Hall
Scott D. Landolt
Howard J. Diamond
Abstract. Gauge-based precipitation measurements suffer from undercatch due to the effects of wind, with solid precipitation measurements especially susceptible to such errors. When it is snowing and windy, unshielded precipitation gauges can catch less than half of the amount of precipitation of a gauge that is protected from the wind. For this reason, the US Climate Reference Network (USCRN) developed a large, double layer, wooden wind shield called the Small Double Fence Intercomparison Reference (SDFIR). In past studies, the SDFIR has been demonstrated to be the most effective wind shield in use in any weather or climate network, reducing solid precipitation undercatch to less than 10 % in wind speeds up to 8 m s−1. However, the wooden SDFIRs are subject to decay, they are difficult to replace and maintain, and they hinder access to maintaining the gauge. For these reasons, a new precipitation gauge wind shield called the Low Porosity Double Fence (LPDF) has been developed for use in the USCRN. Tested at three separate sites chosen for prevalent windy and snowy weather, the precipitation measurements recorded within the LPDF compared well to the SDFIR. After more than two years of measurements, the total precipitation recorded by the LPDF at each individual site differed by ± 1.2 %, and the total LPDF accumulation from all sites was 0.03 % greater than the SDFIR accumulation. For the measurement of solid precipitation, the LPDF-shielded measurements were statistically indistinguishable from the SDFIR, and the time series of accumulation from precipitation gauges shielded by the SDFIR and the LPDF were almost identical. This new wind shield is much smaller and easier to install and maintain than any other reference-quality wind shield for the measurement of solid precipitation, and may be of use within other meteorological, hydrological, and climate networks. It could also serve as a secondary reference precipitation measurement for precipitation intercomparisons held in remote locations where the construction of a full-sized Double Fence Intercomparison Reference (DFIR) shield is not feasible.
John Kochendorfer et al.
Status: final response (author comments only)
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RC1: 'Comment on amt-2023-2', Anonymous Referee #1, 03 May 2023
Congratulations for your article is very interesting and well treated. The paper is an important example of using alternatives to solid precipitation measurements in operational networks taking into account cost-value decisions. It is well suited to the audience of the journal and worth being published.
I like to remark the good experimental design and the strong methodology with 3 different sites for intercomparison. In my opinion, this is very important because it shows that replication in other sites is possible. The results are clear and the quality control of data is consistent with other similar studiesHowever, some details and explanations are required in order to reproduce the LPDF in other sites, either for other intercomparisons or just for operational measurements.
I would suggest to include a more detailed description of the LPDF including a complete diagram (i.e cross section) and some details how the slats are installed within the chain link fence panels (before/after), how to avoid displacement of LPDF under strong winds, approximate dimensions of concrete footing and how to anchor and elevate the LPDF etc
Another important point for discussion is to analyze if given the objective of 25% of porosity the design can/could be slightly different (i.e panel dimensions, slats width, etc) obtaining similar results
Another important point is a more detailed discussion about durability of LPDF compared with SDFIR and the approximate price different on material and time for installation
Also some minor comments are provided below that I would ask the authors to consider before the paper can be accepted for publication.1) Remove DFIR on the caption for figure 6 y 8
2) Percentage of cases Ugh> 9 m/sCitation: https://doi.org/10.5194/amt-2023-2-RC1 -
RC2: 'Comment on amt-2023-2', Anonymous Referee #2, 16 May 2023
In this manuscript Kochendorfer et al. present a new type of precipitation gauge wind shield to mitigate undercatch of solid precipitation in windy conditions. The study describes the Low Porosity Double Fence (LPDF) which is smaller, more durable and easier to install and maintain in remote locations then the current reference-quality wind shields (such as the DFIR and the SDFIR) ((small) Double Fence Intercomparison Reference). I believe the work therefore presents a substantial new method and would recommend the publication of this manuscript after some minor revisions.
Below some more detailed remarks:
Page 1, lines 25-25: “This new wind shield is much smaller and easier to install and maintain” – is it also cheaper? In many organisations (and increasingly so) budget constraints can be an important factor.
Page 2, line 64: perhaps the authors could briefly define/explain the meaning of porosity in the context of windshields, and how it is estimated/calculated.
Page 3, line 95-97: “the design of the LPDF also allows it to be raised much more easily than the DFIR or SDFIR” – here and in general, it would be nice to include a technical drawing of the LPDF. This would also improve reproducibility of the work.
Page 4, site selection. Regarding the site selection procedure, how representative are the chosen sites for USCRN sites overall? I’m also missing a map with the site locations as well as wind statistics for the Marshall site in Figure 1. (consider having a,b and c panels in Figures 1 and 2 to be referring to the same sites).
Page 5, lines 142-155: In this paragraph the authors claim hourly and daily precipitation measurements are subject to random errors and therefore not appropriate for intercomparison studies. This seems in contradiction with paragraph 3.4 (and figures 10 and 11) where hourly catch efficiency measurements are shown. It also seems at odds with the introduction (page 2, lines 33-35) where several short term consequences of precipitation are mentioned. For avalanche predictions for example, accurate precipitation estimates at the precipitation event level would be more useful. Have the authors considered comparisons at the (long) event scale for example?
Page 5, line 152: why is a comparison of long-term accumulation more demanding? Surely on the contrary, it has the effect of averaging out small errors?
Page 6, line 167: “serviced with oil” might be a confusing term here. Perhaps a brief description in the methods section on the anti-freeze (if used) and oil layer - and why these are used, could be helpful to readers unfamiliar with weighing gauges.
Page 6, line 178: could the authors comment on how prevalent situations were in which the SDFIR accumulated more than 0.25 mm in an hour and LPDF less than 0.25 mm, and vice versa? Was this negligible?
Page 7, line 197-200: again, what percentage of total measurements did this represent? Based on Fig 2, windspeeds above 9 m/s must have been a very rare phenomenon.
Page 7-8 paragraph 3.2 and Figure 7: Single events seem to have most affected the difference between the accumulations of solid and mixed precipitation in Chatham. Have the authors looked into this or could they comment on this?
Minor
Page 3, line 1: In addition .. additional (repetition).
Page 4, line 102: “conterminous” not sure what conterminous is supposed to mean in this context – or why it is important that USCRN sites are conterminous.
Page 4, lines 105-108: “ Wind speeds during the snow days .. USCRN sites (e.g. Fig. 2).” These sentences seem unnecessarily repetitive, please consider revising them.
Page 7, lines 216-217: consider adding causal link between these two sentences for better comprehension, i.e. “precipitation shown in Fig.4. This is because the phase discriminated measurements” etc.
Page 8, lines 231-232: consider reporting SDFIR and LPDF values in the same order throughout the manuscript.
Citation: https://doi.org/10.5194/amt-2023-2-RC2
John Kochendorfer et al.
John Kochendorfer et al.
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