Standard-type rain gages are visited weekly or at no more than one month intervals. Storage gages have higher capacity and might be visited as few as two times per year, after and before the rainy season (spring and fall). The longest running standard gage is at the Climatic Station at WS2. Totals from this gage were used to adjust both the daily and high resolution precipitation records recorded by the Universal recording gage (1957-2013) and now the Noah IV recording gage (2013-present). Similarly, standard gages at Hi-15 (1963) and Mack Creek (1979) have run alongside recording gages since their original installation. All of the standard and storage gages have been paired with the highest correlating recording gage to build daily records.
The 8-inch non-recording standard rain gage (SRG) is an open mouth can with straight sides with 20-inch capacity and is the National Weather System standard. While there is a collector funnel and measuring tube in the traditional gage, the outer overflow can is used as the primary means of collection to better capture frequent snow events. Originally turbine oil and now food-grade mineral oil (150 ml) is added to the SRG to prevent evaporation and RV antifreeze (.5-1 liter) is added in winter to prevent freezing. The can is weighed and compared with a tare weight to determine millimeters of precipitation. The SRGs have typically been placed in small clearings without an alter shield. The Belfort Universal recording rain and snow gauge has an 8" orifice diameter and 12-inch capacity with accuracy of 0.3%.
The locally crafted SRG is made from 2' sections of schedule 26 PVC pipe, wall thickness of 5/16". The bottom is capped and the top edge beveled to prevent rain from splashing in. The average inside diameter is 7 7/8". These have 30" holding capacity. Water from these gages is weighed and converted to millimeters.
The Sacramento Storage Gage has an 8" orifice diameter with approximately 200 inches storage capacity and is mounted on platforms. Water depth is measured with tapes and calibrated to inches through individual rating tables for each gage. The Sacramento storage gage consists of a 15-gal oil drum and a sheet metal cone assembly. The oil drum serves as the storage can. The cone assembly has three parts. The cone and inner skirt are cut from 24-gage and the catch ring from 22-gage galvanized sheet metal. The top of the catch ring is beveled from the outside to form a cutting edge. The inner skirt prevents loss of precipitation between the cone and can. The complete gage is mounted on a tower to keep the top of the gage well above maximum snow depth.
The stand-alone rain gage is composed of 10-inch standing pipe w/tank gage, a propane-heated 20-inch diameter orifice and surrounded by a Valdai-style double wind fence. A temperature probe controls orifice heating by turning on/off a pump and heater. The capacity is about 28 inches.
The shelter-top design requires a shelter for the storage wells and other equipment with the orifice mounted on the roof of the shelter with alter wind shield. The orifice is heated by directing the heat from a propane heater to the orifice via duct pipe and turned on/off based on a controlling temperature sensor. The storage well depth is measured to determine precipitation.
The follow link describes data collection methods (by date range and resolution) that have been used by each unique probe. Results are filtered by database code, sitecode, parameter, and probe.
https://andlter.forestry.oregonstate.edu/MethodCode/View_History.aspx
Please follow this link to view climate data collection methods that have been used over time at select stations. Results can be filtered by parameter, climate station, and date range. A general text search is also available.
https://hjandrews.shinyapps.io/im_methods_history/
Precipitation records are generally evaluated every 5 minutes and data points are output to capture 5 minute resolution. In actuality, not all of the gauges are designed for accurate recording at this high temporal frequency except during periods of high intensity rain/snowfall. This is generally due to the sensitivity of the magnetostrictive tank gauge and associated tank diameter in measuring fluid level. The "stand-alone" gauges at UPLMET, VANMET and CENMET are designed for greater sensitivity to changes in tank depth and the 5 minute output is good during most precipitation events. The "shelter gauges" at those sites are not as sensitive to a change in fluid depth. The tipping bucket gauge at PRIMET reliably outputs tips on a 5 minute basis, although this record is somewhat artificial at 5 minute resolution, especially in light rain situations where the gage does not tip in every 5 minute segment and 15 minute resolution is probably more realistic. Early chart data at CS2MET and the H15MET have been digitized and are generally accurate at 15 minutes resolution.
The longest continuous precipitation record on the Andrews is at the Climatic Station on Watershed 2 (CS2MET): 1957-10-01 to Present. Data is collected weekly from a standard US Weather Bureau standard 8” rain gauge and an adjacent Universal recording gauge (chart). The weekly charts were originally hand digitized on a daily basis, and adjusted to the standard gauge total. Subsequently, all charts have been electronically digitized, and data can be reliably output at a 15 minute resolution. This high resolution chart data has also been corrected to the standard gage total on a weekly basis. This Universal rain gauge was originally positioned at another location on the Andrews (at FORKS) and that record can be used to extend the daily CS2MET precipitation record back to December, 1951. A ETI Instruments NOAH IV gauge was installed in 2011 and runs concurrently with the Universal gauge and the standard gauge
At the Hi-15 Meteorological Station (H15MET), a standard rain gauge has always been maintained along with an accompanying recording rain gauge. Historically, the charts were hand digitized on a daily basis, and the daily record corrected to the standard gauge periodic total using a prorating technique. Beginning in 1992 a more reliable recording gauge was installed using a pressure transducer to measure fluid depth, and this record is available with no correction to the standard gauge, although the standard gauge is still operational.
At both the Upper Lookout (UPLMET) and Central (CENMET) Stations, two gauges are in operation: a stand-alone gauge with two concentric, encircling wind fences, and a second gauge atop the station shelter. The orifice of the stand alone gauge is heated by a thermistatically-controlled propane heater. This heated gauge with the shielding fences has dramatically improved our precipitation catch, particularly in heavy snow conditions, and has prevented snow bridging over the gauge orifice. The shelter gauge is located on top of our station shelter and heated through ducts from the shelter's propane heating system. This gauge has also improved catch over the more traditionally heated rain gauges, but is protected only with an alter wind shield and catches less than the stand-alone.
At Vanilla Leaf (VANMET) the original gauge in the clearcut was installed in 1987 but the record is discontinued in 1996. This gauge suffered from its openly exposed siting in this high elevation clearcut. Heavy snow and inadequate wind shielding were major problems. A stand-alone type gauge similar in design to those used at UPLMET and CENMET was installed in the adjacent and naturally sheltered meadow above the VANMET clearcut in 1998. This site takes advantage of the naturally-protected meadow and the wind fences are not employed here.
The prorating process builds daily data from periodic precipitation totals of the non-recording standard or storage rain gages (SRG). Once precipitation is determined through a field check of the SRG for each measurement period, totals from the paired recording rain gage are determined for the same intervals. A ratio between the standard (or storage) gage (SRG) and the recording gage is determined. The daily record from the recording gage is multiplied by its ratio to the SRG to estimate the daily precipitation for the SRG. If the total SRG precipitation total is flagged in any way (e.g., estimated, questionable, missing), this flag is applied to each day within the SRG collection interval. Should a significant portion of the recording gage record be missing for a given interval, an alternate recording gage will be used to "prorate" the SRG record into daily values. The paired recording gage used to prorate the SRG total is recorded and listed for each date.
The paired recording gage for each SRG was originally determined through regression analysis of corresponding precipitation totals of the SRG versus each of three recording gages. The three recording gages used were gages operational in 1994: CS2MET, H15MET and GSMACK. These three are still used for the remaining five SRG (standard or storage gages), and CENMET is used as an alternate should there be missing data for any of these.
