Rainfall point measurement uncertainty
Typical quantitative results of rainfall uncertainty studies: Point Measurements.
This table originated from McMillan et al. (2012) but is now open to the community to add to and use as a resource.
| Uncertainty Type | Estimation Method | Magnitude | Location | Reference |
| Systematic Errors | ||||
| Wind loss curves dependent on wind speed & raindrop size | Theoretical calculation using wind velocity field from wind tunnel experiments | 1 mm drops: -10 % (6 m s-1), -40 % (9 m s-1), -80 % (12 m s-1); 2 mm drops: -10 % (9 m s-1), -20 % (12 m s-1); 3-5 mm drops: no effect up to 15 m s-1 | Mueller & Kidder (1972) | |
| Wind loss curves | Comparison with shielded gauge | Approx. linear 1 % under-catch per 1 mph wind speed | Danville, Vermont, USA | Larson & Peck (1974); also wind loss curves for snow |
| Undercatch for gauge mounted at 1 m height | Comparison with pit gauge | 5-16 % average undercatch (over 53-321 events), 0-75 % per storm | USA: Reynolds Creek, Idaho; Pullman, Washington; Sidney, Montana; Ekalaka, Montana | Neff (1977) |
| Loss due to wind field deformation | WMO literature survey & pit gauge comparisons | 2-10 % (rain), 10-50 % (snow) | Sevruk (1982); extensive literature survey is still widely quoted; correction equations are given dependent on gauge type & meteorological conditions | |
| Wetting loss | 2-15 % (summer), 1-8 % (winter) | |||
| Evaporation loss from open container | 0-4 % | |||
| Splash-in/out | 1-2 % | |||
| Undercatch for shielded gauge at 12 inches height & turf wall gauge | Comparison with pit gauge | 5 % (unshielded), 2 % (turf wall) annual undercatch | County Londonderry, Ireland. Lowland, coastal, rainfall 900-1100 mm yr-1. | Essery & Wilcock (1991); 1976-1988 |
| Wind-induced error depending on wind speed, rain drop size distribution & gauge design | Comparison between exposed & pit gauges | 2–10 % (hourly data; even after popular correction algorithms) | ARS Goodwin Creek experimental watershed, Mississippi, USA. 21.4 km2, rainfall 1400 mm yr-1, 71-128 m a.s.l. | Sieck et al. (2007) |
| Tipping error per 1 mm rain | Field calibration with known water delivery rate | Up to 10 % dependent on gauge type & rain rate | ||
| Random Errors | ||||
| Coefficient of variation of random errors | 12 co-located standard rain gauges | Approx. 5 % for single storm, independent of total storm rainfall | Mount Cargill, Dunedin, New Zealand. Exposed site at 560 m a.s.l. | Hutchinson (1969) |
| Coefficient of variation of non-recording gauges | 9 co-located recording & non-recording gauges | 4-5 % for storms >15 mm (monsoon season thunderstorms) | USDA Walnut Gulch Experimental Watershed, Arizona, USA. 4.4 ha, semi-arid, 1250-1585 m a.s.l. | Goodrich et al. (1995) |
| Total error of recording gauge | Standard error between single gauges & average of 15 co-located tipping buckets | Decreases with rain rate & accumulation time, e.g. 4.9 % (5 min) & 2.9 % (15 min) at rain rate of 10 mm h-1 | USDA field station in Chickasha, Oklahoma, USA | Ciach (2003) |
References
Ciach, G.J., 2003. Local random errors in tipping-bucket rain gauge measurements. Journal of Atmospheric and Oceanic Technology, 20(5): 752-759.
Essery, C.I., Wilcock, D.N., 1991. The variation in rainfall catch from standard UK Meteorological-Office rain-gages - A 12 year case-study. Hydrological Sciences Journal-Journal Des Sciences Hydrologiques, 36(1): 23-34.
Goodrich, D.C., Faures, J.M., Woolhiser, D.A., Lane, L.J., Sorooshian, S., 1995. Measurement and analysis of small-scale convective storm rainfall variability. Journal of Hydrology, 173(1-4): 283-308.
Hutchinson, P., 1969. A note on random rain-gauge errors. Journal of Hydrology (NZ), 8(1): 8-10.
Larson, L.W., Peck, E.L., 1974. Accuracy of precipitation measurements for hydrologic models. Water Resources Research, 10(4): 857-863.
McMillan, H., Krueger, T., Freer, J., 2012. Benchmarking observational uncertainties for hydrology: Rainfall, river discharge and water quality. Hydrological Processes 26(26): 4078–4111
Mueller, C.C., Kidder, E.H., 1972. Rain gage catch variation due to air-flow disturbances around a standard rain gage. Water Resources Research, 8(4): 1077-1082.
Neff, E.L., 1977. How much rain does a rain gauge gauge? Journal of Hydrology, 35: 213-220.
Sevruk, B., 1982. Methods of correction for systematic error in point precipitation measurement. World Meteorological Organisation, Operational Hydrology Report No. 21, WMO-No.589. Geneva, Switzerland.
Sieck, L.C., Burges, S.J., Steiner, M., 2007. Challenges in obtaining reliable measurements of point rainfall. Water Resources Research, 43(1): W01420.