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.