The representativeness problem of a station net applied to the verification of a precipitation forecast based on areas

Abstract

ABSTRACT:The results and conclusions obtained in a verification process can be strongly influenced by its methodology, especially when some assumptions are made in order to avoid the limitations of the observational data (i.e., the lack of representativeness of the data or poor area coverage). Several aspects of the verification process must be studied if reliable conclusions are to be obtained. This paper discusses the problems related to the development of a verification method for a precipitation forecast defined over continuous areas using observational data from discrete points in space (meteorological stations). To tackle this asymmetry, the concept of the station net quality is first introduced.The verification approach is based on deterministic categorical scores. The effects of the number of stations, the spatial distribution of the station net and the precipitation thresholds used in the verification process are shown. Using different sets of precipitation stations, the scores show a strong sensitivity to the station net quality. The suitability of the scores used in this study is also analysed and the verification process is finally adapted to compensate for undesired effects.

An approach to combine radar and gauge based rainfall data under consideration of their qualities in low mountain ranges of Saxony

“…10a) that the combined product includes the small-scale variability of radar data. Our results confirm with the findings of Moszkowicz (2000), Bárdossy and Brommundt (2008) and Datta et al (2003), where radar data are considered as a practical instrument to preserve the information of the small scale variability of precipitation. The studies showed high correlation values of radar data for low distances.…”

“…Here, the comparison between the BIAS values of a one hour time step to the average BIAS of short-time periods (8 hours) showed a decreasing value with increasing time scale. Ballester and Moré (2007) reported similar results for precipitation events between 0.2 and 0.4 mm for time scales between 12 and 36 h. Our study confirmed with the known tendency of radar to underestimate gauge measurements for small rain rates. The HSS for convective rain was not as high as for advective events.…”

“…Due to the high spatial variability of rainfall and the complex error characteristic of radar data, we assume that the differences between radar and gauge are only valid for a limited area around the gauge. We followed the study of Ballester and Moré (2007) and replaced Q dyn by Q stat if less than eight stations are available.…”

“…Nowadays, it is possible to provide the data in a very high temporal resolution (up to one minute). But, as discussed by Cherubini et al (2002) as well as by Ballester and Moré (2007), an accurate representation of the spatial distribution of rainfall requires a high-resolution network. Curtis (1996), Fuchs et al (2001), Michelson (2004) and Sevruk (2004) analysed problems of local measurements of less than one hour, daily and monthly resolutions.…”

Weather model performance on extreme rainfall events simulation's over Western Iberian Peninsula

“…Further, these results support the choice of the simulation domain as well achieved in simulating the month precipitation where one has to pay attention to problems with discontinuities due to orographic complexities. Citing Ballester and Moré (2007), "On the other hand, if the areas are large enough, weather forecast uncertainties derived from spatial precipitation discontinuities can more easily be avoided, especially in areas with complex orography and a high frequency of convection phenomena".…”