Nazario Tartaglione

Relationship between Precipitation Forecast Errors and Skill Scores of Dichotomous Forecasts

In this paper, the sensitivities of the equitable threat score (ETS) and the true skill score (TSS), obtained with a 2 3 2 contingency table, to continuous precipitation forecast errors are investigated. Two idealized error models are adopted to describe the difference between forecasts and perfect observations. The observations consist of a time series generated by a multiplicative cascade model. The forecasts are constructed by adding the modeled errors to the observations. Two examples that are representative of two precipitation regimes are considered. Monte Carlo simulations of the modeled errors are performed to compute the score uncertainties. Monotonic relationships between the precipitation forecast errors and the two skill scores are found. It is shown that the precipitation regime and the event frequency influence these relationships and the score uncertainties. The score uncertainties also depend on the forecast errors. Furthermore, it is shown that a relationship exists between the ETS and TSS when the forecast errors are very large. Results suggest that more information should be provided together with the scores and their uncertainties in order to provide a complete picture of the forecast performance.

Sensitivity of forecast rainfall verification to a radar adjustment technique

A ground-based radar (GR) has to measure rain from close to the radar to large distances from it. Consequently, the scattering volume of the GR changes significantly. As an advantage, the scattering volume of a space-borne radar is of similar size at all locations, thus allowing the compensation of the decreasing spatial resolution of the GR with range (range-adjustment). Adjustment with range is here performed by means of data observed by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) using a ∼10 dB per decade factor. For instance, about 8 dB are added to the measured reflectivity at 100 km, while 2 dB are subtracted at 10 km from the radar site. Thus, two different radar datasets, the range-adjusted data and the original ones, can be compared with forecast precipitation. In the framework of the EU VOLTAIRE project (Fifth Framework Programme), where observations from rain gauges, GR, TRMM PR and forecast precipitation were available for the island of Cyprus, such a kind of study was performed. The chosen comparison method was a contiguous rain area (CRA) analysis. Three pattern-matching criteria, involving mean square error, mean absolute error and correlation, have been used to match forecast and observed precipitation patterns. In this paper, we show that the results of the comparison in a selected case study are sensitive to the application of a range-adjustment technique. Observational analysis, obtained by merging rain gauge data with the adjusted GR data, seems to give more stable results when changing the pattern-matching criterion, and proposing it as the better field reconstruction in the comparison.

Multisensor Comparison and Numerical Modeling of Atmospheric Water Fields: A VOLTAIRE Case Study over Cyprus

Abstract This paper presents a study performed within the framework of the European Union’s (EU) VOLTAIRE project (Fifth Framework Programme). Among other tasks, the project aimed at the integration of the Tropical Rainfall Measuring Mission (TRMM) data with ground-based observations and at the comparison between water fields (precipitation and total column water vapor) as estimated by multisensor observations and predicted by NWP models. In particular, the VOLTAIRE project had as one of its main objectives the goal of assessing the application of satellite-borne instrument measures to model verification. The island of Cyprus was chosen as the main “test bed,” because it is one of the few European territories covered by the passage of the TRMM Precipitation Radar (PR) and it has a dense rain gauge network and an operational weather radar. TRMM PR provides, until now, the most reliable space-borne spatial high-resolution precipitation measurements. Attention is focused on the attempt to define a methodolog...