Abstract
Abstract. The influence of targeted observations on short-range forecasts is tested over two different periods of PREVIEW (2008) and MEDEX (2009) data targeting field campaigns for a set of Mediterranean high-impact weather events. As targeted observations we have used not only extra radiosondes, but also enhanced satellite data observed in singular vector (SV)-based sensitive regions. Three parallel observing system experiments, based on the High-Resolution Limited-Area Model (HIRLAM) data assimilation and forecast system, have been conducted. Forecasts of the three experiments have been assessed using both verifying analyses for upper-air fields, and surface observations for several meteorological parameters. Furthermore, quantitative precipitation forecasts (QPF) have been objectively verified using the novel feature oriented Structure–Amplitude–Location (SAL) method. The results obtained show that extra radiosondes have an overall positive impact on the forecasts (average improvement of all upper-air variables and vertical levels studied is 3.6%). When in addition to extra radiosonde data also enhanced satellite data are assimilated, the overall forecast skill is almost doubled. However, a distinct behaviour is found between the PREVIEW and MEDEX cases. While for MEDEX cases the improvement is slight, for PREVIEW cases the improvement is significant (average improvements of 1.7% and 8.9%, respectively, for the experiment with enhanced satellite data). It is suggested that this is due to the location of the target areas and the spatial distribution of the composite observing system and to the different atmospheric predictability in these two periods.
Highlights
Numerical weather prediction (NWP) has steadily improved forecast skill over the last decades (Navascués et al, 2013)
Ensemble forecasting, a technique that runs a finite number of deterministic models to build such a probability density function (PDF), has shown to be a valuable tool used in most operational centres (García-Moya et al, 2011)
During the MEDEX and PREvention Information and Early Warning (PREVIEW) Data Targeting System (DTS) campaigns all the additional observations were disseminated through the Global Telecommunications System (GTS) and assimilated by the European Centre for Medium-Range Weather Forecasts (ECMWF) global model a few hours later than High-Resolution Limited-Area Model (HIRLAM)
Summary
Numerical weather prediction (NWP) has steadily improved forecast skill over the last decades (Navascués et al, 2013). This paper presents new results concerning different aspects of data targeting experimentation: the impact of targeted observations on short-range (1–2 days) forecasts of high-impact weather events in the Mediterranean, the usage of adaptive observations screening strategies within the DA system to ameliorate the satellite data sampling, and the assessment of the forecast skill of surface meteorological parameters of high social impact (rainfall, wind) in addition to that of upper-air variables These three issues are on the list of recommendations concerning data targeting made by the Working Group on Data Assimilation and Observing Systems of the WMO program THORPEX (Majumdar et al, 2011).
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