A new high-resolution BOLAM-MOLOCH suite for the SIMM forecasting system: assessment over two HyMeX intense observation periods

Abstract

Abstract. High-resolution numerical models can be effective in monitoring and predicting natural hazards, especially when dealing with Mediterranean atmospheric and marine intense/severe events characterised by a wide range of interacting scales. The understanding of the key factors associated to these Mediterranean phenomena, and the usefulness of adopting high-resolution numerical models in their simulation, are among the aims of the international initiative HyMeX -HYdrological cycle in Mediterranean EXperiment. At the turn of 2013, two monitoring campaigns (SOPs -Special Observation Periods) were devoted to these issues. For this purpose, a new high-resolution BOlogna Limited Area Model-MOdello LOCale (BOLAM-MOLOCH) suite was implemented in the Institute for Environmental Protection and Research (ISPRA) hydro-meteo-marine forecasting system (SIMM -Sistema Idro-Meteo-Mare) as a possible alternative to the operational meteorological component based on the BOLAM model self-nested over two lower-resolution domains. The present paper provides an assessment of this new configuration of SIMM with respect to the operational one that was also used during the two SOPs. More in details, it investigates the forecast performance of these SIMM configurations during two of the Intense Observation Periods (IOPs) declared in the first SOP campaign. These IOPs were characterised by high precipitations and very intense and exceptional high waters over the northern Adriatic Sea (acqua alta). Concerning the meteorological component, the high-resolution BOLAM-MOLOCH forecasts are compared against the lower-resolution BOLAM forecasts over three areas -mostly corresponding to the Italian HyMeX hydrometeorological sites -using the rainfall observations collected in the HyMeX database. Three-month categorical scores are also calculated for the MOLOCH model. Despite the presence of a slight positive bias of the MOLOCH model, the results show that the precipitation forecast turns out to improve with increasing resolution. In both SIMM configurations, the sea storm surge component is based on the same version of the Shallow water HYdrodynamic Finite Element Model (SHYFEM). Hence, it is evaluated the impact of the meteorological forcing provided by the two adopted BO-LAM configurations on the SHYFEM forecasts for six tidegauge stations. A benchmark for this part of the study is given by the performance of the SHYFEM model forced by the ECMWF IFS forecast fields. For this component, both BOLAM-SHYFEM configurations clearly outperform the benchmark. The results are, however, strongly affected by the predictability of the weather systems associated to the IOPs, thus suggesting the opportunity to develop and test a time-lagged multi-model ensemble for the prediction of high storm surge events.

Improvement of RAMS precipitation forecast at the short-range through lightning data assimilation

“…The 27 October 2012 case study, also referred as IOP16a, belongs to this class of events, and it eventually evolved in a cut-off at 500 hPa on 28-29 October (IOP16c). This event, characterized by widespread convection and intense lightning activity, caused huge precipitation all along the peninsula and also peak values of water level on the Venice Lagoon, where the sea level exceeded twice the warning level of 120 cm (Casaioli et al, 2013;Mariani et al, 2015). Figure 3 shows the synoptic situation at 12:00 UTC on 27 October 2012.…”

Can an early-warning system help minimize the impacts of coastal storms? A case study of the 2012 Halloween storm, northern Italy

“…scirocco) winds blowing over the length of the Adriatic (Mariani et al, 2015). At Ravenna, wind speeds began to develop from 15:00 GMT and peaked at a value of 15.5 m s −1 (ca.…”

“…With specific regards to coastal storm hazards, the development of EWSs has until recently focused on hydrodynamic forecasts for vulnerable low-lying areas. Some examples of these systems around the world include the acqua alta surge forecast system for the Venice lagoon (Bajo and Umgiesser, 2010;Ferrarin et al, 2013;Mariani et al, 2015), the UK joint Met Office-EA Flood Forecasting Centre (Stephens and Cloke, 2014), the US National Hurricane Center forecast system (Morrow et al, 2014) and the Bangladesh storm surge EWS (Dube et al, 2009). When performing successfully, the early warnings provided by these systems have been credited with having greatly reduced the impacts and loss of life of various extreme events (e.g.…”

Can an early warning system help minimize the impacts of coastal storms? A case study of the 2012 Halloween storm, Northern Italy

“…With specific regards to coastal storm hazards, the development of EWSs has until recently focused on hydrodynamic forecasts for vulnerable low-lying areas. Some examples of these systems around the world include the acqua alta surge forecast system for the Venice lagoon (Bajo and Umgiesser, 2010;Ferrarin et al, 2013;Mariani et al, 2015), the UK joint Met Office-EA Flood Forecasting Centre (Stephens and Cloke, 2014), the US National Hurricane Center forecast system (Morrow et al, 2014) and the Bangladesh storm surge EWS (Dube et al, 2009). When performing successfully, the early warnings provided by these systems have been credited with having greatly reduced the impacts and loss of life of various extreme events (e.g.…”

“…On the night of 31 October 2012, a large storm occurred in the Adriatic Sea that resulted in elevated water levels along the entire Emilia-Romagna coastline and characteristic of a 1-in-20-to 1-in-50-year event (Masina and Ciavola, 2011). Referred to in the media as the "Halloween storm", the resulting widespread coastal flooding and erosion called into question whether more effort was needed to enhance the regional preparedness to such events.…”