Stochastic background from extra dimensions

The existence of extra dimensions is a common feature in almost all quantum theories of gravity. These extra dimensions, whose size and number vary from theory to theory, have a signature on the gravitational stochastic background. Here we review the predictions of the individual theories and the hope of revealing such signals with earthbound detectors

Italian research on the Antarctic atmosphere

In this work after a short introduction on the structure of Programma Nazionale di Ricerche in Antartide, the different researches on atmospheric physics developed by Italian scientists are presented. The international activities are described, with particular attention both to APE experiment and the setting up of the new base in Dome-C. The results obtained are also discussed and the new projects proposed by SCAR or other international bodies are recalled. The reduction of funds and fall in young people interested in scientifi c studies represent the main problems for the future work

Numerical simulation of Crotone flood: Storm evolution

A nested-grid primitive equation model (RAMS, version 4.3) is used to simulate a high-precipitation (HP) storm which occurred in Calabria, Southern Italy. Storm produced intense rainfall over the city of Crotone, in the central Ionian coast of Calabrian peninsula, during the morning of 14 October 1996. Precipitation spell lasted for two hours, was highly localized and rainfall rates were intense (> 60 mm/h). The aim of this paper is to reproduce precipitation measured by raingauges and to highlight local and synoptic conditions that determined the storm, in order to acquire insight into the convective environment that produced the event. Four telescoping nested grids allow to simulate scales ranging from the synoptic scale down to the high-precipitation storm. All convection in the simulation is initiated by resolving explicitly vertical motion and subsequent condensation-latent heating from the model microphysics;no warm bubbles are used to start or trigger the storm. The model is able to well simulate measured precipitation both in terms of total precipitation and rain intensity. Also the position of the major spell is acceptable

Quantitative precipitation forecast of the Soverato flood: The role of orography and surface fluxes

During the night between 9 and 10 September 2000 a strong flood occurred in Soverato, a small town of Ionian coast of Calabria, killing 13 people. This was the top of an intense precipitation event occurred over the region during 8th, 9th, 10th September. In this paper the study of this event is performed, both analysing the synoptical aspects and using a numerical meteorological model either to reproduce the precipitation fields or to highlight some mesoscale features that determined the very intense and abundant rainfall. After a short description of the case study and presentation of measured rainfall fields, simulations are discussed. The study is based on three numerical simulations performed using the CSU-RAMS model (Regional mesoscale Modeling System) developed at Colorado State University and daily used at Crati Scrl to produce weather forecasts over Calabria peninsula. The first run is the control case and assesses the model ability to reproduce the flood cumulated rainfall by comparison with rain gauge data collected by the “Istituto Idrografico e Mareografico-Dipartimento di Catanzaro”. Second simulation is made to assess the influence of orographic barriers on the precipitation field, while third simulation evaluates the sensitivity to latent and sensible heat fluxes. Results indicate that the model simulate in satisfactory way the location and amount of rainfall, even if some problems are open and require more investigations

The application of LEPS technique for Quantitative Precipitation Forecast (QPF) in Southern Italy

International audienceThis paper reports preliminary results of a Limited area model Ensemble Prediction System (LEPS), based on RAMS, for eight case studies of moderate-intense precipitation over Calabria, the southernmost tip of the Italian peninsula. LEPS aims to transfer the benefits of a probabilistic forecast from global to regional scales in countries where local orographic forcing is a key factor to force convection. To accomplish this task and to limit computational time, in order to implement LEPS operational, we perform a cluster analysis of ECMWF-EPS runs. Starting from the 51 members that forms the ECMWF-EPS we generate five clusters. For each cluster a representative member is selected and used to provide initial and dynamic boundary conditions to RAMS, whose integrations generate LEPS. RAMS runs have 12 km horizontal resolution. Hereafter this ensemble will be referred also as LEPS_12L30. To analyze the impact of enhanced horizontal resolution on quantitative precipitation forecast, LEPS_12L30 forecasts are compared to a lower resolution ensemble, based on RAMS that has 50 km horizontal resolution and 51 members, nested in each ECMWF-EPS member. Hereafter this ensemble will be also referred as LEPS_50L30. LEPS_12L30 and LEPS_50L30 results were compared subjectively for all case studies but, for brevity, results are reported for two "representative" cases only. Subjective analysis is based on ensemble-mean precipitation and probability maps. Moreover, a short summary of objective scores. Maps and scores are evaluated against reports of Calabria regional raingauges network. Results show better LEPS_12L30 performance compared to LEPS_50L30. This is obtained for all case studies selected and strongly suggests the importance of the enhanced horizontal resolution, compared to ensemble population, for Calabria, at least for set-ups and case studies selected in this work

The meteorological model RAMS at Crati Scrl

International audienceAt Crati Scrl an operational version of RAMS 4.3 (Regional Atmospheric Modeling System) was implemented in January 2001. This paper aims to give a first assessment of model performances for quantitative precipitation forecast (QPF). In essence, the effects of enhanced horizontal grid resolution over Calabria, using a 6km spacing domain nested in a 30km resolution parent grid, is studied. To cope with this problem two integrations sets are discussed using two model resolutions. Integrations are performed daily for six months. ECMWF 12:00UTC forecast cycle is used for initial and dynamic boundary conditions. Performances are evaluated by scores computed from model outputs and raingauge measurements coming from Calabrian regional network

The precipitation field over Calabria: Large-scale correlations

In this paper we analyze the variability of the precipitation field over Calabria for the period 1948-1990 and its correlation with large-scale flow. Precipitation data are from “Istituto Mareografico ed Idrografico” database, have a monthly basis and cover the period 1921-1990. It is shown that precipitation is concentrated in the cold semester, from October to April, and that there is a large annual-to-annual variability. After studying correlation between precipitation and North Atlantic Oscillation (NAO), rainfall variability is further discussed by relating the precipitation standardized anomaly index to surface pressure, 500 hPa geopotential height and sea surface temperature. These dataset are derived from NCAR reanalysis project, and cover the 1948-2002 period. Due to temporal coverage of our databases the analysis is limited to 1948-1990. While a weaker correlation with NAO emerges, compared to other areas of the Mediterranean basin, precipitation over Calabria shows an interesting correlation with another dipolar structure located further East. This correlation is mainly related to the strength of Azores anticyclone over the Mediterranean area in the cold season and to the oscillation of Siberian high

On the performance of a limited area model for quantitative precipitation forecast over Calabria

At Crati Scrl an operational version of RAMS 4.3 (Regional Atmospheric Modeling System), with a son grid over Calabria, was implemented in January 2001. This paper aims to give a first assessment of model performances for quantitative precipitation forecast (QPF). In particular two issues of weather forecast are discussed. First problem refers to effects introduced by enhanced resolution over Calabria, using a 6 km resolution grid nested in a 30 km parent grid. Second issue discusses forecast deterioration with increasing forecast time. To cope with these problems, two sets of integrations are discussed using two different model configurations. Differences between configurations are only due to model resolutions. Integrations are performed daily for six months. Each integration starts at 12 UTC and lasts for 60 h, with 12 h spin-up time. ECMWF 12 UTC analysis and following forecast are used as initial and dynamic boundary conditions. Models performances are evaluated computing scores by comparing model outputs with raingauges data coming from Calabria regional network. Results show better performances of finergrid resolution compared to the coarser one and confirms the usefulness of enhanced resolution over complex terrain. In addition, performances decrease with increasing forecast time with first integration day performing better than second forecast day but differences are not statistically significant at 5% level

Atmospheric convergence diabatically generated in the CBL over a mountainous peninsula

The mesoscale atmospheric flow is investigated that is diabatically forced by the diurnal warming in the convective boundary layer (CBL) over Calabria, a mountainous peninsula in southern Italy. This study, carried out using a 3D nonlinear numerical model, is concerned with summer time when the large-scale flow is weak. Owing to several favourable conditions, strong sea-breeze and mountain valley flows are developed over this area. The thermal gradients associated with contrast of either mountain peaks-free atmosphere or land-sea merge together generating wide and intense circulation. The results show strong convergence in the lower and divergence in the mid and upper troposphere. The depth of the CBL is of the order of two thousand metres, while the depth of the mesoscale atmospheric response is of the order of the troposphere height, and has a horizontal scale of the order of two Rossby radii. The main effect of such circulation is the reorganisation of the humid air over the region. Indeed the humid air, that comes from the lower levels, is advected upward by breeze circulation, determining the onset of cumulus cloud and triggering summer thunderstorm over the region. The model provides successful simulations of the convective development observed by ground stations

Application of the LEPS technique for Quantitative Precipitation Forecasting (QPF) in Southern Italy: a preliminary study

International audienceThis paper reports preliminary results for a Limited area model Ensemble Prediction System (LEPS), based on RAMS (Regional Atmospheric Modelling System), for eight case studies of moderate-intense precipitation over Calabria, the southernmost tip of the Italian peninsula. LEPS aims to transfer the benefits of a probabilistic forecast from global to regional scales in countries where local orographic forcing is a key factor to force convection. To accomplish this task and to limit computational time in an operational implementation of LEPS, we perform a cluster analysis of ECMWF-EPS runs. Starting from the 51 members that form the ECMWF-EPS we generate five clusters. For each cluster a representative member is selected and used to provide initial and dynamic boundary conditions to RAMS, whose integrations generate LEPS. RAMS runs have 12-km horizontal resolution. To analyze the impact of enhanced horizontal resolution on quantitative precipitation forecasts, LEPS forecasts are compared to a full Brute Force (BF) ensemble. This ensemble is based on RAMS, has 36 km horizontal resolution and is generated by 51 members, nested in each ECMWF-EPS member. LEPS and BF results are compared subjectively and by objective scores. Subjective analysis is based on precipitation and probability maps of case studies whereas objective analysis is made by deterministic and probabilistic scores. Scores and maps are calculated by comparing ensemble precipitation forecasts against reports from the Calabria regional raingauge network. Results show that LEPS provided better rainfall predictions than BF for all case studies selected. This strongly suggests the importance of the enhanced horizontal resolution, compared to ensemble population, for Calabria for these cases. To further explore the impact of local physiographic features on QPF (Quantitative Precipitation Forecasting), LEPS results are also compared with a 6-km horizontal resolution deterministic forecast. Due to local and mesoscale forcing, the high resolution forecast (Hi-Res) has better performance compared to the ensemble mean for rainfall thresholds larger than 10mm but it tends to overestimate precipitation for lower amounts. This yields larger false alarms that have a detrimental effect on objective scores for lower thresholds. To exploit the advantages of a probabilistic forecast compared to a deterministic one, the relation between the ECMWF-EPS 700 hPa geopotential height spread and LEPS performance is analyzed. Results are promising even if additional studies are required