Detection of heat and cold waves in Montevergine time series (1884–2015)

Abstract. In recent years, extreme events related to cooling and heating have taken high resonance, motivating the scientific community to carry out an intensive research activity, aimed to detect their variability and frequency. In this work, we have investigated about the frequency, the duration, the severity and the intensity of heat and cold waves in a Southern Italy high-altitude region, by analysing the climatological time series collected in Montevergine observatory. Following the guidelines provided by CLIVAR project (Climate and Ocean Variability, Predictability and Change), we have adopted indicators based on percentiles and duration to define a heat wave and cold event. Main results have highlighted a strong and significant positive trend in the last 40 years (1974–2015) in heat waves frequency, severity and intensity. On the contrary, in recent decades, cold wave events have exhibited a significant and positive trend only in intensity. Moreover, through the usage of two Wavelet Analysis tools, the Cross Wavelet Transform and the Wavelet Coherence, we have investigated about the connections between the extreme temperature events occurred in Montevergine and the large-scale atmospheric patterns. The heat wave events have exhibited relevant relationships with the Western European Zonal Circulation and the North Atlantic Oscillation, whereas the variability of cold wave events have shown linkages with the Eastern Mediterranean Pattern and the North Sea Caspian Pattern. In addition, the main features of synoptic patterns that have caused summer heat waves and winter cold waves in Montevergine site are presented

The evolution of density currents and nepheloid bottom layers in the Ross Sea (Antarctica)

In this study we have analyzed the thermohaline, light transmission and particulate matter data, obtained in the western sector of the Ross Sea during the X Italian Expedition, for the purpose of investigating the evolution of the High Salinity Shelf Water in this area. In particular CTD data were used to estimate the baroclinic velocity field. Light transmission and total particulate matter data (from Niskin bottles mounted on a Carousel water sampler) were used to analyze the nepheloid layers and the evolution of the suspended sediments. This basin is characterized by a northward flow of very dense High Salinity Shelf Water (θ ∼ −1.95°C, S ∼ 34.90), much colder than the incoming Circumpolar Deep Water (θ ∼ 1.20°C, S ∼ 34.70). We obtained a scenario in which the High Salinity Shelf Water interacts with the Circumpolar Deep Water along the Antarctic Slope Front, and deviates from its geostrophic equilibrium. Interestingly, this cold dense water mixes with Circumpolar Deep Water at the shelf break and flows downward until it seems to disappear. Below this cold flow, a thin turbulent current has been observed, again moving northward with a high velocity ∼ 0.2–1.0 m s−1. This thin flow also contains high concentration of suspended matter produced by the interaction of the dense water and the bottom sediments. The various elementary mechanisms ruling the dynamics of such down-flows, namely the effects of topographic irregularities, bottom friction, Ekman benthic boundary layers or the effect of the variability of the Antarctic Circumpolar Current, which can push offshore the dense water, are discussed in this paper

On the dense water spreading off the Ross Sea shelf (Southern Ocean)

In this study, current meter and hydrological data obtained during the X Italian Expedition in the Ross Sea (CLIMA Project) are analyzed. Our data show a nice agreement with previous data referring to the water masses present in this area and their dynamics. Here, they are used to further analyze the mixing and deepening processes of Deep Ice Shelf Water (DISW) over the northern shelf break of the Ross Sea. In more detail, our work is focused on the elementary mechanisms that are the most efficient in removing dense water from the shelf: either classical mixing effects or density currents that interact with some topographic irregularity in order to drop to deeper levels, or also the variability of the Antarctic Circumpolar Current (ACC) which, in its meandering, can push the dense water off the shelf, thus interrupting its geostrophic flow. We also discuss in detail the (partial) evidence of dramatic interactions of the dense water with bottom particulate, of geological or biological origin, thus generating impulsive or quasi-steady density-turbidity currents. This complex interaction allows one to consider bottom particular and dense water as a unique self-interacting system. In synthesis, this is a first tentative analysis of the effect of bottom particulate on the dense water dynamics in the Ross Sea

Synoptic control over winter snowfall variability observed in a remote site of Apennine Mountains (Italy), 1884–2015

This work presents a new, very long snowfall time series collected in a remote site of Italian Apennine mountains (Montevergine Observatory, 1280 m above sea level). After a careful check, based on quality control tests and homogenization procedures, the available data (i.e. daily height of new snow) have been aggregated over winter season (December–February) to study the long-term variability for the period 1884–2020. The main evidence emerging from this analysis lies in (i) the strong interannual variability of winter snowfall amounts, (ii) the absence of a relevant trend from the late 19th century to the mid-1970s, (iii) the strong reduction in the snowfall amount and frequency of occurrence from the mid-1970s to the end of the 1990s and (iv) the increase in average snowfall amount and frequency of occurrence in the past 20 years. Moreover, this study shed light on the relationship between the snowfall variability observed in Montevergine and the large-scale atmospheric circulation. Six different synoptic types, describing the meteorological scenarios triggering the snow events in the study area, have been identified by means of a cluster analysis, using two essential atmospheric variables, the 500 hPa geopotential height and the sea level pressure (both retrieved from the third version of the Twentieth Century Reanalysis dataset, which is available for the 1884–2015 period). Such patterns trace out scenarios characterized by the presence of a blocking high-pressure anomaly over Scandinavia or the North Atlantic and by a cold air outbreak involving both maritime and continental cold air masses. A further analysis demonstrates that the identified synoptic types are strongly related with different teleconnection patterns, i.e. the Arctic Oscillation (AO), the Eastern Atlantic Western Russia (EAWR), the Eastern Mediterranean Pattern (EMP), the North Atlantic Oscillation (NAO) and the Scandinavian pattern (SCAND), that govern the European winter atmospheric variability. The relevant decline in snowfall frequency and amounts between the 1970s and 1990s can be mainly ascribed to the strong positive trend of AO and NAO indices, which determined, in turn, a decrease in the incidence of patterns associated with the advection, in central Mediterranean area, of moist and cold arctic maritime air masses. The recent increase in average snowfall amounts can be explained by the reverse trend of the AO index and by the prevalence of a neutral or negative EAWR pattern

Synoptic control over winter snowfall variability observed in a remote site of Apennine Mountains (Italy), 1884–2015

This work presents a new, very long snowfall time series collected in a remote site of Italian Apennine mountains (Montevergine Observatory, 1280 m above sea level). After a careful check, based on quality control tests and homogenization procedures, the available data (i.e. daily height of new snow) have been aggregated over winter season (December–February) to study the long-term variability for the period 1884–2020. The main evidence emerging from this analysis lies in (i) the strong interannual variability of winter snowfall amounts, (ii) the absence of a relevant trend from the late 19th century to the mid-1970s, (iii) the strong reduction in the snowfall amount and frequency of occurrence from the mid-1970s to the end of the 1990s and (iv) the increase in average snowfall amount and frequency of occurrence in the past 20 years. Moreover, this study shed light on the relationship between the snowfall variability observed in Montevergine and the large-scale atmospheric circulation. Six different synoptic types, describing the meteorological scenarios triggering the snow events in the study area, have been identified by means of a cluster analysis, using two essential atmospheric variables, the 500 hPa geopotential height and the sea level pressure (both retrieved from the third version of the Twentieth Century Reanalysis dataset, which is available for the 1884–2015 period). Such patterns trace out scenarios characterized by the presence of a blocking high-pressure anomaly over Scandinavia or the North Atlantic and by a cold air outbreak involving both maritime and continental cold air masses. A further analysis demonstrates that the identified synoptic types are strongly related with different teleconnection patterns, i.e. the Arctic Oscillation (AO), the Eastern Atlantic Western Russia (EAWR), the Eastern Mediterranean Pattern (EMP), the North Atlantic Oscillation (NAO) and the Scandinavian pattern (SCAND), that govern the European winter atmospheric variability. The relevant decline in snowfall frequency and amounts between the 1970s and 1990s can be mainly ascribed to the strong positive trend of AO and NAO indices, which determined, in turn, a decrease in the incidence of patterns associated with the advection, in central Mediterranean area, of moist and cold arctic maritime air masses. The recent increase in average snowfall amounts can be explained by the reverse trend of the AO index and by the prevalence of a neutral or negative EAWR pattern

Comparison between 3D-Var and 4D-Var data assimilation methods for the simulation of a heavy rainfall case in central Italy

Abstract. This work aims to provide a comparison between three dimensional and four dimensional variational data assimilation methods (3D-Var and 4D-Var) for a heavy rainfall case in central Italy. To evaluate the impact of the assimilation of reflectivity and radial velocity acquired from Monte Midia Doppler radar into the Weather Research Forecasting (WRF) model, the quantitative precipitation forecast (QPF) is used.The two methods are compared for a heavy rainfall event that occurred in central Italy on 14 September 2012 during the first Special Observation Period (SOP1) of the HyMeX (HYdrological cycle in Mediterranean EXperiment) campaign. This event, characterized by a deep low pressure system over the Tyrrhenian Sea, produced flash floods over the Marche and Abruzzo regions, where rainfall maxima reached more than 150 mm 24 h−1.To identify the best QPF, nine experiments are performed using 3D-Var and 4D-Var data assimilation techniques. All simulations are compared in terms of rainfall forecast and precipitation measured by the gauges through three statistical indicators: probability of detection (POD), critical success index (CSI) and false alarm ratio (FAR). The assimilation of conventional observations with 4D-Var method improves the QPF compared to 3D-Var. In addition, the use of radar measurements in 4D-Var simulations enhances the performances of statistical scores for higher rainfall thresholds

Characteristics and coastal effects of a destructive marine storm in the Gulf of Naples (southern Italy)

Destructive marine storms bring large waves and unusually high surges of water to coastal areas, resulting in significant damages and economic loss. This study analyses the characteristics of a destructive marine storm on the strongly inhabited coastal area of Gulf of Naples, along the Italian coasts of the Tyrrhenian Sea. This is highly vulnerable to marine storms due to the accelerated relative sea level rise trend and the increased anthropogenic impact on the coastal area. The marine storm, which occurred on 28 December 2020, was analyzed through an unstructured wind-wave coupled model that takes into account the main marine weather components of the coastal setup. The model, validated with in situ data, allowed the establishment of threshold values for the most significant marine and atmospheric parameters (i.e., wind intensity and duration) beyond which an event can produce destructive effects. Finally, a first assessment of the return period of this event was evaluated using local press reports on damage to urban furniture and port infrastructures

On the use of ABACUS high resolution glider observations for the assessment of phytoplankton ocean biomass from CMEMS model products

Ocean biomass distribution has a growing importance in the world economy as a global strategic reserve, due to environmental and industrial applications and its variability related to climate change. Satellite imagery allows multi-resolution methodologies to obtain estimation, and hopefully classification, of biomass content over sea surface. This information is largely used in numerical simulations and nowadays represents an important contribute to future projections. Nevertheless, satellite, models and classical in situ monitoring resolution/accuracy sometimes cannot provide data at the finer spatial scales needed to describe the complex three-dimensional water column system. On the other hand, glider surveys allow scientists to collect observations of ocean phenomena at very high resolution along the water column, to assess numerical simulations reliability and, eventually, to assimilate these data into ocean models. In this study, we present a quantitative comparison between the glider observations collected in the Algerian Basin (Western Mediterranean Sea) during the ABACUS surveys from 2014 to 2018, and the daily outputs of two co-located CMEMS model products (i.e., GLB and IBI). The achieved results point out that model products are well correlated with glider potential temperature measurements but they still need improvements to provide a correct representation of the chlorophyll concentration variability in the study area. Generally, IBI daily simulations present higher linear correlation with concurrent glider in situ data than GLB ones. IBI products also reproduce better the pattern of the local maxima of chlorophyll concentration across the Algerian Basin. Nevertheless, they largely underestimate glider chlorophyll measurements and present significant differences that limit their capability to reproduce its upper ocean concentration that is needed for accomplishing advanced ecological studies.This work was realized in the framework of the PON R&I 2014–2020 “AIM – Attraction and International Mobility” at Università degli Studi di Napoli Parthenope. Glider missions were performed in the framework of the Algerian BAsin Circulation Unmanned Survey (ABACUS) observational projects. The ABACUS 1 missions (2014) were supported by the Joint European Research Infrastructure network for Coastal Observatories (JERICO) TransNational Access (TNA) third call (grant agreement no. 262584). The ABACUS 2 missions (2015) were realized through the SOCIB glider facility open access programme. The research leading to ABACUS 3 (2016) and ABACUS 4 (2017 and 2018) was supported by the European Union's H2020 Framework Programme (h2020-INFRAIA-2014–2015) (JERICOsingle bondNEXT grant agreement no. 654410).Peer reviewe

Wave run-up prediction and observation in a micro-tidal beach

Abstract. Extreme weather events bear a significant impact on coastal human activities and on the related economy. Forecasting and hindcasting the action of sea storms on piers, coastal structures and beaches is an important tool to mitigate their effects. To this end, with particular regard to low coasts and beaches, we have developed a computational model chain based partly on open-access models and partly on an ad-hoc-developed numerical calculator to evaluate beach wave run-up levels and flooding. The offshore wave simulations are carried out with a version of the WaveWatch III model, implemented by CCMMMA (Campania Centre for Marine and Atmospheric Monitoring and Modelling – University of Naples Parthenope), validated with remote-sensing data. The waves thus computed are in turn used as initial conditions for the run-up calculations, carried out with various empirical formulations; the results were finally validated by a set of specially conceived video-camera-based experiments on a micro-tidal beach located on the Ligurian Sea. Statistical parameters are provided on the agreement between the computed and observed values. It appears that, while the system is a useful tool to properly simulate beach flooding during a storm, empirical run-up formulas, when used in a coastal vulnerability context, have to be carefully chosen, applied and managed, particularly on gravel beaches