Abstract:This study aims at understanding how deep convection is organized and contributes to the intensification of nine Mediterranean tropical-like cyclones which developed between 2005 and 2018. Through a multi-satellite approach, a combination of infrared and microwave diagnostics provides insights into the temporal and spatial evolution of deep convection. ERA5 reanalysis complements the remote-sensing observations and is used to compute the vertical wind shear and vortex tilt to investigate their interactions wit… Show more
“…Because the Mediterranean Sea is a warm sea, it feeds the cyclones with large amounts of water vapor, reinforcing the cyclones and increasing their lifetime [60]. Often, storms form over the Mediterranean Sea [61][62][63], or spend most of their lifetime over the sea, as in the case of Medicanes [64][65][66], and are then advected toward land, causing floods, windstorm, and surges. For these cases, the air-sea interaction plays a major role in the storm evolution.…”
Lightning data assimilation (LDA) is a powerful tool to improve the weather forecast of convective events and has been widely applied with this purpose in the past two decades. Most of these applications refer to events hitting coastal and land areas, where people live. However, a weather forecast over the sea has many important practical applications, and this paper focuses on the impact of LDA on the precipitation forecast over the central Mediterranean Sea around Italy. The 3 h rapid update cycle (RUC) configuration of the weather research and forecasting (WRF) model) has been used to simulate the whole month of November 2019. Two sets of forecasts have been considered: CTRL, without lightning data assimilation, and LIGHT, which assimilates data from the LIghtning detection NETwork (LINET). The 3 h precipitation forecast has been compared with observations of the Integrated Multi-satellitE Retrievals for Global Precipitation Mission (GPM) (IMERG) dataset and with rain gauge observations recorded in six small Italian islands. The comparison of CTRL and LIGHT precipitation forecasts with the IMERG dataset shows a positive impact of LDA. The correlation between predicted and observed precipitation improves over wide areas of the Ionian and Adriatic Seas when LDA is applied. Specifically, the correlation coefficient for the whole domain increases from 0.59 to 0.67, and the anomaly correlation (AC) improves by 5% over land and by 8% over the sea when lightning is assimilated. The impact of LDA on the 3 h precipitation forecast over six small islands is also positive. LDA improves the forecast by both decreasing the false alarms and increasing the hits of the precipitation forecast, although with variability among the islands. The case study of 12 November 2019 (time interval 00–03 UTC) has been used to show how important the impact of LDA can be in practice. In particular, the shifting of the main precipitation pattern from land to the sea caused by LDA gives a much better representation of the precipitation field observed by the IMERG precipitation product.
“…Because the Mediterranean Sea is a warm sea, it feeds the cyclones with large amounts of water vapor, reinforcing the cyclones and increasing their lifetime [60]. Often, storms form over the Mediterranean Sea [61][62][63], or spend most of their lifetime over the sea, as in the case of Medicanes [64][65][66], and are then advected toward land, causing floods, windstorm, and surges. For these cases, the air-sea interaction plays a major role in the storm evolution.…”
Lightning data assimilation (LDA) is a powerful tool to improve the weather forecast of convective events and has been widely applied with this purpose in the past two decades. Most of these applications refer to events hitting coastal and land areas, where people live. However, a weather forecast over the sea has many important practical applications, and this paper focuses on the impact of LDA on the precipitation forecast over the central Mediterranean Sea around Italy. The 3 h rapid update cycle (RUC) configuration of the weather research and forecasting (WRF) model) has been used to simulate the whole month of November 2019. Two sets of forecasts have been considered: CTRL, without lightning data assimilation, and LIGHT, which assimilates data from the LIghtning detection NETwork (LINET). The 3 h precipitation forecast has been compared with observations of the Integrated Multi-satellitE Retrievals for Global Precipitation Mission (GPM) (IMERG) dataset and with rain gauge observations recorded in six small Italian islands. The comparison of CTRL and LIGHT precipitation forecasts with the IMERG dataset shows a positive impact of LDA. The correlation between predicted and observed precipitation improves over wide areas of the Ionian and Adriatic Seas when LDA is applied. Specifically, the correlation coefficient for the whole domain increases from 0.59 to 0.67, and the anomaly correlation (AC) improves by 5% over land and by 8% over the sea when lightning is assimilated. The impact of LDA on the 3 h precipitation forecast over six small islands is also positive. LDA improves the forecast by both decreasing the false alarms and increasing the hits of the precipitation forecast, although with variability among the islands. The case study of 12 November 2019 (time interval 00–03 UTC) has been used to show how important the impact of LDA can be in practice. In particular, the shifting of the main precipitation pattern from land to the sea caused by LDA gives a much better representation of the precipitation field observed by the IMERG precipitation product.
“…This particular region is a semi-arid part of Greece (Mavrakis et al, 2015a, b). In this region, 44 deaths had been documented from the WNV infection, for the year 2018. than 100 casualties on the same day (Alexakis, 2020;Alexakis et al, 2020;EM-DAT, 2020;Vlamaki et al, 2018); e) The "Zorbas" medicane (Mediterranean tropicallike cyclones) on September 29 th , 2018 (Dafis et al, 2020); f) The Kineta's flood of 2019-West Attica (Lekkas et al, 2019).…”
Section: Resultsmentioning
confidence: 99%
“…This seasonal outburst (Figs. 3 and 4 , 2018) had the characteristics of a biological disaster for Greece, including West Attica Prefecture, according to the EM-DAT classification of disasters types (EM-DAT, 2020 ), added to a series of other recorded natural disasters, such as: Two strong earthquakes, dated September 7, 1999, and July 19, 2019, with epicenters located in Thriasio Plain (EM-DAT, 2020 ; Papanikolaou et al, 1999 ; Kapetanidis et al, 2020 ); The catastrophic flash flood of Mandra (West Attica) on November 15, 2017 (Diakakis et al, 2020 ; EM-DAT, 2020 ; Speis et al, 2019 ); The flash flood of June 2018 in the West Attica municipality of Mandra and the local community of Magoula (EM-DAT, 2020 ); The Kineta’s wildfire (West Attica), which burned residential and wild-land areas, and the big fire (July 23, 2018) in Mati (East Attica), with more than 100 casualties on the same day (Alexakis, 2020 ; Alexakis et al, 2020 ; EM-DAT, 2020 ; Vlamaki et al, 2018 ); The “Zorbas” medicane (Mediterranean tropical-like cyclones) on September 29 th , 2018 (Dafis et al, 2020 ); The Kineta’s flood of 2019—West Attica (Lekkas et al, 2019 ). Fig.…”
precipitation during 2018 was extremely high, nearly 500% above the average. These conditions contributed to the increase of soil moisture index anomaly and fAPAR, creating an ideal microenvironment (wet soils and green pastures) for mosquito breeding. This phenomenon was directly associated with a drastic outbreak of West Nile virus cases in the area, compared with earlier years. Our results indicate how unusually high values of summer precipitation may have contributed (both through direct and indirect ecological channels) to the rapid spread of the West Nile virus in West Attica, causing a significant number of confirmed cases and fatalities. Climate change may bring forth other issues aside from natural disasters, including-but not limited to-virus expansion.
“…MR19 concludes that, within the category of Mediterranean tropical-like cyclones, more than one mechanism is at work, although one may dominate, depending on the large-scale and mesoscale environment in which the medicane intensifies. The distinction into different categories provided in MR19, based on the role of baroclinic instability as the development mechanism in the mature stage, was recently confirmed by Dafis et al (2020) through a multi-satellite approach, complemented with ERA5 reanalysis, based on the evolution of deep convection in relation to the cyclone intensification.…”
Section: Introductionmentioning
confidence: 87%
“…The distinction into different categories provided in MR19, based on the role of baroclinic instability as the development mechanism in the mature stage, was recently confirmed by Dafis et al . (2020) through a multi‐satellite approach, complemented with ERA5 reanalysis, based on the evolution of deep convection in relation to the cyclone intensification.…”
Two tropical‐like cyclones in the Mediterranean Sea, aka medicanes, are analysed herein by means of numerical simulations. The cyclones, which were recently investigated in Miglietta and Rotunno, Quarterly Journal of the Royal Meteorological Society, 2019, 145, are reconsidered in the present study, in which we focus on their respective preconditioning phases. In particular, here we analyse how local evaporation and/or long‐range transport of air masses may precondition the environment where the Mediterranean cyclones form. Numerical simulations indicate a rather different behaviour for the two cyclones. The first medicane (December 13–15, 2005) developed over the southern Mediterranean Sea, in a region of high low‐level humidity content, which existed before the cyclone formation; the air, originally dry over the eastern Balkans and the African mainland, gained humidity during its transit over the sea surface. In contrast, the second medicane (October 6–10, 1996) strongly intensified while benefitting from the intense sea‐surface fluxes due to the outbreak of Tramontane and Cierzo winds near the Balearic Islands, where the cyclone developed. Although limited to just two case studies, these results identify two different mechanisms conducive to an environment favourable for the intensification of medicanes in the western or southern Mediterranean. In addition, the role of dry air near the cyclone core, associated with upper‐tropospheric dry intrusions, is analysed. Sensitivity experiments were performed, constraining the relative humidity in the initial and boundary conditions to values above 50%. The advantage of this strategy is the ability to change the humidity content in the dry regions without modifying the associated strong potential vorticity anomalies. For both cases, we find that the humidity increase had the effect of inducing an earlier onset of cyclone development and of producing stronger, longer‐lasting vortices.
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