RECENT SNOW AND SYNOPTIC SITUATIONS BEARERS OF … · In the northern part of the region,...
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RECENT SNOW AND SYNOPTIC SITUATIONS BEARERS OF HEAVY SNOWFALL ON THE MOUNTAINS OF SICILY ISLAND Introduction: Sicily extends over an area of 25,000 square kilometers and it is the largest Island in the Mediterranean Sea (Fig.4); Its population is over 5 million inhabitants. Mountains cover 24% of the total area, and they appear to be many and different in elevation, morphology and geology. In the northern part of the region, overlooking on the Tyrrhenian Sea, lie the mountain ranges of Nebrodis-Peloritani-Madonie with his high peak of Pizzo Carbonara, 1.980 m. Along the eastern coast there is the active volcano Mount Etna - 3,343 meters high. This coastal mountains has a typical Mediterranean rainfall regime - with cool and very wet winters. Despite their altitude between 37 th and 39 th parallel north, snow is quite generous and above 1800 meters it is possible to play winter-sports. On the top of Mount Etna, the snowpack remains generally from late October to mid-June. Massimiliano Fazzini*, Antonino Paladino**, Vincenzo Romeo*** , Antonio Cardillo****, Carmela Vaccaro* *University of Ferrara, Department of Physics and earth sciences, Via Saragat, 1 – 44100 Ferrara – email: [email protected] **Corpo Forestale della Regione Siciliana – Palerme (Italy) *** Corpo Forestale dello Stato - Servizio Meteomont - Rome – Italy **** Regione Molise – Agenzia Regionale di Protezione Civile - Campochiaro – Italy Snow Historical Series : The historical snow data for Sicilia island are poor and discontinuous. Between 1960-1996, the Regional Hydrographic Service monitored the snowpack condition in the winter resort of Floresta - located on Nebrodi Mountain over 1200 meters above sea level. Measures related the snow depth and the snow at ground are collected each 10-days of the month. (figg. 1 -3) For this period , there are no data related the recent snow accumulations. Figure 1 show how in the last forty years studies snowpack over an altitude of 1200 meters reporters an overage of 12 days per year while the snow on the ground is an average of 33 days. In many winter seasons snow was totally missing while in other ones got up to 80 days with continuing snow cover. Particularly in 1980 and 1981 the combination of heavy snowfall and very low temperatures fostered an accumulation of snow on the ground up to 360 cm (fig.2). The most significant snowpack has been reached in the third week of January, that is climatically the cooler moment in these areas. Rarely snowfalls occur before November 20 th or after April 10 th (Fig.3). Finally, for the period 1951-1970, the average seasonal amount of fresh sow is about 226 cm. 0 10 20 30 40 50 60 70 80 1960 1965 1970 1975 1980 1985 1990 1995 2000 snowy days snow at ground 0 2 4 6 8 10 12 14 16 18 J 10 J 20 J 30 F 10 F 20 F 30 M 10 M 20M 30 A 10 A 20 A 30 N 10 N 20N 30 D 10 D 20 D 30 cm decades AVERAGE HEIGHT OF SNOW ON THE GROUND FOR DECADES Recent data - Nowadays data are daily collected by five manual stations, managed by Sicily Forest Service. Stations are located in the mountain ranges of Madonie, Nebrodi and Etna, at an altitudes between 1250 and 1970 m. Snow historical series date back to the winter seasons 2007-08 (fig. 3). First analyzes of data show that the snow is conspicuous over 1500 meters above sea level; snow accumulation varies between 150 and 250 cm, while snow on the ground remains for an average of 55 and 100 days. Snow data collected by all Sicilian stations show that February is the month with a maximum amount of snowfalls while for Madonie and Nebrodi stations is December - favored by the absolute maximum monthly precipitation. We don’t observed any relation between altitude and amount of seasonal snowfall; the coefficient of determination R 2 is particularly low (0.10) highlighting the prevalence of situations at the local scale. Statistically significant are the relationships between altitude and snow depth on the ground - an increase of 22 cm per 100 m of altitude (R2 = 0.75) - and elevation and days with snow on the ground - an increase of almost 8 days every 100 meters of altitude (R2 = 0.81) – figg 5 a,b and c. y = 0,0439x + 143,06 R² = 0,1035 0 50 100 150 200 250 300 1000 1200 1400 1600 1800 2000 2200 A - HEIGHT OF FRESH SEASONAL SNOW - CM y = 0,0715x - 37,631 R² = 0,8097 0 20 40 60 80 100 120 1000 1500 2000 2500 B - DAYS WITH SNOW ON THE GROUND y = 0,2183x - 187,6 R² = 0,7505 0 50 100 150 200 250 300 1000 1200 1400 1600 1800 2000 2200 C - SNOW DEPTH ON THE GROUND - CM In the last two seasons, the snowfalls were very abundant due to the recurring advection of continental or intermediate polar air which affected also the central and southern areas of the Mediterranean basin. In the mid-March 2012 snow depth on the ground exceeded 250 cm at Etna north station and 200 cm at Etna south station (Fig. 6) and Madonie station. In the recent winter seasons 2012-13 snow has not been so abundant but the number of snowy days was on average higher than the 2011-12 seasons (on average 38 days vs. 32), with important snowfalls. The analysis of synoptic conditions determined the most abundant snow in Sicilian mountain, that shows the need of a well- defined pattern (Fig. 7a and b) The heavy phenomena of 9 th January 1981, 1 th March 2006, 9 th January 1985, and 16 th January 1962, - with snowfall even in Palermo - were determined by the presence of a low pressure of the Aegean Sea or the Libyan Sea and always fed by a flow of north-eastern current tense at all elevation Take into consideration that to get heavy snowfall at high altitude and in plains, temperature at 850 hPa geopotential is between -5 and -8° C. With advection term, or continental polar air there is always a situation of Nao - . The cause of continental advection could be found in the presence of a strong thermal anticyclone concentrating between the Balkans and European Russia. In case advection reaches Sicily through the Rhone valley - by NW currents (Fig. 7) - the most abundant snowfalls occur on the northern mountain range (Madonie, Nebrodis.) and on the north of Etna. Whit the flow has a component North-East (fig. 7), the largest snow amounts occur in northern and eastern size of Mount Etna and the easternmost part of the Nebrodis. CONCLUSION - The analysis of snow Sicilian data carried out by historical series are too short to define the climatology of snow. However, the first data show a very abundant snowfall over 1500-1800 m a. s. l., with a persistence of snow on the ground until early spring. The advection of intermediate or continental polar air caused in the last 5-7 years the heavy and significant snowfalls in the central and southern Apennines. This survey is just a first step to understand and solve some problems: Are we facing a significant change in the winter atmospheric circulation in the southern basin of the Mediterranean? is the Increase of snow events associated with a decline in security in snowy areas mountain? The combination of higher accumulations of new snow with increase of the temperature after the snowfall, will it increase the overall risk of flooding or debris flow in the valleys leading down to the Mediterranean? 0 20 40 60 80 100 120 D J F M A ETNA NORD - NIVOMETRIC REGIME HFS AV (CM) DSG AV (DAYS) 0 20 40 60 80 100 120 D J F M A ETNA SUD - NIVOMETRIC REGIME HFS AV (CM) DSG AV (DAYS) 0 20 40 60 80 100 120 D J F M A NEBRODI W - NIVOMETRIC REGIME HFS AV (CM) DSG AV (DAYS) 0 20 40 60 80 100 120 D J F M A NEBRODI E - NIVOMETRIC REGIME HFS AV (CM) DSG AV (DAYS) 0 20 40 60 80 100 120 D J F M A MADONIE - NIVOMETRIC REGIME HFS AV (CM) DSG AV (DAYS) Figure 1 - Trend for any days with snowfall and the days with snow on the ground - Floresta station (1250 m) Figure 2 – View of Floresta during the snowfalls of 1981 Figure 3 - Decadal average of snow cover at Floresta (period 1960-1998) Figure 4 - Placement of the snow fields considered in the study: for each of them, photo and the nivometric regime for the period 2007-2013 are shows (GIS elaboration Francesco Cimino) Figure 7 – Synoptic pattern with north-eastern advection (left) and north-western advection (right) Figure 6 – Thermal and nivometric features at station “Etna Nord (left); wiew of Rifugio Sapienza - near Etna sud station - in march 2012 (right) Figure 5 - Relationship between altitude and amount of fresh snow (A), days with snow at ground (B) and snow depth (C)
Transcript of RECENT SNOW AND SYNOPTIC SITUATIONS BEARERS OF … · In the northern part of the region,...
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RECENT SNOW AND SYNOPTIC SITUATIONS BEARERS OF HEAVY SNOWFALL ON THE MOUNTAINS OF SICILY ISLAND
Introduction: Sicily extends over an area of 25,000 square kilometers and it is the largest Island in the Mediterranean Sea (Fig.4); Its population is over 5 million inhabitants. Mountains cover 24% of the total area, and they appear to be many anddifferent in elevation, morphology and geology. In the northern part of the region, overlooking on the Tyrrhenian Sea, lie the mountain ranges of Nebrodis-Peloritani-Madonie with his high peak of Pizzo Carbonara, 1.980 m. Along the eastern coast thereis the active volcano Mount Etna - 3,343 meters high. This coastal mountains has a typical Mediterranean rainfall regime - with cool and very wet winters. Despite their altitude between 37th and 39th parallel north, snow is quite generous and above1800 meters it is possible to play winter-sports. On the top of Mount Etna, the snowpack remains generally from late October to mid-June.
Massimiliano Fazzini*, Antonino Paladino**, Vincenzo Romeo*** , Antonio Cardillo****, Carmela Vaccaro**University of Ferrara, Department of Physics and earth sciences, Via Saragat, 1 – 44100 Ferrara – email: [email protected]
**Corpo Forestale della Regione Siciliana – Palerme (Italy) *** Corpo Forestale dello Stato - Servizio Meteomont - Rome – Italy
**** Regione Molise – Agenzia Regionale di Protezione Civile - Campochiaro – Italy
Snow Historical Series : The historical snow data for Sicilia island are poor and discontinuous. Between 1960-1996, the Regional Hydrographic Service monitored the snowpack condition in the winter resort of Floresta - located on Nebrodi Mountainover 1200 meters above sea level. Measures related the snow depth and the snow at ground are collected each 10-days of the month. (figg. 1 -3) For this period , there are no data related the recent snow accumulations.
Figure 1 show how in the last forty years studies snowpack over an altitude of 1200meters reporters an overage of 12 days per year while the snow on the ground is anaverage of 33 days. In many winter seasons snow was totally missing while in otherones got up to 80 days with continuing snow cover. Particularly in 1980 and 1981 thecombination of heavy snowfall and very low temperatures fostered an accumulation ofsnow on the ground up to 360 cm (fig.2). The most significant snowpack has beenreached in the third week of January, that is climatically the cooler moment in theseareas. Rarely snowfalls occur before November 20th or after April 10th (Fig.3). Finally,for the period 1951-1970, the average seasonal amount of fresh sow is about 226 cm.0
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Recent data - Nowadays data are daily collected by five manual stations, managed by Sicily Forest Service. Stations are located in the mountain ranges of Madonie, Nebrodi and Etna, at an altitudes between 1250 and 1970 m. Snow historical series dateback to the winter seasons 2007-08 (fig. 3).
First analyzes of data show that the snow is conspicuous over 1500 meters above sea level; snow accumulation varies between 150 and 250 cm, while snow on the ground remains for an average of 55 and 100 days. Snow data collected by all Sicilianstations show that February is the month with a maximum amount of snowfalls while for Madonie and Nebrodi stations is December - favored by the absolute maximum monthly precipitation. We don’t observed any relation between altitude andamount of seasonal snowfall; the coefficient of determination R2 is particularly low (0.10) highlighting the prevalence of situations at the local scale. Statistically significant are the relationships between altitude and snow depth on the ground - anincrease of 22 cm per 100 m of altitude (R2 = 0.75) - and elevation and days with snow on the ground - an increase of almost 8 days every 100 meters of altitude (R2 = 0.81) – figg 5 a,b and c.
y = 0,0439x + 143,06R² = 0,1035
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In the last two seasons, the snowfalls were very abundant due to the recurring advection of continental or intermediate polar air whichaffected also the central and southern areas of the Mediterranean basin. In the mid-March 2012 snow depth on the ground exceeded 250 cm atEtna north station and 200 cm at Etna south station (Fig. 6) and Madonie station. In the recent winter seasons 2012-13 snow has not been soabundant but the number of snowy days was on average higher than the 2011-12 seasons (on average 38 days vs. 32), with importantsnowfalls. The analysis of synoptic conditions determined the most abundant snow in Sicilian mountain, that shows the need of a well-defined pattern (Fig. 7a and b) The heavy phenomena of 9th January 1981, 1 th March 2006, 9 th January 1985, and 16 th January 1962, - withsnowfall even in Palermo - were determined by the presence of a low pressure of the Aegean Sea or the Libyan Sea and always fed by a flow ofnorth-eastern current tense at all elevation Take into consideration that to get heavy snowfall at high altitude and in plains, temperature at 850hPa geopotential is between -5 and -8° C. With advection term, or continental polar air there is always a situation of Nao-. The cause ofcontinental advection could be found in the presence of a strong thermal anticyclone concentrating between the Balkans and European Russia.In case advection reaches Sicily through the Rhone valley - by NW currents (Fig. 7) - the most abundant snowfalls occur on the northernmountain range (Madonie, Nebrodis.) and on the north of Etna. Whit the flow has a component North-East (fig. 7), the largest snow amountsoccur in northern and eastern size of Mount Etna and the easternmost part of the Nebrodis.
CONCLUSION - The analysis of snow Sicilian data carried out by historical series are too short to define the climatology of snow. However, the first data show a very abundant snowfall over 1500-1800 m a. s. l., with a persistence of snow on the grounduntil early spring. The advection of intermediate or continental polar air caused in the last 5-7 years the heavy and significant snowfalls in the central and southern Apennines. This survey is just a first step to understand and solve some problems: Arewe facing a significant change in the winter atmospheric circulation in the southern basin of the Mediterranean? is the Increase of snow events associated with a decline in security in snowy areas mountain? The combination of higher accumulations ofnew snow with increase of the temperature after the snowfall, will it increase the overall risk of flooding or debris flow in the valleys leading down to the Mediterranean?
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Figure 1 - Trend for any days with snowfall and the days with snow on the ground - Floresta station (1250 m)
Figure 2 – View of Floresta during the snowfalls of 1981 Figure 3 - Decadal average of snow cover at Floresta (period 1960-1998)
Figure 4 - Placement of the snow fields considered in the study: for each of them, photo and the nivometric regime for the period 2007-2013 are shows (GIS elaboration Francesco Cimino)
Figure 7 – Synoptic pattern with north-eastern advection (left) and north-western advection (right)
Figure 6 – Thermal and nivometric features at station “Etna Nord (left); wiew of Rifugio Sapienza - near Etna sud station - in march 2012 (right) Figure 5 - Relationship between altitude and amount of fresh snow (A), days with snow at ground (B) and snow depth (C)
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