For naturalists, is specially interesting knowing about the bioclimate, this is the climate defined by main parameters that condition life. In order to define the bioclimate of Bages, we will use the conventions of Bagnouls & Gaussen and their acknowledged climogram. But we must keep in mind that this system does not represent all the important situations for the plants because it is based on the average, while vegetal life often depends on extreme values and on the frequency of the deviations. There are examples in the havocs that the extreme cold of January 1985 and the drought during the spring of 1994 (since March to August the rainfall was one third of the average) caused on the vegetation. In this case, if we had considered only the total annual precipitation (492,3 mm in Manresa), we would have thought that 1994 had not been an exceptionally dry year, but this is a mistake in bioclimatic terms.
O. de Bolós and J. Vigo consider that Manresa and most of Bages, as Balaguer, Cervera, Tàrrega, Flix and Lleida, belong to the Mediterranean climate of low altitude which is characterized by a wide thermic oscillation. In this group, the authors define the Manresa type as a Mediterranean subhumid climate with continental tendency, quite cold in winter (1-2 months with 0-5ºC averaged temperature) and 1-2 arid months in summer when the expected monthly precipitation in mm is between the averaged temperature in ºC and twice this score. Besides Manresa, Ponts (362 m height) and the hydroelectric plant of Santa Anna reservoir (294 m height) in Castillonroi municipality (la Llitera), have the same bioclimate.
In the south of Bages, the maritime influence reduces the thermic oscillation. The temperature decreases (0,65 0 C per each 100 meters) and the precipitation increases as the altitude is higher. The comparison of precipitation between Moià (700 m height) and Montserrat ‘s monastery (740 m of height) shows a different distribution along the year: summer drought is heavier in Montserrat than in Moià. In fact, Moià’s climate cannot be strictly considered Mediterranean. It is in fact a Submediterranean climate which, opposite to the Mediterranean one, the precipitation’s graph surpasses the temperature all along the year . In these climograms, the graph of the averaged monthly temperatures in Celsius degrees and the graph of the monthly precipitation in millimeters are overlaped. In vertical axis, 1 ºC temperature corresponds to 2 mm rain. For instance, a specific point of the graphic displays at once either 20ºC averaged temperature or 40 mm monthly rainfall. In case of the graph of the temperatures is over the graph of precipitations, then there’s an arid or dry period.
The evolution of the temperatures in Manresa cloncludes on that the climate has been exceptionally warm during the last years. These data support the hypothesis of the global warming as a result of the greenhouse effect caused by human activities. On the contrary, the period of 60’s decade plus the first half of the 70’s was a relatively cold one with outstanding 137 frosty days in 1973. In all four graphics, the thickest horizontal line shows the average.
The annual rainfall graph in Manresa shows the huge variability of the rain in this country, a typical Mediterranean treat. The extreme precipitation scores in Manresa are 328,2 mm in 1973 and 951,8 mm in 1996.
Extreme cold and snowfall
The year 2001 said good-bye to Catalonia with a memorable cold wave that was specially intense on the inner plains. The cold wave began in December the 14th with a large fell of snow over Catalonia, leaving 33 cm of snow in Manresa. The snow remained in Bages district for seventeen days, until it rained.
The snow created an unusual and quiet landscape of white fields, ice on the streets and frozen water . In Christmas day, the meteorological station of Universitat Politècnica of Manresa recorded -12ºC.
Even more rigorous was the cold wave of January of 1985. It began in December 5 th afternoon and stay on for two weeks. The UPC’s meteorological station recorded 9 days with temperatures below -10 0 C and an absolute minimum temperature of -17 0 C in Manresa. This cold wave damaged the vegetation and killed a lot of Aleppo pines and farmed trees like the old olive trees.
Snowfalls are not frequent in Bages (the average of snowfalls in Manresa is slightly more than one day per year). The snowfall of December 1962, with 63 cm in Manresa, is the record in the recent history. The snowfall of January 2006 damages a lot of trees.
Heat waves and droughts
Droughts and heats have been really exceptional in some summers, they’ve damaged the wild vegetation and they’ve set the conditions for large fires.
1994 was the warmest year of the 20th century in Manresa, with an annual temperature two degrees above the average, with 27 summer days of temperature over 35 ºC and with 94 days over 30 ºC. In 1994, the great heat of summer followed the drought that had begun in spring.
The extreme and persistent drought and the absence of rainfalls were suffered in 2003 summer as well. Although less painfull than that of 1994, the drought of 2003 damaged the vegetation, mainly that that were living on thin soils. The drought suddenly went to an end with the violent storm of August the 17th. However, according to the records, the most extreme drought was in year 2005. In the meteorological year 2004-05, the rainfall in most of Bages was only one third of the mean.
Floods, storms and gales
Floods are a typical phenomenon of the volatile Mediterranean climate. The most catastrophic river swelling was caused by the intense rainfalls in the west half of the Cardener basin in 1907, October the 12th. The river Cardener water reached 10 meters up its normal level in Manresa.
The rainfalls of autumn 1994 caused big floods in the river Calders and in the stream of Mura, in addition to a high swelling in river Llobregat.
In June the 10th, 2000, the day of the big floods in Monserrat and its surroundings, the maximum rainfall rate was recorded. In that day, the meteorological station of la Culla reported 187,5 mm water in Manresa, 45,5 mm of them from 6 to 7 hours in the morning and 36,0 mm from 8 to 9 h. The streams that drain the southwest of the district, so the streams of Rajadell, Guardiola, Castellet and Marganell, suddenly became big rivers that carried away bridges, stones, trees and even houses that were built on flood sensitive areas.
Bages is not a windy countryside because it is protected by the relief. Anyway, the control and report of the wind is quite recent. However, sometimes strong, associated with storms gales play havocs in small areas. The recent dates of the most serious gales are 1987 October the 10th with a maximum wind speed of 137 Km/h in Manresa, 1999, September the 14th which mainly kicked on Sant Fruitós de Bages village, and August the 17th, 2003. That Sunday morning suddenly turned to a stormy and dark night. The anemometer of la Culla peaked its top, 170 km/h. But in fact this speed was overcome, the wind was a real hurricane. The gale knocked down trees and played havocs with significant losses between Manresa and Calders, mainly in Sant Fruitós and Navarcles. In 09.12.2014, the meteorological station of Montserrat-Sant Dimes registered a peak of 128 km/h; though it was in Vacarisses, Terrassa and Sabadell (Vallès Occidental) where the wind caused most of the damages this day. In 25.01.2015 morning, same station reported a wind streak of 107 km/h; most of the damages of this windy day all over Catalonia were located in the northern districts of Solsonès, Berguedà and Ripollès.
[Florenci Vallès with the contribution of Jordi Badia]
- See the article Pertorbacions, in Catalan, by Jordi Badia.