SAROS CYCLE IN METEOROLOGY. Ion Isaia 1

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1 PRESENT ENVIRONMENT AND SUSTAINABLE DEVELOPMENT, NR. 3, 2009 SAROS CYCLE IN METEOROLOGY Ion Isaia 1 Key words: Saros cycle, synodic revolution, anomalistic revolution, tropic revolution, sidereal revolution, draconic revolution. Abstract. This work is trying to demonstrate that there is a meteorological cycle (almost perfect) that has the same duration with Sares astronomic cycle. Saros cycle from astronomy (of approximately 18 years and 11 days) shows us, taking into consideration this period of 2 time, that both the Moon and the Sun eclipses repeat in the same order. Knowing that the Moon and the Sun are heavenly bodies that determine the characteristics of the atmospheric tide, results that this one is a tidal cycle too. Through Rossby waves (planetary), Saros cycle reflects very well in the evolution of some meteorological elements, especially in the daily development of the maximum and minimum air temperatures. Introduction The try of determining a tie between the astronomic cycles (selenian) and the atmospheric tides on one hand, and Rossby waves (planetary) and the evolution of some meteorological elements on the other hand, are not new. Beforehand, other astronomical cycles (selenian) were described and they reflect in meteorological cycles. In this category we can find the selenian cycles of less than a year (of 28, 55, 82, 110, 137, 164, 192, 220, 246, 274, 301, 328, and 355 days). In other category we can find the selenian cycles of 4 and 8 months. There are also monthly-solar cycles of 4 years, 8 years, 11 years, 19 years (Meton s cycle) and the 23 years cycle. A special category is represented by the cycles with duration in arithmetic progression as those of 9 years minus 9 days; 18 years minus 18 days; 27 years minus 27 days; 36 years minus 36 days and so on. All these astronomic cycles reflect themselves in a great measure in the evolution of some meteorological elements, especially in the daily development of the maximum and minimum air temperatures. 1 University of Galaţi, România, isaia_ion@yahoo.com

2 218 Ion Isaia Saros cycle from astronomy (approximately 18 years + 11 days) is the most complete one, and in the same time, the closest to perfection, because all the elements from the Moon evolvement (taken as independent variables) repeat after its passing through. The demonstrations that follow represent arguments that sustain this tie between Saros astronomic cycle and the evolution of some meteorological elements (especially the maximum and minimum daily temperatures). 1. Saros astronomic cycle Long time ago, it was noticed that the Moon and Sun eclipses have a cyclic evolvement, meaning that these repeat almost perfectly (in the same order) after a certain period of time. As it is known, a Sun eclipse is produced only when there is New Moon (the Moon being situated between the Earth and the Sun). The Sun and the Moon must have the same declination. Another condition is given by the distance of the Moon towards the Earth, being emphasised by Selena s parallax, during the anomalistic revolution. A Moon eclipse is produced only during Full Moon (the Earth being situated between the Sun and the Moon). The Sun and the Moon must have the declination that equals zero or other value, but with an opposite sign. There is also important the distance of the Moon towards Terra. Thus, in order to foresee the Sun and the Moon eclipses one must take into consideration the Moon synodic revolution (29, days), that shows its declination, and the Moon anomalistic revolution (27, days), that presents its distance towards the Earth and also the tropic year duration (365,24236 days). A common multiple of these independent variables is the period of time of approximately 6585,5 days (6585,3624 days), meaning 18 tropic years and 11 days. The calculations show that: 6585,3624 days : 29, (synodic revolution) = 223,00164; 6585,3624 days : 27, (anomalistic revolution) = 238,99094; 6585,3624 days : 27, (tropic revolution) = 241,032. This is Saros cycle in astronomy. Thus, during 6585,3624 days (Saros cycle) there are 223 synodic revolutions, 239 anomalistic revolutions and 241 tropic revolutions of the Moon. Moreover, during these 6585,3624 days there take place 242 draconic revolutions (27,2125 days) and 241 sidereal revolutions (27, days, almost equal to the duration of the tropic revolution) of the Moon according to the calculations: 6585,3624 days : 27,2125 (draconic revolution) = 241,99769; 6585,3624 days : 27, (sidereal revolution) = 241,032.

3 Saros'cycle in meteorology 219 Saros cycle is made up of 71 eclipses, 43 Sun eclipses and 28 Moon eclipses. Saros cycle is almost equal as duration to the moon cycle of almost 18 years and 8 months (6818 days), while during this period the maximum declination of the Moon varies between 18º18 and 28º36. Out of what has already been demonstrated it results that the Saros astronomical cycle is the most complete and the closest to perfection. The fact that the atmospheric tides are produced by the Moon and the Sun attraction means that this cycle is, in the same time, a tidal one. Through the planetary waves (Roosby), which have a tidal cause when they are formed, Saros astronomic cycle is very well felt in the daily development of the maximum and minimum air temperatures, as we will see soon. 2. Saros cycle in meteorology In order to prove the existence of this cycle in meteorology too, there were used meteorological data from the meteorological station in Braila, during Out of the statistical data there were used only those which referred to the maximum and minimum daily air temperatures, and partially, the medium daily values of the atmospheric pressure. In order not to overload this work with too many pictures, there were used graphics for demonstration for each and every month but from different years. In fig it is presented the daily development of maximum and minimum air temperatures in Braila for each month for a period of 18 years + 11 days (Saros cycle). As it can be seen, the main warm and cold advections are produced approximately in the same moments during the cycle.this fact proves that in the pair periods used to be compared (for a difference of 18 years + 11 days), the atmospheric circulation was produced almost identical. In other words, the barometric field at sole level for our country (at least) in the periods used for comparison, had the same distribution of the cyclones and anticyclones. In many situations, the maximum and minimum temperatures had almost the same value. This means that the air that had an almost the same circulation had a similar temperature too. In fig. 1 it is presented the daily development of the atmospheric pressure (daily medium values) in Braila, for February 2006 in comparison with 18 years and 11 days earlier (Saros cycle). As can be plainly seen, the oscillations of the atmospheric pressure in February 2006 are similar to those of 21 st January 17th February 1988 (a difference of 18 years + 11 days). The differences are only seen in the amplitude of the oscillations.

4 220 Ion Isaia Fig. 1 - Daily development of maximum and minimum air temperatures in Braila for each month for a period of 18 years + 11 days (Saros cycle) - I

5 Saros'cycle in meteorology 221 Fig. 2 - Daily development of maximum and minimum air temperatures in Braila for each month for a period of 18 years + 11 days (Saros cycle) - II

6 222 Ion Isaia Fig. 3 - The daily development of the atmospheric pressure (daily medium values) in Braila, for February 2006 in comparison with 18 years and 11 days earlier and september 2007 in comparision with and respectively (Saros cycle) Fig. 4 - The daily development of maximum and minimum air temperatures in Braila during periods of 2 Saros cycles (36 years + 21 days) 3 Saros cycles (54 years + 32 days) and 4 Saros cycles (72 years + 43 days)

7 Saros'cycle in meteorology 223 In fig. 3 it is presented the daily development of the atmospheric pressure (daily medium values) for September and October 2007, in Braila, in comparison with and respectively In this case, the oscillations of the atmospheric pressure are more similar. The daily development of the atmospheric pressure, presented in fig. 1 and 2, proves that in our country area (at least), the field of atmospheric pressure at the sole level, and also its daily oscillations, are very similar in a Saros cycle. The similar barometric field imprinted a similar atmospheric circulation that lead to similarities in the evolution of maximum and minimum air temperatures, which was proved in fig.1-2. For a thorough demonstration of this in meteorology too, in the graphics from fig. 4 there is presented the daily development of maximum and minimum air temperatures in Braila during periods of 2 Saros cycles (36 years + 21 days) 3 Saros cycles (54 years + 32 days) and 4 Saros cycles (72 years + 43 days). As it can be plainly seen especially in picture 16 (3 Saros cycles) the similarities are very evident, being almost close to identity. In comparison with other astronomic and meteorological cycles (moon cycles) described in other works, Saros cycle has the greatest probability of fulfilment. Thus, the calculations made for a period of 43 years have proved that in June, the probability that this cycle to be fulfilled is of 96% (the biggest). The other months have a probability comprised between 89% and 95%. It was also seen that during the mild period of year (May October) the probability of fulfilment of this cycle is greater than in the cold period (November April). That means that this cycle is mainly tied to the West circulation. As it is known, this circulation becomes more intensified together with the worm season in the temperate area of Europe. As Saros cycle in astronomy is a planetary one that means that its reflection in a meteorological cycle is also at a planetary level. The following researches will prove this truth. Conclusions The Saros cycle from astronomy (almost perfect) is a reality that can not be doubted. As the Moon and the Sun are heavenly bodies that produce atmospheric tides, that means that this cycle can be considered a tidal one. Through the Rossby waves (planetary) that have a tidal cause in their formation, Saros cycle reflects in a good measure in their evolution some meteorological elements, especially in the daily development of the maximum and minimum air temperatures. Thus, the astronomic Saros cycle becomes a

8 224 Ion Isaia meteorological cycle too. As the astronomic Saros cycle is not perfect thus the meteorological resulted cycle is not perfect too. Saros meteorological cycle has the greatest probability to take place in the warm period of the year, meaning that it is tied to the intensification of west circulation, at least to the latitude of our country and by the Rossby waves (planetary), with its wave length (λ) smaller than 5400 km, waves that spread from west to east. The waves that have λ bigger than 5400 km spread from east to west. The knowledge of this cycle represents a theoretical importance because it proves that the Earth atmosphere undergoes not only to daily and season heating and cooling processes but also to the attraction influences mainly from the Moon. This fact is reflected finally in the presence of Saros cycle in meteorology. Practically, the knowledge of this cycle helps us develop a meteorological broadcast on long term, with a greater probability, using the previous meteorological data and also the astronomic ones from the past and future, accurately calculated. References Airinei, St. (1992), Pământul ca planetă, Editura Albatros, Bucure]ti. Cristea, C. - (1965), Astronomie, Editura Didactica şi Pedagogică, Bucureşti. Drăghici, I. (1988), Dinamica atmosferei, Editura Tehnică, Bucureşti. Holton, J. (1996), Introducere în meteorologia dimanică, Editura Tehnică, Bucureşti. Isaia, I. (2002), Doua cicluri selenare şi impactul lor meteorologic, Lucrările Seminarului Geografic Dimitrie Cantemir, Iaşi. Isaia, I. (2004), Un ciclu mareic de 23 de ani şi consecinţele lui meteorologice, Lucrările Seminarului Geografic Dimitrie Cantemir, Iaşi. Isaia, I. (2006), Ciclul lui Meton în meteorologie, Lucrări de Geografie, Editura Universităţii Bucureşti, Vol.IX. *** ( ), Anuarele astronomice, Institutul de Astronomie, Bucureşti. *** ( ), Arhiva A.N.M. Bucureşti.