Ritmo climático e extração do sal em Cabo Frio

Resumo

To begin with, we shall submit a rapid overview of "CABO FRIO IN THE BRAZILIAN SALT PRODUCTION FRAMEWORK", hinging on the role played by the salt extraction industry in the municipios economy and its reflexes on the overall picture in the state ·and even in the region.

Alongside this and, dealing with the area, the tonnage and the production value, a summary correlation will then be developed with the salt production region of the Northeast, under climate conditions that are extremely favorable to salt extraction operations, and, consequently, able to offer a better quality product than the one coming from Cabo Frio, since this latter suffers from less favorable regional atmospheric conditions, due to the dynamism of more complex variations of meteorologic elements, chiefly of rainfall.

Nevertheless, the neighborhood of important consumer centers and, principally, the high burden of the transportation costs, are a decisive factor and of considerable bearing on the salt-works activities in the State of Rio de Janeiro concentrated around Lake Araruama and, more especially, in Cabo Frio, due to the special local conditions whereby this site accounts for around 70% of the production in the State.

After defining the position of Cabo Frio in the Brazilian salt production framework, we shall endeavor to identify the position of the municipio in the "'REGIONAL CLIMATIC FRAMEWORK" considering how it appears as a "dry spot", a veritable local geoecological enclave in the humid regional context of the Southeast coastal zone of the country.

In an attempt to provide an explanation for the special geographic conditions reigning over the small salt-works establishment of the State of Rio de Janeiro, concentrated on the banks of Lake Araruama, we shall initially have recourse to the "normal" meteorological data of Cabo Frio so as to point out its fundamental climatic attributes, such as reveal the behavioral uniformity of the various meteorological elements.

Together with the "normal" predicates, considered insufficient, we shall undertake a duplication of the analysis, in its monthly variations, throughout the 1961 to 1970 decade, for a better appraisal of the characteristics of the pluviometric regime and the other climatic elements over years, for purpose of situating the problem of the variations over a period of time.

This representation provides a closer view of the true behavior of the meteorological elements in terms of monthly oscillations. It is, however, worthwhile noting that whilst the variation occurring in nearly all of these follows a regular and well defined pattern, it fails to do so when it comes to pluviosity and this applies not only to the total figures but also to their breakdown by month, thus obviating any relatively standardized characterization of a "pluviometric regime" good for Cabo Frio.

Likewise, the analysis of the development of the wind systems, one of the fundamental climatic variables and of considerable portent in the said extraction process, because of the part it plays in the evaporation procedure and because of the possibility it affords of providing wind power for operating its own mechanisms, evidences prevalence of a speed regularity and the predominance of winds in the Northeast in no matter what season of the year, emphasizing a direct relationship with the development of the secondary circulation.

The local peculiarities that were demonstrated, led us to be concerned with the extension or the regional formation of Cabo Frio:

- Are the pluviosity characteristics that appear in Cabo Frio limited to the range of this locality? Or up to what point do they affect other adjoining localities?

We were hence impelled to complete the analysis by adding a spatial projection, through correlation with other municipios of the State of Rio de Janeiro that are located near the studied area, when they possessed meteorological data covering an identical period.

In this manner, within the frame of the State of Rio de Janeiro, we drew the line of an axis running West to East (Niteroi-Cabo Frio), then another running Southwest to Northeast (Cabo Frio-Macaé-Campos) and yet a third one going from Southeast to Northeast (Cabo Frio-Nova Friburgo), aiming to compare localities in various situations in the regional ensemble: Niteroi, Cabo Frio and Macaé along the coast; Campos, somewhat towards interior, to the Northeast of the State and Nova Friburgo, at the upper reaches of the Serra do Mar, at practically the same latitude as Cabo Frio.

This analysis provided confirmation of the sul generis climatic character of Cabo Frio.

Evidence of the climatic individuality of Cabo Frio, alien to the context of other localities compared therewith and bearing no likeness with any of the coastal or inland regions of the State of Rio de Janeiro plain although under the influence of practically the same air circulation, added to its own shape of a headland projecting itself as it does into the sea, plus the presence of Lake Araruama, and the distance from the Serra do Mar, and the sudden change in the coastline, with furthermore the presence of chilled waters due to the re-emergence phenomenon, give this municipio the character of a singular physiographic unit in the coastal context of the eastern part of the state. Consequently, Gabo Frio's climatic originality comes from a local geoecological individuality, affording it the necessary requirements for salt production.

THE PROPOSITION OF THE THEME, IT’S OBJECTIVES, ITS SOURCES AND THE

DEVELOPMENT OF THE RESEARCH.

When dealing with this theme - the production of salt - a natural asset extraction whereof is governed by special climate conditions, one cannot overlook the fact that the regularity of its concentration and, consequently, greater or lesser productivity depends directly on harmony of variation of the different states of the atmosphere.

Hence, salt extraction is subject to conditions imposed by the behavioral development of the climatic rhythm, mainly insofar as the fundamental variable - pluviosity - in concerned, applying both to its quantitative terms and, above all, to its distribution over the whole year.

At a first approximation, the pluviometric totals reflect what would be, within the definition of local characteristics, "good" years for the production and what might been, in a manner of speaking, "anti-salt" ones.

In this manner, we shall endeavor to relate the production of salt to the annual rainfall records in the 1961 to 1970 decade (Flg. 10), and this enables us to select the basic years of the analysis.

However, although when examining the chart we see very clearly that the great pluviometrical reductions coincide with the highest points reached by the production curve, the increase in rainfall does not respond, in the same proportion and with the same clarity, to the drops in the curve.

This correlation between annual rainfall levels and the production of salt has a twofold merit: First, such a binomial taken in its annual totals is thereby revealed insufficient for explaining what appears to be quite obvious: drought favors the extraction of salt - CONFIRMED, whereas a high level of rainfall renders it more difficult - UNCONFIRMED, at least in the same proportion. Secondly there is the revelation of two succeeding years in which the correlations between annual pluviosity and salt production attain two extremes of variation, drawing our attention to the three years of 1963, 1964 and 1965, where the total tonnage falls from a maximum occurred during the first year to a minimum in the second year and reverting to an ascending trend in the third year.

Hence the choice of 1963 to be considered as a "first-rate" year for salt production, 1964 as an "anti-salt year and 1965 to be allowed as an "average" year, constituting the temporal segment applying to this analysis.

Starting from the dynamic climate concept proposed by Sorre and resting on the Fundamenta1 Hypothesis whereby neither the simple consideration of the annual rainfall totals nor even their breakdown per month can sufficiently explain the relation between climate conditions and salt extraction, we sought an understandable explanation direct approach to the daily scale readings since they might show how the linking of the various atmospheric states is tied up to the differences in salt production.

To this end, we adopted the paradigm of rhythmic analysis proposed by Monteiro, since it answers more adequately to the near entirety of the initial1y declared objectives, inasmuch as the thing that will show clearly up when the topic, climate conditions-salt extraction is dealt with, the matter that is of real interest is the rhythmic behavior of the various atmospheric states, the manner in which they evolve, the types of weather they determine, in short, the dynamic background that renders a salt-extraction agenda possible.

Thereinafter we developed the Methodological Proposition, given in abridged form in the general table (Fig. 11) which condenses in its articulations, the entire development of the research ·at its various stages and which, at the same time, expresses in an overall view, the adopted methodology.

The whole research hinges on an articulation between the binomial salt extraction and climate conditions favorable thereto, and was developed at three methodological levels: theory, observation and conclusion.

At the Theory level (conceptual), the salt extraction technique's direct dependence on climate conditions was underscored, based on Sorre's concept and on Monteiro's paradigm of rhythmic analysis, in correlation with the hypotheses and the objectives proposed.

At the Observation level (operational-analysis), the understanding of the technique of salt extraction, backed by the scanty bibliographic elements of information, led us to undertake work out in the field and this afforded us a specific knowledge of salt extraction procedures and the meteorological conditions that are admitted as the best suitable for proper conduct of operations, until attaining the annual agenda, based always on the climatic analysis involving the two basic preoccupations: the Regional Circulation that is responsible for the mechanisms that engender the atmospheric states, and the Local Response in Cabo Frio.

Taking as a starting point the base years in the 1961 to 1970 decade and selecting the three-year span of 1963, 1964 and 1965, it was possible, through charts drawn on rhythmic analysis joined to the secondary circulation, to propose a typology of "types of weather" and to identify, amongst these, a given element, taken as the most expressive in view of the most appropriate conditions.

In order to arrive at the annual salt-works. agenda and its characteristics in Cabo Frio, not overlooking the diagnostic of the base years, we developed, at the same time, an analysis of the frequency and the seasonal linkage, assumed to be the best way of understanding the character of the annual rhythm and of defining the quality of the respective agenda o! salt production.

Finally, at the level of Conclusions (summary), we examined the possibilities of an identification of trends in the 11961 to 1970 decade, besides the fact that our intention was to arrive at an ideal model in a position to express the climatic rhythm and the "'habitual" salt agenda. To this end, we attempted projecting the analysis to the period running from 1931 to 1970, however, the lack of data covering salt production prevented us from attaining the generalization objective.

THE ANALYSIS AND ITS RESULTS

The specific bibliographic limitations of the salt-works region of the State of Rio de Janeiro, led us to intensify the field work in order to be able to determine the salt producing agenda, as well as to acquire familiarity with the production techniques.

In short, this consisted in gradually raising, through evaporation, the density of the sea, until the critical point of 25°5 Baumé (Bé) was reached; at this point the crystallization of the chloride of sodium begins; then pursuing until the maximum point of 28°5 Bé was reached.

This process embraces four different phases (Fig. 12): In the first, water is collected from Araruama Lake with an average density of 5º5 BÉ and fed to the loading tanks where it remains until 7º BÉ are attained. The water is than transferred from the loading tanks to the pre-concentrators (2nd. phase) and left standing until 16º BÉ are reached, when it flows into the concentrators (3rd. phase) until the 24º BÉ point is arrived at. Finally, the brine is fed into the crystalizers where precipitation of the chloride of sodium occurs from the 25°5 BÉ point to the maximum point of 28º5 BÉ.

Thus, in the endeavor to establish the rapport: salt production versus types of weather, it seemed to us important to take into consideration two fundamental variables:

1st. - an understanding of the ideal atmospheric state or those that are considered to be favorable to production.

2nd. - The necessary length of time required for raising the density of the water from 5º5 BÉ (which was estimated to be: at end of spring, 5 to 6 days; in summer, 2 to 3 days; at beginning of fall, 6 to 7 days; in the winter there is practically no salt produced).

The answer to these two variables related to the climatic rhythm, enabled us to identify, in a time chart, a typology of the atmospheric states determined by the performance of the Atmospheric Systems and to arrive at a conclusion in connection with the "type of weather" and the consequent habitual succession of linkages admitted as "first-rate" or "favorable" for production (Northeastern Anticyclonic Tropical Atlantic weather with Clear Sky and, Northeast with Partially Clouded Sky) and, furthermore, to recognize the periods that are the most appropriate for salt production.

The separate counting of the frequency and the linkage in linear sequence, wherein we took account of the articulation of the various atmospheric states, their duration and confrontation with the quantitative attributes, hinging on the rhythm, enabled us to arrive at a diagnosis of the years under study and identification of the trends in the decade from 1961 to 1970.

This confrontation showed us that the contrasting years, as in the case of the ones we analyzed, which present a productivity maximum and minimum inversely associated with pluviosity, can perfectly well present performance coefficients almost similar in the diverse systems. Nevertheless, the characteristics of the Agenda and of Production were completely different, inasmuch as these are directly dependent on their duration and the manner in which they link up with the different types of weather in habitual succession.

Thus, in the year where the presence of "Northeastern Weather with Clear Sky" was most frequent and long-lasting, there occurred a more constant linkage between "Northeast with a Partially Clouded Sky" and state considered "first-rate" and "favorable" for salt extraction, principally in the summer the volume of the production in tonnage was higher, enabling us to arrive at a generalization of the identification of the trends applying to the other years of the decade, once it has been proved that the general trend of the production curve is in direct ratio to the interval of performance of the different atmospheric states that articulate one with the other.

APPRAISAL OF THE RESULTS AND THE PROSPECTS OF GENERALIZATION AND/OR EXTENSION

In this chapter consisting of a summarized study, we proceeded to pursue estimates of the results achieved in correlation with the objectives we proposed to obtain, and which can be resumed as follows:

l - The analysis of the regional circulation together with the local reactions in Cabo Frio during period under consideration, confirm the hypothesis that had been formulated, inasmuch as the rhythm engendered by the successive linkage of the types of weather was sufficiently expressive for characterizing the salt extraction agenda and, consequently, for explaining the curve in the production.

2 - The proposition of a typology of atmospheric state represents what we believe to be a contribution for the characterization of the local climate in Cabo Frio, permitting a truer confrontation with other localities in the State of Rio de Janeiro.

3 - Through this typology it becomes possible to point to the most_ ideally satisfactory conditions as well as those that are unfavorable to the production of salt.

4 - A complete definition of the salt extraction's annual agenda cannot be obtained only going by the results of a separate dynamic analysis, even when it is completed by seasonal and annual balances of its frequency. The perception of the true linkage of the atmospheric states has been shown to be more noteworthy than the above.

5 - This true linkage, even though it has not established conditions for determining a "habitual rhythm model" and a corresponding salt-works agenda, did permit the proposition of analogies when faced with the fundamental types of flows proposed by Monteiro in his thesis

6 - Bearing in mind that salt production meteorology has, quite rightly, to be oriented towards a greater extractive productivity, this being in direct ratio to the successive linkage of the more favorable types of weather and, inasmuch as this succession is beyond man's control, its reaction, aiming to improve the yield derived from salt extraction's procedures, must be applied to the rationalization of technique to the meteorological conditions to which it is still subject, in a complete state of dependency.

It is suggested that a study be made to better profit from semi-finished raw material which is very often completely lost because of a simple change of weather, by storing same in vast covered tanks and restoring it to the concentrators when the atmospheric conditions return to stable.

7 - Finally, we believe that the qualitative and elementary quantitative analysis herein developed through the observation of specific realities and fundamental analogies in the definition of the types of weather and in the dynamics of the polar flows, intermediate stages in the search for an "ideal model", is more in the light of a contribution to be added to the results already obtained by the Climatological Laboratory of the Geographic Institute of the University of São Paulo, and it will serve as a helpful element when seeking to establish the parameters for a more objective definition of the types of weather generated by the various atmospheric systems and their rhythmic linkage in habitual succession.