Pro-Pluvia Rogation Ceremonies in Extremadura (Spain): Are They a Good Proxy of Winter NAO?

atmosphere

Article Pro-Pluvia Rogation Ceremonies in Extremadura (Spain): Are They a Good Proxy of Winter NAO?

Nieves Bravo-Paredes 1,*, María Cruz Gallego 1, Fernando Domínguez-Castro 2,3 , José Agustín García 1 and José Manuel Vaquero 4

1 Departamento de Física, Universidad de Extremadura, 06006 Badajoz, Spain; [email protected] (M.C.G.); [email protected] (J.A.G.) 2 Fundación ARAID, 50018 Zaragoza, Spain; [email protected] 3 Departamento de Geografía y Ordenación del Territorio, Universidad de Zaragoza, 50009 Zaragoza, Spain 4 Departamento de Física, Centro Universitario de Mérida, Universidad de Extremadura, Avda. Santa Teresa de Jornet 38, 06800 Mérida, Badajoz, Spain; [email protected] * Correspondence: [email protected]

Received: 14 February 2020; Accepted: 12 March 2020; Published: 14 March 2020

Abstract: Rogation ceremonies are religious requests to God. Pro-pluvia rogations were celebrated during dry conditions to ask God for rain. In this work, we have recovered 37 pro-pluvia rogations from 14 documentary sources (e.g.,: ecclesiastical manuscripts, books, and different magazines and newspapers). All of the rogations were celebrated in Extremadura region (interior of southwest of Spain) during the period 1824–1931. Climate of Extremadura is strongly dominated by the North Atlantic Oscillation (NAO). Therefore, pro-pluvia rogations have been associated to the NAO index and the relationship between them has been analyzed. The most relevant results are found in the relationship between pro-pluvia rogations in month n and the positive values of the NAO index for months n-1 and n-2, being statistically significant at 95% confidence level. Thus, the results evidence that the rogation ceremonies of Extremadura are a good proxy for the NAO index.

Keywords: NAO; pro-pluvia rogation ceremonies; proxy; drought; documentary sources

1. Introduction Climate proxies, i.e., non climatic variables with a high correlation with climate parameters, are required to know the pre-instrumental climate. There are many natural proxies, such as ice-cores, speleothems, tree-rings, or sea and lake sediments, which have been used to numerous climate reconstructions [1–7]. Out of the natural proxies, documentary sources preserved in archive and libraries are an important source of information to understand the past climate variability. Documentary sources provide instrumental [8,9] and non-instrumental [10,11] measurements of climate variables, direct description of meteorological events [12], and climate proxies (e.g., grape harvest dates, dates of freezing on rivers) [13]. One of the most used documentary proxies in the Mediterranean region for drought reconstruction is the rogation ceremonies [14]. Rogations are religious rites celebrated in order to ask God for certain intentions (take care of kings, wars, appropriate weather, etc.). Rogation ceremonies are common in Catholic religion and they have been celebrated throughout history, since 15th century to the present. For climate reconstruction, rogations related with agriculture and livestock are particularly useful. For example, when there was a notable drought during sowing time, farmers asked God for rain. Rogation ceremonies celebrated in these conditions are called pro-pluvia rogations. On the contrary, when people asked God to stop the rain and severe weather, they are called pro-serenitate rogations. Therefore, pro-pluvia and pro-serenitate rogations are useful documentary proxies to identify dry and wet extremes, respectively. Due to

Atmosphere 2020, 11, 282; doi:10.3390/atmos11030282 www.mdpi.com/journal/atmosphere Atmosphere 2020, 11, 282 2 of 15 the rogations can be found where Catholic religion was established and historical manuscripts were preserved, rogations can be found in different parts of the world as Europe (mainly), America, and old colonies (as Philippines) [15–21]. Pro-pluvia rogations have been studied, among others, to reconstruct periods of drought in the past [17,19,20,22–27]; to reconstruct seasonal and annual rainfall in the Iberian Peninsula (hereafter IP) from 16th century to 20th century [28]; and, to identify climate extremes [16,29]. Also, Vicente-Serrano & Cuadrat [30] used pro-pluvia and pro-serenitate rogations celebrated in Zaragoza (Spain) as a proxy of the North Atlantic Oscillation (NAO) index. Different types of documentary sources contain information about the celebration of the rogation ceremonies. In earlier epochs (16th–19th centuries), rogations were registered mainly in ecclesiastical and civil archives. Currently, there are 18 series of rogation ceremonies compiled in the IP [14,23]. Most of these series have been extracted from chapter acts (documents that register the discussion and decisions made during the assemblies of local authorities) and cover from the 16th or 17th to the first half of the 19th. The chapter acts have important advantages to record rogation ceremonies: (i) they can provide continuous series when all the documentation has been preserved (ii) they have around weekly resolution (iii) they are primary sources. Nevertheless, they have an important weakness until now because most of the long and continuous series come from archives of large cities (e.g., Barcelona, Toledo, and Seville). With the industrialization, these cities have been losing its agricultural character. This, joint with changes in the bureaucracy and the French occupation caused a quick drop in the record of rogation ceremonies in Chapter acts during the 19th century [24]. For this reason, the studied period of the works that use rogation ceremonies as climate proxies in Spain ends in the first half of the 19th century. This is an important problem in the use of rogation ceremonies because the overlapping period with meteorological measurements is frequently short or non-existent. The effect of industrialization is lower in rural areas of Iberia, in which is possible to find rogation ceremonies nowadays [31,32]. Unfortunately, in rural areas, frequently, the documentary sources useful to generate long and continuous series of rogations have been lost or are uncatalogued. In this article, different documentary sources as books, newspapers, and magazines have been consulted in order to retrieve rogation ceremonies from rural areas celebrated during the 19th and 20th centuries. The NAO is the dominant mode of the climate variability in Northern Atlantic winter [33], being its influence very important for the European climate [34–36]. Some authors show this influence in the IP [37–42]. To quantify the NAO strength, the NAO index is defined as the sea-level pressure difference between the Iceland Low and the Azores High [43]. When the NAO index is positive, dry conditions appear mainly in the climate of the IP due to the northward shift of Azores anticyclone blocks the entry of westerlies in this region. On the contrary, wet conditions appear in the climate of IP when the NAO index is negative. The temporal variability of NAO is high and their influence on the European climate is non-linear [44–47]. Nevertheless, the longest NAO index based on instrumental pressure observations begin in 1821 [43]. Therefore, it is necessary to extend our knowledge of NAO with accurate proxy records for a better understanding of the long term variability of NAO [5,7,44,48,49]. The main aim of the present work is to analyze the relationship between pro-pluvia rogations in Extremadura region (interior of southwest of Spain) and the NAO index from 19th century to early 20th century. To reach this objective, we have collected rogation ceremonies from different documentary sources (newspapers and magazines among others) in this region, in which droughts are highly correlated with NAO, as was aforementioned.

2. Study Area and Data

2.1. Study Area

The region of Extremadura is located in interior of the southwest of Spain (latitude between 37◦570 and 40◦290 N, longitude between 4◦390 and 7◦330 W). Figure1 (on the bottom) shows all the locations inside this region where rogation ceremonies (in this work recovered) were celebrated. Atmosphere 20202020,, 1111,, 282x FOR PEER REVIEW 3 of 15

Figure 1. On top, the situation of the region of Extremadura in the Iberian Peninsula. On the bottom, map of Extremadura region (courtesy of Infraestructura de Datos Espaciales de Extremadura - IDE Figure 1. On top, the situation of the region of Extremadura in the Iberian Peninsula. On the bottom, Extremadura) containing the locations where rogation ceremonies were celebrated. map of Extremadura region (courtesy of Infraestructura de Datos Espaciales de Extremadura - IDE TheExtremadura) climate ofcontaining Extremadura the locations is Mediterranean where rogation with ceremonies dry summers were celebrated. and mild winters. Figure2 shows the mean monthly precipitation of the city of Badajoz (dark grey vertical bars) for the period The climate of Extremadura is Mediterranean with dry summers and mild winters. Figure 22 1981–2010 and the mean monthly precipitation of the city of Cáceres (light grey vertical bars) for the shows the mean monthly precipitation of the city of Badajoz (dark grey vertical bars) for the period period 1982–2010. It can be seen that the monthly distribution of the precipitation is similar in both 1981–2010 and the mean monthly precipitation of the city of Cáceres (light grey vertical bars) for the cases (Badajoz and Cáceres), being the values of the mean monthly precipitation of Cáceres slightly period 1982–2010. It can be seen that the monthly distribution of the precipitation is similar in both higher. The mean annual precipitation of Badajoz and Cáceres is 447 mm and 551 mm, respectively. cases (Badajoz and Cáceres), being the values of the mean monthly precipitation of Cáceres slightly These cities are in plane areas, but the annual accumulated precipitation exceeds 1000 mm in mountain higher. The mean annual precipitation of Badajoz and Cáceres is 447 mm and 551 mm, respectively. areas. Regarding to droughts, Domínguez-Castro et al. [50] analyzed the climatology of droughts in These cities are in plane areas, but the annual accumulated precipitation exceeds 1000 mm in Spain based on SPI and SPEI indexes for the period 1961–2014. At scales related with agricultural mountain areas. Regarding to droughts, Domínguez-Castro et al. [50] analyzed the climatology of droughts (3 to 6 months), Extremadura region shows a low number of drought events, but with droughts in Spain based on SPI and SPEI indexes for the period 1961–2014. At scales related with agricultural droughts (3 to 6 months), Extremadura region shows a low number of drought events,

Atmosphere 2020, 11, 282 4 of 15 Atmosphere 2020, 11, x FOR PEER REVIEW 4 of 15 thebut highestwith the duration highest and duration magnitude. and magnitude. The climate Th ofe Extremadura climate of Extremadura region is strongly region dominated is strongly by thedominated NAO due by tothe the NAO proximity due to the to the proximity Atlantic to Ocean the Atlantic (mean Ocean distance (mean around distance 250 km) around and the250 lackkm) ofand important the lack of orographic important barriers orographic [37– 41barriers]. Some [3 authors7–41]. Some demonstrated authors demonstrated the inﬂuence the of theinfluence NAO onof precipitationthe NAO on andprecipitation droughts and in the droughts southwest in the ofthe southwest IP [37,38 of,40 the,51 ,IP52 ].[37,38,40,51,52]. In the studies ofIn the the IP, studies Gallego of etthe al. IP, [37 Gallego] found et a correlational. [37] foun approx.d a correlation equal to approx.0.6 between equal to the −0.6 winter between NAO the and winter daily rainfallNAO and (several daily − indicesrainfall related(several to indices frequency related and to intensity) frequency for and the intensity) period 1958–1997. for the period The 1958–1997. value of the The correlation value of the in thecorrelation other seasons in the other are lower seasons (approx. are lower equal (approx. to 0.2). equal L ótopez-Moreno −0.2). López-Moreno and Vicente-Serrano and Vicente-Serrano [51] and − Vicente-Serrano[51] and Vicente-Serrano et al. [52] highlightset al. [52] thehighlights outstanding the outstanding inﬂuence of influence positive and of negativepositive and phases negative of the wintertimephases of the NAO wintertime on droughts NAO conditions on droughts during condit theions succeeding during the months succeeding for the months periods for 1901–2000 the periods and 1901–2006,1901−2000 respectively.and 1901−2006, In the respectively. studies of the In southwestthe studies of of the the IP, Trigosouthwest et al. [41of ]the studied IP, Trigo the relationship et al. [41] betweenstudied the NAO relationship index and between river basin NAO average index precipitation; and river basin the highestaverage absoluteprecipitation; correlation the highest value wasabsolute found correlation in December value for was the Guadianafound in December basin (equal for to the0.83 Guadiana for the periodbasin (equal 1973–1998). to −0.83 Therefore, for the − Extremaduraperiod 1973−1998). is a great Therefore, region toExtremadura carry out the is study a great of theregi relationon to carry between out the rogation study ceremonies of the relation and thebetween NAO rogation index. ceremonies and the NAO index.

Figure 2. TheThe mean mean monthly monthly precipitation of Badajoz (dark grey vertical bars) for the period 1981 1981–2010−2010 and CCáceresáceres (light(light grey grey vertical vertical bars) bars) for for the the period period 1982–2010. 1982−2010. Black Black line line shows shows the number the number of pro-pluvia of pro- rogationspluvia rogations celebrated celebrated in Extremadura in Extrem regionadura region in the periodin the period 1824–1931. 1824−1931.

2.2. Data 2.2. Data Archivos Eclesi sticos de M rida-Badajoz Ecclesiastical manuscripts of didifferentﬀerent locations kept in Archivos Eclesiásticosá de Mérida-Badajozé (Ecclesiastical(Ecclesiastical ArchivesArchives of Mé rida-Badajoz)of Mérida-Badajoz) and digitized newspapers and (https:digitized//prensahistorica.mcu.es newspapers) pro-pluvia have(https://prensahistorica.mcu.es) been consulted to carry out have the task been of consulted retrieving to carry outrogation the task ceremonies. of retrieving Table pro-pluvia1 shows therogation diﬀerent ceremonies. documentary Table sources 1 shows consulted the differen and theirt documentary main characteristics. sources Figureconsulted3 shows and an their example main Nuevo d a: diario de la provincia de C ceres ofcharacteristics. a rogation ceremony Figure 3 registeredshows an example in the newspaper of a rogation ceremonyí registered in the newspaperá in Nuevo May 1927día: diario in Cilleros de la provincia (north of de Extremadura) Cáceres in May and 1927 it canin Cilleros be read: (north “Religious of Extremadura) act. Cilleros and brings it can its be patron read: saint,“Religious the Virgin act. Cilleros of Navelonga, brings its to patron the parish saint, in the a prayer Virgin for of rain.Navelonga, [ ... ] severeto the parish damages in a occurred prayer for in agriculture,rain. […] severe due todamages an extensive occurred drought in agriculture, that is taking due place to an during extensive thecurrent drought spring. that is [ taking... ]”. place during the current spring. […]”.

Atmosphere 2020, 11, 282 5 of 15

Table 1. The diﬀerent documentary sources consulted.

Type of Documentary Description of the Documentary Source Documentary Source Consulted Source Ecclesiastical manuscripts of: Archivo Histórico Municipal de Zafra; These manuscripts keep a record of everything related to Archivo del Convento de Santa Clara the parish life of each village or city (papal bull, rogation de Zafra; Archivo Parroquia Nuestra Señora de la Candelaria de Zafra. Ecclesiastical ceremonies, elections, etc.). In the case of rogation (Zafra). {1} manuscript ceremonies, the information is usually extended and contains the date (sometimes only the year), a Libro de acuerdos y elecciones de description of the religious procession and the reasons alcalde de mayordomo y jurados de la for the celebration (drought, severe weather, civil war, cofradía de Nra. Sra. de la Soledad. etc.). They are a primary documentary source. (La Zarza) (Archivo Diocesano de Mérida-Badajoz). {2} La región extremeña: diario republicano. {3} Correo de la mañana. {4} Correo extremeño. {5} Newspapers register the most important things that Nuevo diario de Badajoz: periódico happened in a region (in villages and towns), such as político y de intereses generales. {6} rogation ceremonies. Usually, newspapers gave the Nuevo día: diario de la provincia de information of rogations one day after their completion. Newspaper Cáceres. {7} In some cases, they announced future events. The information is usually brief and contains the date (as Crónica de Badajoz: periódico de they are newspapers, the full date always appear), some intereses morales y materiales, de details of the religious procession and the reasons of the literatura, artes, modas y anuncios. celebration (drought, severe weather, etc.). They are {8} primary documentary sources. La montaña: diario de Cáceres. {9} Boletín oﬁcial de la provincia de Cáceres. {10} El adarve: peródico político, literatio y de noticias. {11} Blanco y negro. {12} The information contained in magazines is similar than Magazine newspapers. Revista de estudios extremeños–[53,54]. {13} The author recovers the history of a village or town. The author is based on diﬀerent documentary sources, such Book [55,56] {14} as ecclesiastical manuscripts, civil archives, etc. It is a secondary documentary source.

In total, 37 pro-pluvia rogations celebrated in 24 locations of Extremadura (see Figure1) have been recovered from 1824 to 1931. For each rogation, it has been recorded the month and the year of the celebration. 30 rogations were celebrated in spring, 2 in autumn, and 5 in winter. As most rogations were celebrated in spring months, only pro-pluvia rogations celebrated in spring are considered to carry out the study. To analyze the inﬂuence of NAO in the celebration of these rogation ceremonies, we have used the monthly NAO index that was computed by Jones et al. [43]. This NAO index has been computed from the sea-level pressure in Gibraltar and Reykjavik from 1821. It is the unique instrumental NAO index available that completely covers our study period (1824–1931). This index has been widely used in climatological studies over Europe [34–36] and over IP [37–42]. Atmosphere 2020, 11, 282 6 of 15 Atmosphere 2020, 11, x FOR PEER REVIEW 6 of 15

Figure 3. AnAn example example of of a a rogation ceremony registered in the newspaper Nuevo ddía:ía: diario de la provincia de Cáceres Cáceres in May 1927 in Cilleros (north of of Extremadur Extremadura)a) and it can be read: “Religious “Religious act. act. Cilleros brings its patronpatron saint,saint, thethe VirginVirgin of of Navelonga, Navelonga, to to the the parish parish in in a a prayer prayer for for rain. rain. [ ...[…]] severe damages occurred in agriculture, due to an extensiv extensivee drought that is taking place during the current spring. […]”. [ ... ]”.

3. MethodIn total, 37 pro-pluvia rogations celebrated in 24 locations of Extremadura (see Figure 1) have been Itrecovered is known from that there1824 to is 1931. a positive For each (negative) rogation association, it has been between recorded the the NAO month index and and the dry year (wet) of theevents celebration. in the IP and,30 rogations in particular, were in celebrated the Extremadura in spring, region. 2 in Rogationautumn, ceremoniesand 5 in winter. occurred As whenmost rogationsthese events were began celebrated to worry in the spring population months, about only their pro-pluvia duration rogations and intensity, celebrated and the in rogations spring andare consideredthe NAO index to carry could out be the associated. study. ToRogations analyze were the influence celebrated of in NAO a given in datethe celebration (month n and of these year). rogation To analyze ceremonies, the relationship we have between used thepro-pluvia monthlyrogations NAO index and thethat NAO was computed index, the valueby Jones of theet al. NAO [43]. index This NAO in that index date has been computed associated fromto the the rogation. sea-level Moreover, pressure in in Gibraltar the set of and 30 rogationsReykjavik celebrated from 1821. in It springis the unique (March, instrumental April, and May),NAO indexthere areavailable months that containing completely more covers than our one study rogation period celebrated (1824–1931). in the This same index year has (i.e., been rogations widely wereused incelebrated climatological in diﬀerent studies locations over Europe in the same[34–36] month and over and year).IP [37–42]. Only one rogation is considered in these months. In this manner, one NAO event (NAO index in a given date, month, and year) is associated 3.with Method one rogation and there are no NAO events with more weight than the others. In total, 21 dates of springIt is rogation known ceremoniesthat there is (7a positive in March, (negative) 10 in April, association and 4 in between May) are the used NAO in theindex analysis. and dry Table (wet)2 eventssummarize in the the IP 21and, dates in particular, of rogations in and the theExtr principalemadura data region. of them. Rogation ceremonies occurred when these events began to worry the population about their duration and intensity, and the rogations and the NAO index could be associated. Rogations were celebrated in a given date (month n and year). To analyze the relationship between pro-pluvia rogations and the NAO index, the value of the NAO index in that date has been associated to the rogation. Moreover, in the set of 30 rogations celebrated in spring (March, April, and May), there are months containing more than one rogation celebrated in the same year (i.e., rogations were celebrated in different locations in the same month and year). Only one rogation is considered in these months. In this manner, one NAO event (NAO index in a given date, month, and year) is associated with one rogation and there are no NAO events with more weight than the others. In total, 21 dates of spring rogation ceremonies (7 in March, 10 in April, and 4 in May) are used in the analysis. Table 2 summarize the 21 dates of rogations and the principal data of them.

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Table 2. 21 dates of spring rogation ceremonies and the principal data of them.

Date Locations Documentary Sources (see Table1) 04/1824 Fregenal de la Sierra {1} 03/1835 Cáceres {10} Atmosphere 2020, 11, x FOR PEER REVIEW 8 of 15 03/1849 La Zarza, Fregenal de la Sierra {2}, {14} 03/1859 Olivenza {13} between04 the/1859 percentage of pro-pluvia Fregenal rogations de la Sierra and the NAO index is analyzed {14} by means of a chi- squared05 test/1867 at the 95% confidence level, Badajoz being the null hypothesis (H0) the no-dependency {8} of both series. 03/1868 Cabeza del Buey {14} To 04carry/1869 out the study, the analysis Talav hasán been divided into three parts: {10} 04/1881 La Zarza {2} 1. From a general point of view, the relationship between pro-pluvia rogations in month n and the 05/1891 Fregenal de la Sierra {14} NAO04/ 1896index in months n, n-1, n-2 Badajozand n-3 has been analyzed. A contingency {1}, {3} table was made for each05 /case1896 with 20 degrees of Fregenal freedom. de la Sierra {14} 2. Rogations04/1903 are celebrated in a given Cá dayceres (a rogation could be celebrated at the {12} beginning or at the end03 of/1905 the month, and the NAO Azuagaindex contribute in the same way in both {6} cases). Due to that, 04/1905 La Haba, Fregenal de la Sierra {6}, {14} two running averages of the NAO index are calculated taking two and three months for the 03/1907 Different locations (not specified) {11} windows04/1907 length. For the series calculated Zafra with a window length of two months, {1} the mean value of months05/1925 n and n-1 and Coria, the Reina, mean Fuente value del of Arcomonths n-1 and n-2 of the {9}, NAO {4} index has been associated04/1927 to the rogation celebrated Cilleros, in Coria month n. For the series calculated with {7} a window length Magacela, La Albuera, Arroyo de San of three04/1929 months, the mean value of months n, n-1 and n-2 and the mean {5},value {7} of months n-1, n- Serván, Coria, Alcántara 2 and03/1931 n-3 of the NAO index has Miajadas been associated to the rogation celebrated {7} in month n. A contingency table was made for each case with 16 degrees of freedom. 3. Two NAO winter indexes have been calculated: namely, NAODJF, equal to the mean value of the 3.1. Anomalies in the NAO Index NAO index in months December, January, and February; and NAODJFM, equal to the mean value Pro-pluviaof the NAOrogations index in were months celebrated Decemb whener, January, there truly February was aand need March. for rain. Pro-pluvia So, a deficitrogations of precipitationcelebrated had in occurredthe same in year the are previous grouped months. and the As value was aforementionedof the NAO winter in Section index has2.1., been the agriculturalassociated droughts with them. (3 to 6A months) contingency in Extremadura table was made region for show each the case highest with 13 mean (NAO durationDJF) and i.e., 12 from(NAO 10 to 20DJFM weeks.) degrees Therefore, of freedom. it is possible to find out anomalies in the monthly NAO index in previous months related to the precipitation deficits. Specifically, this fact occurs in winter months when4. Results the influence and Discussion of NAO in the precipitation is higher. NAO index anomalies are calculated using as reference period the complete study period (1824–1931). To study the possible influence of two As was aforementioned, we are going to work with 21 dates of spring pro-pluvia rogations, previous winters on the months of the celebration of the rogation, anomalies in the monthly NAO looking for anomalies in the monthly NAO index. Figure 4 shows the monthly anomalies of the NAO index are calculated from the month of the celebration of the rogation up to two winters before(that is index averaged for the 21 spring rogations, from the month of the celebration of the rogation 15 months, see Figure4). Monthly anomalies are computed for each of the 21 dates of rogations and ceremonies (March, April, or May; at right end of the x axis) to two winters back in time (left end of the monthly average is calculated. the x axis). Dark grey bar is the statistical significant anomaly at the 95% confidence level.

Figure 4. Monthly anomalies in the NAO index from the month of the celebration of the rogation Figure 4. Monthly anomalies in the NAO index from the month of the celebration of the rogation ceremonies (right end of the x axis) to two winters back in time (left end of the x axis). Dark grey bar is ceremonies (right end of the x axis) to two winters back in time (left end of the x axis). Dark grey bar the statistical significant anomaly at the 95% confidence level. is the statistical significant anomaly at the 95% confidence level. To study the statistical significance of the anomalies, Piechota and Dracup [57] used a bootstrap resamplingFigure procedure. 4 indicates A that similar winter method anomalies is used are in nega this study.tive. This 21 randomindicates values that, ofin thethese NAO months, index the in Azores anticyclone is northward shift giving higher positive values of the NAO index than the normal conditions. Only the anomaly value of the previous February to the celebration of rogations is statistically significant. In any case, anomalies are negative since July. The fact that the immediately previous February presents a high anomaly value is indicative of unusual dry conditions. Therefore, the celebration of the pro-pluvia rogations after this month could not be casual. In fact, as it can be seen in Figure 2, there are two maximums in the precipitation of Badajoz and Cáceres (spring and autumn) coinciding when pro-pluvia rogations are celebrated (black line). Pro-pluvia rogations are directly connected with agriculture and livestock, as can be seen in Figure 2. In Extremadura, sowing time is in

Atmosphere 2020, 11, 282 8 of 15 each month of the year are selected to form an aggregate composite, and anomalies are calculated in each month. This method is performed 500 times, and the monthly mean and the standard deviation of the dataset of the bootstrap resampling are calculated to determine signiﬁcance anomalies in the NAO index at the 90% conﬁdence level.

3.2. Relationship between Pro-Pluvia Rogations and the NAO Index In order to study the statistical signiﬁcance of the anomalies, the values of the NAO index in the previous months (n-1, n-2 and n-3) have been linked to the rogation in month n. Association between two or more qualitative variables can be analyzed through contingency tables. Two variables comprise the contingency tables in this study: the NAO index (which is sorted in rows in intervals of 0.5) and the pro-pluvia rogations celebrated (and not celebrated). Considering the total months of the NAO index in each interval, the percentage of pro-pluvia rogations celebrated (and not celebrated) is calculated in each interval. Also, the distribution of the no dependency of both series is calculated as the average of the percentages calculated before. Finally, the relationship between the percentage of pro-pluvia rogations and the NAO index is analyzed by means of a chi-squared test at the 95% conﬁdence level, being the null hypothesis (H0) the no-dependency of both series. To carry out the study, the analysis has been divided into three parts:

1. From a general point of view, the relationship between pro-pluvia rogations in month n and the NAO index in months n, n-1, n-2 and n-3 has been analyzed. A contingency table was made for each case with 20 degrees of freedom. 2. Rogations are celebrated in a given day (a rogation could be celebrated at the beginning or at the end of the month, and the NAO index contribute in the same way in both cases). Due to that, two running averages of the NAO index are calculated taking two and three months for the windows length. For the series calculated with a window length of two months, the mean value of months n and n-1 and the mean value of months n-1 and n-2 of the NAO index has been associated to the rogation celebrated in month n. For the series calculated with a window length of three months, the mean value of months n, n-1 and n-2 and the mean value of months n-1, n-2 and n-3 of the NAO index has been associated to the rogation celebrated in month n. A contingency table was made for each case with 16 degrees of freedom.

3. Two NAO winter indexes have been calculated: namely, NAODJF, equal to the mean value of the NAO index in months December, January, and February; and NAODJFM, equal to the mean value of the NAO index in months December, January, February and March. Pro-pluvia rogations celebrated in the same year are grouped and the value of the NAO winter index has been associated with them. A contingency table was made for each case with 13 (NAODJF) and 12 (NAODJFM) degrees of freedom.

4. Results and Discussion As was aforementioned, we are going to work with 21 dates of spring pro-pluvia rogations, looking for anomalies in the monthly NAO index. Figure4 shows the monthly anomalies of the NAO index averaged for the 21 spring rogations, from the month of the celebration of the rogation ceremonies (March, April, or May; at right end of the x axis) to two winters back in time (left end of the x axis). Dark grey bar is the statistical significant anomaly at the 95% confidence level. Figure4 indicates that winter anomalies are negative. This indicates that, in these months, the Azores anticyclone is northward shift giving higher positive values of the NAO index than the normal conditions. Only the anomaly value of the previous February to the celebration of rogations is statistically significant. In any case, anomalies are negative since July. The fact that the immediately previous February presents a high anomaly value is indicative of unusual dry conditions. Therefore, the celebration of the pro-pluvia rogations after this month could not be casual. In fact, as it can be seen in Figure2, there are two maximums in the precipitation of Badajoz and C áceres (spring and Atmosphere 2020, 11, 282 9 of 15 autumn) coinciding when pro-pluvia rogations are celebrated (black line). Pro-pluvia rogations are directlyAtmosphere connected 2020, 11, x FOR with PEER agriculture REVIEW and livestock, as can be seen in Figure2. In Extremadura, sowing9 of 15 time is in spring and autumn and the mean precipitation in autumn is greater than that of spring. Therefore,spring and autumn fields are and wet the in mean autumn precipitation months andin autumn there areis greater fewer than rogations that of celebratedspring. Therefore, when waterfields availabilityare wet in autumn permits months normal and crop th growing.ere are fewer Also, rogations the vegetation celebrated activity when in springwater monthsavailability is high permits and dependentnormal crop on growing. sufficient Also, rainfall the vegetation [58]. On the activity contrary, in spring as the months mean precipitation is high and dependent is lower in on spring, sufficient it is possiblerainfall [58]. that On a dry the wintercontrary, can as trigger the mean severe precipitation drought conditions is lower in di spring,fficult it to is alleviate possible with that a early dry winter spring precipitations.can trigger severe So, drought fields are conditions dry andit difficult can be ato problem alleviateif with the early rain is spring scarce. precipitations. Thus, the precipitation So, fields are in winterdry and can it can be playingbe a problem an important if the rain role is in scarce. the celebration Thus, the ofprecipitation rogation ceremonies in winter can in spring be playing months. an Theimportant development role in the of celebration drought occurs of rogation progressively ceremonies and in its spring effects months. appear The in agriculture development when of drought several monthsoccurs progressively of scarce rainfall and haveits effects accumulated. appear in So, agricu therelture could when be aseveral relationship months between of scarce the rainfall celebration have ofaccumulated.pro-pluvia rogations So, there andcould the be NAO a relationship index in previous between months.the celebration of pro-pluvia rogations and the NAOKeeping index in inprevious mind these months. results, the relationship between the celebration of pro-pluvia rogations in monthKeepingn and in themind monthly these results, NAO index the relationship in previous between months (then, n celebration-1, n-2 and ofn-3) pro-pluvia will be studied rogations in morein month detail n and while the using monthly the contingency NAO index tables. in previous Figure months5 shows ( then, n percentage-1, n-2 and ofn-3)pro-pluvia will be studiedrogations in celebratedmore detail corresponding while using the to contingency each interval ta ofbles. the Figure NAO index.5 shows Figure the percentage5 shows the of association pro-pluvia rogations between pro-pluviacelebratedrogations corresponding and the to each NAO interval index inof monthsthe NAOn (a),index.n-1 Figure (b), n-2 5 (c)shows and then-3 association (d). Black linesbetween are thepro-pluvia distribution rogations of the and null the hypothesisNAO index (no-dependencyin months n (a), n of-1 both(b), n series)-2 (c) and for n each-3 (d). case. Black Regarding lines are the to rogationsdistribution were of celebratedthe null hypothesis when dry conditions(no-dependency appear of and both these series) conditions for each are case. related Regarding to positive to valuesrogations of thewere NAO celebrated index [30 when,41,59 dry], it canconditions be seen appe in Figurear and5b–d these that conditions the number are of related positive to values positive of thevalues NAO of indexthe NAO is greater index than[30,41,59], the number it can ofbe negativeseen in Figure values, 5b, that 5c, is, and focusing Figure only 5d that on the the NAO number index of axis.positive On values the contrary, of the inNAO Figure index5a, negativeis greater values than the of thenumber NAO of index negative are almost values, equal that tois, the focusing number only of positiveon the NAO values. index A possible axis. On explanation the contrary, could in Figure be in the 5a, day negative of the values celebration of the of NAO the pro-pluvia index arerogation: almost ifequal the rogationto the number ceremony of positive is celebrated values. at A the possible beginning explanation of the month, could the be ninNAO the day index of the has celebration no relation withof the the pro-pluvia drought rogation: that trigger if the the rogation rogation ceremony ceremony. is celebrated at the beginning of the month, the n NAO index has no relation with the drought that trigger the rogation ceremony.

Figure 5. All plots show the percentage of pro-pluvia rogations celebrated in spring associated to the n a n b n c n d NAO index in months n (a), n-1 (b), n-2 ((c)) andand n-3-3 ((d).). All black lines are the distribution of the null hypothesis for each case. hypothesis for each case. Focusing on the percentages: the extreme intervals of the contingency tables (not shown) contain Focusing on the percentages: the extreme intervals of the contingency tables (not shown) contain fewer NAO events than the central intervals; if there are rogations associated to values of the NAO fewer NAO events than the central intervals; if there are rogations associated to values of the NAO index in these intervals, the percentage of pro-pluvia rogations increases. In Figure 5, the results for months n-1 and n-2 agree with the fact of drought are related to the positive values of the NAO index due to the high percentage of pro-pluvia rogations related to positive intervals. Also, results for the month n disagree, the percentage of pro-pluvia rogations related to positive values of the NAO index

Atmosphere 2020, 11, 282 10 of 15 index in these intervals, the percentage of pro-pluvia rogations increases. In Figure5, the results for months n-1 and n-2 agree with the fact of drought are related to the positive values of the NAO index due to the high percentage of pro-pluvia rogations related to positive intervals. Also, results for the monthAtmospheren disagree, 2020, 11, x FOR the percentagePEER REVIEW of pro-pluvia rogations related to positive values of the NAO10 index of 15 are less than the negative values. The highest percentage is found in a high negative value of the NAO index.are less Results than the for negative month n-3 values show. thatThe ahighest high percentage percentage corresponds is found in to a positivehigh negative values value of the of NAO the index.NAO index. Nevertheless, Results thefor highestmonth n percentage-3 show that is founda high inpercentage a negative corr valueesponds of the to NAO positive index. values This couldof the NAO index. Nevertheless, the highest percentage is found in a negative value of the NAO index. This be an outlier. could be an outlier. Trying to smooth the problem of the day of the celebration of the rogation (mentioned before), Trying to smooth the problem of the day of the celebration of the rogation (mentioned before), two running averages are calculated, as was described in Section3. Figure6 shows the percentage of two running averages are calculated, as was described in Section 3. Figure 6 shows the percentage of pro-pluvia rogations celebrated corresponding to each interval of the running averages of the NAO pro-pluvia rogations celebrated corresponding to each interval of the running averages of the NAO index. Figure6 shows the association between pro-pluvia rogations celebrated and the mean value of index. Figure 6 shows the association between pro-pluvia rogations celebrated and the mean value of months: n and n-1 of the NAO index (a); n, n-1 and n-2 (b); n-1 and n-2 (c); n-1, n-2 and n-3 (d). Black months: n and n-1 of the NAO index (a); n, n-1 and n-2 (b); n-1 and n-2 (c); n-1, n-2 and n-3 (d). Black line is the distribution of the null hypothesis for each case. line is the distribution of the null hypothesis for each case.

Figure 6. Percentage of pro-pluvia rogations associated to the average value of NAO for: (a) n and Figure 6. Percentage of pro-pluvia rogations associated to the average value of NAO for: (a) n and n-1; n-1; (b) n, n-1 and n-2; (c) n-1 and n-2; (d) n-1, n-2 and n-3. Black line is the distribution of the null (b) n, n-1 and n-2; (c) n-1 and n-2; (d) n-1, n-2 and n-3. Black line is the distribution of the null hypothesis for each case. hypothesis for each case. Unlike Figure5a, the number of negative values of the NAO index is less than the number of positiveUnlike values Figure in Figure 5a, the6a,b number (focusing of onlynegative in the values NAO of index the axisNAO and index in plots is less with than month the numbern). This isof duepositive to running values averagesin Figure are 6a calculatedand Figure with 6b (focusing the previous only months in the (inNAO Figure index5 there axis areand more in plots positive with valuesmonth ofn). the This NAO is due index to running in previous averages months). are calculated with the previous months (in Figure 5 there are moreIn the positive case of thevalues percentages, of the NAO it can index be seenin previous the same months). asin Figure 5 (in previous months). There is a highIn percentage the case of ofthepro-pluvia percentages,rogations it can corresponding be seen the same to positiveasin Figure values 5 (in of previous the NAO months). index and There the highestis a high percentages percentage are of pro-pluvia related to highrogations positive corresponding values of the to NAO positi index.ve values That of is, the it occursNAO index when and the NAOthe highest index inpercentages month n does are related not take to part high in positive the analysis values (Figure of the6b,c). NAO As index. we have That aforementioned is, it occurs when in thethe discussionNAO index of in Figure month5, this n does is very not reasonable, take part in because the analysis the month (Figure in which 6c and the Figure rogation 6b). is As celebrated we have hasaforementioned less inﬂuence in in the the discussion drought thatof Figure trigger 5, this the rogationis very reasonable, than the previous because the months. month Additionally, in which the droughtsrogation areis celebrated long duration has less events, influence speciﬁcally in the in dr southwestought that of trigger Spain [the50]. rogation than the previous months. Additionally, droughts are long duration events, specifically in southwest of Spain [50]. Finally, two NAO winter indexes were computed. Figure 7 shows the percentage of pro-pluvia rogations celebrated (grouped in the same year) corresponding to each interval of the NAO winter index: NAODJF (a) and NAODJFM (b). Black line is the distribution of the null hypothesis for each case. It can be seen in both plots (Figure 7a and Figure 7b) that the number of positive values of the NAO winter index are much greater than negative values. Also, most percentages correspond to positive values in both. In this analysis, only the average of the NAO index in winter is considered; i.e., month n is removed from the analysis and the direct effect of the previous month are shown.

Atmosphere 2020, 11, 282 11 of 15

Finally, two NAO winter indexes were computed. Figure7 shows the percentage of pro-pluvia rogations celebrated (grouped in the same year) corresponding to each interval of the NAO winter Atmosphere 2020, 11, x FOR PEER REVIEW 11 of 15 index: NAODJF (a) and NAODJFM (b). Black line is the distribution of the null hypothesis for each case.

Figure 7. Percentage of pro-pluvia rogations celebrated in each interval of the NAODJF (a) and NAODJFM (Figureb). Black 7. Percentage line is the distributionof pro-pluvia of rogations the null celebrated hypothesis in for each each interval case. of the NAODJF (a) and NAODJFM (b). Black line is the distribution of the null hypothesis for each case. It can be seen in both plots (Figure7a,b) that the number of positive values of the NAO winter indexConsidering are much greater the results, than negative pro-pluvia values. rogations Also, are most associated percentages with correspond negative values to positive of the values NAO inindex both. in Inthe this month analysis, n, while only positive the average values of of the the NAO NAO index index in are winter associated is considered; in most cases i.e., monthwith othern is removedmonths. This from means the analysis that it andwould the not direct be appropriate effect of the to previous associate month pro-pluvia are shown. rogations with month n. ConsideringThe desynchronization the results, pro-pluviabetween pro-pluviarogations arerogations associated (celebrated with negative in the valuesmonth of n) the and NAO the indexNAO inindex the month(monthsn, n while-1, n-2 positive and n-3) values can be of explained the NAO index by the are long associated average in drought most cases duration with otherin southwest months. Thisof Spain. means The that average it would duration not be is appropriate around 15 weeks to associate in agriculturalpro-pluvia droughtsrogations [50]. with In month addition,n. there is a delayThe of desynchronization one month between between the NAOpro-pluvia index androgations the hydrological (celebrated variables in the month in then) IP. and Trigo the NAOet al. index[41] found (months thisn delay-1, n-2 between and n-3) NAO can be winter explained index by (DJF) the long and averagerivers flow. drought duration in southwest of Spain.The The chi-squared average duration test was is aroundcomputed 15 weeksfor the in three agricultural parts of droughts the analysis [50]. (Section In addition, 3.2). there Table is a3 delaysummarizes of one monththe results between of the the chi-squared NAO index test and (p-value) the hydrological for all cases. variables All of the in the cases IP. Trigoare statistically et al. [41] foundsignificant this delayat the between95% confidence NAO winter level. indexThe most (DJF) relevant and rivers cases flow. have an asterisk. The chi-squared test was computed for the three parts of the analysis (Section 3.2). Table3 summarizesTable 3. Results the results of the of chi-squared the chi-squared test for testall analysis (p-value) of the for relationship all cases. Allbetween of the pro-pluvia cases are rogations statistically significantand the at NAO the 95%index. confidence Asterisks (*) level. show The the mostmost relevant cases. cases 1., have 2., and an 3.: asterisk. see Section 3.2. Month n n-1 n-2 n-3 Table1. 3. Results of the chi-squared test for all analysis of the relationship between pro-pluvia rogations p-value 5.34 × 10−6 7.30 × 10−7* 6.37 × 10−18* 1.07 × 10−5 and the NAO index. Asterisks (*) show the most relevant cases. 1., 2., and 3.: see Section 3.2. Average of months n and n-1 n, n-1 and n-2 n-1 and n-2 n-1, n-2 and n-3 2. p-valueMonth 7.57 × 10n−6 5.47 × 10− n20-1 2.62 × 10−36*n -2 2.68 × 10−17 n-3 1. NAO winterp index NAODJF 6 NAODJFM 7 18 5 3. -value 5.34 10− 7.30 10− * 6.37 10− * 1.07 10− ×−51 −130× × × Averagep-value of months 2.55n ×and 10 n-1 2.82 ×n ,10n-1 and* n-2 n-1 and n-2 n-1, n-2 and n-3 2. p-value 7.57 10 6 5.47 10 20 2.62 10 36* 2.68 10 17 As Table 3 shows, in the study 1, the× lowest− values of× the− p-value are found× − in the analysis× −in the NAO winter index NAO NAO months3. n-1 and n-2. In the study 2, the averageDJF of monthsDJFM n-1 and n-2 shows the smallest p-value. 51 130 This is in accordancep -valuewith the results2.55 show10 in− Figure2.82 5 and10 Figure− * 6 and the sense of the celebration × × of pro-pluvia rogations. That is, rogations were celebrated when dry conditions appear. On the contrary,As Table when3 shows, the month in the n study takes 1, part the lowestin the analysis, values of results the p-value get worse. are found Finally, in the the analysis relationship in the monthsbetweenn pro-pluvia-1 and n-2. rogations In the study and 2, the the NAO average winter of months index (NAOn-1 andDJFMn)-2 shows shows the the best smallest resultsp-value. (in Figures This isand in Table accordance 3). All with of this the results results are show in accordance in Figures5 withand6 that and shown the sense in the of thefigures. celebration of pro-pluvia rogations.Thus, results That is, suggest rogations that were pro-pluvia celebrated rogations when are dry a good conditions proxy for appear. the NAO On theindex contrary, (in particular when thefor the month NAOn takeswinter part index). in the Moreover, analysis, pro-pluvia results get rogations worse. Finally, should the be relationshipassociated to between the NAOpro-pluvia index in previous months (specifically in month n-1 and n-2). rogations and the NAO winter index (NAODJFM) shows the best results (in Figures and Table3). All of this results are in accordance with that shown in the figures. 5. Conclusions Ecclesiastical manuscripts and different newspapers and magazines have been consulted to carry out the task of retrieving rogation ceremonies. Other studies about rogation ceremonies are done in cities where historical archives are preserved and only ecclesiastical or municipal documents are taken into account. Books, and different newspapers and magazines, have also been consulted in

Atmosphere 2020, 11, 282 12 of 15

Thus, results suggest that pro-pluvia rogations are a good proxy for the NAO index (in particular for the NAO winter index). Moreover, pro-pluvia rogations should be associated to the NAO index in previous months (speciﬁcally in month n-1 and n-2).

5. Conclusions Ecclesiastical manuscripts and different newspapers and magazines have been consulted to carry out the task of retrieving rogation ceremonies. Other studies about rogation ceremonies are done in cities where historical archives are preserved and only ecclesiastical or municipal documents are taken into account. Books, and different newspapers and magazines, have also been consulted in this work. The advantage of these documentary sources lies in the preservation of this information in rural areas, in which the municipal and ecclesiastical documentary sources are frequently lost or not available. Also, these documentary sources cover the 19th and 20th centuries. Thus, the documentary sources consulted in this study have a great potential to extend the knowledge of rogation ceremonies in the IP during the second half of 19th century and during the 20th century. A set of 37 pro-pluvia rogations celebrated in different locations have been retrieved from 1824 to 1931 in Extremadura region (SW of Spain). Among them, 30 pro-pluvia rogations were celebrated in spring, 2 in autumn, and 5 in winter. Finally, 21 dates of spring pro-pluvia rogations (corresponding to 30 different rogations ceremonies in several places) are used to carry out the analysis. Results from the analysis of the NAO monthly anomalies averaged for our 21 dates of spring pro-pluvia rogations show that the value for February is statistically significant at the 95% confidence level. Although the values for previous months are not statistically significant, anomalies are negative since July. That is, continuous dry conditions are present in the months before the celebration of rogations ceremonies. There is not a clear relationship between the celebration of pro-pluvia rogations in month n and the NAO index of this month. This is due to the fact that pro-pluvia rogations correspond largely to negative values of the NAO index in month n. While positive values of the NAO index are associated in most cases with other months. In fact, the results of the analysis of the relationship between pro-pluvia rogations celebrated in month n and the NAO index for months n-1 and n-2 show high correlations, specifically in month n-2. Therefore, our results indicate that historical spring pro-pluvia rogations celebrated in Extremadura region are a good proxy for the reconstruction of historical positive values of NAO index during the previous winter or early spring. This work has important implications for the study of rogation ceremonies as climate proxy. Firstly, we have demonstrated that rogation ceremonies in Extremadura region have a significant NAO signal. This opens the possibility to reconstruct NAO positive values in pre-instrumental period from rogation ceremonies series of the region. There are many documentary sources in Extremadura with high potential to provide information about rogation ceremonies in pre instrumental period (e.g., Zafra rogation ceremony series from 1750 to 1850, Dominguez- Castro et al. [23]). Secondly, this study has demonstrated that rogation ceremonies in rural areas during the 19th and early 20th century have an important climate signal and can be retrieved from different documentary sources. This finding opens the way to enlarge the available rogation ceremony series from cities with information from nearby rural areas up to the early 20th century. This work must be done with caution due to the possible influence of technological development and other socioeconomic factors, but this will allow understanding of the better the climate signal of the rogations thanks to a longer overlapping period among rogation and instrumental series.

Author Contributions: Conceptualization, J.M.V.; methodology, N.B.-P., M.C.G., F.D.-C., and J.M.V.; formal analysis, N.B.-P.; investigation, N.B.-P., M.C.G., F.D.-C., and J.M.V.; writing—original draft preparation, N.B.-P.; writing—review and editing, M.C.G., F.D.-C., J.A.G. and J.M.V.; supervision, M.C.G. and J.M.V.; project administration, M.C.G.; funding acquisition, M.C.G. and J.M.V. All authors have read and agree to the published version of the manuscript. Atmosphere 2020, 11, 282 13 of 15

Funding: This work was partly funded by the Department of Economy and Infrastructure of the Junta of Extremadura through project IB16127 and grant GR18097 (co-financed by the European Regional Development Fund), and by the Ministerio de Economía y Competitividad of the Spanish Government (CGL2017-87917-P and CGL2017-83866-C3-1-R). The research of N. Bravo-Paredes has been supported by the predoctoral fellowship PRE2018-084897 from Agencia Estatal de Investigación (Ministerio de Ciencia, Innovación y Universidades) of the Spanish Government. Acknowledgments: We are in debt to all the archivists and librarians who have helped us in locating the historical sources used in this work. Conflicts of Interest: The authors declare no conflict of interest.

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