Western Mediterranean precipitation over the last 300 years from instrumental observations

The paper reports the results of the analysis of the 14 longest precipitation instrumental series, covering the last 300 years, that have been recovered in six subareas of the Western Mediterranean basin, i.e., Portugal, Northern and Southern Spain, Southern France, Northern and Southern Italy. This study extends back by one century our knowledge about the instrumental precipitation over theWestern Mediterranean, and by two centuries in some specific subareas. All the time series show repeated swings. No specific trends have been found over the whole period, except in a few cases, but with modest time changes and sometimes having opposite tendency. The same can be said for the most recent decades although with some more marked departures from the average. The correlation between the various Mediterranean subareas is generally not significant, or almost uncorrelated. The Wavelet Spectral Analysis applied to the precipitation identifies only a minor 56-year cycle in autumn, i.e., the same return period that has been found in literature for the Sea Surface Temperature over North Atlantic. A comparison with a gridded dataset reconstruction based on mixed multiproxy and instrumental observations, shows that the grid reconstruction is in good agreement with the observed data for the period after 1900, less for the previous period

Modelling risk for commodities in Brazil: An application for live cattle spot and futures prices

This study analyses a series of live cattle spot and futures prices from the Boi Gordo Index (BGI) in Brazil. The objective is to develop a model that best portrays this commodity’s behaviour to estimate futures prices more accurately. The database created contains 2010 daily entries in which trade in futures contracts occurs, as well as BGI spot sales in the market, from 1 December 2006 to 30 April 2015. One of the most important reasons why this type of risk needs to be measured is to set loss limits. To identify patterns in price behaviour in order to improve future transaction results, investors must analyse fluctuations in asset values for longer periods. Bibliographic research reveals that no other study has conducted a comprehensive analysis of this commodity using this approach. Cattle ranching is big business in Brazil given that in 2021, this sector moved BRL 913.14 billion (USD 169.29 billion). In that year, agribusiness contributed 26.6% of Brazil’s total gross domestic product. Using the proposed risk modelling technique, economic agents can make the best decision about which options within these investors’ reach produce more effective risk management. The methodology is based on Holt–Winters exponential smoothing algorithm, autoregressive integrated moving-average (ARIMA), ARIMA with exogenous inputs, generalised autoregressive conditionally heteroskedastic and generalised autoregressive moving-average (GARMA) models. More specifically, five different methods are applied that allow a comparison of 12 different models as ways to portray and predict the BGI commodity behaviours. The results show that GARMA with order c(2,1) and without intercept is the best model. Investors equipped with such precise modelling insights stand at an advantageous position in the market, promoting informed investment decisions and optimising returns.info:eu-repo/semantics/publishedVersio

Modelling risk for commodities in Brazil: an application to live cattle spot and futures prices

This study analysed a series of live cattle spot and futures prices from the Boi Gordo Index (BGI) in Brazil. The objective was to develop a model that best portrays this commodity’s behaviour to estimate futures prices more accurately. The database created contained 2,010 daily entries in which trade in futures contracts occurred, as well as BGI spot sales in the market, from 1 December 2006 to 30 April 2015. One of the most important reasons why this type of risk needs to be measured is to set loss limits. To identify patterns in price behaviour in order to improve future transactions’ results, investors must analyse fluctuations in assets’ value for longer periods. Bibliographic research revealed that no other study has conducted a comprehensive analysis of this commodity using this approach. Cattle ranching is big business in Brazil given that in 2017, this sector moved 523.25 billion Brazilian reals (about 130.5 billion United States dollars). In that year, agribusiness contributed 22% of Brazil’s total gross domestic product. Using the proposed risk modelling technique, economic agents can make the best decision about which options within these investors’ reach produce more effective risk management. The methodology was based on Holt-Winters exponential smoothing algorithm, autoregressive integrated moving average (ARIMA), ARIMA with exogenous inputs, generalised autoregressive conditionally heteroskedastic and generalised autoregressive moving average (GARMA) models. More specifically, 5 different methods were applied that allowed a comparison of 12 different models as ways to portray and predict the BGI commodity’s behaviour. The results show that GARMA with order c(2,1) and without intercept is the best model..info:eu-repo/semantics/publishedVersio

Modelling risk for commodities in Brazil: an application to live cattle spot and futures prices

This study analysed a series of live cattle spot and futures prices from the Boi Gordo Index (BGI) in Brazil. The objective was to develop a model that best portrays this commodity’s behaviour to estimate futures prices more accurately. The database created contained 2,010 daily entries in which trade in futures contracts occurred, as well as BGI spot sales in the market, from 1 December 2006 to 30 April 2015. One of the most important reasons why this type of risk needs to be measured is to set loss limits. To identify patterns in price behaviour in order to improve future transactions’ results, investors must analyse fluctuations in assets’ value for longer periods. Bibliographic research revealed that no other study has conducted a comprehensive analysis of this commodity using this approach. Cattle ranching is big business in Brazil given that in 2017, this sector moved 523.25 billion Brazilian reals (about 130.5 billion United States dollars). In that year, agribusiness contributed 22% of Brazil’s total gross domestic product. Using the proposed risk modelling technique, economic agents can make the best decision about which options within these investors’ reach produce more effective risk management. The methodology was based on Holt-Winters exponential smoothing algorithm, autoregressive integrated moving average (ARIMA), ARIMA with exogenous inputs, generalised autoregressive conditionally heteroskedastic and generalised autoregressive moving average (GARMA) models. More specifically, 5 different methods were applied that allowed a comparison of 12 different models as ways to portray and predict the BGI commodity’s behaviour. The results show that GARMA with order c(2,1) and without intercept is the best model..info:eu-repo/semantics/publishedVersio

Metodos para reduzir o tempo de germinacao de sementes de bacuri (Platonia insignis Mart.).

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Métodos para reduzir o tempo de germinação de sementes de bacuri (Platonia insignis Mart.).

Este trabalho teve como objetivo avaliar métodos para acelerar a germinação de sementes de bacuri (Platonia insignis Mart.). O experimento foi conduzido no Laboratório de Fisiologia Vegetal e na Câmara de Nebulização da Embrapa Meio-Norte, Teresina-PI, no delineamento de blocos ao acaso, com dez tratamentos e quatro repetições, sendo a unidade experimental constituída por dez sementes. Foram testados os seguintes tratamentos: testemunha (Tl); remoção do tegumento da semente (T2); remoção do meristema fundamental corticai, através de cortes em planos perpendiculares ao plano dorsalíventd, nos dois lados da semente, sem atingir o menstema fundamental medular (T3); T3 mais a remoção do meristema fundamental cortical através de cortes em planos paralelos ao plano dorsai-.ventrai, na região dorsal, sem atingir o menstema fundamental medular (T4); T3 mantido em água a 40 "C por 20 minutos (T5); T4 mantido em água a 40 'C por 20 minutos (T6); T3 mantido em etanol 80% por 5 minutos (T7); T4 mantido em etanol 80% por 5 minutos (T8); T3 mantido em acetona 80% por 5 minutos (T9); e T4 mantido em acetona 80% por 5 minutos (TIO). As variáveis estudadas foram: percentagem de emergência da radícula aos 14 (PErl4), 2 1 (PEr2 l), 28 (PEr28), e 35 (PEr35) dias após a semeadura e índice de velocidade de emergência da radicula (IVEr) no 35' dia após a semeadura. As sementes submetidas aos tratamentos T2, T3, T4, T5 e T6 apresentaram PErl4 de 72,5%; 65,0%; 72,5%; 52,5% e 67,5%, respectivamente, sendo superiores (p<0,05) aos demais tratamentos. Todos os tratamentos foram superiores @<0,05) a testemunha em relação a PEr21 (35,0%) e não houve diferença significativa entre os tratamentos em relação a PEr28 e PEr35. Quanto ao IVEr, os tratamentos T2, T3, T4, T5 e T6 apresentaram os valores de 0,59; 0,57; 0,61; 0,54 e 0,59, respectivamente, superando (p<0,05) os demais tratamentos, os quais não diferiram da testemunha (0,36).bitstream/item/35780/1/BP25.pd

Atmospheric electric field measurements in urban environment and the pollutant aerosol weekly dependence

The weekly dependence of pollutant aerosols in the urban environment of Lisbon (Portugal) is inferred from the records of atmospheric electric field at Portela meteorological station (38°47′N,9°08′W). Measurements were made with a Bendorf electrograph. The data set exists from 1955 to 1990, but due to the contaminating effect of the radioactive fallout during 1960 and 1970s, only the period between 1980 and 1990 is considered here. Using a relative difference method a weekly dependence of the atmospheric electric field is found in these records, which shows an increasing trend between 1980 and 1990. This is consistent with a growth of population in the Lisbon metropolitan area and consequently urban activity, mainly traffic. Complementarily, using a Lomb–Scargle periodogram technique the presence of a daily and weekly cycle is also found. Moreover, to follow the evolution of theses cycles, in the period considered, a simple representation in a colour surface plot representation of the annual periodograms is presented. Further, a noise analysis of the periodograms is made, which validates the results found. Two datasets were considered: all days in the period, and fair-weather days only