Results of the Rio de Janeiro magnetic observations 1781−1788

Abstract

Abstract.We have compiled a relatively extensive catalogue of geomagnetic declination measurements performed by the Portuguese Bento Sanches Dorta in Rio de Janeiro (Brazil) between 1781 and 1788. All the information was retrieved from printed documents compiled in the first three volumes of the Memories of the Portuguese Royal Academy of Sciences. During this period Sanches Dorta performed roughly 20 000 individual observations, however, only a fraction of this data is presently available. In this work, all available information about these measurements is analysed. The annual change (variability and trend) and the daily cycle of geomagnetic declination at monthly scale are discussed.

Trends in frequency indices of daily precipitation over the Iberian Peninsula during the last century

“…The completed European Community (EC) funded project EMULATE (European and North Atlantic daily to MULtidecadal climATE variability) has developed new daily data sets of observations since 1850 over Europe, having fostered a number of studies with sea level pressure [ Ansell et al , 2006], precipitation, and temperature [ Moberg et al , 2006; Della‐Marta et al , 2007]. From a different perspective the ongoing Portuguese funded project SIGN (SIGNatures of environmental change in the observations of the Geophysical Institutes) is engaged in a similar task to digitize and make publicly available large amounts of data from the Portuguese mainland, Atlantic islands, and former colonies including astronomical [e.g., Vaquero et al , 2005], geophysical [e.g., Vaquero and Trigo , 2005a, 2006], and meteorological [e.g., Vaquero and Trigo , 2005b; Trigo et al , 2009; Fragoso et al , 2010] data. In any case, both projects have made available a considerably larger number of long‐term daily precipitation time series, since the late nineteenth or early twentieth century.…”

Witnessing the impact of the 1783–1784 Laki eruption in the Southern Hemisphere

“…As a member of the recently formed Portuguese Academy of Sciences he was particularly careful with his observations. In recent works the authors have made extensive use of Sanches Dorta's data, namely (a) to reconstruct solar activity (Vaquero et al 2005), (b) to study ancient geomagnetic time series for Rio de Janeiro (Vaquero and Trigo 2005a), (c) to associate daily geomagnetic declination anomalies with rare auroral observations (Vaquero and Trigo 2005b), (d) to estimate stratospheric turbidity during total lunar eclipses (Stothers 2004). A complete assessment of BSD meteorological data (about 10,000 observations) is beyond the scope of this work.…”

The HISTMAG database: combining historical, archaeomagnetic and volcanic data

“…Hemmer 1788). Furthermore, it is noted, when authors suggest a correction of records due to sudden changes during the measurement series, as for example, Vaquero & Trigo (2005). Corrections due to the influence of iron objects as well as recognized magnetic storms as in case of Maximilian Hell's measurements in Vardø (Hansen & Aspaas 2005) are also documented in the comment field.…”

“…For instance, Vaquero & Trigo (2005) summarized declination observations in Rio de Janeiro by Bento Sanches Dorta from 1781 to 1788. Smith & Needham (1967) compiled 18 declination observations from China covering a period from 720 to 1829 AD (Fig.…”

“…Schellander (1871) estimated an accuracy of about 6 -10 for declination measurements at the Adriatic coasts by Marieni in the beginning of the 19th century. Vaquero & Trigo (2005) considered an error of 10 as appropriate for Sanches Dorta's observations in Rio. As in case of the Chinese data set (Smith & Needham 1967), the measurement error was deviated from the statement describing the record.…”