The climate in Zafra from 1750 to 1840: temperature indexes from documentary sources

This article shows the first monthly series of a temperature index for the region of Zafra, located in the southwest of Spain, during the period 1750–1840 using weekly weather descriptions. Three different index categories are established (−1, 0, and 1). We compare the index series of temperature in Zafra with the early instrumental data available in the southwest of Iberian Peninsula in order to assess the quality of these indices series. In addition, we characterize the synoptic situation over the North Atlantic region during the period 1750–1840 for the seasons with highest seasonal percentages of cold and warm weeks in each season. The overall configuration of the particularly cold (warm) weeks is seasonally dependent and makes sense from a synoptic perspective. Finally, we analyze the effects on climate in Zafra of important eruptions which took place during the period 1750–1840.