A simple approach for the study of the relationship between temperature and precipitation

Abstract

The relationship between temperature and precipitation is not simple. Several physical processes can determine whether this relationship is positive or negative, depending on the geographic location and the season. This paper proposes new indices for studying this relationship at a seasonal level, based on daily data of accumulated precipitation and mean temperature: the R_t(T₇₅) index is defined as the percentage of precipitation corresponding to warm days in the year t, and R_t(T₂₅) the one corresponding to cold days. The so-called contribution index is defined as the measurement and extent in which the R_t(T₂₅) and R_t(T₇₅) indices contribute to each interval of percentage precipitation values. To synthesize the behavior of these indices, the index IR_t = R_t(T₇₅) − R_t(T₂₅) is proposed and compared to the IT_t index, defined as the difference between the average temperature of wet days and that of dry days. These indices are analyzed for four meteorological stations that represent the main climatic domains of the Iberian Peninsula from 1951 to 2019. The results show a negative relationship between temperatures and precipitation, except for the two westernmost stations in winter. The role of atmospheric circulation in this result, particularly the NAO, EA, and WeMO teleconnection patterns, is discussed. Finally, future avenues of research are proposed.