The climate of Bulgaria during 19th and 20th centuries by instrumental and indirect data : Solar modulated cycles and their evolution

TL;DR

This study analyzes 200 years of Bulgarian climate data, revealing solar-modulated cycles and their evolution, with implications for understanding climate variability linked to solar activity.

Contribution

It identifies and characterizes solar-modulated climate cycles in Bulgaria over two centuries using instrumental and dendrochronological data, highlighting their evolution and solar analogs.

Findings

Quasi-20-22 yr cycles in summer rainfall and temperature

Quasi-11 yr cycle in winter temperature

Presence of 54, 67, and 115-year cycles with solar analogs

Abstract

Two types of data sets for investigation of solar- modulated cycles in the climate of Bulgaria during the last ~ 200 years has been used in this study: 1. Instrumental data for the rainfalls and temperatures in 26 stations during the period AD 1899-1994; A smoothing dendrochronological data series of the tree rings width of a beech sample (Fagus) for the period of AD 1780-1982. The data proceedings has been provided separately for the "winter" (November-April) and "summer" (May-October) half- years. A well expressed quasi-20-22 and 54 yr cycles in the rains and temperature instrumental "summer" series as well as quasi 11yr cycle for the "winter" temeperature data has been established for the studied period 1899-1994. However there are also very serious variations of the 11 and 22 yr cycle magnitudes. The quasi 20-22 yr ("summer") cycle is weak expressed before AD 1930, while the 11 yr (winter) cycle is faded rapidly after ~AD 1975/76. The existence of 20-22 yr climatic cycle could be traced since the end of the supercenturial solar Dalton minimum (AD 1795-1830) in the beech tree ring width series. Strong cycles by duration of 54, 67 and 115 years are also found in this series. All they have solar analogs (in the coronal activity as well as in the "cosmogenic" 10Be and aurora activity data series). Extreme little tree ring widths during the Dalton minimum has been detected.