Climate forcings and their influence in Cordillera Blanca, Perú, deduced from spectral analysis techniques.

Climate forcings are natural processes that drive climate variability in the short, medium and long term. Characterizing the forcings behind climate variability is important to understand the functioning of the regional atmospheric system. Since investigations typically reveal only the link and extent of the influence of climate forcings in specific regions, the magnitude of that influence in meteorological records remains usually unclear.

The central peruvian Andes are affected by most of the common climate forcings of tropical areas, such as Intertropical Convergence Zone (ITCZ), Sea Surface Temperature, Solar irradiance, Madden Julian Oscillation (MJO), Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO). They are also affected by regional processes that are exclusive from South America, such as South American Low Level Jet (SALLJ), South American Monsoon System, Bolivian High and Humboldt Current.

The aim of this research is to study the climate variability of precipitation, maximum temperature and minimum temperature records over Cordillera Blanca (Peru) in order to link this climate variability with the intensity and periodicity of the common climate forcings that affects this region. To achieve this aim, a spectral analysis based on Lomb’s Periodogram has been performed over meteorological records (1986 - 2019 period) and over different climate forcing Indexes.

Results show a coincidence in periodicity between MJO and SALLJ with monthly cycles for precipitation and temperature (27 days, 56 days, 90 days cycles). The most intense periodicities, such as annual (365 days) and biannual (182 and 122 days) cycles in meteorological variables, possibly would be led by ITCZ and ENSO together, as well as a combination of Humboldt current and SALLJ. Interannual periodicities (3 years, 4.5 years, 5.6 - 7 years and 11 years cycles) would have coincidence with the ENSO - Solar combination, while the longest cycles (16 years) could match PDO variability.