We present the first systematic classification of circulation regimes that characterize the Tropical Andes during the dry season (May–August). We apply the hierarchical k-means clustering method to ERA-Interim reanalysis data of daily mean geopotential height at 500- and 200-hPa levels for the period 1981–2015. Specifically, by combining the variability in intensity and location of geopotential anomalies we identify 12 circulation types (CTs). We then establish the relationship between the CTs and surface conditions in the Peruvian Andes (PA) analysing high-resolution gridded datasets of daily mean temperature and rainfall. Our results indicate that intense precipitations and low minimum temperatures are often associated with an Upper Tropospheric Trough (UTT) centred at subtropical latitudes (~30°S) and between 80° and 70°W of longitude. Moreover, drier and warmer conditions acro...

Cutoff lows (COLs) are infrequent events in the tropics that can cause extreme rainfall, flash flooding and landslides in arid areas, such as western South America. In this study, the life cycle of a COL in the southeastern Pacific at the beginning of April 2012 was analysed using the ERA-Interim reanalysis dataset. This paper examines: (1) the precursor flow evolution prior to the COL, its development and dissipation by applying the quasi-geostrophic and vorticity equations; and (2) the influence of the COL in the heavy precipitation events over the western Peruvian Andes. During April 2012, the highest amount of precipitation was recorded in Chosica (850 masl) with 37 mm on 5 April. Days prior to the formation of the COL, a subtropical trough deepened by the amplification of a ridge over the tropical Pacific and the incursion of cold air from medium and low levels into the trough. The ...

Tropical high‐mountain permafrost has a unique thermal regime due to its exposure to strong solar radiation and to rough surface snow morphology, which reduce ground heat transfer from the surface. Latent heat transfer and higher albedo that occur during the snow‐covered season contribute to positive feedback that supports the presence of permafrost. This preliminary study reports on the thermal state characteristics of tropical mountain permafrost in Peru. This work also evaluates the potential combined impact of the El Niño–Southern Oscillation (ENSO) in the mountain permafrost of the Coropuna and Chachani volcanic complexes, both located at the western edge of the southern Peruvian Altiplano. Temperature monitoring boreholes were established at 5,217 m at Coropuna and 5,331 m at Chachani, and electrical resistivity was surveyed in both sites. This 7‐year discontinuous record ...

This work investigates the timing, paleoclimatic framework and inter-hemispheric teleconnections inferred from the glaciers last maximum extension and the deglaciation onset in the Arid Tropical Andes. A study area was selected to the northeastward of the Nevado Coropuna, the volcano currently covered by the largest tropical glacier on Earth. The current glacier extent, the moraines deposited in the past and paleoglaciers at their maximum extension have been mapped. The present and past Equilibrium Line Altitudes (ELA and paleoELA) have been reconstructed and the chlorine-36 ages have been calculated, for preliminary absolute dating of glacial and volcanic processes. The paleoELA depression, the thermometers installed in the study area and the accumulation data previously published allowed development of paleotemperature and paleoprecipitation models. The Coropuna glaciers were in maximu...

Precipitation variability in tropical high mountains is a fundamental yet poorly understood factor influencing local climatic expression and a variety of environmental processes, including glacier behavior and water resources. Precipitation type, diurnality, frequency, and amount influence hydrological runoff, surface albedo, and soil moisture, whereas cloud cover associated with precipitation events reduces solar irradiance at the surface. Considerable uncertainty remains in the multiscale atmospheric processes influencing precipitation patterns and their associated regional variability in the tropical Andes—particularly related to precipitation phase, timing, and vertical structure. Using data from a variety of sources—including new citizen science precipitation stations; new high-elevation comprehensive precipitation monitoring stations at Chacaltaya, Bolivia, and the Quelccaya Ic...

Tropical high‐mountain permafrost has a unique thermal regime due to its exposure to strong solar radiation and to rough surface snow morphology, which reduce ground heat transfer from the surface. Latent heat transfer and higher albedo that occur during the snow‐covered season contribute to positive feedback that supports the presence of permafrost. This preliminary study reports on the thermal state characteristics of tropical mountain permafrost in Peru. This work also evaluates the potential combined impact of the El Niño–Southern Oscillation (ENSO) in the mountain permafrost of the Coropuna and Chachani volcanic complexes, both located at the western edge of the southern Peruvian Altiplano. Temperature monitoring boreholes were established at 5,217 m at Coropuna and 5,331 m at Chachani, and electrical resistivity was surveyed in both sites. This 7‐year discontinuous record ...