ORCID

https://orcid.org/0009-0007-2975-5545

Date of Award

Summer 2026

Language

English

Embargo Period

7-29-2026

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College/School/Department

Department of Atmospheric and Environmental Sciences

Program

Atmospheric Science

First Advisor

Mathias Vuille

Committee Members

Paul Roundy

Keywords

Altiplano, Extreme Precipitation, Climate Change

Subject Categories

Atmospheric Sciences | Climate

Abstract

Extreme precipitation events in the South American Altiplano present significant hazards to communities in the Andean region, yet their future characteristics under anthropogenic climate change remain uncertain because of complex terrain and limitations of course-resolution climate models. This study evaluates the ability of South America Affinity Group Weather Research and Forecasting (SAAG-WRF) model with 4-km grid-spacing to reproduce 2000-2015 temperature, precipitation, and extreme precipitation events over the Altiplano. Examination of projected future changes is completed using the SAAG-WRF pseudo global warming (WRF PGW) simulation representing an approximately 3°C warmer global climate. The historical/control simulation (WRF CTL) was evaluated against DECADE temperature observations, SC-PREC4SA precipitation observations, CHIRPS precipitation estimates, and ERA5 reanalysis. Extreme precipitation events were defined as wet-day precipitation at or exceeding the 95th percentile (P95) at 10 or more stations above 3000 m elevation.

WRF CTL successfully reproduced the large-scale spatial distribution of temperature and precipitation, environmental lapse rates, interannual variability, and ENSO-related anomalies. However, a cold temperature bias was identified associated with elevation differences between grid elevation and weather station locations. A dry precipitation bias in the lowlands and on the Altiplano was also identified, as was a narrow, wet bias along the eastern slope of the Altiplano. The WRF CTL model underestimates observed P95 precipitation thresholds, particularly during the austral summer. Further analysis of the timing of P95 exceedances showed that many exceedances were reproduced when a ±1- or ±2-day window of tolerance was allowed, indicating that the model often captured extreme precipitation despite small timing errors. Atmospheric circulation event composite anomalies for the austral summer (DJF) showed that extreme precipitation events in that season are accompanied by enhanced upper-level easterly wind anomalies and increased mid-tropospheric water vapor mixing ratio anomalies extending across the Altiplano westward to the Pacific Ocean, consistent with previous studies.

The WRF PGW simulation projects widespread warming of 2-5 °C and increased seasonal precipitation across much of the region. Seasonal P95 thresholds increased by approximately 108-135% relative to WRF CTL, indicating a substantial intensification of extreme precipitation under future warming. Frequency of P95 threshold exceedances also increases under the WRF PGW simulation with historical 1-in-20 wet day events occurring approximately once every 4 wet days in the future. These results are a step toward further understanding hydroclimate extremes over complex mountainous terrain and provide insight into future extreme precipitation changes across the Altiplano region.

License

This work is licensed under the University at Albany Standard Author Agreement.

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