Title

Changing climate in the Bolivian Altiplano

Date of Completion

January 2010

Keywords

Physical Geography|Climate Change|Atmospheric Sciences

Degree

Ph.D.

Abstract

Rural agriculture in the Bolivian Altiplano is vulnerable to climate related shocks. Projections of eight precipitation and temperature extreme indices for the Altiplano are examined. Increases in observed warm nights and warm spells are consistent with increasing temperatures in the tropical Andes. Projections of warm nights, frost days, and heat waves are consistent with projected annual cycle temperature increases. Projected increases in precipitation extremes are consistent with trends at Patacamaya and annual cycle projections indicating a later rainy season characterized by less frequent, more intense precipitation. PDFs of Patacamaya precipitation suggest that precipitation changes may occur earlier than projected. The observed increase in frost days can be understood within the context of precipitation changes and increased radiative cooling. Consistencies between simulated and observed extremes suggest the projected directions of change are reliable. ^ The ability of the CMIP3 models to simulate relationships between Altiplano precipitation anomalies and large-scale atmospheric variables for spring and summer is examined. A majority of models simulate an easterly/wet-westerly/dry relationship between upper-level winds and Altiplano precipitation in spring and summer, consistent with observations. ^ Examination of future precipitation variability under conditions of greenhouse warming suggests the requirement of moisture transport from the east will not change. Atmospheric circulation changes associated with expansion of the Hadley circulation reduces the frequency of upper-level easterly winds, explaining springtime drying. Increased tropical tropospheric warming reduces the frequency of summertime upper-level easterly winds, explaining less frequent summertime rainfall. ^ Springtime soil moisture is expected to decrease throughout the 21 st century, consistent with projections for increased temperature and decreased precipitation. Reductions in springtime soil moisture are likely to affect sowing times and plant survival. Reductions in summertime soil moisture are expected from the mid-century onward because small precipitation increases may not offset increased evapotranspiration related to higher temperatures. ^ Consistencies between the results and expected large-scale changes in atmospheric circulation provide confidence in the projections. The results have serious implications for water resources and food security in the Altiplano, and provide a first step toward providing the critical information necessary to reduce the effects of changing climate in the Altiplano. ^