Variable landscape response to drought in Guanacaste, Costa Rica

Authors: Savannah Cooley*, Clark University, Chris Williams, Clark University, Josh B Fisher, NASA JPL, Johan Perret, EARTH University, Gregory Halverson, NASA JPL, Christine Lee, NASA JPL, Christine Lee*, NASA JPL
Topics: Earth Science
Keywords: Drought estimation, conceptual framework, drought response, Evapotranspiration, Evaporative Stress Index, resilience, Guanacaste, Costa Rica
Session Type: Paper
Day: 4/12/2018
Start / End Time: 5:20 PM / 7:00 PM
Room: Bayside B, Sheraton, 4th Floor
Presentation File: No File Uploaded

This research evaluates landscape response to drought using precipitation and non-precipitation (evapotranspiration) based measures. These measures are used to evaluate drought in Guanacaste, Costa Rica. First, the study quantifies changes in 60 year record of historical rainfall patterns with the Standard Precipitation Index (SPI) using combined precipitation datasets from the Global Precipitation Climatology Centre and the Costa Rica Instituto Meteorologico Nacional. It then compares the precipitation-based measure of drought with vegetation stress by computing anomalies in the wet season (May - October) from 2002-2015 for normalized difference vegetation index (NDVI) data at 30m spatial resolution as well as coarser 1km ET, potential evapotranspiration (PET) and evaporative stress index (ESI) derived with the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model. Finally, the study investigates the differences in vegetation stress and drought resilience, as measured by ESI, observed across forest, grassland and agricultural landscapes. Results suggest that Guanacaste experienced a long-term negative trend in precipitation over the past 15 years, with 2015 having the most severe negative anomaly (annual SPI = -4.07). However, 2015 did not significantly differ from the baseline nor the other two previous drought years across NDVI, ET, PET and ESI indicators. Differences in vegetation stress across land use categories varied significantly (p<0.001), with forested areas consistently exhibiting lower plant stress compared to grassland. The findings of this research point to the added value measures of vegetation stress, including NDVI, ET, PET and ESI, provide to precipitation-based drought assessments.

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