Projected twenty-first-century changes in the Central American mid-summer drought using statistically downscaled climate projections

In addition to periodic long-term drought, much of Central America experiences a rainy season with two peaks separated by a dry period of weeks to over a month in duration, termed the mid-summer drought (MSD). Farmers in the region have adapted their activities to accommodate this phenomenon, anticipating its arrival and estimating its duration. Among the many impacts of global warming on the region are projected changes in precipitation amount, variability, and timing, with potential to affect agriculture and food security. Using gridded daily precipitation for a historic period with future projections, we characterize the MSD across much of Central America using four measures: onset date, duration, intensity, and minimum, and test for significant changes by the end of the twenty-first century. Our findings indicate that the most significant changes are for the duration, which is projected to increase by an average of over a week, and the MSD minimum precipitation, which is projected to decrease by an average of over 26%, with statistically significant changes for the mountains and Pacific side in most of Nicaragua, Honduras, El Salvador, and Guatemala (assuming a higher emissions pathway through the twenty-first century). These changes could portend important impacts on food security for vulnerable communities through the region. We find that for the four metrics, the changes in interannual variability are small compared to historical variability and are generally statistically insignificant.