Multiscale trends and precipitation extremes in the Central American Midsummer Drought

Abstract

Anecdotal evidence suggests that the timing and intensity of the Central American Midsummer Drought (MSD) may be changing, while observations from limited meteorological station data and paleoclimate reconstructions show neither significant nor consistent trends in seasonal rainfall. Climate model simulations project robust future drying across the region, but internal variability is expected to dominate until the end of the century. Here we use a high-resolution gridded precipitation dataset to investigate these apparent discrepancies and to quantify the spatiotemporal complexities of the MSD. We detect spatially variable trends in MSD timing, the amount of rainy season precipitation, the number of consecutive and total dry days, and extreme wet events at the local scale. At the regional scale, we find a positive trend in the duration, but not the magnitude of the MSD, which is dominated by spatially heterogeneous trends and interannual variability linked to large-scale modes of oceanatmosphere circulation. Although the current climate still reflects predominantly internal variability, some Central American communities are already experiencing significant changes in local characteristics of the MSD. A detailed spatiotemporal understanding of MSD trends and variability can contribute to evidence-based adaptation planning and help reduce the vulnerability of Central American communities to both natural rainfall variability and anthropogenic change.

Evaluation of methods to detect and quantify the bimodal precipitation over Central America and Mexico

“…Similar approach has also been used in Anderson et al . (2019), but for pentadal data. Using annual daily precipitation data, Zhao et al .…”

“…Maldonado et al (2016) detected and quantified bimodal precipitation in Central America by observing the minimum precipitation during the rainy season and matching this to corresponding inflection points. Similar approach has also been used in Anderson et al (2019), but for pentadal data. Using annual daily precipitation data, Zhao et al (2020) initially determined areas exhibiting climatological bimodal signals, then detected and quantified bimodal signals for each year in each grid.…”

Atlantic‐Pacific Gradients Drive Last Millennium Hydroclimate Variability in Mesoamerica

“…Instrumental data and historical model simulations provide robust evidence of a region‐wide twentieth century drying trend (Anderson et al., 2019; Marvel et al., 2019; Neelin et al., 2006). Observed drying has been attributed to both higher temperatures and reductions in precipitation (Fuentes‐Franco et al., 2015; Herrera et al., 2018; Rauscher et al., 2011).…”

“…Models project additional drying by the end of the 21st century (Rauscher et al., 2011). However, the limited instrumental record hinders our ability to understand how the magnitude of historical or projected drying compares to natural climate variability, which in many areas is larger than observed drying trends (Anderson et al., 2019). Longer‐term records of hydroclimate are therefore essential to adequately characterize regional climate variability and contextualize future projections.…”

Aridity Trends in Central America: A Spatial Correlation Analysis

“…Except for a few places, precipitation trends are non-significant, although this depends greatly on the database used in the assessment ( [14,15]). Additionally, precipitation trends do not show a robust pattern over the isthmus as surface temperature do, because precipitation trends are constructed over multiscale processes ( [16,17]). As a working hypothesis we argue that those stations showing a warming trend combined with a non-significant precipitation trend will result in increases of their aridity, as the demand of water from the atmosphere associated with increases in PET (due to warming) are not compensated by increases in the water supply from precipitation.…”