Role of moisture transport for Central American precipitation

Abstract

Abstract.A climatology of moisture sources linked with Central American precipitation was computed based upon Lagrangian trajectories for the analysis period 1980-2013. The response of the annual cycle of precipitation in terms of moisture supply from the sources was analysed. Regional precipitation patterns are mostly driven by moisture transport from the Caribbean Sea (CS). Moisture supply from the eastern tropical Pacific (ETPac) and northern South America (NSA) exhibits a strong seasonal pattern but weaker compared to CS. The regional distribution of rainfall is largely influenced by a local signal associated with surface fluxes during the first part of the rainy season, whereas large-scale dynamics forces rainfall during the second part of the rainy season. The Caribbean Low Level Jet (CLLJ) and the Chocó Jet (CJ) are the main conveyors of regional moisture, being key to define the seasonality of large-scale forced rainfall. Therefore, interannual variability of rainfall is highly dependent of the regional LLJs to the atmospheric variability modes. The El Niño-Southern Oscillation (ENSO) was found to be the dominant mode affecting moisture supply for Central American precipitation via the modulation of regional phenomena. Evaporative sources show opposite anomaly patterns during warm and cold ENSO phases, as a result of the strengthening and weakening, respectively, of the CLLJ during the summer months. Trends in both moisture supply and precipitation over the last three decades were computed, results suggest that precipitation trends are not homogeneous for Central America. Trends in moisture supply from the sources identified show a marked north-south seesaw, with an increasing supply from the CS Sea to northern Central America. Long-term trends in moisture supply are larger for the transition months (March and October). This might have important implications given that any changes in the conditions seen during the transition to the rainy season may induce stronger precipitation trends.

Moisture transport and seasonal variations in the stable isotopic composition of rainfall in Central American and Andean Páramo during El Niño conditions (2015–2016)

“…Durán-Quesada et al, 2010;Durán-Quesada et al, 2017). In addition, with regard to SSTs in the region, a clear spatial and temporal positive(negative) correlation between SST anomalies in the Pacific Ocean (Caribbean Sea) and δ 18 O of rainfall in Central America has been reported (Lachniet, 2009).…”

“…Models of this type, such as HYSPLIT, offer air mass back trajectory analysis, which has been particularly useful to diagnose net changes in the specific moisture along air parcel trajectories (Stein et al, 2015). HYSPLIT was successfully applied in studies aiming at identifying sources of moisture in different regions of the world (e.g., Aravena et al, 1999;Bershaw, Penny, & Garzione, 2012;Yang et al, 2012;Windhorst et al, 2013;Drumond et al, 2014;Corrales, Sánchez-Murillo, Esquivel-Hernández, Herrera, & Boll, 2016;Sánchez-Murillo, Durán-Quesada, et al, 2016;Cai, Tian, & Bowen, 2017;Durán-Quesada, Gimeno, & Amador, 2017;He, Goodkin, Jackish, et al, 2018).…”

“…A maximum anomaly was recorded in September-October-November 2015 (average increment: 2.3°C using a combined El Niño 3.4/Southern Oscillation Index (SOI) index; Sánchez-Murillo,Durán-Quesada, et al, 2016), whereas in the El Niño, 1.2 region the SST anomalies in this period were reported with an average increment of 2.4°C. During El Niño, easterlies intensification decreases the moisture transport from the eastern Pacific Ocean and increases the transport of moisture from the Caribbean and northern South America to Central America, whereas the SALLJ is also more active, and there is an intensification of the trade winds blowing from the North tropical Atlantic to South America(Durán-Quesada et al, 2017;Silva & Ambrizzi, 2006).…”

Tracking the moisture transport from the Pacific towards Central and northern South America since the late 19th century

“…The main advantage of these so-called "directional indices" is that by design, they only require the knowledge of the wind direction, a variable that has been routinely measured aboard ships since the end of the 17th century and avoid the uncertainties associated with the measurement of wind speed for early times (Prieto et al, 2005;Gallego et al, 2007). As a result of several data recovery projects (García-Herrera et al, 2005;Allan et al, 2011;Wilkinson et al, 2011, among others), millions of these early wind observations are today incorporated into the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) database (Freeman et al, 2017). In its most recent release ICOADS holds over 456 million individual marine reports, covering the period 1662-2014.…”

The Apparent Resilience of the Dry Tropical Forests of the Nicaraguan Region of the Central American Dry Corridor to Variations in Climate Over the Last C. 1200 Years

“…Significant losses in food production across the Central American Isthmus (Isthmus of Tehuantepec south to the Isthmus of Darien) resulting from a deficit in precipitation at the beginning of the harvest in 2015 rendered an estimated 2.2 million people at risk of moderate or severe food insecurity [1]. This episode is indicative of the vulnerability of the flora, fauna and human population of the Central American Dry Corridor (CADC) to seasonal patterns of rainfall, impacting agrarian practices, food and water security [2,3]. Given this recent episode of apparent vulnerability of the CADC to hydroclimatic changes, the aim of this research was to identify past hydroclimatic changes and assess their impacts upon the dominant vegetation type, Dry Tropical Forests (DTF), for the Central Pacific lowlands of Nicaragua spanning the last c. 1200 years ( Figure 1).…”