A climatology of low level wind regimes over Central America using a weather type classification approach

Abstract

Based on the potential of the weather types classification method to study synoptic features, this study proposes the application of such methodology for the identification of the main large scale patterns related with weather in Central America. Using ERA Interim low-level winds in a domain that encompasses the intra-Americas sea, the eastern tropical Pacific, southern North America, Central America and northern South America, the K-means clustering algorithm was applied to find recurrent regimes of low-level winds. Eleven regimes were identified and good coherency between the results and known features of regional circulation was found. It was determined that the main large scale patterns can be either locally forced or a response to tropical-extratropical interactions. Moreover, the local forcing dominates the summer regimes whereas mid latitude interactions lead to winter regimes. The study of the relationship between the large scale patterns and regional precipitation shows that winter regimes are related with the Caribbean-Pacific precipitation seesaw. Summer regimes, on the other hand, enhance the Caribbean-Pacific precipitation with contrasting distribution as a function of the dominant regimes. A strong influence of ENSO on the frequency and duration of the regimes was found. It was determined that the specific effect of ENSO on the regimes depends on whether the circulation is locally forced or lead by the interaction between the tropics and the mid-latitudes. The study of the cold surges using the information of the identified regimes revealed that three regimes are linkable with the occurrence of cold surges that affect Central America and its precipitation. As the winter regimes are largely dependent of mid-latitude interaction with the tropics, the effect that ENSO has on the Jet Stream is reflected in the winter regimes. An automated analysis of large scale conditions based on reanalysis and/or model data seems useful for both dynamical studies and as a tool to support forecasting. The application of the approach implemented in this study may be promising to improve current understanding on how large scale conditions affect regional weather.

Role of moisture transport for Central American precipitation

“…The increase in the contributions for warm ENSO is proposed to be linked to the effect of rainproducing systems. These systems can be associated with the penetration of cold surges, known to increase during El Niño events (Magaña et al, 2003) and to modify the regional distribution of precipitation (Sáenz and Durán-Quesada, 2015). During summer, the negative correlation between the moisture supply from the ETPac and the ENSO can be explained by an enhanced deep convection linked to the ITCZ for cold ENSO events as revealed by OLR composites (not shown).…”

“…As the relevance of the GoM as a moisture source for the region is constrained by mid-latitude interactions. This source acquires importance in association with winter circulation patterns related to cold surges, which have been found to contribute to the precipitation over Central America during a relatively dry period (Sáenz and Durán-Quesada, 2015).…”

“…A large deep convective core is located over the Panama Bight (Zuluaga and Houze Jr., 2015), with an extended area of stratiform precipitation that becomes relevant for overall rainfall. The effect of mid-latitude interactions is known to be mostly related to the occurrence of rainfall during the dry period on the Pacific slope between November and February (Zárate, 2013;Sáenz and Durán-Quesada, 2015;Moron et al, 2016).…”

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

“…These air masses had little interaction with the surrounding landmasses, with the exception of air masses that travelled over northern South America (10% frequency). These trajectories most likely were influenced by the north-east trade winds in the region(Saénz and Quesada, 2015). Air masses coming from the Pacific Ocean contributed approximately 20.4% of the total rainfall recorded during the study period (294 mm between April 2015 and May 2016) and mainly originated from the Pacific coast of Costa Rica and Panamá.For the Andean Páramo at Cajas, the air masses originating from the Amazonia contributed approximately 79.0% of the total precipitation recorded during the study period (1,278 mm between January 2015 and May 2016).…”

Circulation Weather types as a tool in atmospheric, climate and environmental research

“…Furthermore, Hidalgo et al (2014) shows that circulation weather types can be used to generate long term near surface climatic time series at high temporal frequencies suitable to force Soil-Vegetation-Atmosphere transfer models. Regarding tropical regions, cold surge activity over the Gulf of Mexico (Pérez et al, 2014) and low level wind regimes over Central America (Sáenz and Durán-Quesada, 2015) are addressed with a circulation weather types approach. Finally, three papers focus on the Southern Hemisphere.…”