Teleconnection patterns in the Southern Hemisphere represented by ECMWF and NCEP S2S project models and influences on South America precipitation

Abstract

Precipitation predictions in the sub-seasonal timescale are very important for several sectors such as agriculture and energy in regions of South America that are very much affected by precipitation extremes, both excess and lack of rain.The aim of the present study is to investigate the ability of two S2S project models (ECMWF and NCEP) to detect the Southern Hemisphere teleconnections in model hindcasts and the associated anomalous precipitation over South America. The period of analyses is 1999-2010 for the austral summer season (December-January-February). Both models represented adequately the Southern Annular Mode (SAM) pattern in predictions up to 4 weeks ahead and the Pacific South America (PSA) pattern up to 3 weeks. Atmospheric variables of observed extreme cases of SAM were well predicted by the two models, 2 and 3 weeks in advance. The models predicted well atmospheric variables in observed extreme cases of PSA, 2 weeks in advance and with less intensity in the third week. Precipitation anomaly signals associated with these modes were well predicted 2 weeks in advance, although with different intensities. The good ability of the models hindcast in predicting teleconnection patterns and precipitation anomalies over South America provides more confidence to use predictions at sub-seasonal timescale.

Literature survey of subseasonal‐to‐seasonal predictions in the southern hemisphere

“…Soil moisture is one of the most important land surface features for S2S predictability and significantly modulates evaporation and ultimately precipitation through local and regional water and energy circles (Cavalcanti et al, 2021;Chevuturi et al, 2021). The memory of soil moisture can last several weeks, which can influence the atmosphere through changes in evaporation and surface energy budget and can affect the forecast of air temperature and precipitation on subseasonal timescales (Arsego et al, 2023;Koster et al, 2000).…”

“…ENSO plays an important role in the S2S timescale in that it provides a large source of equatorial Pacific SST boundary forcing that can act as an important source of subseasonal prediction (e.g., Cavalcanti et al, 2021). ENSO is a coupled atmosphere–ocean mode of variability that involves slow variations in the equatorial Pacific that impact SSTs in the central and eastern Pacific, and associated changes in surface pressure and winds in the atmosphere that extend over most of the tropical regions (e.g., Horel & Wallace, 1981; Izumo et al, 2010; Rautenbach & Smith, 2001; Ropelewski & Halpert, 1987).…”

“…In the SH, only two climatic teleconnection patterns, namely, the Pacific–South American (PSA) and SAM patterns, have been identified (Cavalcanti et al, 2021; Stan et al, 2017). Cavalcanti et al (2021) investigated the skill of the ECMWF and NCEP S2S project models in predicting the PSA and SAM patterns and found skill up to 4 weeks and 3 weeks ahead, respectively. Precipitation anomaly signals associated with these teleconnection patterns were well predicted 2 weeks ahead.…”

“…The S2S timescale is relevant to planning and preparedness in sectors such as public health, water management, energy, and agriculture (e.g., Cavalcanti et al, 2021; White et al, 2017). The potential application sectors are briefly discussed below:…”

Potential applications for climate services originated from the CLIMAX project

“…The ability of global sub-seasonal prediction models in representing the spatial precipitation and associated atmospheric circulation patterns was also investigated (Cavalcanti et al, 2021;Klingaman et al, 2021). The two main Southern Hemisphere teleconnection patterns (SAM and PSA) were well represented in subseasonal hindcasts of the Subseasonal to Seasonal (S2S) project, and predictions by ECMWF and NCEP models 2 weeks in advance were able to identify precipitation anomalies over South America associated with those teleconnections.…”