253
mm/year, although there are 8 months with less than 40 mm precipitation. Precipitation
concentrates from May to August, with more of 80% of the annual precipitation.
Intensity of precipitations and wind in winter can even reach intensities proper of storms.
The main source of climatic variability in this zone is ENSO, a natural climatic
event that is cyclic and recurrent (Espino 1999), but not periodic (Capel 1999), that
occurs in the central Equatorial Pacific from 7000 years ago (Arntz and Farhbach
1996). This phenomenon is characterized by unusually warm and humid conditions
in the eastern equatorial Pacific Ocean that generate sea surface temperature and wind
anomalies in the tropical Pacific. These anomalies affect the whole planet (Ramesh
and Murtugudde 2013) and represent the most important source of interannual climatic variability (Guevara 2008), perturbing the meteorological conditions through
droughts, floods, and heat and cold waves (Johnson 2014); what turns into severe
environmental impacts and effects on the economic activities around the world.
There are several indexes to characterize the ENSO phenomenon. The southern
oscillation index (SOI) measures the difference of the monthly mean atmospheric
pressure between Tahiti and Darwin. El Niño 3.4 measures the anomaly of the sea
surface temperature (SST) in the 5°N–5°S, 120°–170°W region. Finally, the Oceanic
Niño Index (ONI) allows to identify El Niño (warm) and La Niña (cool) events in the
tropical Pacific. It is the running 3-month mean SST anomaly for the Niño 3.4 region.
Events are defined as five consecutive overlapping 3 -month periods at or above the
+0.5 °C anomaly for warm (El Niño) events and at or below the −0.5 anomaly for
cold (La Niña) events. The threshold is further broken down into Weak (with a 0.5–
0.9 SST anomaly), Moderate (1.0–1.4), Strong (1.5–1.9) and Very Strong (≥2.0)
events. There is uncertainty about how ENSO is going to respond to contemporary
global warming, even though and increase in its frequency is being observed.
A comparison between the monthly anomalies of the SST off Valparaíso and the
El Niño 3.4 from 1945 to 2015 is shown in Fig. 8.4. Very strong El Niño 1982/1983
and 1997/1998 events are associated to important positive anomalies of
SST. However, the last ENSO 2015/2016 did not show a significant SST anomaly.
The warm phase of ENSO, known as El Niño, presents an increase of the SST
and a decrease of the easterlies in the Pacific Ocean. These anomalous conditions
generate strong precipitations (Fernández and Fernández 2002; Aceituno 1992), and
notable changes in climate (Pizarro and Montecinos 2004) and fisheries (Parada
et al. 2013: Arcos et al. 2004; Cañón 2004; Valdivia and Arntz 1985; Alvial et al.
1994). These anomalies are observed in riverine countries of the Southeastern
Pacific (Colombia, Ecuador, Peru and Chile) and other parts of the continent, like
Panama (Corredor-Acosta et al. 2011), Mexico (Aguirre-Gómez et al. 2012),
Bolivia (Miranda 1998), Brazil (De Meló 1998; Coutinho et al. 1998), Argentina
(Capüto et al. 1998) and so distance places as the Indian Peninsula (Yadav 2012).
The cold phase of ENSO, known as La Niña, is characterized for presenting
lower SST than normal, intensification of easterlies in the eastern Pacific Ocean and
periods of droughts.
Precipitations registered in Rapel location, along with the ONI and the adjusted
linear trend are shown in Fig. 8.5. A decrease rate can be observed. In general, large
intra-annual variations in precipitation can be explained by variations of ONI, what is
8 El Yali National Reserve: A System of Coastal Wetlands in the Southern…
mm/year, although there are 8 months with less than 40 mm precipitation. Precipitation
concentrates from May to August, with more of 80% of the annual precipitation.
Intensity of precipitations and wind in winter can even reach intensities proper of storms.
The main source of climatic variability in this zone is ENSO, a natural climatic
event that is cyclic and recurrent (Espino 1999), but not periodic (Capel 1999), that
occurs in the central Equatorial Pacific from 7000 years ago (Arntz and Farhbach
1996). This phenomenon is characterized by unusually warm and humid conditions
in the eastern equatorial Pacific Ocean that generate sea surface temperature and wind
anomalies in the tropical Pacific. These anomalies affect the whole planet (Ramesh
and Murtugudde 2013) and represent the most important source of interannual climatic variability (Guevara 2008), perturbing the meteorological conditions through
droughts, floods, and heat and cold waves (Johnson 2014); what turns into severe
environmental impacts and effects on the economic activities around the world.
There are several indexes to characterize the ENSO phenomenon. The southern
oscillation index (SOI) measures the difference of the monthly mean atmospheric
pressure between Tahiti and Darwin. El Niño 3.4 measures the anomaly of the sea
surface temperature (SST) in the 5°N–5°S, 120°–170°W region. Finally, the Oceanic
Niño Index (ONI) allows to identify El Niño (warm) and La Niña (cool) events in the
tropical Pacific. It is the running 3-month mean SST anomaly for the Niño 3.4 region.
Events are defined as five consecutive overlapping 3 -month periods at or above the
+0.5 °C anomaly for warm (El Niño) events and at or below the −0.5 anomaly for
cold (La Niña) events. The threshold is further broken down into Weak (with a 0.5–
0.9 SST anomaly), Moderate (1.0–1.4), Strong (1.5–1.9) and Very Strong (≥2.0)
events. There is uncertainty about how ENSO is going to respond to contemporary
global warming, even though and increase in its frequency is being observed.
A comparison between the monthly anomalies of the SST off Valparaíso and the
El Niño 3.4 from 1945 to 2015 is shown in Fig. 8.4. Very strong El Niño 1982/1983
and 1997/1998 events are associated to important positive anomalies of
SST. However, the last ENSO 2015/2016 did not show a significant SST anomaly.
The warm phase of ENSO, known as El Niño, presents an increase of the SST
and a decrease of the easterlies in the Pacific Ocean. These anomalous conditions
generate strong precipitations (Fernández and Fernández 2002; Aceituno 1992), and
notable changes in climate (Pizarro and Montecinos 2004) and fisheries (Parada
et al. 2013: Arcos et al. 2004; Cañón 2004; Valdivia and Arntz 1985; Alvial et al.
1994). These anomalies are observed in riverine countries of the Southeastern
Pacific (Colombia, Ecuador, Peru and Chile) and other parts of the continent, like
Panama (Corredor-Acosta et al. 2011), Mexico (Aguirre-Gómez et al. 2012),
Bolivia (Miranda 1998), Brazil (De Meló 1998; Coutinho et al. 1998), Argentina
(Capüto et al. 1998) and so distance places as the Indian Peninsula (Yadav 2012).
The cold phase of ENSO, known as La Niña, is characterized for presenting
lower SST than normal, intensification of easterlies in the eastern Pacific Ocean and
periods of droughts.
Precipitations registered in Rapel location, along with the ONI and the adjusted
linear trend are shown in Fig. 8.5. A decrease rate can be observed. In general, large
intra-annual variations in precipitation can be explained by variations of ONI, what is
8 El Yali National Reserve: A System of Coastal Wetlands in the Southern…