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El Nind La Ni

The impact of El Ni and La Ni on the climate of Hong Kong




El Ni

 

In winter (Dec-Feb) and spring (Mar-May), El Niffects the atmospheric circulation over the northern part of the South China Sea, bringing generally more rainfall to the coastal region compared to the ENSO-neutral state (Figure 1a and 1b). Rainfall charts for other seasons can be found here.

 

Winter rainfall of Hong Kong

Figure 1a    Winter (Dec-Feb) rainfall of Hong Kong, 1950-2015.  
 

 

Spring rainfall of Hong Kong
Figure 1b    Spring (Mar-May) rainfall of Hong Kong, 1950-2015.


 Temperature and rainfall statistics during El Nisprings, summers, autumns & winters in recent decades



During El Nithere are fewer tropical cyclones developed in April and May and the genesis positions are usually located further east over the western North Pacific compared to the ENSO-neutral state. Hence, tropical cyclones are unlikely to affect the territory before June (Figure 2).

 
Number of TC coming within 500 km of HK
 Figure 2    Number of tropical cyclones coming within 500 km of Hong Kong, 1961-2015.

 


 

La Ni

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During La Nithe northeast monsoon over southern China is generally stronger in autumn (Sep-Nov) and winter (Dec-Feb), bringing lower temperature in Hong Kong compared to the ENSO-neutral state (Figure 3a and 3b).

 

Autumn temperature of Hong Kong
Figure 3a    Autumn (Sep-Nov) temperature of Hong Kong, 1950-2015.

 

Winter temperature of Hong Kong
Figure 3b    Winter (Dec-Feb) temperature of Hong Kong, 1950-2015.



 Temperature and rainfall statistics during La Nisprings, summers, autumns & winters in recent decades


During La Nitropical cyclones in August-October are likely driven by an anomalous steering flow into the South China Sea and hence more tropical cyclones are likely to affect Hong Kong compared to the ENSO-neutral state (Figure 4).

Number of TC coming within 500 km of HK in Aug-Oct
Figure 4 Number of tropical cyclones coming within 500 km of Hong Kong in August-October, 1961-2015.
 

Note:
1. The ENSO-neutral state refers to the situation with neither an El Nior a La Nin place.


Related links:
What are El NiLa NiENSO?
Latest status of El Nind La Ni
Seasonal and annual rainfall charts
Blogs relating to El Nia Ni
References on El Nind La Ni
Seasonal forecastAnnual outlookClimate change


Last revision date: <04 Nov 2016>