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CLIMATE AND METEOROLOGY
 
 
     
     The areas included in the Metro Manila Air Shed belong to Type I of the modified Coronas classification of Philippine climate. This climatic type is characterized by two pronounced seasons, dry from November to April and wet from June to October.

 
 
  Large-Scale Surface Wind

     The large-scale wind flow in the entire air shed is influenced by the major air streams that seasonally prevail over the country. These are the northeast monsoon, the southwest monsoon, and the north Pacific trades.

     The northeast monsoon prevails from October to March. It reaches the air shed with a generally northeasterly direction although local topographic features could slightly alter its direction.

     The southwest monsoon is prevalent over the air shed from late May until early October. This wind stream is responsible for most of the rainfall within the air shed.

     The north Pacific trades bring hot and humid air to the Metro Manila air shed during the months of April and May. This wind stream reaches the area with an easterly or southeasterly direction.

     For any given season, the large-scale wind flow over the Metro Manila Air Shed shows significant homogeneity, i.e., generally uniform over the entire air shed.

Sea and Land Breezes

     Besides the influence of the large-scale prevailing wind streams, the surface wind field within the air shed is perturbed by local circulations, particularly the sea and land breezes. This type of local circulation is driven by the differences in temperatures of adjoining land and sea surfaces.

     The Metro Manila air shed is prominently influenced by the Manila Bay and to a lesser extent by the Laguna de Bay. Extensive studies on this phenomenon showed that sea breeze could penetrate up to 50 km inland. In general, sea breezes are more intense than land breezes. Typically, a sea breeze could reach up to a speed of 5 m s-1 depending on the difference between land and sea surface temperatures.

 
     

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