By using computer model analyses, the past 72-hour backward trajectory of the air mass reaching Hong Kong is estimated by the Observatory on a daily basis. The daily trajectories are compiled into the Monthly Backward Trajectory Map. The Monthly Map for April 2012 is now available on the following webpage:
In April 2012, the origin of air masses reaching Hong Kong turned gradually from the north, through northeast to the south, indicating that the territory came increasingly under the influence of warm and humid maritime airstreams.
Backward Trajectory of Air Mass reaching Hong Kong in April 2012
For Daily or Seasonal Backward Trajectory Maps, please visit the following webpages: