ESS124
Prof. Jin-Yi Yu
Observation Time for Weather Map
q Weather organizations throughout the
world use the UTC (Coordinated Universal Time) as the
reference clock for weather observations.
q UTC is also denoted by the
abbreviation GMT (Greenwich Meridian Time) or, often as the last two zeroes
omitted, Z (Zulu).
q Observations of the upper atmosphere
are coordinately internationally to be made at 0000 UTC (midnight at
Greenwich; 0Z; 0GMT) and 1200 UTC (noon at Greenwich; 12Z; 12GMT).
q Synoptic observations have
traditionally been done every 6 hours or every 3 hours, depending
on the station.
q Local time should be 1 hour earlier
for every (360/24)=15° of longitude west of Greenwich.
èLocal time in Los Angeles (118 ° W) and the
rest of the Pacific Standard Time is 8 (= 118°/15°) hours
earlier than Greenwich.