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The Weather of March 2007

    March 2007 was cloudier and warmer than normal. The mean cloud amount was 84 percent against a normal of 76 percent. The mean minimum temperature of 18.4 degrees was 1.9 degrees higher than normal, the eighth highest for the month. The monthly rainfall of 27.6 millimetres was about 59 percent less than the normal figure of 66.9 millimetres. The accumulated rainfall in the first three months of the year was 64.1 millimetres, about 54 percent below the normal figure of 138.3 millimetres for the same period.

    Under the influence of the northeast monsoon, it was mainly cloudy with a few light rain patches on the first day of the month. As the northeast monsoon was replaced by a maritime airstream, it was warm with sunny periods on 2 March and the following two days. After the passage of a cold front across the coast of Guangdong on the morning of 5 March, the weather became cool with some rain that night. It was rainy and rather cool on 6 March. The temperature dropped further to 10.6 degrees on the morning of 7 March, the lowest in the month. The weather stayed cool with a few rain patches on 8 and 9 March.

    A humid maritime airstream affected the south China coast again on 10 and 11 March, bringing foggy weather to Hong Kong. The visibility at the Hong Kong International Airport fell below 1000 metres. Humid and misty weather persisted in the next four days. It was warm with sunny periods on 16 March.

    The arrival of a cold front brought a few rain patches to the territory on 17 March. The weather became cooler in the ensuing four days. A broad cloud band over southern China brought cloudy weather to Hong Kong on 22 and 23 March. The weather became warm with some mist and rain on 24 March and the following three days as Hong Kong came under the influence of a maritime airstream. With sunny periods during the day, the temperature rose to 27.8 degrees on 27 March, the highest in the month.

    It was cloudy with winds freshening from the east on 28 March. The clouds thinned out and there were sunny periods next day. The weather remained warm with sunny periods in the last two days of the month.

    Only one tropical cyclone occurred in the western North Pacific in the month.

    Details of issuance and cancellation of various warnings/signals in the month are summarized in Tables 1.1 to 1.3.  Monthly meteorological figures and departures from normal for March are tabulated in Table 2.


 

Warnings and Signals issued in March 2007


Table 1.1   Strong Monsoon Signal

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
1 / 3 0010 1 / 3 0945
6 / 3 0200 6 / 3 0600
17 / 3 0845 18 / 3 0745


Table 1.2   Thunderstorm Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
19 / 3 0315 19 / 3 0745


Table 1.3   Cold Weather Warning

Beginning Time Ending Time
Day/Month HKT Day/Month HKT
7 / 3 0400 8 / 3 0945


Table 2   Figures and Departures from Normal - March 2007

Meteorological Element Figure of the Month Departure from Normal*
Mean Daily Maximum Air Temperature 22.7 degrees C 1.4 degrees above normal
Mean Air Temperature 20.2 degrees C 1.7 degrees above normal
Mean Daily Minimum Air Temperature 18.4 degrees C 1.9 degrees above normal
Mean Dew Point Temperature 17.5 degrees C 2.5 degrees above normal
Mean Relative Humidity 84 % 3 % above normal
Mean Cloud Amount 84 % 8 % above normal
Total Rainfall 27.6 mm 39.3 mm below normal
Number of hours of Reduced VisibilityΔ 102 hours 11.7 hours below normal§
Total Bright Sunshine Duration 76.1 hours 20.3 hours below normal
Mean Daily Global Solar Radiation 9.69 Megajoule / square metre 1.55 Megajoule below normal
Total Evaporation 62.5 mm 29.7 mm below normal


  Remarks : All measurements were made at the Hong Kong Observatory except sunshine, solar radiation and evaporation which were recorded at King's Park Meteorological Station and visibility which was observed at the Hong Kong International Airport.
  Δ

The visibility readings at the Hong Kong International Airport are based on hourly observations by professional meteorological observers in 2004 and before, and average readings over the 10-minute period before the clock hour of the visibility meter near the middle of the south runway from 2005 onwards. The change of the data source in 2005 is an improvement of the visibility assessment using instrumented observations following the international trend.

Before 10 October 2007, the number of hours of reduced visibility at the Hong Kong International Airport in 2005 and thereafter displayed in this web page was based on hourly visibility observations by professional meteorological observers. Since 10 October 2007, the data have been revised using the average visibility readings over the 10-minute period before the clock hour, as recorded by the visibility meter near the middle of the south runway.


 

The calibration factors of the pyranometer at King's Park in 2006 and 2007 have been re-computed based on the results of a regional instrument comparison in Asia in 2007. The readings of total global solar radiation at King's Park in 2006 and 2007 displayed in this web page before 13 June 2008 have been revised on 13 June 2008 using the new calibration factors.

  *   Departure from 1961-1990 climatological normal, except for number of hours of reduced visibility.
  §   Departure from mean value between 1997 and 2006.
daily values of selected meteorological elements for HK for March 2007

Extract of Meteorological Observations in Hong Kong for March 2007