Climate of Hong Kong

The weather chart symbols

Anticyclone

Area of high pressureCharacteristics:Isobars are circularPressure is highest at the centre and decreases away from itWinds are weakAir sinks at the centre and winds has a clockwise direction

Weather conditions

Occurs in winterSkies are clear and air is dryIt is cool at night and warm during the dayLight winds from the northeastWeather is calm and fine

Ridge of high pressure

A tongue-shaped area of high pressureExtend from a high pressure centreCharacteristics:Occurs in winter and early springLooks like a tongueWinds blows outwards from a ridge

Weather condition

Fig.21.4Weather is fine and calmThe temperature was 160CWind from south-east2.5 m/s

Tropical cyclone/typhoon

A very low pressure systemCharacteristicsPressure at centre below 1000 hPaIsobars are circular and closely spacedWinds blow anticlockwise and inwards (northern hemisphere)Heavy downpour and thunderstorm

Overcast skies and cumulonimbus cloudsEye is characterised by sinking air and fine weatherDies when it moves inlandWhen warm moist air is cut offMountain barriers increase the friction of movement

Weather of approaching typhoon

Weather is fineSome high cloudsTemperature and humidity are highWinds are light or calmPressure falls

Front vortex arrived in HK

Weather is getting worseRainfall increases with heavy downpoursAir pressure drops rapidlyWind from NE, NW to E.Wind speed is highRelative humidity is high

Eye over HK

A period of fine weatherNo rain and few cloudsWind is light or calmAir pressure is the lowest

Eye moves away

Weather is badWind direction is reversed and changed to southwestWind is strongRainfall increasesAir pressure rises rapidly

Typhoon has passed:

Weather is betterSky no longer overcastRainfall gradually stopsTemperature and pressure rises to normal again

Trough of low pressure

A tongue-shaped area of LPExtending out from a low pressure centreCharacteristicsNarrow zone of low pressureWind blows to the axis of trough

Weather conditionsOccurs in late spring and early summerThe pressure fallsTemperature and relative humidity riseRising of air in the troughUnsettled weather with heavy rain

Cold front

A front is a surface between two different air masses. The cold air is advancing when it meets warm air

Characteristics

Cold air moved beneath the warm airWarm air is forced to riseBad weather is resultedDevelop in winter and early spring when the cold air flow outward from an anticyclone

Before cold front arrives at HK

Weather is relatively warmFine weather and little cloud coverCalm or light winds blowing onshoreRelatively low air pressure

Cold front arrived

Temperature begins to fallRelative humidity increasesLight to heavy rain falls

What type of rain is formed?Describe the processes taking place along the cold front………

Cyclonic rain formed

It is cyclonic / frontal rainWind speed increases Wind direction changes from S to northAir pressure rises

Cold front has passed

Under the influence of an anticycloneTemperature drops a few degreesClear skyRelative humidity is low / air dryOff-shore winds blow from N to NEAir pressure is highCold dry weather

Depression

A depression is an area of low pressureCharacteristicsDevelop over China in summerGentle winds blow inward in an anticlockwise direction (N. Hemp)

Weather conditions

Air is warm and wetCloudy with showers, sometimes heavy downpoursThunderstormsSunny periods separated by showers

Factors influencing the climate of HK

1. The Asian monsoon system

Winter monsoonTemperature is low in N ChinaPressure is high over N ChinaPressure is low over the ocean/AustraliaWinds blow from high pressure area to low pressure areaHK has offshore winds

HK is cool in winterThe sky is sunny with little cloudRainfall is littleRelative humidity is lowStrong NE winds

Summer monsoon

Temperature is high in Asian continentLow pressure developsBut high pressure develops over warmer oceanWinds blow from the ocean to the landHK has onshore winds

HK is hot in summerMost rain falls in summer with heavy downpoursLight winds blow from SE to SW directionHigh relative humidity

2. latitude

Located on the latitude 22o20’N

3. Nearness to the sea

The sea makes the climate humidAnnual temperature range moderate

4. relief

Highland in HK causes relief rain in the eastern partLower rainfall in the western part

The four seasons