ENVIRONMENTAL SCIENCE I

ELEMENTS OF CLIMATE

BALKHIZ ISMAIL . FSPU, UiTM SARAWAK

♦ The weather elements are used to describe climate and also to determine the type of climate for a region.

♦ Three most significant climate elements used to determine climate are temperature(1), precipitation(2) and wind(3) .

♦ The other parameters are humidity(4), vapor pressure(5), vegetation(6), solar radiation(7) and sky condition(8).

Introduction

1. Temperature• Measured in degree Celsius

(ºC) with a mercury thermometer.

• The dry -bulb te m p e ra ture or ‘True Air Te m p e ra ture ’– value taken in the shade– thermometer being mounted

inside a louvered wooden box – Stevenson Screen at a height of 1.2 to 1.8m

– place at open area or space

1. Temperature (cont’d)

STEVENSON SCREEN

Louvered Wooden Box

1.20 m to 1.80 meter high from ground

1. Temperature (cont’d)

2. Humidity Defined as the mass of water vapor present in unit

volume of air or space and is expressed in g/kg or g/m3

1. Absolute Humidity (AH)The actual amount of moisture present in unit mass of air

2. Saturation-point Humidity (SH)The amount of moisture the air can hold

3. Relative Humidity (RH)The ratio of the actual amount of moisture present to the amount of moisture the air could hold at the given temperature

RH = AH/SH x 100%

2. Humidity (cont’d)• Measured with wet and dry-bulb hygrometer• Hygrometer consists of 2 ordinary mercury

thermometer mounted side by side• The first one measured the air (dry-bulb)

temperature (DBT) and the other one is covered with a gauze or wick and is kept wet which measures the wet-bulb temperature (WBT)

Dry and wet bulb hygrometer

Whirling sling hygrometer

3. Precipitation• the collective term used for rain, snow, hail, dew

and frost – all forms of water deposited from the atmosphere

• measured by rain gauges and expressed in millimeters per time unit = mm/month, mm/day

Rain gauges

3. Precipitation (cont’d)

• Convectional rain- results from the heating of the earth’s surface that causes air to rise rapidly- as the air rises, it cools and moisture condenses into clouds and precipitation

3. Precipitation (cont’d)

• Orographic rain- results when warm moist air of the ocean is forced to rise by large mountains- as the air rises it cools, moisture in the air condenses and clouds and precipitation result on the windward side of the mountain while the leeward side receives very little- common in British Columbia    

3. Precipitation (cont’d)

4. Vapor pressure• the partial pressure of water present in the air• varies in different places from time to time• temperatures gives the main influence to vapour

pressure• measured in the standard SI pressure unit, N/m2 or

milibar (mb)• measured with Barometer

5. Wind / Air movement• resulting from the differences of two vapour

pressures• there are three global belts of winds in each

hemisphere : trade winds, westerlies and polar winds

• there are wind systems known as the monsoons which are the result of annual differences in heating of land and sea areas

6. Vegetation• can influence the local or site climate• it is an important element in the design of outdoor

spaces, providing sun shading and protection from glare

• their shape and color, also their preferred orientation and situation will give the influence to the climate

7. Solar radiation• an electromagnetic radiation emitted from the sun• the solar spectrum is broadly divided into three

regions : ultra violet (uv), visible light and infra red (ir)

• the solar energy at upper limit of the atmosphere varies from 1.8 – 2.0 cal/cm2/min according to the earth’s distance from the sun and the solar activity

• selectively absorbed in the atmosphere according to the wavelength

7. Solar radiation (cont’d)

8. Sky condition• usually described in terms of presence or absence

of clouds• the sky conditions between morning and afternoon

are different and this will affect the design of roofs, overhangs and shading devices

• sky luminance values are needed if daylighting in buildings is to be predicted

8. Sky condition (cont’d)Cloud• can be differentiate by its shape and height• can be divided into 3 categories :

i) Low cloud – ground level to 6000 feet, made of water drops, name start with cumuloii) High cloud – 20000 to and above, made of ice crystal, name start with cirro or cirrusiii) Intermediate cloud – 6000 to 20000 feet, made of water drops and ice crystal, name start with alto

8. Sky condition (cont’d)

A LOCAL FACTORS IN PLANNING &

DESIGNING

BALKHIZ ISMAIL . FSPU, UiTM SARAWAK

Factors in Planning & DesigningA study of local climate is needed in planning &

design. The factors to be considered are :

1. Wind Directions2. Selection of Materials3. Radiation (direction of sun)4. Condition of surrounding5. Precipitation6. Air movement

Factors in Planning & Designing

i) Wind Direction ~ Should be recognize to make sure other building

are not obstructed.

A good of building arrangement

Poor of building arrangement

i) Wind Direction(cont’d) ~ It is also influenced by the roof shape of the building.

Wind direction

Flat roof

Wind direction

Pitch roof

Factors in Planning & Designing

ii) Selection of building material ~ Depends on climate.

~ In example, used of cavity brick to reduce heat loss from buildings.

iii) The Direction of sunrise & sunset (Radiation) ~ The balcony is built to prevent radiation from entering

the buildings. ~ Built a window hood.

Factors in Planning & Designing

iv) The condition of surrounding area ~ Eg. In industrial area

~ Building materials must be durable to acid rain

v) Precipitation ~ Heavy rain for the whole year ~ Pitch roof is used ~ Gutter built to ensure the rain water goes to the drains ~ Corridor to prevent dirty on wall

vi) Air Movement ~ Large opening for doors & window

~ Enable warm air flow outside the building.

Factors in Planning & Designing

FACTORS THE DIFFERENCE OF

WEATHER CONDITION WITH SURROUNDING

AREABALKHIZ ISMAIL . FSPU, UiTM SARAWAK

1) Radiation ~ Direct radiation – esp. in the desert, no obstruction ~ Indirect radiation – Vegetation – obstruct the sun radiation

2) Humidity ~ Different region/place will experience the different humidity/moisture content of air. ~ It’s depends on the amount of rainfall & evaporation process

Factors – Weather vs. Surrounding

3) Altitude ~ The higher the place, the temperature is become lower ~ Eg : Fraser Hill, Cameron Highland

4) Vegetation ~ Vegetation (trees) absorbed the heat / radiation. ~ Evaporation rate is reduce.

Factors – Weather vs. Surrounding

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