3B2 Recap on Weather & Climate (RH & Cloud Formation)

Recap on Weather & Climate

What have we learnt so far!

Multiple Choice

Relative humidity refers to the ratio between the ________ amount of water vapour present in a mass of air and the ________ amount of water vapour the air could hold at a __________ temperature

• present, current, given

• current, maximum, room

• current, maximum, given

• present, maximum, room

What is the relationship between temperature and RH?

When temperature increases, relative humidity decreases

Pitstop 3 Q1: Describe the relationship between temperature and the capacity of air to hold water vapour [1]

The higher the temperature, the __________ the capacity of air to hold water vapour

2a) On a 40 degrees celsius day, how much water vapour is in the saturated air? [1]

50g

2b) Under what conditions will condensation occur? (State the conditions) [1]

• When air is saturated, and RH = 100%

• This means that current amount of water vapour in the air is the same as maximum amount of water vapour that can be held in the air

Explain the steps required to measure relative humidity

• 1. Dip the wick of the wet bulb thermometer in water

• 2. Use wrist action to rotate the sling at a steady pace, about 2 turns per second. Keep psychrometer far from body. Sling the instrument for about a minute.

• 3. After 1 minute, stop, read and record the temperature on wet bulb thermometer.

Explain the steps required to measure relative humidity

• 4. Continue swinging the sling psychrometer for another minute, stop, read and record the temperature on the wet bulb thermometer

• 5. Read and record the temperature on the dry bulb thermometer

• 6. Calculate the difference between the dry bulb and wet bulb temperatures. Refer to the RH chart to find out the RH

Describe safety precautions to take to ensure accurate results

• Make sure the wet bulb wick is fully saturated with clear water. Do not hold the wick with your hands. Why?

• Stand in a shady spot. Why?

• •Keep the sling psychrometer far enough from your body and face into the wind. Why?

• •Be careful with the sling psychrometer and don’t hit any objects