Let's address the questions based on the graph and problem provided in the image.

We have:

• Temperature of the air parcel: 24°C
• Vapor pressure of the air parcel: 10 hPa (marked as a red dot on the graph)

a) Is this air parcel saturated?

Answer: No, the air parcel is not saturated. Saturation occurs when the vapor pressure of the air parcel equals the saturation vapor pressure at that temperature. From the graph, the saturation vapor pressure at 24°C appears to be much higher than 10 hPa (closer to around 30 hPa). Since the current vapor pressure (10 hPa) is less than the saturation value, the air is not saturated.

b) What is the saturation vapor pressure at the temperature of 24°C?

Answer: Based on the graph, the saturation vapor pressure at 24°C is approximately 30 hPa.

c) What is the relative humidity of the air parcel?

Answer: The relative humidity is the ratio of the current vapor pressure to the saturation vapor pressure, expressed as a percentage.

$\text{Relative Humidity} = \left( \frac{\text{Vapor Pressure}}{\text{Saturation Vapor Pressure}} \right) \times 100$

Given:

• Vapor pressure = 10 hPa
• Saturation vapor pressure = 30 hPa

$\text{Relative Humidity} = \left( \frac{10}{30} \right) \times 100 = 33.33\%$

So, the relative humidity of the air parcel is 33.33%.

d) If the air parcel cools down while its vapor pressure stays constant, will relative humidity increase or decrease?

Answer: The relative humidity will increase. As the temperature decreases, the saturation vapor pressure decreases (as seen from the graph). Since the actual vapor pressure remains constant, the relative humidity will increase because the ratio of vapor pressure to saturation vapor pressure becomes larger at lower temperatures.

e) What, approximately, is the dew point temperature, i.e., the temperature at which the air would need to cool to become saturated?

Answer: The dew point temperature is the temperature at which the vapor pressure equals the saturation vapor pressure. From the graph, the saturation vapor pressure equals 10 hPa at approximately 11°C. Therefore, the dew point temperature is 11°C.

f) Approximately how much water vapor (in hPa) would the air need to gain to become saturated without changing temperature?

Answer: To become saturated at 24°C, the air parcel needs a vapor pressure of 30 hPa. Since the current vapor pressure is 10 hPa, the air needs to gain:

$30 - 10 = 20 \text{ hPa}$

Thus, the air parcel needs to gain 20 hPa of water vapor to become saturated at 24°C.

Let me know if you'd like further details or explanations on any of these answers!

Related Questions:

1. How does the saturation vapor pressure change with temperature?
2. What happens to the dew point if the air temperature increases without any change in vapor pressure?
3. How can relative humidity be used to predict weather conditions?
4. How is dew point related to human comfort levels, especially in high humidity areas?
5. What are the common ways to measure vapor pressure in the atmosphere?

Tip:

Always remember that the closer the air temperature is to the dew point, the higher the relative humidity will be!