A dry-bulb temperature of 30°C and a wet-bulb temperature of 29°C were recorded at a weather station. What are the relative humidity and the most likely weather conditions?
1. Relative humidity is 29% with clear skies.
2. Relative humidity is 29% with a good chance of snow.
3. Relative humidity is 93% with clear skies.
4. Relative humidity is 93% with a good chance of rain.
How do you determine the correct answer?
Answer (3)
The answer is most likely 4 but I think you need a table or a marked hygrometer to work this out. You can't really work out humidity by the given temperatures. All you can know for sure is that there is a strong chance of rain because dew point is only 1 degree away. (I think what they want you to do is 29/30 x100)
Determining Relative Humidity and Weather Conditions
To determine the relative humidity and likely weather conditions from the given dry-bulb temperature of 30°C and a wet-bulb temperature of 29°C, we need to understand the concepts of wet-bulb temperature and relative humidity. Wet-bulb temperature is the temperature at which air becomes fully saturated with water vapor (100% relative humidity) when water is evaporated into it, cooling the air for that water to evaporate requires heat energy from the air itself.
The difference between the dry-bulb and wet-bulb temperatures is known as the wet bulb depression. The relative humidity can be estimated using the wet bulb depression. As the wet bulb depression in this case is small (1°C), it indicates that the air is nearly saturated and relative humidity is high.
By consulting a psychrometric chart or using appropriate calculations, we would find that the relative humidity is close to 93%. Therefore, the correct answer is either (3) or (4), since both options report 93% relative humidity. Now, considering the air temperature of 30°C, it is more likely that option (4) is correct with a "good chance of rain" rather than clear skies, as high humidity and warm temperatures can lead to the development of rain.
The relative humidity is approximately 96.67%, which indicates high humidity levels. This suggests that the most likely weather condition is cloudy with a good chance of rain. Therefore, the correct option is 4, stating a relative humidity of 93% with a good chance of rain.
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