Water, Precipitation, and Humidity Flashcards
True or False: earth is a closed system in terms of water
True
What is the Hydrological Cycle?
All water is recycled in what is called the hydrological cycle
___________ is crucial to the idea of humidity and water cycles.
Latent heat
What are the five Atmospheric Humidity Indices?
-Vapor pressure (mb or kPa)
-Mixing ratio (grams per kilogram of dry air)
- Specific humidity (grams per kilogram of air (water in the air+air))
-Relative humidity (%)
-Dew-point temperature (°C)
_____________; The atmospheric pressure (in millibars; mb) associated with the gaseous water in the air. How much pressure is that gaseous water exerting.
Vapor Pressure
Is vapour pressure affected by temperature changes?
No
True or False: If you change the air parcel’s temperature, the vapour pressure doesn’t change (as long as you don’t add or remove water)
True
True or False: Saturation Vapour Pressure remains constant, no matter the change in temperature.
False, it changes with temperature changes.
________________: Maximum amount of vapor pressure that the air can hold at a given temperature, impacted by temperature.
Saturation Vapour Pressure
Does hot air hold less or more moisture?
more
**True or False: Air hovering over a liquid water surface can hold more moisture than air hovering over a frozen water surface. **
True.
What does Unsaturated Air over liquid water mean?
If the air over this water is unsaturated, it means that more water molecules are evaporating from the surface than are condensing onto the surface.
What does Saturated air over liquid water mean?
If the air over this water is saturated, it means that there are equal numbers of water molecules evaporating and condensing.
For a given temperature, what does it mean when we have reached equilibrium?
We have reached the maximum vapor pressure for that temperature: the saturation vapor pressure.
What happens when the saturation temperature has been reached?
We cannot hold any more moisture. And we get condensation out of the air if more moisture is added.
What does Saturated air over frozen water mean?
Saturation over ice occurs with fewer water molecules in the air than over liquid water at the same temperature, because the ice particles aren’t as likely to escape as water vapor.
Saturation over ice occurs with ______________ in the air than over liquid water at the same temperature, because the ice particles aren’t as likely to escape as water vapour.
fewer water molecules
True or False: Saturation is reached sooner with air over frozen water.
True
The saturation vapour pressure over ice is _______ than the saturation vapour pressure over water.
lower
What is it called when water that is still liquid at temperatures below 0°C?
Super Cooled Water
Define Mixing Ratios:
The number of grams of water vapor for every kilogram of dry air (not including the water vapor).
True or False: Mixing Ratios are affected by temperature changes.
False, it is not affected by temperature changes.
If you change the air parcels temperature, the mixing ratio ______ change (as long as you don’t add or remove water).
does not
Define Saturation Mixing Ratio:
Saturation mixing ratio (g/kg) is the maximum number of g/kg (this increases as temperature increases).
Will Saturation Mixing Ratio change with temperature changes?
Yes, it will.
________________: The number of grams of water vapor for every kilogram of air (including the water vapor).
Specific Humidity
Is Specific Humidity affected by temperature changes?
No, it is not.
What is Saturation Specific Humidity?
Saturation specific humidity (g/kg) is the maximum number of g/kg (this increases as temperature increases).
What is Humidity?
How much water is in the air
What units is humidity measured in? (3)
-Vapor Pressure (mb)
-Mixing Ratio (g/kg): -g of water vapor per kg of dry air
-Specific Humidity (g/kg):g of water vapor per kg of air
What is relative humidity?
The ratio of the amount of water vapor present to the amount that could be present (at the same temperature).
In short, what is relative humidity?
How much water is in the air vs. How much it could handle at that temperature.
Is relative humidity affected by temperature change?
Yes
What form of humidity is most affected by temperature change?
Relative humidity
How is relative humidity expressed?
In percentages.
True or False: If you change the air parcels temperature, the relative humidity will change.
True
How is relative humidity calculated?
Relative humidity= (Actual water vapor in the air)/ (Maximum water vapor possible in the air at that temperature) x100
When do we often have low relative humidity?
We often have low relative humidity around noon, when we reach the highest temperatures of the day.
Why is it that we have low relative humidity around noon?
The air is warm and can handle a lot more moisture, therefore, relative humidity decreases regardless of whether we have added water or not.
Why does relative humidity increase in the evening?
Overnight temperatures decrease, relative humidity increases because it is less able to retain moisture.
Why is relative humidity very affected by temperature?
Air temperature very much impacts relative humidity because it impacts the ability of air to hold on to moisture
Define Dew Point Temperature:
The temperature to which the air must be lowered to make it saturated (e.g., RH = 100%)
In short, what is Dew Point Temperature?
How much must we cool down water to reach saturation.
Is Dew Point Temperature affected by temperature changes?
No
Why is Dew Point Temperature not affected by changes in temperature?
Based only on how much moisture is in the air and temperature to reach that point.
Regarding Dew Point Temperature, If the temperature is below freezing, it is sometimes called the _____________________.
frost-point temperature
True or False: At saturation, evaporation rate is equal to condensation rate (equilibrium).
True
What is another way to define Dew Point Temperature?
The dew-point temperature is the temperature at which a given mass of air becomes saturated and net condensation begins to form water droplets.
Give an example, step by step, of Saturation due to Decreasing Air Temperature.
It is why we have water on the side of a cold glass, ice cold water cooler down the surface, the cold glass chills the surrounding air layer (pulling energy from the air). It cools down the air around the glass to saturation. We know as the air cools; the air is no longer able to hold on to that much moisture. That excess moisture beyond saturation in that, thin layer or air around the glass it reaches. It reaches dew point, and we get condensation on the glass.
What are two humidity instruments?
Hair Hygrometer and Sling Psychrometer
How does the Hair Hygrometer work?
Principle: Human hair changes in length (up to 4%) with respect to changes in relative humidity (0 – 100%).
How does the Sling Psychrometer work?
Principal: more evaporation when there is less humidity in the air (the air is more capable of accepting additional moisture). Evaporation dominates in this balance between evaporation and condensation. The question is by how much. One thermometer has a sock on it, another bulb is exposed to the air, wet the cloth and spin psychrometer above your head, getting evaporation off the cloth. The evaporation dictates how much moisture in the air, latent heat dictates the result.
Regarding the Sling Psychrometer, what is relative humidity dictated by?
Relative humidity depends on the difference in temperature between the dry bulb and the wet bulb to dictates how much evaporation we had and how much latent heat of evaporation occurred.
-AKA, Relative humidity depends on the difference between Td and Tw.
How do we measure relative humidity regarding a sling psychrometer?
We can find out by measuring the latent heat of evaporation.