Download presentation
Presentation is loading. Please wait.
Published byKellie Cain Modified over 10 years ago
1
RRB Pg 117
2
Saturation: When the air contains as much moisture as it can hold The higher the temperature, the more moisture air can hold If air temperature of moist air is lowered enough, the air will become saturated If the temp falls below the dew point, water vapor usually turns into liquid water
4
Moisture in the form of water vapor enters the atmosphere by evaporation, sublimation to a gas, and transpiration Evapotranspiration: Evaporation and Transpiration together Large amounts of energy are needed to change liquid water into water vapor during evaporation and transpiration, most of which comes from insolation EUREKA!! EUREKA!! Transpiration- a flashback to biology Transpiration- a flashback to biology
6
Sling psychrometer: has two thermometers mounted so they can be slung through the air. One thermometer records air temp (dry bulb temp) and the other has a wet cloth which measures the wet bulb temp Evaporation causes cooling The drier the air, the greater the evaporational cooling, the greater the difference between the dry-bulb and wet- bulb temps Use a dew point temperature table to determine the dew-point. ESRT pg 12
8
Dew point is expressed using a unit of temperature (Celsius or Fahrenheit) Dew point: the temp to which air must be cooled to become saturated The only way to change the dew point is by adding or removing moisture from the air
9
Locate the dry-bulb (air temperature) reading on the left hand side of the chart Subtract the wet-bulb reading (measure of how dry or saturated the air is) from the dry- bulb reading Locate the difference between the wet-bulb and dry-bulb readings across the top of the chart Follow the horizontal row for the dry-bulb reading to the right until it meets the vertical column running down from the difference between the wet-bulb and dry- bulb readings
10
If the dry-bulb temperature is 8 degrees Celsius and the wet-bulb temperature is 2 degrees Celsius, find the dew point Note that the wet-bulb temp will always be the same or colder than the dry-bulb
11
If the dry-bulb temperature is 26 degrees Celsius and the wet-bulb temperature is 25 degrees Celsius, find the dew point
13
Relative humidity: the ratio of the amount of water vapor in the air (absolute humidify) to the maximum amount it can hold (moisture capacity) Relative humidity is expressed as a percent of saturation Air that is saturated = 100% To determine RH, you need a sling psychrometer and a RH table- ESRT 12
14
If the RH is 50%, the air could contain twice as much water vapor As the temperature of the air approaches the dew point, the relative humidity approaches 100%
15
Locate the dry-bulb reading on the left-hand side of the Relative Humidity chart Subtract the wet-bulb reading from the dry- bulb reading Locate the difference between the wet-bulb and dry-bulb readings across the top of the chart Follow the horizontal row for the dry-bulb reading to the right until it meets the vertical column running down from the top
16
1. Find the RH when the dry-bulb temperature is 18 degrees Celsius and the wet-bulb temperature is 13 degrees Celsius 2. Find the RH when the dry-bulb temperature is 10 degrees Celsius and the wet-bulb temperature is 9 degrees Celsius
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.