Part 2 A: Moisture in the Atmosphere Over 99% of the atmosphere is composed of t

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Part 2
A: Moisture in the Atmosphere Over 99% of the atmosphere is composed of two gasses, oxygen (O) and nitrogen (N), while small proportion, water vapor (H20) has the most important effect on weather. The amount of water in the atmosphere is described by its humidity. Humidity is expressed by several different measures including vapor pressure, dew point temperature, specific humidity, and relative humidity. A common instrument for measuring humidity is the sling psychrometer. A sling psychrometer consists of two mercury thermometers. The bulb of one of thermometers is encased in a cloth saturated in water. As the psychrometer is spun in the air, water from the cloth evaporates, cooling the bulb. The amount of cooling of the bulb is limited by the humidity of the air and eventually the temperature will stop decreasing. This temperature is known as the wet-bulb temperature. The other thermometer measures the air temperature, known as the dry-bulb temperature. The difference between the wet and dry bulb temperatures is used to calculate the humidity of the air View the video of the sling psychrometer in operation. Inside the lab: wet Bulb outside the lab: wet Bulb = 84"F, Dry Bulb 65°F, Dry Bulb = 69"F . . 75 °F. 14. Enter the dry and wet bulb temperatures for both locations in Table 4. To help in your later calculations, we have included an example where the dry-bulb and wet bulb temperatures are 90 and 75 F respectively. These values are recorded in Table 4 Temperature Conversions 15. In order to calculate the humidity measures, the temperatures will need to be converted from Fahrenheit to Celsius. You may use the temperature converter at http://www.srh.noaa Rov/epz/?n=wxcalc or the following formula: Te=9x(7-32) For our example, the dry and wet bulb temperatures are 32 and 24 "C entered in Table 4 Convert the observed wet and dry bulb temperatures for both locations and enter them in Table 4 Calculating Dew Point The dew point is the temperature at which the air becomes completely saturated. The formulas for calculating it are complex, but it may be calculated by using Table 5 using the following procedure. First subtract the wet-bulb temperature from the dry-bulb temperature to get the wet-bulb depression. The find the dry-bulb temperature (in 'C) in the left hand column and the wet-bulb depression in the top row of Table S. The dew point is the entry in the table where the left column and top row values intersect. In our example, the dry-bulb temperature is 32 and the wet-bulb depression 8 °C. The two values intersect at 21. This is the dew-point in 'C Repeat this procedure for the observations at both locations and enter the results in Table 4

Explanation / Answer

18 ) molecule of water evaporates by absorbing energy from yhe surrounding . the energy required for conversion of liquid to gaseous state ( latent heat ) is provided by the molecules of surface. In this way when evaporation occurs it causes cooling . thus lowering the temperature of wet bulb .

19 ) The cooling is more if the evaporation is more. so on a very humid day the saturation of the air occurs quicker , and thus less evaporation and less change in temperature . cooling in an earthen pot filled withwater is good example of it.

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