Lab 4 LAB 4-Humidity and Adiabatics Key Ideas Absolute humidity Saturation humid

Question

Lab 4 LAB 4-Humidity and Adiabatics Key Ideas Absolute humidity Saturation humidity Relative humidity Dew point temperature Dry bulb temperature Wet bulb temperature Web bulb depression Psychrometric tables Moist adiabatic lapse rate (MALR) Dry adiabatic lapse rate (DALR) Environmental lapse rate (ELR) Stable air Unstable air Conditionally unstable air Discussion Water and States of Matter Water exists naturally on earth in the three states of matter: solid, liquid, and gas. Of the three types of matter, gas is the least dense: it has the fewest molecules per unit volume. Because gas is also the least ordered of the three states, when put into a sealed container gas molecules do not accumulate on the bottom but space themselves out to fill the container uniformly. The contained gas molecules, however, are in high speed motion. They collide with each other and bump against the walls of the container. Gases are easily compressed. If the size of the sealed container is reduced while keeping the same number of gas molecules, the molecules will be more closely spaced than before and a larger number of collisions will occur Liquids are more ordered than gases. The molecules in a liquid state are closer together than those in the gas state, but liquid molecules can still change their position by moving past one another Contained liquid molecules don't float all over the volume of the container, they acumulate on the bottom. Solids are the most ordered type of matter. Molecules in a solid canot change their positions if Water is common on earth in all three states and it also commonly changes from one state to another. Whenever a water molecule changes state, energy is either added to it or removed from it. When going from a less ordered state to a more ordered state, energy is released from the water molecule to the surrounding environment. When water changes from a more to a less ordered state, energy is required and is taken from the surrounding environment. The energy involved is heat energy. Releasing energy to the atmosphere warms the atmosphere, whereas taking energy from the atmosphere cools it. Table 4-1 lists the processes by which water changes from one state to another. Table 4-1 Erom To Process Energy solid liquid melting eeded liquid gas evaporation needed solid gas sublimation needed liquid solid freezing released gas liquid condensation released 29 GEO 121 D-G- Spring 2018

Explanation / Answer

At 2000 ft, it is given that T = 72° F, AH= 4 g/ft3, SH = 8.6 g/ft3. So, RH= AH/SH *100 = 46.51% and DPT = 72 - (100-46.51)/5 = 61.3° F

Note that

Dew point temperature is estimated as :

DPT= T - ((100-RH)/5)

While ascending to 6000 ft, air rises dry adiabatically since it is unsaturated, so T = 72 - (5.5*4) = 50° F (note that 4000m is normalized to 4)

Since AH= 4 g/ft3, SH =4 g/ft3 (according to T), RH = 100%. Thus, DPT =T =50° F

While ascending to 12000 ft, air rises moist adiabatically since it is saturated, so T = 50 - (3*6) = 32° F

Since AH= 4 g/ft3, SH =2.2 g/ft3 (according to T), RH = 181.8%. Thus, DPT = 32 + 16.36 = 48.36° F

While descending to 6000 ft, air moves dry adiabatically as it loses moisture, so T = 32 + (5.5*6) = 65° F

Since AH= 4 g/ft3, SH =7 g/ft3 (according to T), RH = 57.14%. Thus, DPT = 65 - 8.57 = 56.42° F

While descending to 2000 ft, air moves dry adiabatically as it loses moisture, so T = 65 + (5.5*4) = 87° F

Since AH= 4 g/ft3, SH =13.8 g/ft3 (according to T), RH = 28.98%. Thus, DPT = 87 - 14.2 = 72.78° F

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