Adiabatic Processes and the Orographic Effect: GEOG 101L-A. Mindes (Onlne) (7221

Question

Adiabatic Processes and the Orographic Effect: GEOG 101L-A. Mindes (Onlne) (72213-72222) nic Processes and the Orographic Effedt sparcel of air rises, it decreases in pressure and expands. As the air expands, it cools "adiabatically hout a gain or loss of heat). Conversely, as air descends, it increases in pressure and compresses. As the air ompresses, it warms adiabatically. The rate in which a rising parcel (piece) of air cools (assuming the relative humidity is less than 100%) is called the dry adiabatic lapse rate" (DALR), which is rate of 5.5 degrees F per 1000 feet. As the air rises and cools, it may cool enough to reach its dew point. (Remember, the colder the air, the less moisture it can hold, so the main way saturation is reached is by cooling the air.) The level at which a parcel of air reaches the dew point is called the lifting condensation level (LCL), and at this point, condensation and cloud formation can begin. If the parcel of air keeps rising while condensation is taking place, the air will continuc to cool adiabatically, but at a slower rate. Saturated air cools at the wet or "saturated adiabatic lapse rate" (SALR) of about 3.3 degrees F per 1000 feet. The SALR varies, depending on how humid the air is. When the mixing ratio is higher (the air is more humid), more water vapor condensates out of the air. This causes the cooling of the rising air to SLOW, which is why the SALR is a slower rate of cooling. The cooling slows because of the release of "latent heat" (energy) in the conversion of water vapor to liquid water (to form the clouds). When air descends, it warms at the dry adiabatic lapse rate (DALR) because of the compression of the descending air. It always warms at 5.5 degrees F per 1000 feet. In Figure 1 (below), the rising parcel of air reaches saturation at 2000. You know this because the base of the clouds and the LCL marks the point at which saturation is reached. Thus, the dew point temperature is 59 degrees. Since you know the dew point temperature, 59F, you know the mixing ratio (see Table I from Lab 5 notes). The mixing ratio is about I1gkg. (You'll need to interpolate.) Since the mixing ratio is IIgkg at 2000', you know what the mixing ratio is at 0' on the windward side of the mountain-it's also 11g/kg. SALR) (DALR) 209063.4 64.5 DALR) 68.9 Figure 14-1: Tempersnure changes in a hypothtical parcel of air passing over a mouetain

Explanation / Answer

As per the Chegg Policy, we are allowed to answer only 4 subparts of a question. Also, for the 8th question to be answered, we need details of 6th and 7th question. Please repost the questions from 5th to 17th again by dividing them into 4 questions each time. Please find the answer below for question no. 1-4:

As it rises in the windward side of the mountain the parcel gets cooler at the Dry adiabatic lapse rate of 5.5o F/1000 feet till it reaches the LCL. Once it has reached the LCL at 3000 ft. it starts to cool little slower at what is called the saturated adiabatic lapse rate which is in this case 3o F/ 1000 ft.  

Therefore, at 1000 ft., the temperature of the air parcel is = 76.5 - 5.5 = 71o F (QUESTION 1)

at 2000 ft., = 71 - 5.5 = 65.5o F

at 3000 ft., = 65.5 - 5.5 = 60o F (QUESTION 2)

At this point the LCL is reached and beyond this SALR will be applicable.

Therefore, at 4000 ft., = 60 - 3 = 57o F

at 5000 ft., = 57 - 3 = 54o F

at 3000 ft., = 54 - 3 = 51o F (QUESTION 3)

Now that the height of the mountain is 6000 ft., the air parcel will start to fall from the leeward side and begins to warm at the DALR throughout the slope.

Therefore, the temperature at the sea level on the leeward side would be,

= 51 (temp. at 6000ft.) + (6 * 5.5 (since it falls all the way down from 6000 ft to 0))

= 51 + (6*5.5) = 51 + 33 = 84o F (QUESTION 4)

Bonus: Ans. to Q. 8 is CLOUDS

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