446_01c_test1_practice

446_01c_test1_practice - Neglecting the settling velocity...

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Sample problems for test # 1 1) Calculate the minimum relative humidity necessary to cause condensation on each of the particles shown below, where r = 0.2 µ m. Assume a temperature of 298 K. Solution droplet that formed on a (NH 4 ) 2 SO 4 aerosol that had a radius of 0.03 µ m Metal cube (non- hygroscopic) Pure water sphere r r 2r 2) Although we have assumed that surface tension is approximately constant, in reality it increases with increasing salt concentration. Would this make salt aerosols more or less likely to activate at a given supersaturation? 3) If 3 kg of NaCl is mixed in 28 liters of water, what would the equilibrium relative humidity above the solution be? 4) Consider a cloud droplet with a radius of 2 µ m that is near the cloud base. The updraft velocity in this cloud is 1.3 m/s and the average supersaturation is 0.4%.
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Unformatted text preview: Neglecting the settling velocity (fall speed) of the droplet, how high in the cloud would it reach before reaching precipitation size (r = 1 mm)? Is this still in the troposphere? 5) If a cloud droplet doubles in size in 5 minutes due to condensation, how long would you estimate it would take to triple in size? 6) All else being equal, will the peak supersaturation in a cloud forming in a polluted region be higher or lower than a cloud forming in a pristine region, and why? 7) The aerosol size distribution shown below was measured over the ocean where most aerosols are composed of ammonium sulfate. Based on what you know about cloud processing, what would you estimate the peak supersaturation in nearby clouds to be? | 0.5 | 0.1 Radius ( m) | 0.02 Number concentration...
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