9. Determine the atmospheric stability category of the following observations. a
ID: 1714640 • Letter: 9
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9. Determine the atmospheric stability category of the following observations. a) Clear summer afternoon at 1:00 PM, wind speed 1.6 m/s b) Clear summer afternoon at 1:00 PM, wind speed 5.6 m/s c) Summer afternoon at 1:00 PM with broken low clouds, wind speed of 5.2 m/s d) Clear winter morning at 9:00, wind speed of 6.6 m/s TABLE 9-13 Key to stability categories Night Surface wind speed (at 10 m) (m/s) Incoming solar radiation Thinly overcast or Strong Moderate Slight 1/2 Low cloud s 3/8 Cloud 2-3 A-B A-B B-C C-D 3-5 C >6 "The neutral class, D, should be assumed for overcast conditions during day or night. Note that "thinly overcast is not equivalent to "overcast. Notes: Class A is the most unstable and class F is the most stable class considered here. Night refers to the period from one hour before sunset to one hour after sunrise. Note that the neutral class, D, can be assumed for overcast conditions during day or night, regardless of wind speed. "Strong" incoming solar radiation corresponds to a solar altitude greater than 60° with clear skies; "slight" insolation corresponds to a solar altitude from 15° to 35° with clear skies. Table 170, Solar Altitude and Azimuth, in the Smithsonian Meteorological Tables, can be used in determining solar radiation. Incoming radiation that would be strong with clear skies can be expected to be reduced to moderate with broken (5/8 to 18 cloud cover) middle clouds and to slight with broken low clouds Source: Tuner, 1967.)Explanation / Answer
(a) Clear summer afternoon at 1:00 PM shows strong incoming solar radiation. Wind speed is 1.6 m/sec. Which in total is "class A" of atmospheric stability conditions.
(b) Strong solar radiation and 5.6 m/sec wind velocity shows "class C" of atmospheric stability conditions.
(c) Broken low clouds at 1:00 PM in summer will turn solar radiation to moderate type. Also, wind speed is 5.2 m/sec, which is showing transition of "class C" to "class D". But as class D is assumed for overcast conditions, in this case we have to assume "class C" of atmospheric stability conditions.
(d) Clear winter morning at 9:00 AM indicates slight incoming solar radiation. 6.6 m/sec wind speed shows existence of "class D" of atmospheric stability conditions.
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