Tutorial 1B

Department of Geography and Environmental Management GEOG 303 University of Waterloo Tutorial 1 – Part B Saturated conditions Due: September 26, 23:59 pm Submit your assignment document digitally (pdf or doc) via LEARN. Demonstrate your calculations. In the previous lecture, we learned about the mechanisms of precipitation generation and the importance of achieving saturated conditions for water vapour to condensate. For the development of this activity, please consider: The saturation vapour curve (Figure 1), and its approximate equation (Eq. 1), as presented by (Hendriks, 2010). The relative humidity equation (Eq. 2). The simplified relationship between dew point and air temperature (Eq. 3) Figure 1. The saturation vapour curve 𝑒 𝑠 = 0.6108 𝑘𝑃𝑎 × 𝑒 17.27× 𝑇 237.3°𝐶+𝑇 Eq. 1, Where T is air temperature (in o C), 𝑒 𝑠 is saturation vapour pressure. Consider e = 2.71 𝑅𝐻 = ? 𝑎 ? 𝑠 × 100 Eq. 2, Where RH is relative humidity and 𝑒 𝑎 is the actual vapour pressure.

Department of Geography and Environmental Management GEOG 303 University of Waterloo 𝑇 ??𝑤 ≈ 𝑇 − ( 100−𝑅𝐻 5 ) Eq. 3, Where 𝑇 ??𝑤 is the dew point (in o C). Now, let us consider we have set up an experiment to determine relative humidity here in Waterloo, where elevation is 329 m.a.s.l. To assess relative humidity, we are using a wet and dry hygrometer that consists in a wet- and a dry-bulb thermometers. The hygrometer readings are as shown in Table 1. July 04 2:00 am July 04 2:00 pm T db (dry bulb in o C) 10.6 23.9 T wb (wet bulb in o C) 10.0 16.7 According to Allaby (2015), a wet- bulb thermometer is: “A thermometer, the bulb of which is kept moist by a thin cloth (e.g. muslin) bag connected by a wick to a bath of clean (preferably distilled) water. As long as the air is not saturated, evaporation from the muslin keeps the wet-bulb thermometer at a lower temperature than the dry- bulb thermometer beside it, with which its readings are compared”. Table 1: Relative humidity values. For use at elevations between 501 and 1900 feet above sea level. (Adapted from NOAA). 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 50 7 12 17 22 28 33 39 44 50 56 62 68 74 80 87 93 100 51 4 9 14 19 24 29 35 40 46 51 57 63 69 75 81 87 93 100 52 1 6 11 15 20 25 31 36 41 47 52 58 63 69 75 81 87 94 100 53 3 7 12 17 22 27 32 37 42 48 53 58 64 70 76 82 88 94 100 54 5 9 14 19 23 28 33 38 43 49 54 59 65 70 76 82 88 94 100 56 57 58 59 60 55 2 6 11 15 20 25 30 34 39 44 49 55 60 65 71 76 82 88 94 100 56 4 8 13 17 21 26 31 36 40 45 50 55 61 66 71 77 82 88 94 100 57 1 6 10 14 18 23 27 32 37 41 46 51 56 61 67 72 77 83 88 94 100 58 3 7 11 16 20 24 29 33 38 42 47 52 57 62 67 72 78 83 89 94 100 59 1 5 9 13 17 21 25 30 34 39 43 48 53 58 63 68 73 78 83 89 94 100 61 62 63 64 65 60 3 7 10 14 18 23 27 31 35 40 44 49 54 58 63 68 73 78 84 89 94 100 61 1 4 8 12 16 20 24 28 32 36 41 45 50 54 59 64 69 74 79 84 89 95 100 62 2 6 10 13 17 21 25 29 33 37 42 46 50 55 60 64 69 74 79 84 89 95 100 63 4 7 11 15 19 22 26 30 34 38 43 47 51 56 60 65 70 74 79 84 89 95 100 64 2 5 9 12 16 20 24 27 31 35 39 43 48 52 56 61 65 70 75 80 85 90 95 100 65 3 7 10 14 17 21 25 29 32 36 40 44 48 53 57 61 66 70 75 80 85 90 95 100 66 2 5 8 12 15 19 22 26 30 33 37 41 45 49 53 58 62 66 71 76 80 85 90 95 67 3 6 10 13 16 20 23 27 31 34 38 42 46 50 54 58 63 67 71 76 80 85 90 68 2 5 8 11 14 18 21 24 28 32 35 39 43 47 51 55 59 63 67 72 76 81 85 69 3 6 9 12 16 19 22 26 29 33 36 40 44 47 51 55 59 64 68 72 77 81 70 1 4 7 10 14 17 20 23 27 30 34 37 41 44 48 52 56 60 64 68 72 77 71 3 6 9 12 15 18 21 24 28 31 34 38 42 45 49 53 57 60 65 69 73 72 1 4 7 10 13 16 19 22 25 29 32 35 39 42 46 50 53 57 61 65 69 73 3 5 8 11 14 17 20 23 26 30 33 36 40 43 47 50 55 58 62 65 74 1 4 7 10 12 15 18 21 24 27 30 34 37 40 44 47 51 54 58 62 75 3 5 8 11 13 16 19 22 25 28 31 35 38 41 44 48 51 55 59 76 1 4 7 9 12 15 17 20 23 26 29 32 35 39 42 45 49 52 56 Wet-bulb temperatures (oF) Dry-bulb temperatures (oF)

Department of Geography and Environmental Management GEOG 303 University of Waterloo Reference Allaby, M. (2015). A Dictionary of Ecology (5 ed.). Oxford University Press. https://doi.org/10.1093/acref/9780191793158.001.0001 Hendriks, M. R. (2010). Introduction to Physical Hydrology . Oxford University Press. National Oceanic and Atmospheric Administration (NOAA). (n.d.). Relative Humidity Tables 501-1900 feet above sea level . https://www.wrh.noaa.gov/sto/rhtbl.php Extra information on the wet bulb temperature if it got you curious (note that they use a different table than us): https://www.youtube.com/watch?v=H1kJttETOMo