Part/ Atmospherie Humidity and Precipitable Water (29marks)
Spreadsheet software (e.g. MS excel)is recommended forthe following calculations If you gothis
route, youmay wish tohand ina copy (print out) of your spreadsheet If you do this be sure that
variables, equations, and answers are carefully labelled so that they can be marked accordingly.
1. Consider a 22°C parcel of air sea level, with RH 54% Calculate the following
Saturation vapour pressure
2. Repeat (1) but for the air mass sitting over Victoria today: T= 6°C and RH 89%.
Saturation vapour pressure
3. Look online find the air temperature and relative humidity Igaluit, Nunavut today.
http://weather 2c.ca/canada e.html
What the specific humidity this air?
4. pineapple express system moves air from the subtropical Pacific westem Canada
Assume that this air parcelat sea level has temperature of 32°C with relative humidity of
a. How much does the air need tobe cooled order toreach saturation? (2 marks)
Assume that once saturated the air lifted to height (pressure)or 700 mbar Itcools
through mois adiabatic processes How much water will condense out of each kg ofair as it
is lifted from sea level 700 mbar? (3 marks)
Assume that weare talking about & discrete air mass (e.g. cloud) with initial volume of
100,000 m sea level. How much moisture isi the initial air mass?
How much moisturei in the final air mass, 700 mb?
kg. Ifall of the
vapour that condensed out rained over greater Vancouver (arca 2880km² how much
rainfall would Vancouver receive?
5. Calculate the precipitable water ir cachlayer and the entire atmosphere spreadsheet is
ommended here. What sthe average atmospheric specific humidity?
Parti B: Surface Energy Balance and Evapotranspiration (33 marks)
Evaporation requires an amount of energy O2 -p_L,E for revaporation rate Eand latent heal of
evaporation, 2500Jg Assume that summer sun pouring in at 05-800\ Wm² incident
ona lake withanalbedo of 0.1. If half available solar energy drives evaporation how
in one hour?
7. Melking of snow generally much more efficient than sublimation o snow. Consider the
energetics of this for spring day with Os 400 W m² and snow albedo c 0.6 Use snow
density If all available solar energy drives meliting, how much snow would
melt over 10 hours?
cm Ifthe energy goes sublimation instead how much
snow would sublimate over 10hours?
In reality not all of the available solar energy will goto evaporation meking, sublimation in
questions (6) and(7). Where else might the energy go? (2 marks)
9. Using the Penman Montieth equation answer the following questions
(a) Ina Study on transpiration of eucalyptus trees in an a arid pan of Africa researcher found
average values aerodynamic and canopy resistance of about 10sm and r,-500s
m² (i.e. the leaf stomata/canopy provided most of the resistance transpiration). For
average daily (12 -hour) values(C 300 W m². 28°C. RH- 36% and asite at
1000 elevation, calculate the total daily transpiration nmm/day. (6 marks)
(b) Lets now consider evaporation over amall lake on Vancouver Island For average daily
(12-hour) values 0* 190 m² T- 14°C 65% and wind speed 12ms
(measured (m).and a site at 10m elevations calculate the total daily evaporation in
mm/day. Use a surface roughness value of 0.003 for your calculation (8 marks)
10. Using the same hydr meteorological setting from 9(b). use the Hamon equation to estimate
evaporation over the small lake on Vancouver Island At this site daily average temperature is
10°C mean day length 12-hours marks)
11. (a) List a least one advantage andone disadvantage obtaining evaporation estimates from
both the Penman Montieth and the Hamon Method marks)
(b) There will be days when the Hamon evaporation methods are higher than the Penman-
Month and days when they are lower. Give plausible reasons for why these differences
may occur. Consider that the data used in 9b and 10a are from the spring.
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