Lab2_template_F23
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School
University of Colorado, Boulder *
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Course
1070
Subject
Geography
Date
Dec 6, 2023
Type
docx
Pages
7
Uploaded by ChiefFlowerCapybara13
Lab 2 Report
Name: Frank Diaz_ATOC 1070-006____________
Partners: ___Lucas & Courtney_____________ ,
_______________
Please paste your Excel data and graph below this line. Highlight everything you need in Excel,
copy, and then use ‘Paste Special’ to paste as an image (e.g., PNG, PDF, etc.). You can take a
Locations:
DRY
BULB
(ºF)
WET
BULB
(ºF)
DRY
minus
WET
(ºF)
DEW
POINT
(ºF)
SATURATION
VAPOR
PRESSURE
ACTUAL
VAPOR
PRESSURE
% R.H.
CLASSROOM
74
59
5
50
28.7
12.3
42.857
OUTDOORS
71
56
5
46
25.9
10.6
40.927
ATOC
SKYWATCH
WEATHER
STATION
X
X
.
Question 1 (10pts):
Relative humidity is not a direct measure of the absolute amount of water
vapor in the air, since it also depends on the air temperature. However, RH is
very important in terms of human comfort. If the relative humidity is high,
the air is closer to saturation, and the less comfortable a person feels since it
will limit your body’s ability to cool off via evaporation from the skin. As such,
the media tends to broadcast the relative humidity and not the absolute
humidity.
Try calculating RH yourself, using the formulas given above. Show each
calculation and the formula used!
a. The vapor pressure is 5mb and the saturation vapor pressure is 25mb at
21ºC.
RH=100*vapor pressure/saturation vapor pressure
=100*(5/25) =20%
b. The vapor pressure is 15mb and the saturation vapor pressure is 25mb at
21ºC.
=100*(15/25) =60%
c. The mixing ratio is 10g/kg, and the saturation mixing ratio is 20g/kg at
25ºC
=100*(10/20) =50%
d. The mixing ratio is 10g/kg, and the saturation mixing ratio at 10g/kg at
15ºC
=100*(10/10)
100%
e. Given how your answers changed from (a)è(b) and then from (c)è(d),
explain the two ways that relative humidity values can be changed.
The relative humidity values have changed because the air is closer to
saturation due to the dew point temperature meeting absolute temperature.
The relative humidity is higher if the values of vapor pressure and saturation
pressure are closer together. And vice versa if the mixing ratio and saturation
mixing ratio are closer together the percentage becomes higher.
Question 2 (10pts):
The average
composition of the atmosphere is 78% nitrogen, 21% oxygen,
and 1% “others”, which includes water vapor and other gases. However, the
percentage of water vapor (a gas)
varies
over time and space to between
~0% to 4% in the atmosphere. Avogadro stated long ago that ‘equal
volumes of all gases, at the same temperature and pressure, have the same
number of molecules’. What this means is that an air mass with lots of water
vapor (H
2
O) will have less nitrogen (N
2
) and oxygen (O
2
) molecules than a
drier air mass would (if we assume equal volumes, temperatures, and
pressures for both).
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a. The molar weight of water vapor is about 18g per mole, while the molar
weight of dry air is about 29g per mole since almost all of it is N
2
(28g/mole)
and O
2
(32g/mole). If a moist air mass and a dry air mass of equivalent
volumes were at the same temperature and pressure, which air mass would
be denser?
Dry air because there is a higher number of grams per mole
b. If these two air masses have the same dimensions and collide with one
another at the surface, which air mass would be forced to rise and why?
Water vapor would rise because it is less dense than the dry air.
Question 3 (10pts):
a. Where did the air contain more absolute moisture - inside the lab or
outdoors? What variable from your data log are you basing this on?
Speculate on why the indoors or outdoors had more moisture.
Indoor air has more absolute moisture because the dew point is lower than
the dew point temperature indoors. We can see this on the Excel log that the
Dew Point temperature is 50 indoors and 46 outdoors. In theory, the air takes
less time to cool to that temperature.
b. Where did you find the highest relative humidity – inside the lab or
outdoors? Was this primarily due to differences in air temperature and hence
saturation pressure values, due to absolute moisture amounts, or due to a
combination of the two?
100*(vp/svp)
100* 12.3/28.7= 42.857% Indoors is higher
100* 10.6/25.9= 40.927
This was due to the air temperature and absolute moisture amounts due to
the vapor pressure and temperature of indoor and outdoor.
Question 4 (10pts):
a.
What if you took another psychrometer reading a few minutes later,
and your wet-bulb reading was 1 degree lower than before, while your
dry-bulb temperature and pressure values remained the same. Would
your dew point and relative humidity be higher, lower, or the same?
Explain your answer.
The dew point would be lower because the relative humidity would be
lower, and the explanation for that is that there is less moisture in the air.
When the wet bulb temperature falls there would be a less amount of
moisture in the air.
b. Which variable, temperature or dew point temperature, requires more
measurements to resolve with our setup?
Hint: perhaps refer to the moisture
calculator spreadsheet here
We used the dry-bulb, wet-bulb temperature, and pressure in the moisture
calculator spreadsheet.
c. Given your answer to (b), which variable, temperature or dew point, would
you expect to have a greater standard deviation for a group of
measurements?
Hint: think about what you learned from the ideal gas law
lab about expected errors and uncertainties
.
I think the dew point temperature would have a higher standard deviation
because it consists of both dry and wet bulb variations.
d. For the class’ outdoor data, which variable actually had a greater standard
deviation? If this did not meet your expectations from (c), then what else
might have contributed to this result?
The dew point had a greater standard deviation as expected.
Conclusion Question 1 (10pts):
Provide 1 physical source of error for a single measurement of dew
point using a sling psychrometer. Indicate & explain the expected effect on
the dew point given your chosen source of error (i.e., would it cause a higher
or lower than expected value and why?)
Hint: a physical error could describe some physical way that the sling
psychrometer might need be getting the exact wet and dry bulb temps.
A physical source could be radiant heat from buildings or sunlight which can
lead to an inaccurate measurement. This can increase the temperature of
the wet bulb and can cause a error in the calculation of the dew point.
Conclusion Question 2 (10pts):
Provide 1 experimental source of error for the set of 10 outside
measurements using the sling psychrometers. How could the class have
done the set of observations to help correct for this error?
Hint: the goal was to get an accurate mean of the moisture in the air at an
exact place and time
I think having done the measurements in more open places outside on
campus and have done more observations, in general, to better
accommodate any error. Measurements could be affected by wind direction,
speed, and general movement. This can increase evaporation and lead to
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more errors in calculations. This could be two different observations in a still
environment and one that has wind.
Conclusion Question 3 (10pts):
Wet-bulb temperature can estimate what your skin temperature would be if
you were constantly sweating, so it’s often used to approximate how people
would fare in extreme heat. To be clear, wet bulb temps tell you how cool you
can possibly make your skin by evaporation.
A human internal body temperature of 36.8°C (98.2°F) requires skin
temperatures of 35°C (95°F) to maintain a gradient directing heat outward
from the core. Once the air temperature (dry-bulb) rises above this threshold,
metabolic heat can only be shed by sweat evaporation. However, if wet bulb
temperatures exceed 35°C (95°F), this means your skin can only cool to that
high wet bulb temperature.
Organ damage
(Links to an external site.)
(Links
to an external site.)
from internal heat stress can occur if humans are directly
exposed wet bulb temps equal to or greater than 95°F for three hours or
more.
Studies
(Links to an external site.)
(Links to an external site.)
project
summertime wet bulb temperatures in Middle Eastern coastal areas to
exceed 95°F regularly by 2050.
Discuss one adaptation measure that people in this region could pursue if
these projections turn out to be true. How much does your answer depend on
local poverty levels?
Adaptation measures can be taken in local environments to better adapt to
environmental circumstances. There can be an adaptation to cool down body
temperatures by sweating and increasing them by shivering. So, in all, for
local people who can’t afford to cool themselves with an AC unit or warm
themselves up, compared to rich people who can, then adaptation measures
can be taken.