GEOG1F91_Lab#2_Josh Sra_7570104

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GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 1 TEXT REFERENCE : Chapter 6 – Atmospheric Pressure, Wind and Global Circulation Chapter 7 – Atmospheric Moisture and Precipitation OBJECTIVES: This lab introduces atmospheric motion via convection cells in the atmosphere, and, coupled with adiabatic heating and cooling, describes how this circulation relates to meteorological phenomena such as cloud formation and precipitation. The instructor will first explain the processes of convection and motion, and adiabatic warming and cooling, as summarized in the rest of the introduction, and then you will study the process by means of experiments and demonstrations. The combined mechanisms of movement and heating and cooling lead directly into the evaporation and condensation process covered in the next lab. WHY IS THIS IMPORTANT? In the last lab, we saw that the effect of the energy striking the Earth’s surface is not uniform. Depending on the season or time of day (controlling the sun angle), or the nature of the surface (controlling the albedo, α, or the amount of longwave radiation being emitted, M out ), there can be quite different values of net radiation at the surface. As the atmosphere is heated from below by means of contact with the earth’s surface (via conduction), all of these factors play roles in determining air temperatures in different places. This differential heating is, in turn, responsible for the development of vertical (convective) and horizontal (advective) motions (i.e., wind ) in the atmosphere, resulting in convection cells ranging from thousands of metres (e.g., winds associated with urban heat islands - http://tinyurl.com/nshttoo ) to thousands of kilometres in size (e.g., the Hadley Cell - https://www.metoffice.gov.uk/learning/atmosphere/global-circulation-patterns ). PART ONE – CONVECTION AND MOTION The vertical movement of air may result from, for example, the overriding of warm air over a cold front, or the heating of the air near the Earth's surface by solar radiation (as seen in the previous lab) thus causing it to rise in a process referred to as convection . This experiment most closely resembles the latter example, and is representative of such natural phenomena as the Hadley Cell , thermal low pressure systems which can occur on hot summer days (often resulting in cloudiness and thunderstorms), land and sea breezes experienced along coasts and shorelines, or the urban heat island associated with cities. This portion of the lab illustrates this phenomenon, using water as a substitute for air. The experimental setup is as illustrated in Figure 2.1. As heat is applied to the one flask, “bubbles” or “parcels” of water in contact with the bottom of the flask become heated. These warmed parcels of water are less dense, and, hence, more buoyant than the surrounding water as a result of their higher temperature. Consequently, they begin to rise through the flask (as evident by the billowing plume of purple potassium permanganate used as a marker) and are replaced by cooler, denser

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 2 water from other parts of the flask. In a short time, the entire heated flask is a relatively uniform purple due to this convective mixing. While it is evident that the heated water is less dense than cooler water, it must also be noted that warmer water occupies a larger volume than cooler water. This volumetric expansion is visible, and can be noted as a very slight rise in the water level in the heated flask and the top connecting tube. Note that, due strictly to the heating of the one flask, the water level in the heated flask is above that of the unheated flask.

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 3 Due to this difference in water levels, there is a higher pressure at the top of the heated flask relative to the top of the unheated flask (Figure 2.2). This can also be viewed as a pressure differential, or a horizontal pressure gradient . The result is the spontaneous movement of water down this pressure gradient, from the top of the heated flask (high pressure) to the top of the unheated flask (low pressure), through the top connecting tube. The heated, purple water traces this movement. While attempting to equalize the pressures at the top of the two flasks, this process is transferring mass (i.e., water) from the heated flask to the unheated flask. As the heated flask is emptying, while the unheated flask is filling, there is an increase in pressure at the bottom of the unheated flask relative to the heated flask. (To think of this in another way, if the two flasks were originally balanced on a pan balance, this transfer of water from the heated to the unheated flask would have the effect of tipping the balance in favour of the unheated flask as it became heavier due to the transfer of water.) This establishes another horizontal pressure gradient , from the high pressure at the bottom of the unheated flask to the low pressure at the bottom of the heated flask. In order to balance this pressure differential, cool, unheated water flows across the bottom connecting tube towards the heated flask (Figure 2.3). As the cool water flows into the heated flask, it is heated and thus continues the convection cycle (Figure 2.4).

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GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 4

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 5 You are required to carefully observe and record this process as one flask of water is heated and the adjacent (and connected) flask is left unheated. As you will be working in groups, don’t forget to list the names of your lab partners in the appropriate space in the table. Use the supplied paper copy of the table during the lab to record your rough copy of the data. All of your data, observations and answers must be typed in a neat and organized fashion in the Word document supplied (available on Brightspace). PROCEDURE A. Check and record the initial temperatures of all four thermometers (they should all read approximately the same). S1 = top thermometer; S2 = bottom thermometer. Press the S1/S2 button to toggle back and forth. S1 or S2 will display in the top left corner of the digital readout. B. Observe the height of the water in the flask that will be heated. Once heating begins, it may be possible to see in increase in the water height, if you have a sharp eye and keen attention to detail . This is the result of the increase in water volume as the temperature rises and the density decreases. C. When you are ready to begin, have the Lab Instructor supply a quantity of potassium permanganate to the heated flask. Turn on the hot plate to begin heating the one flask. At this point, begin reading the temperatures of all four thermometers at one-minute intervals . To speed up the reading, have one person read the temperatures in each of the two flasks, while another person records the data. Note that condensation on the flasks may make reading difficult, so be prepared to wipe the flasks quite often. D. Record all visual observations , correlating them with the temperature readings by noting the time after the start of the experiment. E. Continue heating the flask until the purple colour is noted moving back towards the heated flask through the lower connecting tube, or at least until the purple colour has reached the level of the bottom tube in the unheated flask. This should correspond with the 15-minute mark. Question l. Observe and record the details & results of the experiment (i.e., both the temperatures & the visual observations) on the table provided. Save the information in this Word document, making sure to re-name the Word file so it is identified as yours. For example: e.g. GEOG1F91_Lab#2_Doe_John_99887766_Section13

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 6 This is necessary so we don’t receive large numbers of files with the same or similar names e.g. geog1F91assignment2 or 1F91Assignment2 or 1F91lab2 or table1. When you have completed the assignment, upload the Word file (including your data table) to Brightspace. (10 marks) EXPERIMENTAL DATA List your group’s members: TIME (Minutes) TEMPERATURE (°C) VISUAL OBSERVATIONS (at least 6-8 observations over the 15-minute experimental period) Heated Flask Unheated Flask Top Bottom Top Bottom 0 (initial) 21.3 24.5 23.4 21.3 Unheated is transparent and the regular colour of water, after the purple dye was added the water became purple at the bottom with diffusion taking place 1 21.4 24.5 23.4 21.3 Unheated is transparent water colour 2 21.4 24.5 23.4 21.4 3 21.5 24.5 23.4 21.4 Purple colour is spreading to the top of the flask 4 22.0 24.7 23.4 21.5 Unheated flask is transparent, heated flask is fully purple 5 22.3 25.5 23.4 21.5 6 22.8 26.4 23.4 21.6 7 23.3 27.0 23.5 21.7 Unheated is fully purple and unheated is defusing downwards water is slowly turning purple 8 23.8 28.0 23.8 21.9 9 24.8 29.0 24.7 22.1

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GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 7 10 26.2 30.3 26.0 22.3 Unheated is slowly but turning purple completly 11 27.4 31.3 27.5 22.5 12 28.8 33.0 29.1 22.8 Unheated is slowly turning purple (less than a third left) 13 31.2 34.3 30.8 23.0 Unheated is slowly turning purple 14 33.2 35.9 32.5 23.3 Unheated is fully purple with just the bottom left transparent water colour 15 32.2 37.5 34.3 23.7 Unheated flask is fully purple with just the bottom of the flask left with transparent water colour. *** You must have attended the lab to receive the corresponding lab marks for this section . Figure 2.5 : Simplified schematic representation of atmospheric circulation.

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 8 Question 2. Thinking about your experiment in lab and the diagram above (Figure 2.5), the addition to heat under the beaker would be equivalent to the addition of heat to which of the following latitudes in the Hadley Cell Circulation (see Textbook Pg. 123) (1 mark) ☐ a. 5 o N ☐ b. 30 o N ☐ c. 45 o N ☐ d. 65 o N Question 3. Thinking about your experiment in lab, the high-pressure zone created in the bottom of second beaker (right hand beaker in Figure 2.3) of the experiment would be represented by the pressure conditions at which of the following latitudes (1 mark) ☐ a. 5 o N ☐ b. 30 o N ☐ c. 45 o N ☐ d. 65 o N Question 4. Which number in the diagram (Figure 2.5) would correspond to the descending air of the Hadley Cell circulation? (Enter a number) (1 mark) 6 Question 5. Thinking about the diagram (Figure 2.5) and the concept of the Urban Heat Island (see Textbook pp. 105-107), which number would represent the direction of air movement, and/or pressure conditions over the center of the urban core of a large city. (Enter a number) (1 mark) 4 Question 6. The horizontal pressure gradient across the bottom of the beakers produces a movement of liquid from one beaker to the other and this is represented in the diagram (Figure 2.5) by which numbers. (Enter a number) (1 mark) 8 Question 7. With reference to the diagram, the subtropical high in the Hadley Cell circulation experienced on the Earth’s surface would be represented by which number in the diagram (Figure 2.5)? (Enter a number) (1 mark) 7

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 9 Question 8. Thinking of the experiment and the diagram (Figure 2.5), in which direction would advection at the surface take place in a large urban area experiencing the heat island effect? (1 mark) ☐ a. From the urban core to the suburban/rural fringe ☐ b. From the suburban/rural fringe to the urban core Question 9. Air convergence creates an area of low pressure and this is occurring at which number in the diagram (Figure 2.5) in the same way it would occur in the Intertropical convergence zone of the Hadley Cell system? (Enter a number) (1 mark) 2 Question 10. Which number in the diagram (Figure 2.5) would represent the breeze coming off Lake Ontario (onshore breeze) and blowing south into the Niagara Region, if there is warm air rising over the Niagara Region during the day and creating an area of low pressure while high pressure is created by air descending over Lake Ontario. (Enter a number) (1 mark) 7 Question 11. Consider the experiment you conducted, Figure 2.5 (above) and Figure 6.24a in the text. Which number in the diagram would represent the high-pressure conditions experienced on the surface during the Indian Monsoon for the winter season over Northern India, Nepal, Pakistan, Bhutan, Bangladesh and China. (Enter a number) (1 mark) 8

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GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 10 PART TWO – ADIABATIC PROCESSES Although it is generally considered that air temperature decreases with height in a uniform fashion in the troposphere, there are certain exceptions that may result in such meteorological phenomena as cloudiness and thunderstorm activity. In this portion of the lab, we will consider the behavior of air parcels, or "bubbles" of air, which rise from the surface and result in such conditions. A global average rate of temperature decrease with increasing height in the troposphere for all weather conditions is about 6.4 °C per 1000m, and is known as the normal temperature lapse rate (see Text Fig. 5.1 & 5.2 - note the Text quotes a value of 6.5°C per 1000m on pages 90-91). However, the lapse rate can vary considerably depending on local conditions, such as the nature and temperature of the earth's surface, or even the time of day ( remember this effect from the Net Radiation Lab? ). Temperature can even increase with height in a condition referred to as a temperature inversion (this is what’s responsible for the fog we typically see in the morning this time of year). This actual measured temperature change with height is known as the environmental temperature lapse rate (ETLR), and is often obtained by the use of weather balloons or radiosondes . While the overall air temperature varies according to the ETLR, when a parcel of air rises, it cools at a much more specific rate known as the adiabatic rate . This is due to its expansion in response to the decreasing density and pressure of the surrounding atmosphere with height. When this adiabatic cooling occurs in an air parcel that has not yet reached saturation, it does so at the dry adiabatic lapse rate (DALR) of 10°C per 1000m. If, during the ascent of an air parcel, it cools to the dew point temperature and becomes saturated (i.e., a relative humidity of 100%), it will no longer cool at the DALR, but rather at the saturated adiabatic lapse rate (SALR), which is often quoted as being 5°C per 1000m. Figure 2.6 : Radiation Fog

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 11 This value for the SALR, 5°C per 1000m, is not constant, however, and varies according to the temperature, pressure and moisture content of the air. Since the air is saturated, and condensation is actively occurring during the ascent of the air parcel, there is a significant release of the latent heat of condensation, thus adding heat to the system and reducing the rate of cooling. Note, in fact, that the SALR is half the value of the DALR. That is, due to the release of this latent heat of condensation into the parcel of air, it cools only 5°C for every 1000m it rises, rather than the rate of 10°C per 1000m it cools when it is not saturated. The quantity of latent heat release is, as you would expect, dependent on the amount of water vapour in the air. As condensation occurs, this amount decreases, thus reducing the latent heat release and the associated heating effect. For simplicity, however, we will generally consider SALR as having a constant value of 5°C per 1000m. Conversely, if a parcel of air descends, it will warm at the DALR, since as soon as it descends and begins to warm, it will be at a point less than saturation, or 100% relative humidity. It is the relationship between these adiabatic lapse rates and the environmental lapse rates that determines the state of stability of the atmosphere. If a parcel of air rises, and remains cooler than the surrounding air, the parcel will be denser (i.e., heavier) and will tend to sink back down as soon as the force causing it to rise is removed. This situation is referred to as being stable . Air is stable, therefore, when the environmental lapse rate is numerically less than the adiabatic lapse rate (either the DALR or SALR, whichever is applicable at the height in question). If, however, a parcel of air is forced to rise and is warmer than the surrounding environment, it will consequently be more buoyant (i.e., lighter, like a hot air balloon) and will continue to rise. This is an unstable situation. Air is unstable when the environmental lapse rate is greater than the adiabatic rate (either the DALR or SALR whichever is applicable at the height in question). The situation may also occur, where a parcel of air is stable below a certain elevation, but if forced to rise above a certain height would become unstable. This is known as conditional instability , and prevails when the environmental lapse rate lies between the dry and the saturated adiabatic rates. A common situation in which this occurs is during periods of temperature inversions (e.g., see Fig. 5.3, pg. 92 in the Text) . These three situations are diagrammatically represented in Figure 2.7.

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 12 As clouds are merely condensed water vapour in the atmosphere, they begin to form at the elevation at which the air parcel becomes saturated, ceases to cool at the DALR and begins to cool at the SALR. This height is referred to as the Lifting Condensation Level , or LCL The temperature at this height, where saturation is reached and condensation begins, is referred to as the dew point temperature . The cumulus clouds resulting from such instability, as illustrated in Figure 2.6, may lead to the scattered thundershowers sometimes experienced on hot summer days. The Lifting Condensation Level can be easily calculated if the surface temperature and the surface dew point temperature of the air are known. So, here are the formulae and values to use: T LCL = T 0 - H LCL ´ DALR ( ) H LCL = 1000 ´ T 0 - T dew 8.2 æ è ç ö ø ÷ where: T LCL = Temperature of the parcel at the height of the Lifting Condensation Level H LCL = Height of the Lifting Condensation Level, in metres T o = Surface temperature, in °C T dew = Dew Point temperature, in °C DALR = Dry Adiabatic Lapse Rate = 10°C 1000 m -1 Figure 2.7 : Cumulonimbus Cloud resulting from Atmospheric Instability

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GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 13 Figure 2.8 Stable, Unstable, and Conditionally Unstable Atmospheric Conditions

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 14 GRAPH ONE . On a sheet of graph paper (or using Microsoft Excel), plot the specified environmental temperature lapse rate (ETLR), the dry adiabat (DALR), and the saturated adiabat (SALR) corresponding to the following surface conditions: Surface Temperature: 25°C Dew Point Temperature: 15°C Note that from this information you have to calculate the height of the Lifting Condensation Level, from the formula for H LCL , so you know at what height to switch from drawing the DALR (= 10°C 1000 m -1 ) to drawing the SALR (= 5°C 1000 m -1 ). You can confirm this value by also calculating the temperature of the rising parcel of air at the LCL, or the value of T LCL . The point defined by (T LCL , H LCL ) should fall on the line you’ve drawn to represent the DALR. On the same graph, plot an environmental temperature lapse rate (ETLR) of 12°C 1000 m -1 . Note this line begins at the surface at the same temperature as given in Step 1 above, as the parcel and the environment are the same at the surface (i.e., the parcel of air comes from the environment). Question 12. Save the graph as a JPEG or upload a screen capture, scan or a photo of your plot of the specified DALR, SALR and ETLR. Screen captures, photos, or scans should be cropped appropriately to only show your graph and not the area around it. Insert graph here: (5 marks) Question 13. What did you calculate for the following values in this example? (Final answer is fine – rounded to one decimal place) (2 marks) H LCL = 1215.5

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 15 T LCL = 12.8 Question 14. Which stability class is represented by this situation? (1 mark) stable Question 15. With reference to the plot you’ve just made, explain which stability class (i.e., stable, unstable, or conditionally unstable) the parcel of air rising from the surface can be categorized as. (2 marks) stable GRAPH TWO. On a separate sheet of graph paper (or using Microsoft Excel), repeat the steps from graph one for the following conditions: Surface Temperature: 26°C

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GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 16 Dew Point Temperature: 6°C Environmental Temperature Lapse Rate: 5°C per 1000 m Question 16. Save the graph as a JPEG or upload a screen capture, scan or a photo of your plot of the specified DALR, SALR and ETLR. Screen captures, photos, or scans should be cropped appropriately to only show your graph and not the area around it. Insert graph here: (5 marks) Question 17. What did you calculate for the following values in this example? (Final answer is fine – rounded to one decimal place) (2 marks) H LCL = T LCL = Question 18. Which stability class is represented by this situation? (1 mark) Type your answer here : stable

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 17 Question 19. With reference to the plot you’ve just made, explain which stability class (i.e., stable, unstable, or conditionally unstable) the parcel of air rising from the surface can be categorized as. (2 marks) Type your answer here : GRAPH THREE. On a separate sheet of graph paper, repeat Step 1 for the following conditions: Surface Temperature: 25°C Dew Point Temperature: 16°C

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 18 For the environmental lapse rate (ETLR), we’ll now consider the effects of a temperature inversion. In this case, the temperature doesn’t uniformly decrease with height. Rather, the temperature actually increases with height for a while, followed by the usual decrease as you move higher. This situation is very common, particularly when the sky is clear at night (highly negative R n ), and can lead to radiation fog at the surface early in the morning. From the surface, up to a height of 500 m, use an ETLR of 7°C 1000 m -1 showing an increase of temperature with height. At that point, begin using an environmental temperature lapse rate, ETLR, of 15°C 1000 m -1 , showing the usual decrease of temperature with height. Question 20. Save the graph as a JPEG or upload a screen capture, scan or a photo of your plot of the specified DALR, SALR and ETLR. Screen captures, photos, or scans should be cropped appropriately to only show your graph and not the area around it. Insert graph here: (6 marks) Question 21. What did you calculate for the following values in this example? (Final answer is fine – rounded to one decimal place) (2 marks) H LCL =

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GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 19 T LCL = Question 22. Which stability class is represented by this situation? (1 mark) Type your answer here : Question 23. With reference to the plot you’ve just made, explain which stability class (i.e., stable, unstable, or conditionally unstable) the parcel of air rising from the surface can be categorized as. (3 marks) Type your answer here : Please note that all answers will be submitted through the class page on the school LMS. Submitting your Assignment

GEOG 1F91 – Fall 2023 LAB 2 – Convection and Motion and Adiabatic Processes 20  Make sure you have re-named your Word document file containing your answers so that it properly identifies you as the submitter. e.g. GEOG1F91_Lab#2_Doe_John_99887766_Section13  Sign into Brightspace.  Under the ‘Assignments’ tab in the main Navigation bar of the 1F91 Brightspace course site, select Lab Assignment #2.  Once in the Assignment page, upload your Word document file containing your answers. Due Date Lab Assignment #2 “Convection and Motion and Adiabatic Processes” is due by 11:59 pm the night before your next scheduled lab meeting. You have two (2) weeks to complete and submit your assignment by its due date. Make sure to carefully check the schedule to know exactly when your due date is. All submissions through Brightspace are time-stamped. Late assignments will not be marked.

GEOG1F91_Lab#2_Josh Sra_7570104

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