# Physical geography: follow a parcel through a threshold, not a slogan — Study worksheet [Study guides](https://unireadinglist.com/guides/physical-geography/) [Course topic: Physical Geography](https://unireadinglist.com/subjects/geography/#course-physical-geography) Sources checked: 2026-11-04 Study route and exercise: University Reading List editorial project. For learners comfortable with temperature differences, kilometers and linear equations. The worksheet supplies idealized lapse rates and water-removal assumptions; it is not a weather forecast. The free introductory text provides accessible landform and atmosphere context, while the other books support broader systems comparisons. ## Choose your starting point - [ ] I need a free physical-geography entry Use Patrich’s selected Version 2 for the atmosphere, weather and landform context. Turn each process explanation into a diagram with inputs and changes. - [ ] I want an integrated systems survey Use Geosystems to connect atmosphere, water, land and energy. Keep the assigned eleventh-edition print distinct from its later copyright label. - [ ] I want an explicit physical-systems framework Use Smithson, Addison and Atkinson for energy, atmospheric moisture and linked environmental systems. Select physical principles rather than treating an older edition as a current climate-data source. ## Compare the three books ### Physical Geography Jeremy Patrich · 2 · 2023 Free introductory context Choose it when: You want an accessible physical-geography route with regional examples and process diagrams. Use another route when: You need a quantitative meteorology course or assume every linked illustration has identical reuse terms. Selected reading: Selected 2023 Version 2: atmospheric energy, moisture, weather and orographic/rain-shadow discussions, chosen by subject. Limits and trade-offs: The authored text is free under CC BY 4.0 except where otherwise noted. The college catalogue and the specific 2023 text are distinguished from later folder contents. #### Try before choosing Draw an ascent/descent path and mark where expansion, cooling, saturation and water removal enter the model. Check your work: Rising air expands as ambient pressure falls; do not describe cooling as contraction. Saturation is a threshold to calculate, not assume at the foot of every mountain. Your notes: ________________________________ [Official free reading](https://drive.google.com/file/d/19D8e7oOejAuel8GpVYs7F_w7gJN7Glxn/view) [Book record and access options](https://unireadinglist.com/subjects/geography/physical-geography/) ### Geosystems: An Introduction to Physical Geography Robert W. Christopherson; Ginger H. Birkeland · 11 · 2026 Integrated systems survey Choose it when: You need a broad course spine connecting energy, water and landform processes. Use another route when: You want every mountain explained by a single universal lapse rate or by a publisher date alone. Selected reading: Eleventh edition: atmospheric moisture, weather and physical-system connections by topic. Limits and trade-offs: The selected print ISBN 9780135485583 has a 2026 publication listing with ©2027 product labeling. Other digital products have different identifiers. #### Try before choosing Write a system boundary for the parcel and list the exchanges the worksheet excludes. Check your work: A closed classroom path cannot silently import entrainment, radiation, precipitation quantities or observed regional weather. Your notes: ________________________________ ISBN: 9780135485583 [Book record and access options](https://unireadinglist.com/subjects/geography/geosystems-an-introduction-to-physical-geography/) ### Fundamentals of the Physical Environment Peter Smithson; Ken Addison; Ken Atkinson · 4 · 2008 Process-oriented systems reference Choose it when: You want to connect energy flows, moisture and environmental subsystems. Use another route when: You need current observational climate statistics from a 2008 edition or a short first introduction without selection. Selected reading: Fourth edition: energy and atmospheric heat, moisture and precipitation discussions; connect to regional systems afterward. Limits and trade-offs: Its older publication does not invalidate basic physical reasoning, but dated examples and current observations require separate sources. #### Try before choosing Derive the temperature difference’s closing rate before solving the condensation height. Check your work: Subtract the dew-point decline from the dry temperature decline; neither supplied rate alone determines the threshold. Your notes: ________________________________ ISBN: 9780415395168 [Book record and access options](https://unireadinglist.com/subjects/geography/fundamentals-of-the-physical-environment/) ## Check your preparation ### What is a lapse rate here? Your notes: ________________________________ ### When does the rule change? Your notes: ________________________________ ### What controls the return path? Your notes: ________________________________ ## A six-step study plan - [ ] Draw the physical path Selected reading: Patrich atmospheric moisture and weather. What to do: Sketch sea level, summit and sea-level lee end, labeling heights and parcel state. Check your work: Do not confuse a moving parcel’s path with a measured environmental profile. Your notes: ________________________________ - [ ] Specify rates and units Selected reading: Selected heat/moisture reading. What to do: Write separate temperature and dew-point equations below saturation. Check your work: Every rate has units °C/km and every height is in km. Your notes: ________________________________ - [ ] Find the threshold Selected reading: Smithson and colleagues moisture discussion. What to do: Solve T(h)=Td(h) and check it lies below the summit. Check your work: A threshold outside the path cannot trigger the moist segment. Your notes: ________________________________ - [ ] Complete the high path Selected reading: The original worksheet. What to do: Calculate condensation level, summit and lee temperatures in order. Check your work: Use the moist rule only for ascent above the threshold. Your notes: ________________________________ - [ ] Lower the mountain Selected reading: The solved follow-up. What to do: Recompute for a 1 km summit and derive the piecewise lee-temperature function. Check your work: Continuity at 1.5 km is a useful check, not a reason to use the same slope everywhere. Your notes: ________________________________ - [ ] State the physical limits Selected reading: Geosystems linked-system reading. What to do: List what would be needed to infer rainfall amount, humidity or actual local weather. Check your work: Temperature rules alone do not supply a water-mass budget or a forecast. Your notes: ________________________________ ## Worked exercise: Original ideal parcel: a 3 km mountain crosses the saturation threshold At sea level an invented air parcel has temperature T=24°C and dew point Td=12°C. It rises to a 3 km summit and returns to sea level on the lee side. Below saturation T falls 10°C/km and Td falls 2°C/km. Find the condensation height, summit temperature and final lee temperature. Assumptions: Use these exact classroom rules: at T=Td saturation begins; subsequent ascent cools at 6°C/km with Td=T. All condensate is removed, no liquid remains for descent, and descent warms at 10°C/km. Exclude entrainment, radiation and other exchanges. These constants are supplied approximations, not universal moist rates. Your notes: ________________________________ ## Change an assumption: Changed summit: a lower mountain never reaches saturation Change only the summit to 1 km, with the same initial state and path rules. Then express the final sea-level lee temperature as a function of summit height h for 0≤h≤3 km. Your notes: ________________________________ ## Before moving on - I can derive the threshold from two changing temperatures. - I can reproduce the segment ledger and continuous piecewise return function. - I can name the water and exchange assumptions limiting the result. ## Answer and interpretation ### What is a lapse rate here? A stipulated temperature change per kilometer along the parcel’s vertical path, not the surrounding atmosphere’s measured temperature profile. ### When does the rule change? At the first height where parcel temperature equals its dew point. Above that threshold this packet replaces the dry rule with the supplied moist rule. ### What controls the return path? All condensate is removed and no liquid remains available to evaporate during descent. The packet stipulates dry warming on descent; changing that water assumption could change the result. ### Original ideal parcel: a 3 km mountain crosses the saturation threshold 1. Before saturation T(h)=24−10 h and Td(h)=12−2 h, with h in km. Equality gives 12=8 h, so the condensation height is 1.5 km. T=Td=9°C there. 2. The remaining ascent is 3−1.5=1.5 km at 6°C/km, cooling another 9°C. Summit temperature is 0°C. 3. With all condensate removed and dry descent stipulated, 3 km descent warms 30°C. The lee temperature at sea level is 30°C. 4. The parcel ends 6°C warmer than its initial 24°C. In this packet the unequal ascent/descent slopes above condensation explain that difference; no rainfall amount or final relative humidity follows from the given temperature rules alone. Condensation begins at 1.5 km and 9°C; the summit is 0°C; the sea-level lee end is 30°C, 6°C above the start. Test the result: Check every segment’s height and units: −15−9+30=+6°C overall. A rain-shadow context does not authorize a rainfall estimate without additional moisture information. ### Change an assumption: Changed summit: a lower mountain never reaches saturation 1. At 1 km, T=24−10=14°C and Td=12−2=10°C. The parcel is unsaturated, so no moist-ascent segment occurs. Descent adds 10°C and returns T to 24°C. 2. For 0≤h≤1.5 km, the dry ascent loses 10 h and dry descent gains 10 h, giving Tlee=24°C. At exactly 1.5 km there is no positive-length moist segment. 3. For 1.5\