Atmosphere & Weather — Chapter Practice, Grade 9

Trace water and energy through the atmosphere and interpret changing weather evidence.

Problem 1

Which process changes liquid water into water vapor, mostly from the surface of the ocean?
  1. Evaporation
  2. Condensation
  3. Precipitation
  4. Infiltration
Answer and explanation

Evaporation

The sun's energy heats liquid water until it evaporates into invisible water vapor.

Problem 2

What is it called when plants release water vapor through their leaves?
  1. Transpiration
  2. Respiration
  3. Condensation
  4. Sublimation
Answer and explanation

Transpiration

Transpiration is water vapor released through tiny openings in plant leaves; combined with evaporation, it's called evapotranspiration.

Problem 3

Rising air cools, and water vapor changes into the tiny liquid droplets that form clouds. What is this process called?
  1. Precipitation
  2. Condensation
  3. Runoff
  4. Evaporation
Answer and explanation

Condensation

Condensation happens when rising, cooling air causes water vapor to turn back into liquid droplets, forming clouds.

Problem 4

About what percent of all the water on Earth is salty ocean water?
Answer and explanation

97 %

Around 97% of Earth's water is salty ocean water; only about 3% is freshwater, and most of that is locked up as ice.

Problem 5

The water cycle is powered by two forces. Name both, and explain which part of the cycle each one drives.
Answer and explanation

The sun's energy drives evaporation and transpiration, lifting liquid water into the air as vapor. Gravity pulls condensed water back down as precipitation and pulls runoff downhill into rivers, lakes, and groundwater.

Problem 6

A covered cold glass collects water outside. Explain its likely source. Explain the reasoning in your own words.
Answer and explanation

The droplets can come from the air, rather than leaking through the glass.

Moist air contacts the colder surface and cools.

Some water vapor condenses into liquid on the outside.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 7

Name a water-cycle route from soil to atmosphere through plants. Show the reasoning, not just the conclusion.
Hints

Matter cycling does not mean energy follows the same closed loop.

Answer and explanation

Root uptake followed by transpiration releases water to the atmosphere.

Problem 8

Why can a local lake shrink even though global water is conserved?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Its local outflows can exceed inflows; global conservation does not require constant storage in each reservoir.

Problem 9

Equal rainfall can produce different surface pathwaysEqual rainfall can produce different surface pathwaysVolume in one supplied test (mL)Rain input100Runoff35Infiltration45Surface storage20100 = 35 + 45 + 20; equal rain can partition differently.
Original supplied short-test water partition. The 100 mL input is balanced by runoff, infiltration and temporary surface storage. Actual precipitation-to-runoff behavior also depends on conditions and additional terms; the diagram is not a universal landscape partition.
Interpret the supplied visual model. If runoff becomes 55 mL and surface storage stays 20 mL with the same 100 mL input, what infiltration remains under the stated model?
Answer and explanation

25 mL, because 100−55−20 = 25. The calculation assumes all relevant transfers and stores have been included over the matched interval.

Account for all the stated pathways over the same test interval. The bars are volumes rather than rates; the example neglects evaporation during the short test.

25 mL, because 100−55−20 = 25. The calculation assumes all relevant transfers and stores have been included over the matched interval.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 10

A lake starts at 250 m³. Daily input is 40 m³ and output 28 m³ for five days. Find final storage and explain why the height change cannot be determined from these data alone.
Answer and explanation

Net input is 12 m³/day, so storage gains 60 m³ and reaches 310 m³. Lake area/shape or a volume-level relationship is needed for height change.

Subtract 40−28 = 12 m³/day.

Multiply by five days to obtain 60 m³ and add to 250.

Distinguish volume from height and request geometry.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 11

A surface receives 200 units and reflects 50. How many are absorbed if none pass through?
Answer and explanation

150 units

200 − 50 = 150.

Problem 12

Condensation generally…
  1. absorbs energy from surrounding air
  2. releases energy to surrounding air
  3. destroys water molecules
  4. requires sunlight in every case
Answer and explanation

releases energy to surrounding air

The phase change releases energy.

Problem 13

Why can a global wind belt fail to predict wind at one sheltered valley?
Answer and explanation

Local terrain and conditions modify large-scale circulation.

Problem 14

Two identical dry tiles, one dark and one light, receive the same sunlight. Predict a difference and name a control. Explain the reasoning in your own words.
Answer and explanation

The dark tile may warm more under the controlled conditions; real outdoor surfaces require additional evidence.

The dark tile is expected to absorb a larger share of sunlight.

Keep material, thickness, exposure and starting temperature comparable.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 15

Why does unequal solar heating help drive atmospheric circulation? Show the reasoning, not just the conclusion.
Hints

Actual circulation also depends on larger-scale wind and geography.

Answer and explanation

It creates temperature and pressure differences that move air and redistribute energy.

Problem 16

What distinguishes convection from radiation in an atmospheric energy diagram?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Convection transports energy with moving matter; radiation transfers energy electromagnetically.

Problem 17

Right and left are relative to motion, not always east and westRight and left are relative to motion, not always east and westNorthern Hemisphere: right of motionSouthern Hemisphere: left of motionBlue: selected motion. Red: deflection.
Original selected-direction Coriolis diagrams in a top-view Earth frame. Arrows compare direction only and do not represent measured accelerations. The effect depends on latitude and speed; friction and other forces are omitted.
Interpret the supplied visual model. In the Northern Hemisphere, what direction is right of an eastward-moving parcel?
Answer and explanation

Southward. Coriolis changes direction relative to the moving parcel; it does not always deflect east and does not initiate motion from rest.

Turn mentally to face each blue motion arrow, then identify its right or left side. Do not read right as a fixed page compass direction.

Southward. Coriolis changes direction relative to the moving parcel; it does not always deflect east and does not initiate motion from rest.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 18

A Northern Hemisphere air parcel initially moves north, while another moves east. Give the Coriolis deflection direction for each and explain why the effect does not begin a wind from rest.
Answer and explanation

Right of northward motion is east, and right of eastward motion is south. Coriolis modifies existing motion in the rotating Earth frame; pressure-gradient or other forces initiate the wind. The complete wind also depends on friction and other forces.

Right of northward motion is east, and right of eastward motion is south. Coriolis modifies existing motion in the rotating Earth frame; pressure-gradient or other forces initiate the wind. The complete wind also depends on friction and other forces.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 19

A continental polar (cP) air mass is best described as...
  1. Cold and dry
  2. Cold and moist
  3. Warm and dry
  4. Warm and moist
Answer and explanation

Cold and dry

'Continental' means it formed over land (dry), and 'polar' means it formed at a cold latitude.

Problem 20

The boundary where two different air masses meet is called a...
  1. Front
  2. Barometer
  3. Isobar
  4. Station model
Answer and explanation

Front

The boundary between two air masses is a front — it's where the most active weather usually happens.

Problem 21

Which statement correctly compares cold fronts and warm fronts?
  1. Cold fronts move fast and bring brief, intense weather; warm fronts move slowly and bring longer, lighter weather.
  2. Cold fronts move slowly and bring long light rain; warm fronts move fast and bring brief storms.
  3. Both move at the same speed and bring identical weather.
  4. Warm fronts only occur in summer.
Answer and explanation

Cold fronts move fast and bring brief, intense weather; warm fronts move slowly and bring longer, lighter weather.

Cold fronts are steep and fast-moving, causing quick, intense weather; warm fronts are gradual and slow-moving, causing longer, gentler weather.

Problem 22

A region is experiencing sinking air and generally clear, fair weather. This region most likely has...
  1. High pressure
  2. Low pressure
  3. A stationary front
  4. An occluded front
Answer and explanation

High pressure

Sinking air piles up near the ground, creating high pressure and generally fair weather.

Problem 23

Standard sea-level air pressure is about 1013 millibars. A barometer reading of 998 millibars most likely signals...
  1. A low-pressure system, with cloudier, stormier weather ahead
  2. A high-pressure system, with clear, calm weather ahead
  3. No change in the weather at all
  4. A broken barometer
Answer and explanation

A low-pressure system, with cloudier, stormier weather ahead

A reading well below the roughly 1013-millibar average indicates lower-than-average pressure, which is associated with rising air and increasing clouds or storms.

Problem 24

Explain why wind blows from high-pressure areas toward low-pressure areas.
Answer and explanation

Air naturally flows from where it is denser and pressing down harder (high pressure) toward where it is less dense and pressing down less (low pressure), trying to balance out the difference — that flow of air from high to low is what we feel as wind.

Problem 25

A station records a wind shift, falling temperature and a band of rain passing through. What front model fits? Explain the reasoning in your own words.
Answer and explanation

A passing cold front is plausible; a map and additional observations would test it.

A cooler air mass replacing warmer air fits the temperature drop.

The wind shift and precipitation add supporting evidence.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 26

Why can warm air rising along a front form clouds? Show the reasoning, not just the conclusion.
Hints

A front does not guarantee identical weather everywhere.

Answer and explanation

Expansion and cooling can bring air to saturation, allowing condensation.

Problem 27

What information besides pressure helps interpret an air mass?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Temperature, humidity, origin region and movement provide important context.

Problem 28

Frontal geometry can lift air; moisture and stability determine the outcomeFrontal geometry can lift air; moisture and stability determine the outcomeCold front: cooler air advances under warmer airCooler airLifted warmer airUplift plus moisture/stability conditions can support cloud formation.
Original cold-front cross-section with qualitative density contrast and uplift. Layer slopes and arrow lengths are not measured values. The text compares warm-front geometry separately and identifies the conditions omitted from this simple cross-section.
Interpret the supplied visual model. Why does the lifting shown here not prove that every location along the front must have the same precipitation?
Answer and explanation

Available moisture, stability, local flow and timing vary. Lifting supplies a process, while those conditions influence whether and how precipitation develops.

Trace the cool-air advance separately from the warmer-air uplift. The sloping boundary is a schematic cold front, not an identical geometry for every front.

Available moisture, stability, local flow and timing vary. Lifting supplies a process, while those conditions influence whether and how precipitation develops.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 29

Two maps have the same ground scale. Map A shows a 4 hPa change over 100 km; map B a 2 hPa change over 25 km. Compare pressure-gradient magnitudes and explain why neither gives a full wind direction alone.
Answer and explanation

A is 0.04 hPa/km; B is 0.08 hPa/km, twice as large. Actual wind also responds to rotation and friction, so pressure-gradient magnitude alone is not a complete directional forecast.

Calculate 4/100 and 2/25 in matched units.

Compare 0.08 with 0.04: factor two.

Include rotation/friction and distinguish pressure-gradient force from wind.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 30

On a weather map, a line connecting all points with the same air pressure is called a(n)...
  1. Isobar
  2. Isotherm
  3. Front
  4. Station model
Answer and explanation

Isobar

Isobars connect points of equal air pressure — 'iso' means equal and 'bar' refers to pressure.

Problem 31

Which instrument measures air pressure?
  1. Barometer
  2. Anemometer
  3. Hygrometer
  4. Rain gauge
Answer and explanation

Barometer

A barometer measures air pressure; an anemometer measures wind speed, a hygrometer measures humidity, and a rain gauge measures precipitation.

Problem 32

In the mid-latitudes, including New York State, weather systems generally move...
  1. From west to east
  2. From east to west
  3. From north to south only
  4. Randomly, with no general pattern
Answer and explanation

From west to east

The prevailing westerlies and the jet stream generally steer mid-latitude weather from west to east.

Problem 33

Isobars on a weather map are packed very closely together over a region. What does this most likely indicate?
  1. Strong winds, due to a big pressure difference over a short distance
  2. Calm winds, because the pressure is very steady
  3. An approaching heat wave with no wind
  4. That the map has an error
Answer and explanation

Strong winds, due to a big pressure difference over a short distance

Tightly packed isobars mean pressure changes quickly over a short distance, and bigger pressure differences drive stronger winds.

Problem 34

A barometer reads 1020 mb at 6 a.m. and 1002 mb at noon, six hours later. By how many millibars did the pressure fall?
Answer and explanation

18 mb

1020 − 1002 = 18 mb. That's a fairly rapid fall, often a sign that stormier weather is on the way.

Problem 35

A front moves 180 km between maps taken 6 h apart. Find its average speed and one forecasting limit. Explain the reasoning in your own words.
Answer and explanation

30 km/h over the measured interval; a later arrival estimate needs continued observations.

Average speed=180/6=30 km/h.

Future speed or direction can change, so straight extrapolation is an assumption.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 36

A radar image shows precipitation moving east. What extra information improves arrival-time prediction? Show the reasoning, not just the conclusion.
Hints

A forecast is conditional and updated with new evidence.

Answer and explanation

Distance to the location and movement speed/direction over successive images, with allowance for growth or decay.

Problem 37

Why should forecast confidence be lower farther into the future?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Initial-state uncertainty and evolving interactions can amplify differences in predictions.

Problem 38

Agreement about passage can coexist with uncertain arrival timeAgreement about passage can coexist with uncertain arrival timeFront movement from initial position (km)03060901200123Forecast lead time (h)Model A: 40 km/hModel B: 30 km/h
Original illustrative constant-speed front trajectories for timing comparison. They are not an operational forecast ensemble or a calibrated probability interval. The record distinguishes event agreement from uncertainty about timing.
Interpret the supplied visual model. At a place 60 km ahead, what arrival times do the two supplied models imply?
Answer and explanation

1.5 h at 40 km/h and 2 h at 30 km/h, assuming steady speed along the stated path. Actual movement can evolve.

The curves share an initial position and direction but differ in slope. The vertical axis is travel distance, not temperature or precipitation probability.

1.5 h at 40 km/h and 2 h at 30 km/h, assuming steady speed along the stated path. Actual movement can evolve.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 39

A front is 90 km from a town. Model A gives steady motion 30 km/h and model B 45 km/h. Calculate the two arrival times and define a fair observation-based timing check.
Answer and explanation

A gives 3 h and B 2 h. Record the forecast issue time, defined passage indicator/location and predicted intervals, then compare with later observations using the original criteria. Changing criteria after the event undermines verification.

A gives 3 h and B 2 h. Record the forecast issue time, defined passage indicator/location and predicted intervals, then compare with later observations using the original criteria. Changing criteria after the event undermines verification.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 40

OpenSciEd table for Chanute Martin Johnson Station, Kansas, with observation times, temperature in degrees Fahrenheit, relative humidity percent, wind speed and gust in miles per hour during the Fort Scott hail case.
Actual historical station record from the Fort Scott case, OpenSciEd 6.3. Use the 3:52 PM and 4:52 PM rows and distinguish the wind-speed and gust columns. Observed station weather in the Fort Scott case · OpenSciEd · 6.3 Weather, Climate & Water Cycling, Lesson 2, source, CC BY 4.0. Figure excerpt rendered from the PDF and resized for the web.
Using the actual station record, calculate the changes from 3:52 PM to 4:52 PM in temperature (°F and °C), relative humidity (percentage points) and wind speed (mph). For a temperature difference, Δ°C = Δ°F × 5/9. Explain what these simultaneous changes support and why they do not by themselves prove a particular front, exact hailfall location or complete cause.
Answer and explanation

Temperature changes from 68 to 59 °F: −9 °F, equivalent to −5 °C. Relative humidity changes from 68% to 78%: +10 percentage points, not a 10% relative increase. Wind speed changes from 12 to 30 mph: +18 mph. The observations support a changing atmospheric situation at the named station; mapped front/pressure, wind direction, moisture and event-location evidence would help test causes. A humidity increase alone does not prove more water vapor, because saturation conditions change with temperature.

Read matching times and the correct source columns before subtracting.

Subtract later minus earlier: 59−68 = −9 °F; multiply the difference by 5/9 to obtain −5 °C. Do not subtract 32 when converting a temperature difference.

Compute 78−68 = 10 percentage points and 30−12 = 18 mph; gusts are a separate column.

State the station scale and time interval, then request independent mapped/process evidence rather than claim a unique cause.

Response criteria

  • All changes use later minus earlier and retain correct units.
  • Temperature-difference conversion and percentage-point distinction are correct.
  • The inference is limited to the stated record and identifies evidence needed for a causal explanation.

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