Weather and climate quiz

Answer key

1. Nitrogen. Nitrogen accounts for about 78% of dry air, while oxygen contributes about 21%. “Dry” excludes water vapor, whose amount changes with location and conditions.
2. Troposphere. The troposphere starts at the surface and contains almost all weather. Its upper boundary varies in height, so it is a layer rather than one fixed altitude.
3. It is lower. Pressure generally decreases with elevation because less air lies above the station. The atmosphere thins gradually; reaching a mountaintop does not remove all the air.
4. Thermometer. A thermometer measures temperature. Pressure, rainfall, and wind direction are separate weather variables, so their instruments cannot substitute for a temperature measurement.
5. Barometer. Barometers measure atmospheric pressure. Hectopascals and millibars are equivalent pressure units; neither is a unit of wind speed or temperature.
6. Anemometer. An anemometer records how fast air is moving. Wind direction is a different quantity, which is why a station may use both an anemometer and a vane.
7. Wind vane. A wind vane indicates wind direction. Its turning arrow provides a compass direction rather than a temperature, precipitation total, or pressure reading.
8. The depth of water collected for that period. Rain gauges report accumulated precipitation as a water depth over a stated period. The reading describes an amount of rainfall, not cloud height or individual drop size.
9. Measurements of conditions at different heights. A radiosonde measures temperature, humidity, and pressure as it rises and transmits the data. Tracking its movement also helps determine winds above the surface.
10. It sends radio pulses and measures returning echoes. Radar pulses scatter from precipitation particles, and some energy returns to the instrument. The return time helps determine distance, allowing a radar to map precipitation beyond its location.
11. Water vapor is water in an invisible gaseous state. Water vapor is gaseous water and is invisible. A visible cloud contains suspended liquid droplets, ice crystals, or both, rather than being a visible mass of the gas itself.
12. Evaporation. Evaporation changes liquid water into gas and requires energy. Water leaving the puddle enters the atmosphere as vapor; it has not ceased to exist.
13. Condensation. Condensation converts gaseous water into liquid and releases heat. It reverses evaporation; melting instead begins with solid ice, not water vapor.
14. Reaches saturation when cooled. The dew point describes saturation for that air’s existing moisture content. Reaching it does not specify whether precipitation will fall or whether any precipitation will be snow.
15. It decreases. Relative humidity compares water vapor with the saturation amount at the current temperature. Warming raises that saturation amount, so the same vapor content represents a smaller percentage.
16. It expands as surrounding pressure falls. Lower pressure lets rising air expand, which cools the parcel. If it cools sufficiently toward saturation, condensation can form cloud droplets on small particles.
17. Ice crystals. Cirrus form high in the atmosphere and consist of ice crystals. Their wispy appearance differs from the thicker towers and layers associated with other cloud types.
18. Stratus. Stratus refers to a layered cloud form. The word helps distinguish widespread sheets from the separate, puffy masses described by cumulus.
19. Cumulus. Cumulus clouds develop as rising air condenses and often look like separate rounded heaps. A layered sheet is stratus, while high hairlike clouds are cirrus.
20. Its droplets are suspended at Earth’s surface. Fog consists of tiny water droplets suspended near the surface. Like other liquid-water clouds it contains droplets; its position near the ground distinguishes it.
21. From higher pressure toward lower pressure. Differences in pressure create a force toward lower pressure. Earth’s rotation and friction modify actual wind direction, so real winds need not travel in a straight line between pressure centers.
22. Air pressure. Isobars join equal pressure values. Their spacing shows how quickly pressure changes across distance; closely spaced lines indicate a stronger pressure gradient.
23. The north. Wind direction is named for where the wind originates. A northerly wind therefore blows from the north toward the south, rather than toward the north.
24. From water toward land. Land heats more rapidly than nearby water during the day. Rising air over the warmer land helps draw cooler air inland from the sea.
25. The right. The deflection is to the right relative to the direction of travel in the Northern Hemisphere. It is to the left in the Southern Hemisphere, not a universal eastward turn.
26. Air masses with different characteristics. Fronts separate air masses, commonly with contrasts in temperature and moisture. They are atmospheric boundaries and may move or remain nearly stationary.
27. Colder air advances into warmer air. A cold front is the leading edge of advancing colder air. The denser cold air can lift warmer air ahead of it; “cold” describes the advancing side.
28. Stationary front. A stationary front is a boundary with little movement. The word does not mean that winds stop or that weather on either side must be identical.
29. An occluded front forms. Occlusion occurs as the cold front catches the warm front and lifts the intervening warm air above the surface. It is a change in frontal structure, not the end of all weather.
30. A narrow band of strong winds high in the atmosphere. Jet streams are concentrated bands of fast upper-level winds, generally flowing west to east. Their paths shift and bend, influencing the movement of weather systems below.
31. Cumulonimbus. Cumulonimbus clouds grow vertically and can reach high into the atmosphere. Their strong rising air and storm processes distinguish them from thin veils or shallow cloud layers.
32. Moisture, instability, and lift. Moisture supplies water, instability allows air to keep rising, and lift starts that upward motion. No single ingredient guarantees a storm without the others and suitable conditions.
33. An electrical discharge between regions of different charge. Charge separates within a storm, creating an electrical potential difference. Lightning transfers electrical charge through a discharge, which may occur within a cloud or between cloud and ground.
34. Rapid heating and expansion of air along a lightning channel. Lightning heats the surrounding air extremely rapidly. The resulting expansion produces a pressure wave that travels outward as sound; thunder is not the sound of clouds colliding.
35. Light travels much faster than sound. The flash and thunder come from the same discharge, but their signals travel at different speeds. Light reaches an observer far sooner than the sound wave.
36. It keeps ice aloft where supercooled droplets can freeze onto it. Rising air can support hail while supercooled water droplets add ice to it. A stone falls when it becomes too heavy for the updraft to support.
37. The rotating air column reaches the ground. A tornado is a rotating column of air connected to a storm and in contact with the ground. Its condensation funnel may not show the entire column.
38. Heat released when evaporated ocean water condenses. Warm water supplies moisture through evaporation. When vapor condenses in storm clouds, released heat supports rising air and the cyclone’s circulation; warm water alone is not sufficient for formation.
39. In the eye. The eye usually has sinking air, fewer clouds, and lighter winds than its surroundings. The ring of rising thunderstorms around it is the eyewall.
40. The eyewall. The eyewall is a ring of tall thunderstorms around the eye and usually contains the most intense winds and rain. Conditions in the eye do not describe the whole storm.
41. Rain fell at the station this afternoon. Weather concerns atmospheric conditions over a short period. Climate describes patterns and statistics across longer periods, including averages, variability, and seasonal differences.
42. 30 years. Conventional climate normals use a 30-year period to summarize variables such as temperature and precipitation. They provide a reference for comparison rather than a prediction for one particular day.
43. The temperature is 2°C above that baseline average. An anomaly expresses the difference from a reference average. Its interpretation requires the baseline and the area or period being measured; it is not an absolute temperature.
44. It may be above or below 20°C. An average summarizes many observations, which can vary around it. Climate statistics help describe the range and pattern of weather; they do not fix each day’s conditions.
45. Unusually warm surface water in the central and eastern tropical Pacific. El Niño is the warm phase of ENSO, involving the tropical Pacific and its interaction with the atmosphere. It can shift weather patterns, without producing the same effect in every place.
46. Unusually cool surface water in the central and eastern tropical Pacific. La Niña is the cool phase of ENSO in the tropical Pacific. It is linked with atmospheric circulation changes, and its local effects depend on region and season.
47. The leeward, downwind side. Air can rise and lose moisture on the windward slope. Descending air warms on the leeward side, contributing to a drier climate there.
48. Water heats and cools more slowly than land. Water responds to heating more slowly than land. This contrast helps limit coastal temperature swings, although winds, currents, and geography also affect a location’s climate.
49. Longwave infrared radiation. Earth emits energy as infrared radiation. Greenhouse gases absorb much of this outgoing radiation and emit energy themselves, affecting the planet’s energy balance and lower-atmosphere temperature.
50. +3°C. Subtract the baseline average from the observed average: 18 − 15 = +3°C. Reporting the baseline alongside the anomaly makes the comparison meaningful.