Weather Elements, Instruments, and Measurements

25 questions

Question 1Question

During an inspection of a standard meteorological station, geography students noticed that the wooden cabinet containing several measuring instruments was painted white and constructed with double-louvered side panels. Which of the following best explains the purpose of these design features?

Show answer & explanation

Answer: To reflect solar radiation and allow free air circulation while protecting instruments from direct sunlight and precipitation

Answer

The white paint reflects incoming solar radiation to avoid heating the interior, and the double-louvered sides allow free air movement while shielding instruments like thermometers from direct sunlight and rain.
The Stevenson screen is painted white to reflect solar radiation and prevent the enclosure from heating up above ambient shade temperature. The double-louvered sides permit natural air movement while shielding the thermometers inside from direct sunlight, wind gusts, and rain.

Step-by-Step Solution

1
Identify the purpose of a Stevenson screen in a weather station.
A Stevenson screen is designed to shield temperature and humidity instruments from direct solar heat, rain, and ground radiation while allowing ambient air to circulate freely.
Accurate weather measurement requires measuring shade air temperature and natural relative humidity.
2
Evaluate the function of white paint and louvered sides.
White paint reflects sunlight (high albedo), preventing the box from absorbing heat. Louvered sides act like blinds, letting air flow through while blocking direct light and precipitation.
This setup ensures the instruments measure true ambient atmospheric conditions without radiation bias.

Key Concept

Stevenson Screen Construction and Function
Question 2Question

During a fieldwork exercise at a coastal weather station, students were tasked with recording atmospheric pressure and wind speed. Which pair of instruments correctly matches these two weather elements to their corresponding measuring devices?

Show answer & explanation

Answer: Barometer for atmospheric pressure and Anemometer for wind speed

Answer

The barometer is used to measure atmospheric pressure, while the anemometer is used to measure wind speed.
Atmospheric pressure is the force per unit area exerted against a surface by the weight of the atmosphere, measured using a barometer. Wind speed is the velocity of airflow, measured using a cup anemometer. Therefore, pairing the barometer for atmospheric pressure and the anemometer for wind speed correctly identifies both instruments.

Step-by-Step Solution

1
Identify the instrument used for measuring atmospheric pressure
A barometer (either mercury or aneroid) measures atmospheric pressure in units such as millibars (mb) or hectopascals (hPa).
Atmospheric pressure is the weight exerted by the atmosphere per unit area.
2
Identify the instrument used for measuring wind speed
An anemometer (typically a cup anemometer) measures wind speed.
Wind speed measures the velocity of moving air, distinct from wind direction which is measured by a wind vane.
3
Select the correct combination matching both parameters
The option pairing the barometer for atmospheric pressure and the anemometer for wind speed is correct.
Both instruments are correctly linked to their respective atmospheric variables.

Key Concept

Matching meteorological elements to their specialized measuring instruments
Estimated Time:1m 0s
Question 3Question

During a meteorological observation at a weather station in Sokoto, Nigeria, the maximum air temperature recorded using a Six's maximum and minimum thermometer was 41.2C41.2^\circ\text{C}, while the minimum air temperature recorded was 24.8C24.8^\circ\text{C}. What is the diurnal range of temperature in C^\circ\text{C} for this observation period?

Show answer & explanation

Answer: 16.4

Answer

The diurnal temperature range is 16.4C16.4^\circ\text{C}.
The diurnal range of temperature measures the net difference between the maximum temperature during the day and the minimum temperature at night. Subtracting 24.8C24.8^\circ\text{C} from 41.2C41.2^\circ\text{C} gives 16.4C16.4^\circ\text{C}.

Step-by-Step Solution

1
Extract maximum and minimum temperature values from the observation data
Maximum temperature = 41.2C41.2^\circ\text{C}, Minimum temperature = 24.8C24.8^\circ\text{C}
Diurnal range calculation depends strictly on the daily maximum and minimum readings.
2
Subtract the minimum temperature from the maximum temperature
41.2C24.8C=16.4C41.2^\circ\text{C} - 24.8^\circ\text{C} = 16.4^\circ\text{C}
The diurnal range represents the difference between the highest and lowest temperatures within a 24-hour period.

Key Concept

Diurnal Range of Temperature
Estimated Time:1m 0s
Question 4Question

A weather station in Ibadan recorded a daily maximum temperature of 34C34^\circ\text{C} and a daily minimum temperature of 22C22^\circ\text{C}. What is the diurnal range of temperature for that day in C{}^\circ\text{C}?

Show answer & explanation

Answer: 12

Answer

12 °C
The diurnal temperature range is found by subtracting the minimum daily temperature from the maximum daily temperature: 34C22C=12C34^\circ\text{C} - 22^\circ\text{C} = 12^\circ\text{C}.

Step-by-Step Solution

1
Identify the recorded daily maximum and minimum temperatures
Maximum temperature = 34C34^\circ\text{C}, Minimum temperature = 22C22^\circ\text{C}
Diurnal range calculation requires the extreme temperature values recorded within a 24-hour period.
2
Calculate the difference between the maximum and minimum temperatures
34C22C=12C34^\circ\text{C} - 22^\circ\text{C} = 12^\circ\text{C}
The diurnal (daily) range of temperature is defined as the arithmetic difference between the highest and lowest temperatures of the day.

Key Concept

Diurnal Temperature Range
Estimated Time:45s
Question 5Question

A meteorologist at a meteorological station needs to determine the atmospheric pressure of the locality. Which weather instrument should be used for this measurement?

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Answer: Mercury barometer

Answer

Mercury barometer
Atmospheric pressure is the force exerted by the weight of the air column above a unit area. It is measured using a mercury barometer or aneroid barometer, expressed in units of millibars (mb) or millimeters of mercury (mmHg).

Step-by-Step Solution

1
Identify the target weather element from the prompt.
The parameter to measure is atmospheric pressure.
The station objective specifies determining air pressure.
2
Match atmospheric pressure to its standard measuring instrument.
Atmospheric pressure is recorded using a mercury barometer.
Barometers measure the weight per unit area exerted by the atmosphere, typically recorded in millibars (mb).

Key Concept

Atmospheric Pressure Measurement
Question 6Question

At a weather observation station in Jos, Nigeria, a meteorologist recorded the following daily temperature readings using a Six's maximum and minimum thermometer over a four-day period:

- Day 1: Maximum = 31.0C31.0^\circ\text{C}, Minimum = 19.0C19.0^\circ\text{C}
- Day 2: Maximum = 33.5C33.5^\circ\text{C}, Minimum = 17.5C17.5^\circ\text{C}
- Day 3: Maximum = 28.0C28.0^\circ\text{C}, Minimum = 16.0C16.0^\circ\text{C}
- Day 4: Maximum = 29.5C29.5^\circ\text{C}, Minimum = 18.5C18.5^\circ\text{C}

Calculate the mean diurnal (daily) temperature range for this four-day period in degrees Celsius (C^\circ\text{C}).

Show answer & explanation

Answer: 12.75

Answer

The mean diurnal temperature range over the four-day period is 12.75C12.75^\circ\text{C}.
The mean diurnal range measures the average difference between daily peak heat and night cooling over a given period. Subtracting minimum from maximum for each day yields 12.0C12.0^\circ\text{C}, 16.0C16.0^\circ\text{C}, 12.0C12.0^\circ\text{C}, and 11.0C11.0^\circ\text{C}. The average of these four values is 12.75C12.75^\circ\text{C}.

Step-by-Step Solution

1
Find the diurnal range for each individual day
Day 1: 12.0C12.0^\circ\text{C}, Day 2: 16.0C16.0^\circ\text{C}, Day 3: 12.0C12.0^\circ\text{C}, Day 4: 11.0C11.0^\circ\text{C}
The diurnal temperature range is defined as the difference between the maximum and minimum temperatures recorded in a single 24-hour period.
2
Calculate the sum of all daily ranges
51.0C51.0^\circ\text{C}
To compute an average over multiple days, the individual daily ranges must first be aggregated.
3
Compute the arithmetic mean across the 4 days
12.75C12.75^\circ\text{C}
Dividing the aggregate sum by the total number of observation days (4) yields the mean diurnal range.

Key Concept

Diurnal Temperature Range and Mean Calculation
Question 7Question

Inside a Stevenson screen at a meteorological station, a dry-bulb thermometer reads 28C28^\circ\text{C} while a wet-bulb thermometer reads 22C22^\circ\text{C}, yielding a wet-bulb depression of 6C6^\circ\text{C}. Which atmospheric variable is determined using this temperature difference, and which weather instrument would be mistakenly selected if an observer attempted to measure this variable by recording atmospheric pressure instead?

Show answer & explanation

Answer: Relative humidity is determined from the temperature difference; a barometer would be mistakenly selected because it measures atmospheric pressure.

Answer

Relative humidity is derived from the depression of the wet-bulb thermometer (28C22C=6C28^\circ\text{C} - 22^\circ\text{C} = 6^\circ\text{C}) using psychrometric tables. Mistakenly using a barometer targets atmospheric pressure instead of atmospheric moisture.
Relative humidity is the ratio of actual water vapour present in the air to the maximum amount the air can hold at that temperature. It is calculated using the depression of the wet bulb (the difference between dry-bulb and wet-bulb thermometer readings). A barometer is designed specifically to measure atmospheric pressure, so choosing a barometer to assess atmospheric humidity represents an instrument-parameter mismatch.

Step-by-Step Solution

1
Identify the weather element evaluated by a wet-and-dry bulb psychrometer.
The dry-bulb thermometer records ambient air temperature (28C28^\circ\text{C}), while evaporation from the moist muslin sheath lowers the wet-bulb temperature to 22C22^\circ\text{C}.
The rate of evaporation and resulting cooling (wet-bulb depression of 6C6^\circ\text{C}) depends directly on the relative humidity of the air.
2
Identify the mistaken instrument association.
A mercury or aneroid barometer measures atmospheric pressure (force exerted per unit area by the atmosphere).
Selecting a barometer when intending to measure relative humidity confuses pressure measurement with atmospheric moisture measurement.

Key Concept

Weather Elements and Instruments: Hygrometer/Psychrometer for Relative Humidity vs. Barometer for Atmospheric Pressure
Estimated Time:1m 30s
Question 8Question

A weather observer at a meteorological station needs to organize daily readings and equipment records. Match each weather element listed in Column I with its corresponding measuring instrument and standard unit of measurement in Column II. Which pairings correctly align every weather element with its designated instrument?

Click a left item, then click its matching right item

Items

Atmospheric Pressure
Wind Speed
Sunshine Duration
Relative Humidity

Matches

Show answer & explanation

Answer

Atmospheric Pressure matches with Aneroid Barometer (Millibars); Wind Speed matches with Cup Anemometer (Knots); Sunshine Duration matches with Campbell-Stokes Recorder (Hours); Relative Humidity matches with Hygrometer (Percentage).
Each weather element is correctly paired with its dedicated meteorological instrument and standard unit: Atmospheric Pressure is measured with an Aneroid Barometer (Millibars), Wind Speed with a Cup Anemometer (Knots), Sunshine Duration with a Campbell-Stokes Recorder (Hours), and Relative Humidity with a Hygrometer (Percentage).

Step-by-Step Solution

1
Identify the instrument and unit for Atmospheric Pressure
Atmospheric Pressure pairs with Aneroid Barometer (Millibars).
Air pressure is measured with barometers in millibars or hectopascals.
2
Identify the instrument and unit for Wind Speed
Wind Speed pairs with Cup Anemometer (Knots).
The rotation rate of anemometer cups measures wind velocity in knots or m/s.
3
Identify the instrument and unit for Sunshine Duration
Sunshine Duration pairs with Campbell-Stokes Recorder (Hours).
A glass sphere focuses rays onto a sensitized card to record sunshine duration in hours per day.
4
Identify the instrument and unit for Relative Humidity
Relative Humidity pairs with Hygrometer (Percentage).
Moisture relative to saturation level is measured using hygrometers or psychrometers as a percentage.

Key Concept

Weather Elements, Instruments, and Standard Units
Estimated Time:1m 30s
Question 9Question

A weather observer at a meteorological station requires a continuous visual trace of fluctuations in atmospheric pressure over a 24-hour cycle. Which instrument is designed specifically to record these continuous pressure changes on a rotating drum chart?

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Answer: Barograph

Answer

Barograph
The barograph is a self-recording barometer. It contains a series of aneroid capsules that expand and contract with changes in atmospheric pressure. This movement is magnified through levers to a pen arm, which draws a continuous trace (barogram) on a paper chart wrapped around a clockwork-driven rotating cylinder.

Step-by-Step Solution

1
Identify the target atmospheric parameter and measurement format requested in the stem
The target parameter is atmospheric pressure, requiring a continuous graphical record (trace chart) rather than a single instantaneous reading.
Different meteorological instruments serve specific parameters and reading methods (instantaneous vs. self-recording).
2
Match the target parameter to the corresponding self-recording weather instrument
Atmospheric pressure recorded continuously on a rotating chart drum corresponds to a barograph.
The suffix '-graph' indicates a self-recording instrument, and the prefix 'baro-' relates to atmospheric pressure.

Key Concept

Continuous Recording Weather Instruments
Estimated Time:1m 0s
Question 10Question

At a weather station in Port Harcourt, Nigeria, the maximum thermometer recorded a temperature of 33.0C33.0^\circ\text{C} during the day, and the minimum thermometer recorded 21.0C21.0^\circ\text{C} at night. What is the diurnal temperature range in degrees Celsius (C^\circ\text{C}) recorded for that day?

Show answer & explanation

Answer: 12

Answer

The diurnal temperature range recorded for the day is 12.0C12.0^\circ\text{C}.
The diurnal temperature range is defined as the difference between the maximum and minimum temperatures recorded within a single 24-hour day. Subtracting 21.0C21.0^\circ\text{C} from 33.0C33.0^\circ\text{C} yields 12.0C12.0^\circ\text{C}.

Step-by-Step Solution

1
Extract the given maximum and minimum temperature values from the problem statement.
Maximum temperature = 33.0C33.0^\circ\text{C}, Minimum temperature = 21.0C21.0^\circ\text{C}.
Diurnal range requires the daily maximum and minimum readings.
2
Apply the diurnal temperature range formula.
Diurnal Range=Maximum TemperatureMinimum Temperature\text{Diurnal Range} = \text{Maximum Temperature} - \text{Minimum Temperature}.
The diurnal range represents the total temperature variation experienced within a 24-hour period.
3
Perform the subtraction.
33.0C21.0C=12.0C33.0^\circ\text{C} - 21.0^\circ\text{C} = 12.0^\circ\text{C}.
Subtracting the minimum temperature from the maximum temperature gives the numeric difference.

Key Concept

Diurnal Temperature Range Calculation
Question 11Question

At a coastal weather station situated at sea level (0 m0\text{ m}), the recorded dry-bulb air temperature is 31.2C31.2^\circ\text{C}. A secondary meteorological station is established on an adjacent highlands plateau at an altitude of 2,400 m2,400\text{ m}. Assuming a standard environmental lapse rate of 6.5C6.5^\circ\text{C} per 1,000 m1,000\text{ m} of ascent in the troposphere, what is the calculated air temperature at the highlands station in degrees Celsius (C^\circ\text{C})?

Show answer & explanation

Answer: 15.6

Answer

The expected air temperature at the highlands station is 15.6C15.6^\circ\text{C}.
Air temperature in the lowest layer of the atmosphere (troposphere) decreases with altitude at the standard environmental lapse rate of 6.5C6.5^\circ\text{C} per 1,000 m1,000\text{ m} (0.65C0.65^\circ\text{C} per 100 m100\text{ m}). For an elevation increase of 2,400 m2,400\text{ m}, the total temperature drop equals 2.4×6.5C=15.6C2.4 \times 6.5^\circ\text{C} = 15.6^\circ\text{C}. Subtracting this reduction from the baseline sea-level reading of 31.2C31.2^\circ\text{C} gives 15.6C15.6^\circ\text{C}.

Step-by-Step Solution

1
Determine altitude difference in thousands of meters
2.4 units of 1,000 m2.4\text{ units of } 1,000\text{ m}
The environmental lapse rate is specified per 1,000 m1,000\text{ m} elevation gain.
2
Compute total atmospheric temperature drop
15.6C15.6^\circ\text{C} drop
Multiply the elevation change in thousands of meters (2.42.4) by the lapse rate (6.5C6.5^\circ\text{C}).
3
Calculate final temperature at plateau elevation
15.6C15.6^\circ\text{C}
Subtract the total calculated temperature drop from the sea-level temperature (31.2C15.6C31.2^\circ\text{C} - 15.6^\circ\text{C}).

Key Concept

Environmental Lapse Rate and Vertical Temperature Variation
Question 12Question

A weather observer at an agricultural station measures atmospheric moisture using a dry-and-wet bulb psychrometer. The dry-bulb thermometer reads 32C32^\circ\text{C} while the wet-bulb thermometer reads 24C24^\circ\text{C}. If the wet-bulb muslin sleeve dries out completely and is not re-moistened, what will happen to the wet-bulb temperature reading, and what parameter does the psychrometer assess when operating properly?

Show answer & explanation

Answer: The wet-bulb temperature will rise to 32C32^\circ\text{C}, matching the dry-bulb reading; the psychrometer assesses relative humidity via evaporative cooling.

Answer

The wet-bulb temperature will rise to 32C32^\circ\text{C} to equal the dry-bulb temperature because evaporation ceases; the psychrometer measures relative humidity.
The lower temperature on a wet-bulb thermometer is caused by evaporative cooling taking heat away from the bulb. When the muslin wick dries completely, evaporation stops and the thermometer bulb absorbs heat from the surrounding air until it reaches thermal equilibrium with the dry-bulb thermometer (32C32^\circ\text{C}). A wet-and-dry bulb psychrometer is designed specifically to measure relative humidity by using the temperature difference (depression of the wet bulb).

Step-by-Step Solution

1
Analyze the mechanism of a wet-bulb thermometer
The lower reading (24C24^\circ\text{C}) on the wet bulb is maintained by sensible heat loss due to water evaporating from the wet muslin sleeve into surrounding air.
Evaporation requires latent heat, which is extracted from the thermometer bulb, lowering its temperature relative to the dry bulb.
2
Determine the effect of removing moisture from the muslin sleeve
When the muslin dries completely, evaporation stops entirely. With no heat loss occurring, sensible heat transfers from the air to the bulb until equilibrium is reached at 32C32^\circ\text{C}.
Both dry-bulb and dry wet-bulb thermometers exposed to the same ambient air will indicate the actual air temperature.
3
Identify the primary atmospheric parameter measured by a psychrometer
A psychrometer (hygrometer) measures relative humidity and dew point based on the wet-bulb depression (32C24C=8C32^\circ\text{C} - 24^\circ\text{C} = 8^\circ\text{C}).
The rate of evaporation and resulting depression depend directly on the moisture saturation of the atmosphere.

Key Concept

Psychrometer Mechanics and Relative Humidity Measurement
Question 13Question

A meteorological officer at a weather station needs to select the appropriate instruments and standard units of measurement for recording atmospheric pressure and relative humidity. Which pair of instruments and corresponding units should be selected?

Show answer & explanation

Answer: Atmospheric pressure: Barometer (measured in millibars); Relative humidity: Hygrometer (measured in percentage)

Answer

Atmospheric pressure is measured using a barometer in millibars (mb), and relative humidity is measured using a hygrometer in percentage (%).
Atmospheric pressure is the weight of the air column above a given point, measured using a barometer in units of millibars (mb) or hectopascals (hPa). Relative humidity is the ratio of actual water vapor in the air to the maximum amount possible at the current temperature, measured as a percentage (%) using a hygrometer or psychrometer.

Step-by-Step Solution

1
Identify the instrument and unit used for recording atmospheric pressure.
Atmospheric pressure is measured using a barometer, with readings typically expressed in millibars (mb) or hectopascals (hPa).
Atmospheric pressure represents the force exerted by the weight of air per unit surface area.
2
Identify the instrument and unit used for recording relative humidity.
Relative humidity is measured using a hygrometer (such as a dry-and-wet bulb psychrometer), expressed as a percentage (%).
Relative humidity measures the amount of moisture present in the air compared to the maximum amount the air can hold at that specific temperature.
3
Select the option that correctly pairs both weather elements with their respective instruments and units.
The option pairing atmospheric pressure with the barometer (millibars) and relative humidity with the hygrometer (percentage) is correct.
Each weather element is correctly aligned with its standard measuring device and unit.

Key Concept

Weather Elements, Measuring Instruments, and Units
Estimated Time:1m 0s
Question 14Question

Which of the following instruments is specifically used to measure wind speed at a weather station?

Show answer & explanation

Answer: Anemometer

Answer

The instrument specifically used to measure wind speed is the anemometer.
An anemometer is designed with cups or vanes that rotate as wind passes across them; the rotation rate directly corresponds to wind speed.

Step-by-Step Solution

1
Identify the weather element specified in the question stem.
The target weather element to measure is wind speed.
Different atmospheric parameters require specific recording instruments.
2
Match the targeted element (wind speed) to its corresponding standard measuring instrument.
The anemometer (commonly a cup anemometer) is the standard instrument that measures wind speed in meters per second or knots.
The rotating cups of an anemometer spin at a rate proportional to wind speed.

Key Concept

Weather Elements and Instruments
Question 15Question

A meteorological station measures atmospheric moisture levels using two adjacent thermometers mounted together inside a Stevenson screen. Which instrument utilizes a dry bulb and a wet bulb covered in damp muslin to determine relative humidity?

Show answer & explanation

Answer: Wet-and-dry bulb psychrometer

Answer

Wet-and-dry bulb psychrometer
The wet-and-dry bulb psychrometer (hygrometer) measures atmospheric relative humidity by evaluating the difference between dry-bulb air temperature and wet-bulb temperature caused by evaporative cooling.

Step-by-Step Solution

1
Identify the weather parameter being measured in the question stem
The target weather parameter is relative humidity (atmospheric moisture).
The stem describes calculating atmospheric moisture levels using dry and wet bulb temperature readings.
2
Match the specified weather parameter and construction mechanism to the standard meteorological instrument
The wet-and-dry bulb psychrometer (a type of hygrometer) is the instrument designed with two thermometers to measure relative humidity.
Water evaporating from the wet muslin sleeve cools the wet-bulb thermometer, creating a depression that correlates directly with relative humidity.

Key Concept

Measurement of Relative Humidity using a Hygrometer/Psychrometer
Estimated Time:45s
Question 16Question

Match each meteorological instrument on the left with the atmospheric parameter it is designed to measure on the right.

Click a left item, then click its matching right item

Items

Anemometer
Hygrometer (Psychrometer)
Barometer
Campbell-Stokes Recorder

Matches

Show answer & explanation

Answer

Anemometer matches with Wind speed; Hygrometer (Psychrometer) matches with Relative humidity; Barometer matches with Atmospheric pressure; Campbell-Stokes Recorder matches with Duration of bright sunshine.
Each weather instrument is correctly matched with its specific target parameter: the anemometer measures wind speed, the hygrometer/psychrometer measures atmospheric moisture or relative humidity, the barometer measures air pressure, and the Campbell-Stokes recorder logs the duration of sunshine.

Step-by-Step Solution

1
Identify the primary function of each meteorological instrument listed on the left.
Anemometer = wind speed measure; Hygrometer = humidity measure; Barometer = pressure measure; Campbell-Stokes Recorder = sunshine duration measure.
Each instrument has a unique design targeted at recording a specific weather element.
2
Pair each instrument to its corresponding atmospheric parameter.
Match left_1 to right_4, left_2 to right_3, left_3 to right_2, and left_4 to right_1.
This establishes accurate instrument-parameter alignment without misattributing measurement functions.

Key Concept

Weather Instruments and Parameter Measurement
Question 17Question

At a meteorological station in Jos, Nigeria, a weather observer records a maximum daily air temperature of 28.5C28.5^\circ\text{C} and a minimum daily air temperature of 17.5C17.5^\circ\text{C} using a Six's maximum and minimum thermometer. What is the mean daily temperature in C^\circ\text{C}?

Show answer & explanation

Answer: 23

Answer

The mean daily temperature is 23.0C23.0^\circ\text{C}.
The mean daily temperature is determined by taking the average of the daily maximum and minimum temperatures: 28.5C+17.5C2=23.0C\frac{28.5^\circ\text{C} + 17.5^\circ\text{C}}{2} = 23.0^\circ\text{C}.

Step-by-Step Solution

1
Sum the maximum daily temperature and minimum daily temperature recorded at the weather station.
28.5C+17.5C=46.0C28.5^\circ\text{C} + 17.5^\circ\text{C} = 46.0^\circ\text{C}
Finding the total combined temperature extreme values is the first step in calculating the arithmetic mean.
2
Divide the combined total temperature by 2.
46.0C2=23.0C\frac{46.0^\circ\text{C}}{2} = 23.0^\circ\text{C}
The mean daily temperature represents the average temperature over a 24-hour observation period.

Key Concept

Calculation of Mean Daily Temperature
Estimated Time:45s
Question 18Question

Match each weather measuring instrument on the left with its specific operational mechanism or structural feature on the right.

Click a left item, then click its matching right item

Items

Fortin Barometer
Campbell-Stokes Sunshine Recorder
Six's Maximum and Minimum Thermometer
Hair Hygrometer

Matches

Show answer & explanation

Answer

Fortin Barometer matches with the flexible leather cistern and ivory pointer mechanism; Campbell-Stokes Sunshine Recorder matches with the solid glass sphere focusing solar rays; Six's Maximum and Minimum Thermometer matches with the U-shaped tube containing mercury, alcohol, and steel indices; Hair Hygrometer matches with tracking changes in the physical length of organic fibers.
Each instrument correctly corresponds to its distinct mechanical component: the Fortin barometer relies on an adjustable leather cistern with an ivory zero pointer; the Campbell-Stokes sunshine recorder relies on a glass sphere lens; Six's thermometer uses a U-tube with alcohol, mercury, and steel indices; and the hair hygrometer utilizes tension variations in organic hair strands.

Step-by-Step Solution

1
Analyze the operational mechanism for atmospheric pressure measurement
Identify the Fortin Barometer as the instrument utilizing a leather cistern adjusted via a screw until mercury touches an ivory point zero datum.
Precision barometric readings require establishing a fixed reservoir reference level.
2
Analyze the operating principle of sunshine recorders
Identify the Campbell-Stokes recorder as using a glass sphere lens to scorch a line on card strip.
Concentrating direct solar radiation burns paper selectively during sunny intervals.
3
Analyze dual-extreme temperature recording instruments
Identify Six's Thermometer as using a U-tube filled with alcohol and mercury driving steel indices.
Differential thermal expansion of liquid columns pushes steel markers to extreme limits.
4
Analyze humidity measuring principles based on organic material expansion
Identify the hair hygrometer as utilizing human/animal hair elasticity changes caused by humidity.
Hygroscopic organic fibers naturally elongate as moisture absorption increases.

Key Concept

Operating Principles and Structural Features of Weather Station Instruments
Question 19Question

During the installation of a standard Stevenson screen at a meteorological station located in West Africa (Northern Hemisphere), specific orientation rules and structural specifications are strictly enforced. Which of the following best explains why the cabinet door must open facing North, and why the enclosure walls are built with double-louvered side panels?

Show answer & explanation

Answer: The North-facing door prevents direct sunshine from striking the instruments during readings, while double louvres allow free ventilation while screening out direct radiation and rain.

Answer

The North-facing door orientation prevents direct sunlight from falling onto the instruments when opened in the Northern Hemisphere, while the double louvres permit natural air flow while shielding instruments from precipitation and direct radiation.
The correct answer accurately accounts for both the solar path in the Northern Hemisphere and the physical requirements of shade air measurement. Opening the door toward the North keeps the instruments shaded from direct sunlight when observed. Double-louvered walls allow free circulation of air so the thermometers reach equilibrium with true ambient shade temperature without exposure to rain or direct solar radiation.

Step-by-Step Solution

1
Analyze the geographical position and solar angle for the location.
In the Northern Hemisphere (including West Africa), the sun travels along the southern portion of the sky for most of the year.
Orienting the door toward the North ensures the open door faces away from the sun during observations, eliminating direct solar contamination of the thermometers.
2
Evaluate the function of double-louvered side panels in meteorological enclosure design.
Double louvres consist of overlapping wooden slats that allow ambient air to pass through freely.
Continuous ventilation ensures that the instruments measure ambient air shade temperature rather than stagnant, heated cabinet air.

Key Concept

Stevenson Screen Construction and Operational Principles
Question 20Question

At a meteorological station, a weather observer uses a Campbell-Stokes recorder featuring a glass sphere that focuses sunlight onto a calibrated paper card. Which atmospheric parameter is directly measured by this instrument, and what is its standard unit of measurement?

Show answer & explanation

Answer: Duration of bright sunshine, measured in hours

Answer

The Campbell-Stokes recorder measures the duration of bright sunshine in hours.
The Campbell-Stokes sunshine recorder utilizes a spherical glass lens to focus direct rays of the sun onto a specially treated cardboard strip. The focused ray burns a char line whenever the sun shines brightly, allowing observers to measure the total duration of sunshine in hours for a given day.

Step-by-Step Solution

1
Identify the instrument working mechanism
The instrument consists of a solid glass sphere mounted in a bowl frame holding a sensitized paper card.
The glass sphere acts as a lens that focuses direct sunlight into a hot spot.
2
Determine the atmospheric parameter recorded
As the sun moves across the sky, the focused beam burns a path along the calibrated card, indicating the length of time bright sunshine was present.
The burn trace length directly corresponds to sunshine duration, measured in hours per day.
3
Match the parameter with its unit and rule out mismatching instruments
Duration of bright sunshine is measured in hours, while solar radiation intensity (Watts/m²), cloud cover (oktas), and relative humidity (%) require different instruments.
Each meteorological parameter has specific dedicated instrumentation and units.

Key Concept

Weather Elements, Instruments, and Measurements
Estimated Time:1m 0s
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