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Instrumentation, Observation & NWP (Meteorology) Solved Questions & Notes (2026) - Apex Rankers

Meteorology & Atmospheric Sciences > Meteorology > Instrumentation, Observation & NWP

30 Total Solved Questions
~45 mins Estimated Reading Time
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Instrumentation, Observation & NWP

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Q. 1 Meteorology
Difficulty: Easy (1 Mark)
In a standard meteorological weather station, what is the 'Stevenson Screen'?
A
A digital computer screen displaying satellite radar
B
A wooden white-painted, double-louvered shelter designed to shield sensitive meteorological instruments from direct solar radiation and precipitation while allowing free air circulation
✓ Correct
C
A mesh fence preventing animals from entering the station
D
A glass lens on a sunshine recorder
💡 Step-by-Step Explanation & Concept Rationale
The Stevenson screen (invented by Thomas Stevenson) is a white-painted, double-louvered shelter elevated 1.25 to 1.5 meters above ground, housing maximum, minimum, wet-bulb, and dry-bulb thermometers.
Q. 2 Meteorology
Difficulty: Easy (1 Mark)
Why is the door of a Stevenson Screen in the Northern Hemisphere (such as Pakistan) always installed facing North?
A
To align with Earth's magnetic pole
B
To prevent direct solar radiation from falling onto the thermometers when the observer opens the door
✓ Correct
C
Because winds always blow from the North
D
To avoid rain splashes
💡 Step-by-Step Explanation & Concept Rationale
In the Northern Hemisphere, the sun is always to the south at solar noon; facing the door north ensures direct sunlight never strikes the thermometers during observations.
Q. 3 Meteorology
Difficulty: Medium (1 Mark)
What type of thermometer is traditionally used to measure the daily 'Minimum Temperature'?
A
Mercury thermometer
B
Alcohol (spirit) thermometer with an index dumbbell inside the capillary
✓ Correct
C
Platinum resistance thermometer only
D
Bimetallic strip without fluid
💡 Step-by-Step Explanation & Concept Rationale
Minimum thermometers use alcohol (freezing point -114 °C) with a dark glass index marker inside. As temperature drops, the meniscus surface tension pulls the index back, recording the lowest temperature.
Q. 4 Meteorology
Difficulty: Medium (1 Mark)
Why is mercury (freezing point -39 °C) used in maximum thermometers rather than alcohol?
A
Mercury has high thermal conductivity, low vapor pressure, does not wet glass, and expands uniformly up to high temperatures
✓ Correct
B
Mercury is cheaper than water
C
Mercury absorbs UV light
D
Mercury freezes at room temperature
💡 Step-by-Step Explanation & Concept Rationale
Mercury has a high boiling point (357 °C), uniform coefficient of expansion, does not wet the capillary wall, and works with a constriction above the bulb to record the maximum reading.
Q. 5 Meteorology
Difficulty: Easy (1 Mark)
What instrument is used to record the duration of bright sunshine during the day using a solid glass sphere that focuses sunlight onto a treated paper card?
A
Campbell-Stokes sunshine recorder
✓ Correct
B
Pyrheliometer
C
Pyranometer
D
Anemometer
💡 Step-by-Step Explanation & Concept Rationale
The Campbell-Stokes sunshine recorder uses a glass sphere to focus solar rays onto a specially treated card, scorching a trace proportional to bright sunshine duration.
Q. 6 Meteorology
Difficulty: Hard (1 Mark)
What is the difference between a 'Pyranometer' and a 'Pyrheliometer'?
A
A pyranometer measures global (direct + diffuse) solar radiation over a hemispherical field of view, while a pyrheliometer measures only direct beam solar radiation at normal incidence
✓ Correct
B
Pyranometers measure wind; pyrheliometers measure pressure
C
Both are identical instruments
D
A pyrheliometer is only used at night
💡 Step-by-Step Explanation & Concept Rationale
Pyranometers measure total hemispherical shortwave solar irradiance (direct plus diffuse on a flat horizontal surface), whereas pyrheliometers track the sun with a collimating tube to measure direct solar beam radiation.
Q. 7 Meteorology
Difficulty: Easy (1 Mark)
What instrument is used to measure atmospheric pressure continuously on a rotating paper drum chart?
A
Barograph (aneroid barograph)
✓ Correct
B
Thermograph
C
Hygrograph
D
Anemograph
💡 Step-by-Step Explanation & Concept Rationale
A barograph uses evacuated aneroid capsules linked to a mechanical pen arm that continuously records barometric pressure trends on a clockwork chart drum.
Q. 8 Meteorology
Difficulty: Easy (1 Mark)
What standard instrument is used to measure upper-air temperature, humidity, and pressure as it ascends through the atmosphere carried by a weather balloon?
A
Radiosonde
✓ Correct
B
Lysimeter
C
Dropsonde
D
Pitot tube
💡 Step-by-Step Explanation & Concept Rationale
A radiosonde is a battery-powered telemetry instrument package carried into the upper atmosphere by a helium or hydrogen balloon, transmitting in situ vertical profiles of pressure, temperature, and humidity via radio to a ground station.
Q. 9 Meteorology
Difficulty: Medium (1 Mark)
What is a 'Rawinsonde'?
A
A radiosonde whose position is tracked (via GPS or radar) to additionally compute wind speed and wind direction at each altitude
B
An uncalibrated radiosonde
✓ Correct
C
A sounding launched from a submarine
D
A sonic anemometer
💡 Step-by-Step Explanation & Concept Rationale
A rawinsonde (radar/radio-wind sonde) measures vertical profiles of pressure, temperature, and humidity, and is tracked to derive upper-air wind speed and direction.
Q. 10 Meteorology
Difficulty: Medium (1 Mark)
What instrument is dropped from an aircraft with a parachute to measure atmospheric conditions over remote ocean areas during tropical cyclone reconnaissance?
A
Dropsonde
✓ Correct
B
Radiosonde
C
Ceilometer
D
Stevenson screen
💡 Step-by-Step Explanation & Concept Rationale
A dropsonde is an atmospheric sounding device released from hurricane-hunting aircraft, descending by parachute while measuring vertical profiles of pressure, temperature, humidity, and GPS winds down to the sea surface.
Q. 11 Meteorology
Difficulty: Medium (1 Mark)
What ground-based optical instrument uses a pulsed laser (LIDAR) to measure the height of the cloud base (cloud ceiling)?
A
Ceilometer
✓ Correct
B
Bolometer
C
Spectrophotometer
D
Disdrometer
💡 Step-by-Step Explanation & Concept Rationale
A ceilometer measures the transit time of laser light pulses reflected back from cloud droplets to determine the exact vertical height of cloud bases (cloud ceiling) at airports and weather stations.
Q. 12 Meteorology
Difficulty: Hard (1 Mark)
What instrument measures the size distribution and falling velocity of individual raindrops and hydrometeors?
A
Disdrometer
✓ Correct
B
Anemometer
C
Barometer
D
Actinometer
💡 Step-by-Step Explanation & Concept Rationale
A disdrometer is a specialized meteorological instrument used to measure the drop size distribution (DSD) and terminal velocity of falling hydrometeors.
Q. 13 Meteorology
Difficulty: Medium (1 Mark)
What is the standard orifice diameter of a Symons non-recording rain gauge commonly used in South Asia?
A
5 inches (approx 127 mm)
✓ Correct
B
25 inches
C
1 meter
D
2 inches
💡 Step-by-Step Explanation & Concept Rationale
The standard Symons rain gauge has a circular collector rim with an internal diameter of 5 inches (127 mm), set 30 cm above ground level.
Q. 14 Meteorology
Difficulty: Easy (1 Mark)
What type of rain gauge is standard in Automatic Weather Stations (AWS) because it transmits a discrete electrical pulse for every 0.1 mm or 0.2 mm of rain?
A
Tipping bucket rain gauge
✓ Correct
B
Float-type siphon gauge
C
Standard measuring cylinder
D
Snow ruler
💡 Step-by-Step Explanation & Concept Rationale
The tipping-bucket rain gauge features two balanced calibrated buckets that alternate positions when filled with a precise amount (e.g. 0.2 mm) of rain, triggering a magnetic reed switch pulse.
Q. 15 Meteorology
Difficulty: Easy (1 Mark)
In weather radar, what does the Doppler effect enable the radar to measure?
A
The radial velocity of hydrometeors moving toward or away from the radar antenna
✓ Correct
B
The absolute temperature of raindrops
C
The chemical composition of hail
D
The altitude of the ionosphere
💡 Step-by-Step Explanation & Concept Rationale
Doppler weather radar detects the frequency shift between transmitted and backscattered microwave pulses to calculate the radial velocity of precipitation particles along the radar beam.
Q. 16 Meteorology
Difficulty: Easy (1 Mark)
What classic radar reflectivity pattern is the hallmark indicator of a rotating mesocyclone in a tornadic supercell thunderstorm?
A
Hook Echo
✓ Correct
B
Circular bullseye
C
Uniform linear line
D
Bright band
💡 Step-by-Step Explanation & Concept Rationale
A hook echo is a hook-shaped radar reflectivity feature caused by the storm's rotating updraft wrapping precipitation around the rear-flank downdraft, often indicating tornado formation.
Q. 17 Meteorology
Difficulty: Hard (1 Mark)
What is the 'Bright Band' on a weather radar vertical profile of reflectivity?
A
A zone of intense radar reflectivity near the 0 °C melting layer where melting snowflakes become coated with water, appearing as large liquid raindrops to the radar beam
✓ Correct
B
Direct reflection from solar flares
C
A ring of lightning strikes
D
Reflection from an aircraft
💡 Step-by-Step Explanation & Concept Rationale
The bright band is an artifact observed in the melting layer where falling snow crystals acquire a liquid water coating. Because liquid water has a dielectric constant much higher than ice, radar reflectivity surges artificially.
Q. 18 Meteorology
Difficulty: Medium (1 Mark)
Dual-polarization (dual-pol) Doppler weather radar transmits and receives pulses in which two orthogonal orientations?
A
Horizontal and Vertical
✓ Correct
B
Diagonal and Circular
C
Axial and Radial
D
Forward and Reverse
💡 Step-by-Step Explanation & Concept Rationale
Dual-pol radar transmits both horizontal and vertical polarized electromagnetic waves, allowing meteorologists to discern the size, shape (flattened raindrops vs tumbling hail), and type of hydrometeors.
Q. 19 Meteorology
Difficulty: Medium (1 Mark)
In meteorological satellite imagery, what physical property is measured by the Infrared (IR) channel (typically around 10.8 micrometers)?
A
Cloud-top brightness temperature (cold cloud tops appear bright white)
✓ Correct
B
Direct reflected sunlight (available only during daylight)
C
Ocean salinity
D
Atmospheric pressure
💡 Step-by-Step Explanation & Concept Rationale
Infrared satellite sensors detect terrestrial thermal emissions to determine cloud top temperature. Towering clouds with cold tops (like cumulonimbus) appear bright white, available 24 hours a day.
Q. 20 Meteorology
Difficulty: Hard (1 Mark)
What atmospheric feature is uniquely observed by satellite sensors in the 6.7 micrometer 'Water Vapor' absorption channel?
A
Middle-to-upper tropospheric moisture, jet stream circulations, and upper-level troughs/vortices even in the absence of clouds
✓ Correct
B
Surface soil moisture beneath dense forests
C
Sea floor topography
D
Ground-level car emissions
💡 Step-by-Step Explanation & Concept Rationale
The 6.7 micrometer water vapor channel detects radiation emitted by moisture in the mid-to-upper troposphere (between 300 hPa and 600 hPa), revealing flow patterns, upper troughs, and jet stream dynamics.
Q. 21 Meteorology
Difficulty: Easy (1 Mark)
At what altitude do Geostationary Operational Environmental Satellites (such as Meteosat, FY-4, or INSAT) orbit the Earth?
A
800 km (Low Earth Orbit)
B
35,786 km above the Equator
✓ Correct
C
150,000 km
D
2,000 km
💡 Step-by-Step Explanation & Concept Rationale
Geostationary satellites orbit at an altitude of approximately 35,786 km above the Equator, matching Earth's rotation period so they remain stationary relative to a fixed sub-satellite point on the surface.
Q. 22 Meteorology
Difficulty: Medium (1 Mark)
What is the primary operational advantage of Polar-Orbiting satellites (such as NOAA-POES, MetOp) over Geostationary satellites?
A
They provide high-resolution sounding data over the polar regions and global coverage from lower altitudes (~800 km)
✓ Correct
B
They stay over Pakistan permanently
C
They are immune to solar radiation
D
They operate without batteries
💡 Step-by-Step Explanation & Concept Rationale
Polar-orbiting satellites fly in sun-synchronous low Earth orbit (~800 km), providing high-resolution vertical atmospheric soundings and superior coverage of high-latitude/polar regions where geostationary views are distorted.
Q. 23 Meteorology
Difficulty: Medium (1 Mark)
Who was the British mathematician who pioneered the first attempt at numerical weather prediction (NWP) by hand calculations during World War I?
A
Lewis Fry Richardson
✓ Correct
B
John von Neumann
C
Jule Charney
D
Edward Lorenz
💡 Step-by-Step Explanation & Concept Rationale
Lewis Fry Richardson published 'Weather Prediction by Numerical Process' in 1922, attempting a 6-hour forecast by solving primitive differential equations numerically by hand.
Q. 24 Meteorology
Difficulty: Hard (1 Mark)
What is 'Data Assimilation' in modern operational numerical weather prediction?
A
Printing weather maps on paper
B
The mathematical process of combining diverse raw meteorological observations (satellites, radars, radiosondes, surface stations) with a short-range model forecast to produce an optimal estimate of the atmospheric state (the analysis)
✓ Correct
C
Archiving past weather reports on tape
D
Deleting corrupted computer files
💡 Step-by-Step Explanation & Concept Rationale
Data assimilation (e.g., 3D-Var, 4D-Var, EnKF) blends irregularly distributed observational data with model physics and prior forecast errors to generate the best possible initial conditions for NWP models.
Q. 25 Meteorology
Difficulty: Medium (1 Mark)
Why are 'Ensemble Forecasts' (e.g., ECMWF EPS, GEFS) used in operational weather forecasting rather than a single deterministic run?
A
To account for the chaotic nature of the atmosphere and quantify forecast uncertainty by running multiple simulations with slightly perturbed initial conditions and physics parameters
✓ Correct
B
Because running one model is illegal under WMO rules
C
To keep supercomputers running at 100% power
D
To produce 50 identical forecasts
💡 Step-by-Step Explanation & Concept Rationale
Because the atmosphere is a chaotic system exhibiting sensitive dependence on initial conditions (the butterfly effect discovered by Edward Lorenz), ensemble forecasting runs multiple realizations to yield probabilistic guidance.
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