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Difficulty: HardWeather Elements, Instruments, and Measurements

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?

  1. 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
  2. B
    The North-facing door aligns the cabinet directly into prevailing North-East Trade winds, while double louvres measure wind velocity alongside air temperature.
  3. C
    The North-facing door allows solar radiation to illuminate thermometer scales for clear reading, while double louvres prevent atmospheric moisture from escaping.
  4. D
    The North-facing door stabilizes internal atmospheric pressure, while double louvres trap heat inside the screen to keep ambient conditions constant.

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
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Topics

Weather Elements, Instruments, and Measurements

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