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Zorluk: ZorAtmosphere and Weather

In a developing high-pressure system (anticyclone), a large mass of air undergoes subsidence as it sinks toward the Earth's surface. As this descending air encounters greater atmospheric pressure at lower altitudes, which combination of temperature change, relative humidity change, and sky conditions will occur?

  1. A
    The air cools due to expansion, relative humidity increases, and thick stratus clouds produce steady rain.
  2. B
    The air cools as it descends, relative humidity rises to 100%, and widespread overcast conditions develop.
  3. The air warms due to compression, relative humidity decreases, and cloud formation is inhibited, resulting in clear skies.Cevap
  4. D
    The air warms due to compression, relative humidity increases, and rapid convective thunderstorm development occurs.

Cevap

The sinking air warms due to adiabatic compression, its relative humidity decreases, and cloud formation is inhibited, resulting in predominantly clear skies.
In a high-pressure system (anticyclone), air sinks toward the surface. As altitude decreases, atmospheric pressure increases, compressing the air mass and raising its temperature adiabatically. Because warmer air has a higher capacity for moisture, the relative humidity decreases (the dew point depression increases). This drying and warming effect evaporates existing droplets and inhibits cloud development, resulting in fair, clear weather.

Adım Adım Çözüm

1
Analyze the vertical air movement characteristic of an anticyclone (high-pressure system).
Air in a high-pressure system sinks (subsides) from higher altitudes toward the Earth's surface.
Surface divergence in high-pressure centers draws air downward to replace outflowing surface air.
2
Determine the thermodynamic effect of increasing atmospheric pressure on the subsiding air mass.
As the air descends into denser atmospheric layers, higher ambient pressure compresses the air parcel, causing adiabatic warming.
Work done on the parcel by compression increases its internal thermal energy without heat exchange with the surroundings.
3
Evaluate the effect of increasing temperature on the air mass's relative humidity.
Relative humidity decreases as saturation vapor pressure increases while actual moisture content remains constant.
Warmer air can hold more water vapor, so the existing vapor represents a smaller percentage of saturation capacity.
4
Deduce the resulting sky and weather conditions from the reduced relative humidity and downward motion.
Existing clouds evaporate and new cloud formation is suppressed, producing clear, fair skies.
Condensation requires saturation (100%100\% relative humidity), which cannot occur in warm, dry, subsiding air.

Anahtar Kavram

Adiabatic compression, subsidence, and humidity dynamics in high-pressure systems
Tahmini Süre:1m 15s
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Atmosphere and Weather

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