Match the Following: Humidity Parameters and Definitions

Choose the correct option from those given below:

Correct option is B

Introduction:

• This question tests the fundamental distinctions between various humidity parameters used in atmospheric thermodynamics and environmental engineering.
• While all measure atmospheric moisture, the choice of denominator (volume of air, mass of dry air, or mass of total air) determines a parameter's sensitivity to changes in temperature and pressure, which is critical for dynamic atmospheric modeling and industrial processes.

Information Booster:

• Relative Humidity (RH): A dimensionless ratio expressed as a percentage.
• It is the most intuitive measure as it directly indicates the degree of saturation of the air, determining the likelihood of condensation or fog formation. It is highly temperature-dependent.
• ​$$\text{RH} = \frac{\text{Actual Vapour Pressure}}{\text{Saturation Vapour Pressure}} \times 100$$​​
  
• Absolute Humidity (AH): This is the density of water vapour in the air, expressed as mass per unit volume (e.g.$$\text{g}/\text{m}^3$$​).
• Because volume changes with temperature and pressure, AH is not a conserved quantity when an air parcel moves vertically.
• ​$$\text{AH} = \frac{m_{\text{vapour}}}{V_{\text{air}}}$$​​
  
• Specific Humidity (q): This is the mass fraction of water vapour in the total moist air mixture$$text{mass}_{\text{vapour}} / (\text{mass}_{\text{vapour}} + \text{mass}_{\text{dry air}})$$​
• It is a conserved quantity during adiabatic (unmixed) movement of air, making it essential for large-scale weather and climate models.
• ​$$q = \frac{m_{\text{vapour}}}{m_{\text{total}}}$$​​
  
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• Mixing Ratio (r): The ratio of the mass of water vapour to the mass of dry air.
• Since the mass of dry air in an air parcel remains constant, the mixing ratio is also a conserved quantity and is frequently used interchangeably with specific humidity in most meteorological calculations since $$m_{\text{vapour}} \ll m_{\text{dry air}}$$
  
• $$r = \frac{m_{\text{vapour}}}{m_{\text{dry air}}}​$$​

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