General Meteorology

• Assertion (A) is True: In Agrometeorology, the Bowen ratio ($\beta$) is defined as the ratio of sensible heat flux ($H$) to latent heat flux ($\lambda E$): $\beta = \frac{H}{\lambda E}$. Over wet surfaces or well-watered crops, latent heat flux dominates, so $\beta \lt 1$ (often $0.1 - 0.3$). Over dry arid surfaces, sensible heat dominates and $\beta$ is large ($\gt 2.0$).
• Reason (R) is False: An increase in soil moisture increases latent heat flux (evapotranspiration) and decreases surface temperature and sensible heat flux, which decreases the Bowen ratio, not increases it.
• Conclusion: (A) is true but (R) is false (Option 3).

Correct option: (3) (A) is true but (R) is false

• Hydrological Water Balance Concept:
• The quantitative accounting of all inflows, outflows, and storage changes of water within a defined agricultural watershed or root zone over a specified time step:

• Represents the dynamic balance between precipitation, infiltration, surface runoff, soil water storage, and evapotranspiration. (Correct answer: Option 2)

• Direct Field Measurement of Actual Evapotranspiration ($ET_a$):
• Lysimeters (specifically Precision Weighing Lysimeters): The recognized international physical standard instrument for measuring actual crop evapotranspiration.
• Measures the change in mass of an undisturbed soil-vegetation monolith over time, providing direct gravimetric accounting of water loss ($ET_a = \Delta W + \text{Inputs} - \text{Drainage}$).
• Penman-Monteith equations estimate potential/reference $ET_0$, not direct physical $ET_a$. (Correct answer: Option 3)