Forest Biology & Tree improvement

• Khamsin Local Wind:
• scorching, dry, dust-laden southerly or southeasterly wind that blows across Egypt and the Levant during spring.
• Generated by passing Mediterranean frontal depressions drawing hot desert air from the Sahara; named from the Arabic word for "fifty" referring to its intermittent fifty-day season. (Correct answer: Option 1)

• Assertion (A) is True: Delhi experiences a continental semi-arid climate where January is consistently the coldest month of the year due to cold northwesterly winds descending from the Himalayas following western disturbances.
• Reason (R) is False: The Earth is actually at perihelion (closest to the Sun, $\approx 147.1\text{ million km}$) in early January, and at aphelion (farthest from the Sun, $\approx 152.1\text{ million km}$) in early July.
• Climatic Mechanism: Winter in Delhi is caused by the $23.5^\circ$ axial tilt of the Earth tilting the Northern Hemisphere away from the Sun, reducing solar declination and daily insolation, not the Earth-Sun distance.

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

• Surface Boundary Layer Physics:
• The surface layer represents the lowest $10\%$ of the Planetary Boundary Layer (typically the bottom 10–50 meters).
• In this near-surface layer, Coriolis and geostrophic forces are negligible compared to the intense turbulent shear stresses and frictional drag forces generated by ground surface roughness. (Correct answer: Option 4)