Upper-Air Patterns – Jet Stream Ridges and Troughs In planetary-scale wave patterns (Rossby waves), the trough segments correspond to positions where the jet stream dips closest to the:

Introduction / Context:
The mid-latitude jet stream meanders in a wavy pattern. Recognizing where ridges and troughs place the jet helps interpret temperature advection, storm development, and precipitation patterns in synoptic meteorology.

Given Data / Assumptions:

• Ridges are poleward excursions of the jet; troughs are equatorward.
• The question asks specifically about troughs.
• We focus on latitude relationship, not longitude (e.g., prime meridian).

Concept / Approach:
A trough is a southward (Northern Hemisphere) or equatorward displacement of the jet-stream axis, associated with cyclonic curvature and often cooler air. Conversely, a ridge is a poleward bulge with anticyclonic curvature and warmer air advection. Therefore, troughs bring the jet closest to the equator.

Step-by-Step Solution:

Verification / Alternative check:
500-hPa charts show trough axes extending equatorward with cooler, unstable conditions and jet streaks aligned along these dips.

Why Other Options Are Wrong:

• Poles: Correspond to ridges, not troughs.
• Prime meridian: Longitude line; irrelevant to latitude proximity.
• None of the above: Incorrect as “equator” is correct.

Common Pitfalls:
Reversing ridge/trough roles or confusing latitude with longitude terminology.

Final Answer:
equator