An air pressure contour line joins locations in a region having the same atmospheric pressure. The following is an air pressure contour plot of a geographical region. Contour lines are shown at 0.05 bar intervals in this plot. If the possibility of a thunderstorm is given by how fast air pressure rises or drops over a region, which of the following regions is most likely to have a thunderstorm? A. P B. Q C. R D. S
GATE 2017 · General Aptitude · Contour Plots · medium
Answer: Region R (Option C) — it has the most densely packed contour lines, indicating the steepest air pressure gradient and highest thunderstorm likelihood.
- Understand the link between contour density and pressure gradient: Since the contour interval is fixed at 0.05 bar for all regions, the gradient is inversely proportional to the spacing between adjacent lines. Smaller spacing = larger gradient.
- Compare contour line density across regions P, Q, R, S: Examining the plot: Region R has the most tightly clustered contour lines compared to P, Q, and S. The lines in R are packed closely together, indicating a rapid change in atmospheric pressure over a short distance.
- Conclude which region is most storm-prone: Region R has the steepest pressure gradient (|dP/dx| is largest). Therefore, R is the region most likely to experience a thunderstorm.