Final answer:
Option B: Meridional. When the upper-air flow pattern is zonal, the source region for much of the air over the coterminous U.S. is the Pacific Ocean.
Step-by-step explanation:
When the upper-air flow pattern is zonal, the source region for much of the air over the coterminous U.S. is the Pacific Ocean. On the other hand, when the upper-air flow pattern is meridional, the source regions for air masses over the lower 48 states are Canada (where winds are from the northwest) or Mexico or the Gulf of Mexico (where winds are from the southwest). Hence, from west to east across the lower 48 states, temperatures are likely to be more variable with a meridional flow pattern. On the other hand, when the upper-air flow pattern is meridional, the source regions for air masses over the lower 48 states are Canada (where winds are from the northwest) or Mexico or the Gulf of Mexico (where winds are from the southwest). Hence, from west to east across the lower 48 states, temperatures are likely to be more variable with a meridional flow pattern
When considering upper-air flow patterns, temperatures across the lower 48 states of the U.S. are likely to be more variable with a meridional flow pattern. Zonal flow brings air predominantly from the west, specifically the Pacific Ocean, which generally leads to more uniform temperature patterns from west to east. However, meridional flow, which involves air masses moving from the north or south, can lead to more extreme temperature variations as it allows cold air from Canada or warm air from Mexico or the Gulf of Mexico to influence the climate.