Why westerlies are lighter than easterlies?

Westerlies are generally lighter than easterlies due to their origin and the influence of the Coriolis effect. Westerlies originate from the subtropical high-pressure areas and flow towards the poles, encountering lower pressure zones, which can reduce their strength. In contrast, easterlies, which come from the polar regions, are often denser and flow more consistently due to the significant temperature differences between the poles and the equator. This difference in density and the dynamics of high and low-pressure systems contribute to the westerlies being lighter.