13.5. Thermal Wind Balance

The thermal wind is a combination of the hydrostatic balance and geostrophic balance and explains why winds typically intensify with increasing height (stronger winds from the west) in the mid-latitude regions (Fig. 13.5). This balance brings together the relationship between temperature and winds. Cooler surface temperatures mean a shorter vertical distance to a given pressure level, whereas higher surface temperatures would mean a longer vertical distance to a given pressure level. This results in strong pressure gradients aloft, which is in association with the strong jet stream winds observed in the upper troposphere.

Fig. 13.5 Visualization of thermal wind balance where in the colder air pressure decreases more reapidly that in warmer air creating a strong pressure gradient force that increases with height and is maximuzed near the top of the troposphere (near 300 hPa).