A thermal inversion rarely occurs in cities but is common in rural areas. rarely occurs in cities but is common in rural areas. helps remove pollutants from the atmosphere. helps remove pollutants from the atmosphere. leads to decreased amounts of ground-level smog. leads to decreased amounts of ground-level smog. occurs when a warm air layer overlies a cooler layer. occurs when a warm air layer overlies a cooler layer. occurs when a cool air layer overlies a warmer layer.