Behind the Forecast: How humans affect the weather

Behind the Forecast: How humans affect the weather
So far this year we've seen significant deviations from climatological normals including a warmer than average May in Kentucky and Indiana.

Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.

LOUISVILLE, KY (WAVE) - Weather has an impact on our everyday lives but we also have an impact on it.

Here are just a few of the ways that humans actually change the weather.

  1. Air pollution: With all of the cars, trains, planes and other methods of transportation giving off various types of exhaust plus the power plants, food manufacturing plants and other industrial buildings it’s no surprise that we’re pumping a lot of extra particles and gases into the air. Yes, there’s some air pollution that’s caused by natural processes such as wildfire, wildlife and volcanoes but we as humans contribute to a lot of unhealthy particles in the air. Air Quality Alerts are typically issued when there are elevated levels of ground-level ozone or particulate matter in the air. Ground level ozone forms when nitrogen oxides from sources like vehicle exhaust and industrial emissions react with organic compounds in the presence of heat and sunlight, according to the National Weather Service. Particulate matter is comprised of particles, solid and liquid, including smoke, dust and other pollutants from various sources. Sunshine causes some of the pollutants to break down through chemical reactions causing smog.  High temperatures can speed up those chemical reactions. Rain usually washes away pollutants and particulates from the air while wind helps to disperse pollutants. 

  2. Cities create urban heat islands and Louisville is a perfect example of that. The city itself can be several degrees warmer than the surrounding area thanks to concrete, asphalt, bricks and other building materials' ability to absorb heat from the sun. The extra heat can help fuel storms or even change the type of precipitation falling during winter storms. 

  3. All of the pavement in our cities prohibits the drainage of water during heavy rainfall events causing or intensifying flooding issues.  Water builds up in or runs off into areas that typically don’t deal with flooding. Monsoon storms brought heavy rain to Las Vegas on July 12, causing serious flooding issues in parts of the city.
  4. Our buildings can also amplify winds. In densely built-up areas, buildings can act like a wind tunnel, causing breezes to gust stronger than they would in an open field. This can cause serious damage, shoving debris down city streets, pushing over trees and even blowing out windows.
  5. Our planes can actually create clouds, not by pumping chemicals into the air but just by passing through it. It’s normal to look up and notice a condensation trail, or contrail for short, forming behind a plane as it flies to its destination. The water vapor produced by the plane’s engine condenses in the cooler temperatures forming cirrus (high level) clouds. Depending on the wind speed and humidity in the upper levels of the atmosphere, these contrails could either dissipate immediately or last for hours on end. Cirrus clouds typically reflect sunlight but trap heat released by the Earth resulting in a net heating effect.
  6. Humans have to eat. That’s just a fact. Our crops can actually make a hot day feel even hotter. They do this through transpiration, which is when they release water vapor into the atmosphere. Some crops do this more than others; corn, for example, actually transpires during the day and night pumping that extra moisture into the atmosphere all day long. The extra humidity ramps up the heat index. Here's how the National Weather Service defines the heat index: "The Heat Index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature." A relative humidity of 85% can make a 90-degree day feel like 117 degrees!  So while the actual air temperature may be hotter in the city, in some situations, the rural areas may "feel" hotter due to the higher humidity. 

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