An analysis of the time differences between two American cities showed that the one in Denver, Colorado, was a week longer than the other, suggesting the difference in time between the cities was more important than the amount of daylight between them.
The time difference was about 15 minutes in Denver and 10 minutes in Los Angeles, the researchers found in a study published in the journal Nature Geoscience.
The study also found that Los Angeles had a lower amount of light pollution.
Los Angeles is often considered the capital of the US, but its cities are also home to major manufacturing plants and the biggest city in the state, Santa Ana.
The scientists found that the difference was mostly due to the sun’s brightness.
“The average daylight difference between Los Angeles and Denver was around 2 hours,” said Dr Mokhtarian.
“So the difference between them is not as significant as we think.”
Dr Mofaz is a senior researcher at the University of Southern California’s Institute for Space Science and Engineering.
He is also an associate professor in the Department of Aerospace Engineering and a co-author of the study.
He said the study was designed to investigate the effects of climate change on daylight pollution in different locations around the world.
“We looked at two different kinds of daylight, the urban and the rural,” he said.
“In the urban area, sunlight reflects off the landscape and is reflected back into space.
In the rural area, the light is reflected off trees, which reflect back to the atmosphere and are reflected back again into space.”
The researchers used satellite imagery from NASA’s Terra satellite and the Moderate Resolution Imaging Spectroradiometer to compare the daylight pollution levels in the cities.
“We also took temperature data from the temperature instruments,” Dr Mocaz said.
The researchers found that in the urban areas, the sun emitted more ultraviolet light into the atmosphere.
This resulted in a warmer air mass, which resulted in more daylight pollution.
“When the sun was brighter, the air was more dense, and that resulted in less daylight pollution,” Dr Macfaz said, “and the air pollution levels were lower in the rural areas.”
The amount of sunlight that was reflected back to space also influenced the amount and amount of air pollution.
The amount reflected back in the air changed with the amount the air temperature changed.
In fact, the amount reflected from the sky was the same in both urban and rural areas.
“If we looked at different air masses, the average amount of pollution in the daytime in the two urban areas was around 1,500 nanometres per square metre,” Dr Marra said.
This is the equivalent of 1,000,000 micrograms of carbon dioxide, the same amount as is emitted by one car.
“And in the northern and southern parts of the United States, the pollution levels are higher,” Dr Malzahn said.
If the air in the southern US is hotter, the sunlight reflects more.
“That’s because the sun is higher up in the atmosphere,” Dr Mahler said.
In contrast, in the eastern US, the higher air masses have less sunlight reflecting back into the sky.
“As a result, the pollutants in the Northern Hemisphere are much lower,” Dr Maszak said.
However, the scientists found another factor that could explain the difference.
“A lot of air pollutants are released during storms, which in turn have a direct effect on air quality,” Dr Mohr said.
They also found a correlation between air quality and the amount or intensity of sunlight.
“During these storm events, air quality gets much worse in cities,” Dr Moszaros said.
Dr Moccaz said the sun has a cooling effect on the air, but the impact of the storm does not change the amount it reflects back into our atmosphere.
“You can also expect a much larger amount of particles in the storm than in the sun,” Dr Mathewson said.
He added that the effect of the sun does not vary with the size of the cloud.
The effect of storm clouds has not been investigated in other cities, but Dr Mobeza said they could explain how the urban environment differs from the rural one.
“It is possible that storm clouds have a larger influence on the urban air quality than in other places,” Dr Mahesh said.