Do low-lying clouds have an effect on global climate?
Bruce Albrecht, professor of atmospheric sciences at the UM Rosenstiel School of Marine and Atmospheric Science in Miami, Florida claims that low clouds are extremely important to climate systems because stratocumulus and cumulus clouds both reflect solar radiation back into space, they provide the primary cooling of our planet. The research flight took off on July 1 from Sacramento aboard the state-of-the-art National Science Foundation (NSF) Gulfstream V research aircraft is getting the needed data to better understand cloud structure, aerosols, and precipitation which will tell us more about the role these clouds have on the global climate system. The project, “The Cloud Systems Evolution in the Trades (CSET),” will end August 15.
“Our preliminary data are already revealing that aerosol-depleted environments are much more common than previously thought, changing textbook ideas on the low cloud lifecycle,” said Paquita Zuidema, professor of atmospheric sciences at the UM Rosenstiel School and co-investigator of the study. The project scheduled 14 flights to sample the trade wind-driven clouds as they move across the Pacific Ocean to Hawaii. In the last two months researchers focused on stratocumulus and cumulus clouds changing shape in the trade winds. The same cloud areas were sampled again when the aircraft returned to California from Hawaii two days later. The research data also hopes to shed light on how cloud coverage changes as the planet warms.
The blog above does not explain in depth about what happened to the energy released from the sun and what happened to it after that and also the energy released by the surface back to the atmosphere and the Hydrological cycle. Therefore, it may be difficult to understand if you did not talk about the factors that make the clouds exist, why and what they do.
Touching on the solar energy, according to “Universe today’ online ( https://www.universetoday.com/60065/radiation-from-the-sun/ ), when electromagnetic radiation from the Sun strikes the Earth’s atmosphere, some of it is absorbed while the rest proceeds to the Earth’s surface. In particular, this energy is absorbed by the ozone layer and re-emitted as heat, eventually heating up the stratosphere. Some of this heat is re-radiated to outer space while some is sent to the Earth’s surface. In the meantime, the electromagnetic radiation that wasn’t absorbed by the atmosphere proceeds to the Earth’s surface and heats it up. Some of this heat stays there while the rest is re-emitted. Upon reaching the atmosphere, part of it gets absorbed by air molecules as well as by water vapor molecules, leading greenhouse gases to fast increase the temperature. Naturally, the molecules that get absorbed add to the heat already there. The presence of greenhouse gases in the atmosphere makes the atmosphere absorb more heat, reducing the fraction of outbound electromagnetic waves that pass through. Known as the greenhouse effect, this is one of the reasons why heat builds up even more. So far you have an idea of what’s going on in the atmosphere. While you hold on to this information let’s now go over a little bit about the hydrological cycle and cloud formation.
The hydrologic cycle begins with the evaporation of water from the surface of the ocean, lakes, rivers, trees, even from cooking, etc. As moist air is lifted, it cools and water vapor condenses to form clouds. Moisture is transported by the winds around the globe until it returns to the surface as precipitation. Once the water reaches the ground, one of two processes may occur. Some of the water may evaporate back into the atmosphere or the water may penetrate the surface and become groundwater. Groundwater either seeps its way into the oceans, rivers, and streams, or is released back into the atmosphere through transpiration. The balance of water that remains on the earth’s surface is runoff, which empties into lakes, rivers and streams and is carried back to the oceans, where the cycle begins again. Lake effect snowfall is good example of the hydrologic cycle at work. Below is a vertical cross-section summarizing the processes of the hydrologic cycle that contributes to the production of lake effect snow. The cycle begins as cold winds blow across a large lake, a phenomenon that occurs frequently in the late fall and winter months around the Great Lakes. Evaporation of warm surface water increases the amount of moisture in the colder, drier air flowing immediately above the lake surface. With continued evaporation, water vapor in the cold air condenses to form ice-crystal clouds, which are transported toward shore.
Differences in atmospheric pressure generate winds. The Intertropical Convergence Zone (ITCZ), known by sailors as the doldrums or the calms, is the area encircling Earth near the Equator, where the northeast and southeast trade winds converge. At the Equator, the sun warms the water and land more than it does the rest of the globe. Warm equatorial air rises higher into the atmosphere and migrates toward the poles. This is a low-pressure system. At the same time, cooler, denser air moves over Earth’s surface toward the Equator to replace the heated air. This is a high-pressure system. Winds generally blow from high-pressure areas to low-pressure areas. The boundary between these two areas is called a front. The complex relationships between fronts cause different types of wind and weather patterns. Prevailing winds are winds that blow from a single direction over a specific area of the Earth. Areas where prevailing winds meet are called convergence zones. Generally, prevailing winds blow east-west rather than north-south. This happens because Earth’s rotation generates what is known as the Coriolis effect. The Coriolis effect makes wind systems twist counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The Coriolis effect causes some winds to travel along the edges of the high-pressure and low-pressure systems. These are called geostrophic winds. Overall the Earth contains five major wind zones: polar easterlies, westerlies, horse latitudes, trade winds, and the doldrums. Most tropical storms, including hurricanes, cyclones, and typhoons, develop as trade winds. Differences in air pressure over the ocean cause these storms to develop. As the dense, moist winds of the storm encounter the drier winds of the coast, the storm can increase in intensity. Strong trade winds are associated with a lack of precipitation, while weak trade winds carry rainfall far inland. This is to give you an idea what’s going on with water vapor to how we get to the events around to the rainfalls.
Therefore, if we have more clouds than we have more energy reflected back into the atmosphere, this energy for sure will be trapped by greenhouse gases and creates more heat on earth since water vapor will increase and global warming will increase. On the other hand, Clouds are ok to reduce amount of sun radiation directed to the surface but is temporarily like having a fan in the summer.
A wonderfully detailed explanation. Thank you for adding to the post and to our understanding of weather patterns and global warming.