VOCALS scientists will be studying the Southeastern Pacific Climate to better understand the interacitons between the oceans, clouds, atmosphere, and land in this region. Click on image for full size (60 Kb) Robert Wood (University of Washington) and the VOCALS Scientific Working Group

There are several regions in the world where low-lying stratus and stratocumulus clouds are frequently present and an important part of climates. It turns out that these regions also play an important role in Earth's global climate. Examples include the subtropical climates off of the coasts of California (US), Namibia (Africa), and Peru and Chile in South America. The climates of these regions involve interactions and feedbacks between the ocean, clouds, atmosphere, and land. Scientists in the VOCALS field campaign are focusing their experiments in the Southeast Pacific (SEP) Ocean off the coasts of Chile and Peru. They have chosen this area because the feedbacks in the regional climate systems are the clearest.

The climate of the SEP is dependent upon interactions between the Andes Mountains, the upper layer of the ocean, and the lower troposphere. In the SEP, clouds form right above the ocean in an area known as the marine boundary layer or MBL. MBL clouds are of the low stratus type. They create continuous cover over extended regions of the SEP. Precipitation from MBL clouds is mostly in the form of drizzle. It is likely that the amount of drizzle influences the structure and dynamics of SEP cloudiness.

Westerly winds blow thousands of miles across the Pacific Ocean toward South America. The winds are forced to turn north along the coast when they encounter the Andes Mountains range. Evaporative cooling occurs as the winds sweep across the water. The winds in this region cause the water at the ocean surface to move perpindicular to the coastlaine (westward) in a process known as the Ekman transport. The displaced surface water is replaced by colder, nutrient-rich ocean water rising from the deep ocean. The process of upwelling in the SEP is associated with the Humboldt Current system. These cold waters, aided by an air mass, made stable in part by effects of the Andes, help support the largest and most persistent subtropical sheet of stratus and stratocumulus clouds on the planet. This cloud deck, affected by aerosols from both natural and human sources, helps in turn to maintain cool ocean waters beneath.

Limited measurements, model results, and satellite observations indicate that the atmosphere over most of the SEP is very clean. However, copper smelters located in Chile and Peru produce pollutants which become aerosols in the atmosphere. Aerosols are also present naturally in this area from sea salt and plankton. Aerosols are known to affect the formation of clouds and precipitation. If the aerosol concentration is high enough, it is thought the amount of drizzle produced by the MBL clouds could be suppressed. Therefore, VOCALS scientists will test hypotheses about the relationship between aerosols, atmospheric processes in clouds, and precipitation.

The climate system of the Southeast Pacific region Click on image for full size (60 Kb) Robert Wood (University of Washington) and the VOCALS Scientific Working Group

The Southeast Pacific Ocean region off the coastal areas of Peru and Chile is one part of the world where stratus and stratocumulus clouds are frequently present. Other areas include the subtropical climate regimes off the coast of California (US), and Namibia (Africa ). These areas are of great importance not only to regional climates, but to the Earth's global climate as well. The climates of these regions involve feedbacks between the ocean, clouds, atmosphere, and land. Scientists in the VOCALS Field campaign are focusing their experiments in the Southeast Pacific (SEP) Ocean off the coasts of Chile and Peru. They have chosen this area because the feedbacks in the regional climate systems are very clear.

The climate of the Southeast Pacific region is the result of interactions between the Andes Mountains, the ocean, and the atmosphere, including clouds. Clouds form right above the ocean, in an area known as the marine boundary layer. These clouds are of the low stratus type. They create an almost continuous blanket over much of the Southeast Pacific. The precipitation in this region is mostly in the form of drizzle.

Westerly winds blow thousands of miles across the Pacific Ocean toward South America. When they reach land and run into the Andes Mountains, they are forced to turn north. The wind causes the water at the ocean surface to move perpendicular to it, away from the coast, becasue of a process called Ekman transport. When the surface water moves westward, it is replaced by very cold, nutrient rich water from deep in the ocean in a process called upwelling. In the Southeast Pacific Ocean, upwelling is associated with the Humboldt Current system.

It appears that the atmosphere over most of the SEP is very clean. However, copper smelters located in Chile and Peru produce aerosols. Aerosols are also present naturally in this area from sea salt and plankton. Aerosols are known to affect the formation of clouds and precipitation.

The climate system of the Southeast Pacific region Click on image for full size (60 Kb) Robert Wood (University of Washington) and the VOCALS Scientific Working Group

There are a lot of clouds over the Southeast Pacific Ocean off the coasts of Peru and Chile in South America. In fact, this area has the largest amount of stratus and stratocumulus clouds in the world! These important clouds are part of the Southeast Pacific climate system. Other important parts of the climate system in this area include the Southeast Pacific Ocean and the Andes Mountain Range. Scientists in the VOCALS field campaign are going to study this area so they can learn more about the Southeast Pacific Ocean.

The Andes Mountains form a pretty big barrier to the surface winds. flow parallel to the western coast of South America. The winds help bring deep, nutrient-rich waters to the surface. These cold waters help support the largest area of stratocumulus clouds found on the planet.

Strong winds from the west blow thousands of miles across the Pacific Ocean toward South America. When they reach land and run into the Andes Mountains, they are forced to turn north. The winds also push ocean surface water away from the coast to the west in a process scientists call Ekman transport. When the surface water is pushed west it is replaced by very cold water from deep in the ocean. This is known as upwelling.

Most of the air over the Southeast Pacific Ocean is very clean. However, copper smelters located in Chile and Peru produce aerosols. Aerosols can also be found naturally in the Southeast Pacific region from sea salt and plankton. Aerosols are known to impact how clouds are formed.