PNNL

The Science                                

Researchers investigated the movement of energy across space, or energy transport, associated with the motion of damp air, known as moist convection, caused by differences in the land surface. They conducted large eddy simulations with an interactive land model, removing large-scale background wind to isolate the role of land-surface variability during the HI-SCALE field campaign in Oklahoma. By examining energy changes for areas with the same equivalent potential temperature, known as isentropic coordinates, the researchers found that shallow clouds form over locations with high values of energy, specifically reflected by high water vapor in this case. Gradients in soil moisture also affect energy transport—larger gradients are associated with more vigorous energy transport and stronger air mixing.

The Impact

This study sheds new light on the complex interactions between the land and atmosphere that affect weather and climate, providing important insights into energy transport and shallow cloud formation. Examining the effects of different soil moisture distributions on moist convection caused by surface changes produced a deeper understanding of how and where shallow clouds form. These results could lead to improved prediction of rain from convective clouds.

Summary

This study provides novel insights into the transport of energy associated with moist convection triggered by differences in the land surface. Researchers used isentropic coordinates to examine how land differences affect convective cloud formation. They found that the sub-mesoscale flow plays a dominant role in the vertical transport of energy near the surface and that isentropic analysis is a useful tool to illustrate land–atmosphere interactions. The study also examined the effects of initial soil moisture gradients on energy transport. Larger soil moisture gradients are associated with more vigorous energy transport and stronger air parcel mixing. This new understanding of energy transport in moist convection could improve researchers’ ability to predict where convective clouds will form.

PNNL Contact

Jerome Fast, Pacific Northwest National Laboratory, jerome.fast@pnnl.gov

Funding

This study is supported by the Department of Energy, Office of Science, Biological and Environmental Research program as part of the Atmospheric System Research program. The modeling studies were supported by the Cascade computational cluster at EMSL, the Environmental Molecular Sciences Laboratory.