Virendra P. Ghate
Atmospheric Scientist Virendra P. Ghate (EVS) will discuss his Laboratory-Directed Research and Development (LDRD) sponsored work at the LDRD Seminar Series presentation Tuesday, Aug. 22, 2017.
“Cloud Transitions in the North Pacific: Impact on Atmospheric Radiation” begins at 12:30 p.m. in the Bldg. 203 Auditorium. All are welcome to attend.
Abstract
Low-level stratocumulus clouds cover vast areas and are routinely observed over the Northeastern Pacific Ocean off the Californian coast. These stratocumulus clouds reflect greater amount of solar radiation back to space compared to the ocean surface, hence having a net cooling effect on the Earth’s surface. Winds transport the stratocumulus clouds southeast toward the Hawaiian region that has warmer ocean surface. This change in sea surface temperature together with other environmental factors affect the stratocumulus clouds, causing them to transition to broken shallow cumulus clouds. Satellite studies have shown the transition from stratocumulus-to-cumulus cloud regime occurring smoothly over a span of three days with a decrease in cloud cover that is accompanied by an increase in cloud top heights. However, it is challenging for most of the atmospheric models to accurately simulate the transition in cloud systems thereby introducing errors in forecast variables of greater interests like temperature and precipitation. The principle factors that affect this cloud transition are boundary layer radiative cooling, precipitation, latent heat flux and entrainment.
In this study, we have used the observations collected during the MAGIC field campaign to study the transition from stratocumulus to cumulus cloud regime. The Atmospheric Radiation Measurement (ARM)’s Mobile Facility was deployed on board a container ship that made transects from Los Angeles to Hawaii. We have used observations made during one of these transects by multiple instruments including Doppler cloud radars, Lidars, radiometers and radiosondes to retrieve cloud macro- and micro-physical properties. The retrieved variables were used to calculate profiles of radiative fluxes and heating rates through a radiative transfer model, hence enabling quantification of all the factors affecting the cloud transitions. Our initial results are consistent with previous modeling studies and show the transition to occur over a span of three days with deepening and warming of the boundary layer. The relative impact of the different factors on the transition however exhibits diurnal changes.
Biography
Virendra Ghate is an atmospheric scientist working in the Environmental Science Division. His research is mainly focused on studying boundary layer clouds and radiation using observations and simple models. His expertise includes retrieving cloud and precipitation microphysical properties using data collected by active remote sensors like Doppler radars and Lidars. Prior to joining Argonne he worked as a research faculty at Rutgers University for four years. He holds a bachelor’s in mechanical engineering from Nagpur University, and a M.S. and Ph.D. in meteorology from University of Miami.