National Severe Storms Laboratory
Retrieving the cumulus entrainment rate remotely
Dr. Tim Wagner
Department of Atmospheric Sciences
10 July 2014, 10:00 AM
National Weather Center, Room 5600
120 David L. Boren Blvd.
University of Oklahoma
The entrainment of environmental air into cumulus clouds can greatly influence the impact these clouds have on their environment. As cumuli are an important part of the climate system, these impacts must be accounted for in simulations but their small spatial extent means they must be parameterized. The parameterization of cumuli and the impact of entrainment upon them have proven to be difficult problems in part due to the lack of available observations of entrainment. Entrainment has been traditionally measured via direct penetration of clouds by instrumented aircraft but the expense and difficulty associated with this method means that the scope of the available entrainment observations is small.
To expand the number of observations of entrainment available for analysis, a remote retrieval method using ground-based instrumentation has been developed. This method, called the Entrainment Rate In Cumulus Algorithm (ERICA) retrieves the fractional entrainment rate through a Gauss-Newton optimal estimation retrieval. High temporal resolution observations of cumuli and their environment and a guess of the entrainment rate are ingested by a cloud parcel model, in this case the Explicit Mixing Parcel Model (EMPM). The entrainment rate is iteratively adjusted until the modeled cloud matches the observations. ERICA has been shown to correspond well with other methods of retrieving the entrainment rate. Results for both shallow continental cumulus and deep tropical convection will be shown.
For accommodations based on disability, or more details, please call 325-6561. All visitors without NOAA or University of Oklahoma identification must register at the registration desk on arrival. Visitor parking is available for all University visitors. However, faculty/staff/students must have a current multi-purpose parking permit. Additional parking is available at the Lloyd Noble Center (LNC) for those individuals who do not have a parking permit. You do not need a permit to park in one of 1,200 spaces reserved for CART bus riders, although you must ride the CART shuttle to park in the reserved area. This area is on the north central side of the Lloyd Noble Center. Elsewhere at the LNC, permits are required.
The University of Oklahoma is a smoke-free / tobacco-free campus.