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Quasi-Lagrangian Measurements in Convective Boundary Layer Plumes and Their Implications for the Calculation of CAPE

Rennó, Nilton O. and Williams, Earle R. (1995) Quasi-Lagrangian Measurements in Convective Boundary Layer Plumes and Their Implications for the Calculation of CAPE. Monthly Weather Review, 123 (9). pp. 2733-2742. ISSN 0027-0644. doi:10.1175/1520-0493(1995)123<2733:QLMICB>2.0.CO;2.

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Measurements were made to determine the level of origin of air parcels participating in natural convection. Lagrangian measurements of conservative variables are ideal for this purpose. A simple remotely piloted vehicle was developed to make in situ measurements of pressure, temperature, and humidity in the convective boundary layer. These quasi-Lagrangian measurements clearly show that convective plumes originate in the superadiabatic surface layer. The observed boundary layer plumes have virtual temperature excesses of about 0.4 K in a tropical region (Orlando, Florida) and of about 1.5 K in a desert region (Albuquerque, New Mexico). The water vapor contribution to parcel buoyancy was appreciable in Orlando but in Albuquerque was insignificant. These observations indicate that convective available potential energy should he determined by adiabatically lifting air parcels from the surface layer, at screen level.

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Additional Information:© 1995 American Meteorological Society. Manuscript received 28 September 1994, in final form 16 March 1995. The experiments were supported by by MIT Lincoln Laboratory with encouragement from Dr. Mark Weber. Mark Isaminger of MIT Lincoln Laboratory, Charlie Lyles of the National Weather Service in Albuquerque, and Ken Goss of Vaisala, Inc. provided radiosonde equipment Dr. Frank Colby and his graduate students at the University of Lowell assisted with soundings in Orlando. We would like to thank Dennis Boe·cippio for many scientific discussions and extensive assistance with the observations and Maria Carmen Lemos for helping with the construction and operation of the RPV, and for the skillful operation of the video equipment in Orlando. We also would like to thank Mr. Jeff Chaves for technical assistance in Albuquerque, and the entire Williams family for helping with operations, both in Orlando and Albuquerque. Thanks are also due to the LLNL RAS Division and the University of California's Institutional Collaborative Research (InCoR) program for partially supporting this study. Finally, we would like to thank C. Doswell III and an anonymous reviewer for their many suggestions and helpful criticisms that substantially improved the original paper. Doswell also suggested the back of the envelope calculations on the eddy viscosity parameter.
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MIT Lincoln LaboratoryUNSPECIFIED
Issue or Number:9
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ID Code:85253
Deposited By: Ruth Sustaita
Deposited On:12 Mar 2018 21:27
Last Modified:15 Nov 2021 20:27

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