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Juan Fang, Olivier Pauluis, and Fuqing Zhang

) investigated the eastern Pacific tropical cyclogenesis and the external influences on TC intensity via analyzing the isentropic potential vorticity. Merrill and Velden (1996) employed the isentropic coordinate analyses of rawinsondes and cloud motion wind vectors to describe the upper-tropospheric and lower-stratospheric circulation associated with Supertyphoon Flo (1990). More recently, the isentropic analysis has been applied to study various atmospheric flows using the equivalent potential temperature

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Olivier M. Pauluis and Agnieszka A. Mrowiec

advantage of the quasi conservation of entropy to isolate convective overturning from oscillatory motions. The concept of isentropic analysis (i.e., analyzing motions on surfaces of constant entropy) dates back to the early development of dynamical meteorology ( Rossby 1937 ). As potential temperature and entropy are approximately conserved in the free troposphere, the motions of air parcels can be tracked on isentropic surfaces even when a lack of observations prevents determining their vertical

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Agnieszka A. Mrowiec, Olivier M. Pauluis, and Fuqing Zhang

important insights on the nature of hurricanes, the actual behavior of real storms is much more complex owing to a wide range of scales involved. For example, interactions between organized convection in spiral rainbands in the outer convective regions and the eyewall can cause intensity variations and possibly play a role in the rapid intensification or the eyewall replacement cycle. In the present study, we utilize the isentropic analysis technique recently developed by Pauluis and Mrowiec (2013

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Noboru Nakamura and Abraham Solomon

in terms of Kelvin’s circulation and paints a fully Lagrangian-mean picture of general circulation ( Hoskins 1991 ; Nakamura 1995 ). The next section outlines the formalism and discusses the theoretical issues specific to the isentropic coordinate. Section 3 describes the numerical procedures of the diagnostics. Sections 4 and 5 present the analysis of the ERA-40 data and compare the results with the QG analysis in Part I . Section 6 provides a summary. 2. Theory a. Layer mass

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Olivier M. Pauluis

1. Introduction Isentropic analysis is a technique that was originally introduced in the late 1930s to study synoptic-scale motions ( Rossby 1937 ; Namias 1939 ; Namias and Stone 1940 ). It relies on analyzing atmospheric motions on surfaces of constant potential temperature. While not exactly conserved for atmospheric flows, potential temperature varies slowly when compared to its spatial location or to other thermodynamic variables such as pressure or temperature. This makes it possible to

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Agnieszka A. Mrowiec, O. M. Pauluis, A. M. Fridlind, and A. S. Ackerman

( Dunkerton 1997 ). However, at the opposite end of the gravity wave spectrum are small, virtually omnipresent, buoyant oscillations, which are also generated during the convective events. These oscillations do not contribute to the overall mass transport in the convective overturning but are very difficult to filter out using traditional methods of analysis. The concept of isentropic analysis can be traced to the early development of meteorology and works by Shaw (1930) and Rossby (1937) , who took

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Pascal Marquet and Thibaut Dauhut

motivations of these isentropic analysis methods are presented in Bleck (1973) , Roads (1986 ; with contributions from Namias, Smagorinsky, and Eliassen), and Moore (1989 ). In the 1930s, “there was quite a debate over what vertical coordinate system would be most useful for weather analysis and forecasting. German meteorologists and several European colleagues favored a constant pressure coordinate system while the British Commonwealth and the United States favored using a constant height system. But

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Takamichi Shoji, Yuki Kanno, Toshiki Iwasaki, and Koutarou Takaya

measure the equatorward cold airmass flux into the subtropics. The zonal mean meridional circulation analyzed using mass-weighted isentropic zonal means (MIM) depicts a distinct extratropical direct circulation in the winter hemispheres ( Townsend and Johnson 1985 ; Iwasaki 1989 , 1992 ; Juckes et al. 1994 ; Juckes 2001 ; Tanaka et al. 2004 ). The MIM analysis suggests that, in the lower troposphere, the cold air mass generated at high latitudes flows out to middle/low latitudes ( Iwasaki and

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Francis X. Crum and Duane F. Stevens

Atlantic during December 1978 is analyzed fromNMC gridpoint data using isentropic analysis. The advantages of this analysis technique are outlined, specificallywith regard to isentropic potential vorticity. Analysis of the Montgomery streamfunction on the 315 K isentropicsurface is preferable to the more traditional analysis of geopotential height on the 300 mb surface for describingthe evolution of the block. The sea level pressure pattern shows several intense cyclonic storms upstream of theblock

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Robert L. Mancuso, Roy M. Endlich, and L. J. Ehernberger

1326 MONTHLY WEATHER REVIEW VOr.UME 109An Objective Isobaric/Isentropic Technique for Upper Air Analysis ROBERT L. MANCUSO AND ROY M. ENDLICHAtmospheric Science Center, SRI International, Menlo Park, CA 94025 L. J. EHERNBERGERNational Aeronautics and Space Administration, Hugh L. Dryden Flight Research Center, Edwards, CA 93523(Manuscript, received 7 December 1979, in final form 30

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