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Andrew J. Majda and Samuel N. Stechmann

example, precipitation and vertical transports of temperature and moisture can significantly alter the larger-scale thermodynamic environment. A less-understood effect of MCS on their larger-scale environment is convective momentum transport (CMT). A pervasive aspect of this is the idea of “cumulus friction”; however, many studies have also shown that the CMT of some MCS can actually accelerate the background wind ( Wu and Yanai 1994 ; LeMone and Moncrieff 1994 ; Tung and Yanai 2002a , b ). On the

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Akio Arakawa, Joon-Hee Jung, and Chien-Ming Wu

of heat source and moisture sink associated with cloud clusters, and the 3D heat and moisture budgets over the Tibetan plateau. Developed new approaches in data analysis Examples include the power spectrum analysis combined with linearized equations and the analysis of the apparent heat source Q 1 and apparent moisture sink Q 2 . Deduced hidden reality from scarce data Examples include the transition of tropical disturbance from cold-core wave to warm-core vortex, the Yanai wave, and the heat

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Richard H. Johnson, Paul E. Ciesielski, and Thomas M. Rickenbach

1. Introduction A conceptual breakthrough in understanding how tropical cloud systems interact with their environment was achieved through the landmark paper of Yanai et al. (1973) , wherein the now-familiar Q 1 (apparent heat source) and Q 2 (apparent moisture sink) were defined. However, well prior to the 1973 study, Yanai (1961) introduced Q 1 and Q 2 in a paper titled “A detailed analysis of typhoon formation,” which investigated the dynamic and thermodynamic properties of the

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W.-K. Tao, Y. N. Takayabu, S. Lang, S. Shige, W. Olson, A. Hou, G. Skofronick-Jackson, X. Jiang, C. Zhang, W. Lau, T. Krishnamurti, D. Waliser, M. Grecu, P. E. Ciesielski, R. H. Johnson, R. Houze, R. Kakar, K. Nakamura, S. Braun, S. Hagos, R. Oki, and A. Bhardwaj

large-scale horizontal averages. The right-hand side (RHS) is the total derivative of θ , the potential temperature, (times the nondimensional pressure) measurable from radiosonde data. Here the large-scale vertical motion w is diagnosed from the horizontal winds via the kinematic method with appropriate boundary conditions on w at the surface and the tropopause. There is an accompanying equation for the apparent moisture sink or drying ( Q 2 ), which is similar to Eq. (2-1) except that is

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I. Gultepe, A. J. Heymsfield, P. R. Field, and D. Axisa

role for ice crystal growth that is a function of both T and available moisture. Previous studies suggest ice crystal number concentrations N i within a cloud may well exceed those of ice nucleating particles (INPs) based on observations and parameterizations (e.g., Fletcher 1962 ; Hobbs 1975 ). These studies suggested that ice multiplication may have occurred when the measured N i is much larger than predicted by the Fletcher (1962) study for a given temperature. Ice multiplication here

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Ismail Gultepe, Andrew J. Heymsfield, Martin Gallagher, Luisa Ickes, and Darrel Baumgardner

by modulating the heat and moisture fluxes in the surface layer and lower troposphere ( Curry et al. 1996 ; Beesley and Moritz 1999 ). During Arctic winters when temperatures fall well below −30°C and relative humidity with respect to liquid water (RHw) exceeds 80%, even a shallow layer of ice fog will significantly affect the surface energy budget ( Blanchet and Girard 1995 ; Curry et al. 1990 , 1996 ). Sea ice thickness and snow cover also are impacted because of ice fog’s interaction with

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Christopher C. Weiss, Howard B. Bluestein, Andrew L. Pazmany, and Bart Geerts


A case study of a double dryline on 22 May 2002 is presented. Mobile, 3-mm-wavelength Doppler radars from the University of Massachusetts and the University of Wyoming (Wyoming cloud radar) were used to collect very fine resolution vertical-velocity data in the vicinity of each of the moisture gradients associated with the drylines. Very narrow (50–100 m wide) channels of strong upward vertical velocity (up to 8 m s–1) were measured in the convergence zone of the easternmost dryline, larger in magnitude than reported with previous drylines. Distinct areas of descending motion were evident to the east and west of both drylines. Radar data are interpreted in the context of other observational platforms available during the International H2O Project (IHOP-2002). a variational ground-based mobile radar data processing technique was developed and applied to pseudo-dual-Doppler data collected during a rolling range-height indicator deployment. It was found that there was a secondary (vertical) circulation normal to the easternmost moisture gradient; the circulation comprised an easterly component near-surface flow to the east, a strong upward vertical component in the convergence zone, a westerly return, flow above the convective boundary layer, and numerous regions of descending motion, the most prominent approximately 3–5 km to the east of the surface convergence zone.

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John R. Gyakum


Fred Sanders' teaching and research contributions in the area of quasigeostrophic theory are highlighted in this paper. The application of these contributions is made to the topic of extreme cold-season precipitation events in the Saint Lawrence valley in the northeastern United States and southern Quebec.

This research focuses on analyses of Saint Lawrence valley heavy precipitation events. Synoptic- and planetary-scale circulation anomaly precursors are typically identified several days prior to these events. These precursors include transient upper-level troughs, strong moisture transports into the region, and anomalously large precipitable water amounts. The physical insight of Fred Sanders' work is used in the analysis of these composite results. Further details of this insight are provided in analyses of one case of heavy precipitation.

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Larry K. Berg and Peter J. Lamb

1. Setting the research agenda It is well known that the exchange of heat and moisture between the surface and atmosphere plays a key role in the earth’s climate system (e.g., Randall et al. 2007 ). Science questions related to land–atmosphere interactions have remained an active topic of research, both inside and outside of the ARM Program, for a considerable period of time (e.g., Betts et al. 1996 ; Betts 2003 , 2004 ; Dirmeyer et al. 2006 ; Betts 2009 ; Santanello et al. 2009 ; Betts

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Christa D. Peters-Lidard, Faisal Hossain, L. Ruby Leung, Nate McDowell, Matthew Rodell, Francisco J. Tapiador, F. Joe Turk, and Andrew Wood

depending on humid or arid climates, as defined by relative humidity. The most general form of the Penman–Monteith equation utilizes both aerodynamic and canopy resistances in series, where the canopy resistance (or its inverse, the conductance) can be calculated using a Jarvis (1976) approach, which depends on both leaf area and soil moisture (e.g., Lhomme et al. 1998 ). A comprehensive summary of ET theory and methods is given in Brutsaert (1982) and Dolman (2005) . Modern approaches to

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