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Priscilla Cehelsky and Ka Kit Tung

3282 JOURNAL OF THE ATMOSPHERIC SCIENCES VOL. 44, NO. 21Theories of Multiple Equilibria and Weather Regimes--A Critical Reexamination. Part H: Baroclinic Two-Layer Models PRISCILLA CEHELSKY AND KA KIT TUNG*Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 021 $9(Manuscript received 13 October 1986, in final form 1 ~une 1987) ABSTRACT Previous results based on low- and

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Robert R. Lee

Rocky Mountain region (e.g., weathermodification potential, ski industry, avalanche prediction, snow removal, etc.) calls for an understanding ofhow the mountain environment and synoptic weather systems interact to produce precipitating orographiccloud systems. This may be achieved by recognizing that each cloud system can be broken down into individualcloud components. In each of the case studies, a synoptic cloud component, an orographic cloud component,and a convective cloud component were

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Takenari Kinoshita and Kaoru Sato

wave forcing to the mean flow and that 3D-flux-W describes the wave propagation, we show an analysis of European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) data to compare the 3D residual mean flow derived by Kinoshita and Sato (2013) to the divergences of three kinds of 3D wave activity flux (3D-flux-M, 3D-flux-W, and Plumb’s wave activity flux). The direction and magnitude of the three kinds of 3D wave activity flux are compared. a. Data description As

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Melissa kazemirad and Mark A. Miller

the weaker inversions and deeper MBLs that are observed in these environments tend to be more decoupled. These studies motivate us to investigate the applicability of the BW97 deepening–warming hypothesis in the context of MBL cloud transitions often observed in satellite images behind cold fronts in the ENA region. We examine the life cycle of MBL clouds associated with two summertime cold fronts that moved through the ENA region. High-resolution, large-domain simulations using the Weather

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Tianqi Zuo, Alison D. Nugent, and Gregory Thompson


In recent decades, a significant rainfall decline over the Island of Hawai‘i has been noted, with many hypothesizing that the drying is associated with the volcanic aerosols emitted from the Kīlauea Volcano. While it is clear that volcanic emissions can create hazardous air quality for Hawaiian communities, the impacts on rainfall are less clear. Here we investigate the impact of volcanic aerosol emissions on Hawai‘i Island rainfall. Based on observed daily rainfall and SO2 emissions, it is found that days with high SO2 emissions have on average 8 mm day−1 less rainfall downstream of the Kīlauea Volcano. Sensitivity studies with varying volcanic aerosol emission sources from the Kīlauea vent locations have also been conducted by the Weather Research and Forecasting (WRF) Model in order to examine the detailed physical processes. Consistent with SO2 air quality observations, it is found that the diurnal change in aerosol number concentration is strongly dependent on the diurnal variation of local circulations. The added aerosols are lofted into the orographic convection where they modify the microphysical properties of the warm clouds by increasing the cloud droplet number concentration, decreasing the cloud droplet size, increasing cloud water content and enhancing cloud evaporation. The volcanic aerosols also delay precipitation production and modify the spatial distribution of rainfall on the downstream mountainside. The modification of precipitation on an island has far reaching consequences. For this reason, we work to quantify the sensitivity of the orographic precipitation to volcanic aerosols and move beyond hypothesized relationships towork toward understanding the underlying problem.

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V. Lynn Harvey and Matthew H. Hitchman

a detailed examination of 10 years( 1985-1994) of data from the European Centre for Medium-Range Weather Forecasts in the layer 250-10 hPa,the following definition of the "Aleutian High" is proposed: 1 ) 10-hPa heights exceeding 30.8 km in the sector40--80~1, 120-E- 100-W, 2 ) during 1 October- 31 March, 3 ) with areal extent greater than 50- long x 10- lat.,'4) with relative vorticity of less than -2.5 x 10-s s-l, and 5) lasting at least 5 days. More than 60% of daysduring December, January

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David B. Johnson

assistance in obtaining and analyzing ourCCN data. This research was performed under NSFGrant 33373 as part of the research on METROMEX,sponsored by the Weather Modification Program,Research Applications Directorate, National ScienceFoundation.REFERENCESElliott, W. P., and R. Egami, 1975: CCN measurements over theocean. J. Atmos. Sci., 32, 371-374.Fitzgerald, J. w., 1972: A study of the initial phase of cloud droplet growth by condensation: Comparison between theory and observation. Ph

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Wallace E. Howell

, Lexington, Mass.15 February 1965 The findings presented by Braham (1964) are indeedinteresting and valuable; however, their bearing on thequestion of rain stimulation is left rather obscure byomission of the part played by the clouds that were thesubject of this study in the over-all production of summer-time precipitation in the area. The Whitetop Project is one of two cited by the recent report of the Panelon Weather Modification of the National Academy ofScience (1964) as having "led to extremely

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Robert M. Rauber, William Brune, and Walter Robinson

of scholarly work that would serve the needs of the community. Both committees recommended that the AMS set a goal of establishing a new Journal of Atmospheric Chemistry and Aerosols. After discussion within the PC and consultation with the AMS STAC committees for Atmospheric Chemistry, Cloud Physics, Planned and Inadvertent Weather Modification, Atmospheric Radiation, Climate Variability and Change, and Meteorological Aspects of Air Pollution, the PC recommended, and the Council approved, a plan

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Jan Barkmeijer

nonlinear interactionsbetween the evolving permrbafi0n and the reference forecast orbit obstruct the fast-growing property of thesingular vectors. In the modification procedure, part of this nonlinear error dynamics is taken into account. Thespatial pattern~ of modified and origins perturbations still show a great resemblance. Individual cells in thepatterns generally differ only in amplitude, not in their location.1. Introduction One of the basic assumptions in short-range predictability research is

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