Time filter

Source Type

Fargo, ND, United States

Xue L.,U.S. National Center for Atmospheric Research | Chu X.,University of Wyoming | Rasmussen R.,U.S. National Center for Atmospheric Research | Breed D.,U.S. National Center for Atmospheric Research | And 2 more authors.
Journal of Applied Meteorology and Climatology | Year: 2014

A numerical modeling study has been conducted to explore the ability of the Weather Research and Forecasting (WRF) model-based large-eddy simulation (LES) with 100-m grid spacing to reproduce silver iodide (AgI) particle dispersion by comparing the model results with measurements made on 16 February 2011 over theMedicineBowMountains inWyoming. Xue et al.'s recently developed AgI cloud-seeding parameterization was applied in this study to simulate AgI release from ground-based generators. Qualitative and quantitative comparisons between the LES results and observed AgI concentrations were conducted.Analyses of turbulent kinetic energy (TKE) features within the planetary boundary layer (PBL) and comparisons between the 100-m LES and simulations with 500-m grid spacing were performed as well. The results showed the following: 1) Despite the moist bias close to the ground and above 4kmAGL, the LES with 100-m grid spacing captured the essential environmental conditions except for a slightly more stable PBL relative to the observed soundings. 2) Wind shear is the dominantTKE productionmechanism inwintertime PBL over complex terrain and generates a PBL of about 1000-m depth. The terrain-induced turbulent eddies are primarily responsible for the vertical dispersion of AgI particles. 3) The LES-simulated AgI plumes were shallow and narrow, in agreement with observations. The LES overestimated AgI concentrations close to the ground, which is consistent with the higher static stability in the model than is observed. 4) Non-LES simulations using PBL schemes had difficulty in capturing the shear-dominant turbulent PBL structure over complex terrain in wintertime. Therefore, LES of wintertime orographic clouds with grid spacing close to 500m or finer are recommended. © 2014 American Meteorological Society. Source

Krauss T.W.,Weather Modification Inc. | Sin'kevich A.A.,Voeikov Main Geophysical Observatory | Burger R.,University of Witwatersrand | Veremei N.E.,Voeikov Main Geophysical Observatory | And 2 more authors.
Russian Meteorology and Hydrology | Year: 2011

Changes are analyzed of a Cb cloud characteristics due to its merging with feeder clouds, on the data on a long-living Cb cloud in Saudi Arabia on July 4, 2008. Continuous radar and satellite observations of the cloud are carried out during 6 h. The Cb cloud development is also numerically simulated using a nonstationary 11/2 model. It is found that the processes of Cb cloud merging with feeder clouds developing in its vicinities affect significantly the Cb cloud development. This impact demonstrates itself in longer duration of the Cb cloud life span, increasing top height, reflectivity, precipitation duration and intensity. Modification of the feeder clouds can accelerate their development, which eventually can affect notably the Cb cloud. © 2011 Allerton Press, Inc. Source

Krauss T.W.,Weather Modification Inc. | Sin'kevich A.A.,Voeikov Main Geophysical Observatory | Ghulam A.S.,Presidency of Meteorology and Environment
Russian Meteorology and Hydrology | Year: 2012

Presented are the results of radar investigations of cloud merger during their natural cycle of development and after the seeding. The observations were carried out in the southwest of the Kingdom of Saudi Arabia in 2008. It is revealed that the merging was observed under conditions of very unstable atmosphere, when the convective available potential energy exceeded 3000 J/kg. The cloud merger impacts significantly their development. The most considerable changes due to the cloud merging were observed for the cloud mass and precipitation flow increased as a result of this process by two or three times. It is discovered that the impact of the merger of clouds on their characteristics exceeds significantly the effect of seeding carried out for the feeder clouds. © 2012 Allerton Press, Inc. Source

Krauss T.W.,Weather Modification Inc. | Sin'kevich A.A.,Voeikov Main Geophysical Observatory | Ghulam A.S.,Presidency of Meteorology and Environment
Russian Meteorology and Hydrology | Year: 2012

Considered is a case of the cumulonimbus cloud development in the southwestern part of Saudi Arabia with a very high precipitation intensity. The height of the cloud top amounted to 14 km and the radar reflectivity, to 60 dBZ. Carried out is the comparison of remote methods of measuring the intensity of precipitation from the cloud under study: the radar (using the relationship between the reflectivity and precipitation intensity) and satellite IR-radiometric (based on the results of sounding with the SEVERI radiometer installed at the Meteosat-8 satellite) methods. A split-window technique was used for detecting the position of the cloud top from the radiometric observations. The analysis enabled to select the best relationships for estimating the precipitation intensity from the data of radar and satellite measurements. The computations based on these relationships correspond most closely to the ground-based measurements with the precipitation gage. © 2012 Allerton Press, Inc. Source

Sinkevich A.A.,Voeikov Main Geophysical Observatory | Crauss T.W.,Weather Modification Inc.
Russian Meteorology and Hydrology | Year: 2010

The results of experiments to enhance precipitation in Saudi Arabia by Weather Modification Inc. (USA) are presented. Statistical analysis of radar measurements indicates that there are significant changes in cloud characteristics and an increase in precipitation due to seeding. © 2010 Allerton Press, Inc. Source

Discover hidden collaborations