The Impact of Ground-Based Glaciogenic Seeding on Orographic Clouds and Precipitation: A Multisensor Case Study

2014 ◽  
Vol 53 (4) ◽  
pp. 890-909 ◽  
Author(s):  
Binod Pokharel ◽  
Bart Geerts ◽  
Xiaoqin Jing
Keyword(s):  
Band 3 ◽  
Cloud Base ◽  
Near Surface ◽  
Target Region ◽  
Orographic Clouds ◽  
Snow Crystals ◽  
Corroborative Evidence ◽  
Glaciogenic Seeding ◽  
The Impact

AbstractA case study is presented from the 2012 AgI Seeding Cloud Impact Investigation, an experiment conducted over the Sierra Madre in southern Wyoming to study the impact of ground-based glaciogenic seeding on precipitation. In this case, on 21 February, the temperature in the turbulent boundary layer above cloud base in the target region was just below −8°C, the target orographic clouds contained liquid water, and the storm was rather steady during the measurement period, consisting of an untreated period, followed by a treated period. Eight silver iodide (AgI) generators were used, located on the windward mountain slope. This study is unprecedented in its diversity of radar systems, which included the W-band (3 mm) profiling Wyoming Cloud Radar (WCR), a pair of Ka-band (1 cm) profiling Micro Rain Radars (MRRs), and an X-band (3 cm) scanning Doppler-on-Wheels (DOW) radar. The WCR was on board a research aircraft flying geographically fixed tracks, the DOW was located on the main mountain pass in the target region, one MRR was at this pass, and the other was upstream of the generators. Composite data from the three radars indicate that near-surface reflectivity was higher during seeding, a change that could not be accounted for by storm intensification upstream of the generators. Data from a Parsivel disdrometer at the pass indicate that the concentration of snow crystals of all sizes was larger during seeding, although this change was somewhat delayed. This study highlights the challenge of an observational study to unambiguously identify a seeding signal, as well as the value of cumulative corroborative evidence from independent sources.

A Case Study on the Impact of Ground-based Glaciogenic Seeding on Winter Orographic Clouds at Daegwallyeong

2015 ◽  
Vol 36 (4) ◽  
pp. 301-314 ◽  
Author(s):  
Ha-Young Yang ◽  
◽  
Sanghee Chae ◽  
Jin-Yim Jeong ◽  
Seong-Kyu Seo ◽  
...  
Keyword(s):  
Orographic Clouds ◽  
Glaciogenic Seeding ◽  
The Impact

An Airborne Profiling Radar Study of the Impact of Glaciogenic Cloud Seeding on Snowfall from Winter Orographic Clouds

2010 ◽  
Vol 67 (10) ◽  
pp. 3286-3302 ◽  
Author(s):  
Bart Geerts ◽  
Qun Miao ◽  
Yang Yang ◽  
Roy Rasmussen ◽  
Daniel Breed
Keyword(s):  
Doppler Radar ◽  
Weather Conditions ◽  
Cold Season ◽  
Near Surface ◽  
Medicine Bow Mountains ◽  
Orographic Clouds ◽  
Surface Reflectivity ◽  
Glaciogenic Seeding ◽  
The Impact ◽  
Composite Data

Abstract Data from an airborne vertically pointing millimeter-wave Doppler radar are used to study the cloud microphysical effect of glaciogenic seeding of cold-season orographic clouds. Fixed flight tracks were flown downstream of ground-based silver iodide (AgI) generators in the Medicine Bow Mountains of Wyoming. Composite data from seven flights, each with a no-seeding period followed by a seeding period, indicate that radar reflectivity was higher near the ground during the seeding periods. Several physical considerations argue in favor of the hypothesis that the increase in near-surface reflectivity is attributed to AgI seeding. While the increase in near-surface reflectivity and thus snowfall rate are statistically significant, caution is warranted in view of the large natural variability of weather conditions and the small size of the dataset.

scholarly journals Dual-Polarization Radar Data Analysis of the Impact of Ground-Based Glaciogenic Seeding on Winter Orographic Clouds. Part II: Convective Clouds

2015 ◽  
Vol 54 (10) ◽  
pp. 2099-2117 ◽  
Author(s):  
Xiaoqin Jing ◽  
Bart Geerts
Keyword(s):  
Cloud Base ◽  
Base Temperature ◽  
Target Area ◽  
Dual Polarization ◽  
Low Level ◽  
Convective Clouds ◽  
Orographic Clouds ◽  
Orographic Convection ◽  
Glaciogenic Seeding ◽  
The Impact

AbstractThis second paper of a two-part series aims to explore the ground-based glaciogenic seeding impact on wintertime orographic clouds using an X-band dual-polarization radar. It focuses on three cases with shallow to moderately deep orographic convection that were observed in January–February of 2012 as part of the AgI Seeding Cloud Impact Investigation (ASCII) project over the Sierra Madre in Wyoming. In each of the storms the bulk upstream Froude number exceeded 1, suggesting unblocked flow. Low-level potential instability was present, explaining orographic convection. The clouds contained little supercooled liquid water on account of the low cloud-base temperature. Ice-crystal photography shows that snow mainly grew by diffusion and aggregation. To examine the seeding effect of silver iodide (AgI), five study areas are defined: two target areas and three control areas. Comparisons are made between the control and target areas as well as between a treated, or seeded, period and an untreated period. Low-level reflectivity tends to increase in the target areas relative to the control. This increase is larger in the lee target area than in the upwind target area, suggesting that precipitation enhancement is delayed in the presence of convection. The echo tops of the convective cells are not higher during seeding, relative to simultaneous changes in the control regions. This result suggests that the dynamic-seeding mechanism does not apply for the cold-base convective clouds that are studied here. An analysis of differential reflectivity and snow photography suggests that static seeding is the more likely snow-enhancement mechanism in these clouds.

scholarly journals A Case Study of Cloud Radar Observations and Large-Eddy Simulations of a Shallow Stratiform Orographic Cloud, and the Impact of Glaciogenic Seeding

2017 ◽  
Vol 56 (5) ◽  
pp. 1285-1304 ◽  
Author(s):  
Xia Chu ◽  
Bart Geerts ◽  
Lulin Xue ◽  
Binod Pokharel
Keyword(s):  
Liquid Water ◽  
Supercooled Liquid ◽  
Cold Season ◽  
Cloud Base ◽  
Target Area ◽  
Blowing Snow ◽  
Large Eddy ◽  
Orographic Clouds ◽  
Glaciogenic Seeding ◽  
The Impact

AbstractThe impact of glaciogenic seeding on precipitation remains uncertain, mainly because of the noisy nature of precipitation. Operational seeding programs often target cold-season orographic clouds because of their abundance of supercooled liquid water. Such clouds are complicated because of common natural seeding from above (seeder–feeder effect) or from below (blowing snow). Here, observations, mainly from a profiling airborne Doppler radar, and numerical simulations are used to examine the impact of glaciogenic seeding on a very shallow (<1 km), largely blocked cloud that is not naturally seeded from aloft or from below. This cloud has limited but persistent supercooled liquid water, a cloud-base (top) temperature of −12°C (−16°C), and produces only very light snowfall naturally. A Weather Research and Forecasting Model large-eddy simulation at 100-m resolution captures the observed upstream stability and wind profiles and reproduces the essential characteristics of the orographic flow, cloud, and precipitation. Both observations and simulations indicate that seeding locally increases radar (or computed) reflectivity in the target area, even after removal of the natural trend between these two periods in a nearby control region. A model sensitivity run suggests that seeding effectively glaciates the mostly liquid cloud and substantially increases snowfall within the seeding plume. This is due to a dramatic increase in the number of ice particles and not to their size. The increased ice particle concentration facilitates snow growth by vapor deposition in a cloud the temperature range of which is conducive to the Bergeron process.

Dual-Polarization Radar Data Analysis of the Impact of Ground-Based Glaciogenic Seeding on Winter Orographic Clouds. Part I: Mostly Stratiform Clouds

2015 ◽  
Vol 54 (9) ◽  
pp. 1944-1969 ◽  
Author(s):  
Xiaoqin Jing ◽  
Bart Geerts ◽  
Katja Friedrich ◽  
Binod Pokharel
Keyword(s):  
Radar Data ◽  
Control Area ◽  
Target Area ◽  
Dual Polarization ◽  
Stratiform Clouds ◽  
Orographic Clouds ◽  
Close Range ◽  
Glaciogenic Seeding ◽  
Differential Reflectivity ◽  
The Impact

AbstractThe impact of ground-based glaciogenic seeding on wintertime orographic, mostly stratiform clouds is analyzed by means of data from an X-band dual-polarization radar, the Doppler-on-Wheels (DOW) radar, positioned on a mountain pass. This study focuses on six intensive observation periods (IOPs) during the 2012 AgI Seeding Cloud Impact Investigation (ASCII) project in Wyoming. In all six storms, the bulk upstream Froude number below mountaintop exceeded 1 (suggesting unblocked flow), the clouds were relatively shallow (with bases below freezing), some liquid water was present, and orographic flow conditions were mostly steady. To examine the silver iodide (AgI) seeding effect, three study areas are defined (a control area, a target area upwind of the crest, and a lee target area), and comparisons are made between measurements from a treated period and those from an untreated period. Changes in reflectivity and differential reflectivity observed by the DOW at low levels during seeding are consistent with enhanced snow growth, by vapor diffusion and/or aggregation, for a case study and for the composite analysis of all six IOPs, especially at close range upwind of the mountain crest. These low-level changes may have been affected by natural changes aloft, however, as evident from differences in the evolution of the echo-top height in the control and target areas. Even though precipitation in the target region is strongly correlated with that in the control region, the authors cannot definitively attribute the change to seeding because there is a lack of knowledge about natural variability, nor can the outcome be generalized, because the sample size is small.

The impact of ground-based glaciogenic seeding on clouds and precipitation over mountains: A multi-sensor case study of shallow precipitating orographic cumuli

2014 ◽  
Vol 147-148 ◽  
pp. 162-182 ◽  
Author(s):  
Binod Pokharel ◽  
Bart Geerts ◽  
Xiaoqin Jing ◽  
Katja Friedrich ◽  
Joshua Aikins ◽  
...  
Keyword(s):  
Glaciogenic Seeding ◽  
The Impact

scholarly journals Assessing the efficiency of a “buried wall” barrier in the establishment of near-surface long-term storage and disposal facilities for RW

2021 ◽  
Vol 14 (1) ◽  
pp. 96-105
Author(s):  
V. V. Suskin ◽  
◽  
I. V. Kapyrin ◽  
F. V. Grigorev ◽  
◽  
...  
Keyword(s):  
Near Surface ◽  
Transfer Processes ◽  
Long Term Storage ◽  
Mass Transfer Processes ◽  
High Degree ◽  
The Impact ◽  
Term Storage

The article evaluates the impact of a “buried wall” barrier on the long-term safety during the long-term storage1 or in-situ disposal of nuclear legacy facilities, in particular, industrial reservoirs, as well as during the development of near-surface disposal facilities for radioactive waste (RWDF). For assessment purposes, filtration and mass transfer processes have been numerically modelled in the GeRa code based on a case study of a reference near-surface facility. The study explores in which way the available covering screen affects the dynamics of contaminant spread. It evaluates the sensitivity of the results to the dispersion parameter commonly characterized by a high degree of uncertainty.

scholarly journals Impact of surface and near-surface processes on ice crystal concentrations measured at mountain-top research stations

2017 ◽  
Author(s):  
Alexander Beck ◽  
Jan Henneberger ◽  
Jacob P. Fugal ◽  
Robert O. David ◽  
Larissa Lacher ◽  
...  
Keyword(s):  
Ice Crystals ◽  
Surface Processes ◽  
Strong Impact ◽  
Blowing Snow ◽  
Ice Crystal ◽  
Turbulent Layer ◽  
Near Surface ◽  
Orographic Clouds ◽  
The Impact

Abstract. In-situ cloud observations at mountain-top research stations regularly measure ice crystal number concentrations (ICNCs) orders of magnitudes higher than expected from measurements of ice nucleating particle (INP) concentrations. Thus, several studies suggest that mountain-top in-situ measurements are influenced by surface processes, e.g. blowing snow, hoar frost or riming on snow covered trees, rocks and the snow surface. A strong impact on the observed ICNCs on mountain-top stations by surface processes may limit the relevance of such measurements and possibly affects the development of orographic clouds. This study assesses the impact of surface processes on in-situ cloud observations at the Sonnblick Observatory in the Hohen Tauern Region, Austria. Vertical profiles of ICNCs above a snow covered surface were observed up to a height of 10 m. The ICNC decreases at least by a factor of two at 10 m, if the ICNC at the surface is larger than 100 L−1. This decrease can be up to one order of magnitude during in-cloud conditions and reached its maximum of more than two orders of magnitudes when the station was not in cloud. For one case study, the ICNC for regular and irregular ice crystals showed a similar relative decrease with height, which cannot be explained by the above mentioned surface processes. Therefore, two near-surface processes are proposed to enrich ICNCs and explain these finding. Either sedimenting ice crystals are captured in a turbulent layer above the surface or the ICNC is enhanced in a convergence zone, because the cloud is forced over a mountain. These two processes would also have an impact on ICNCs measured at mountain-top stations if the surrounding surface is not snow covered. Conclusively, this study strongly suggests that ICNCs measured at mountain-top stations are not representative for the properties of a cloud further away from the surface.

scholarly journals A Case Study of Radar Observations and WRF LES Simulations of the Impact of Ground-Based Glaciogenic Seeding on Orographic Clouds and Precipitation. Part II: AgI Dispersion and Seeding Signals Simulated by WRF

2016 ◽  
Vol 55 (2) ◽  
pp. 445-464 ◽  
Author(s):  
Lulin Xue ◽  
Xia Chu ◽  
Roy Rasmussen ◽  
Daniel Breed ◽  
Bart Geerts
Keyword(s):  
Nucleation Rate ◽  
Wrf Model ◽  
Grid Spacing ◽  
Medicine Bow Mountains ◽  
Eddy Simulation ◽  
Cloud Dynamics ◽  
Vertical Dispersion ◽  
Orographic Clouds ◽  
Glaciogenic Seeding ◽  
The Impact

AbstractSeveral Weather Research and Forecasting (WRF) Model simulations of natural and seeded clouds have been conducted in non-LES and LES (large-eddy simulation) modes to investigate the seeding impact on wintertime orographic clouds for an actual seeding case on 18 February 2009 in the Medicine Bow Mountains of Wyoming. Part I of this two-part series has shown the capability of WRF LES with 100-m grid spacing to capture the essential environmental conditions by comparing the model results with measurements from a variety of instruments. In this paper, the silver iodide (AgI) dispersion features, the AgI impacts on the turbulent kinetic energy (TKE), the microphysics, and the precipitation are examined in detail using the model data, which leads to five main results. 1) The vertical dispersion of AgI particles is more efficient in cloudy conditions than in clear conditions. 2) The wind shear and the buoyancy are both important TKE production mechanisms in the wintertime PBL over complex terrain in cloudy conditions. The buoyancy-induced eddies are more responsible for the AgI vertical dispersion than the shear-induced eddies are. 3) Seeding has insignificant effects on the cloud dynamics. 4) AgI particles released from the ground-based generators affect the cloud within the boundary layer below 1 km AGL through nucleating extra ice crystals, converting liquid water into ice, depleting more vapor, and generating more precipitation on the ground. The AgI nucleation rate is inversely related to the natural ice nucleation rate. 5) The seeding effects on the ground precipitation are confined within narrow areas. The relative seeding effect ranges between 5% and 20% for the simulations with different grid spacing.

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