Orographically Modified Ice-Phase Precipitation Processes During the Olympic Mountains Experiment (OLYMPEX)

2021 ◽  
Author(s):  
Andrew DeLaFrance ◽  
Lynn McMurdie ◽  
Angela Rowe
Keyword(s):  
Significant Degree ◽  
Phase Precipitation ◽  
Turbulent Layer ◽  
Olympic Mountains ◽  
Precipitation Processes ◽  
Modified Ice ◽  
Orographic Enhancement ◽  
High Concentrations ◽  
Melting Level ◽  
Ice Phase

AbstractOver mountainous terrain, windward enhancement of stratiform precipitation results from a combination of warm-rain and ice-phase processes. In this study, ice-phase precipitation processes are investigated within frontal systems during the Olympic Mountains Experiment (OLYMPEX). An enhanced layer of radar reflectivity (ZH) above the melting level bright band (i.e., a secondary ZH maximum) is observed over both the windward slopes of the Olympic Mountains and the upstream ocean, with a higher frequency of occurrence and higher ZH values over the windward slopes indicating an orographic enhancement of ice-phase precipitation processes. Aircraft-based in situ observations are evaluated for the 01-02 and 03 December 2015 orographically-enhanced precipitation events. Above the secondary ZH maximum, the hydrometeors are primarily horizontally oriented dendritic and branched crystals. Within the secondary ZH maximum, there are high concentrations of large (> ~2 mm diameter) dendrites, plates, and aggregates thereof, with a significant degree of riming. In both events, aggregation and riming appear to be enhanced within a turbulent layer near sheared flow at the top of a low-level jet impinging on the terrain and forced to rise above the melting level. Based on windward ground sites at low-, mid-, and high-elevations, secondary ZH maxima periods during all of OLYMPEX are associated with increased rain rates and larger mass-weighted mean drop diameters compared to periods without a secondary ZH maximum. This result suggests that precipitation originating from secondary ZH maxima layers may contribute to enhanced windward precipitation accumulations through the formation of large, dense particles that accelerate fallout.

Ice-Phase Precipitation

2017 ◽  
Vol 58 ◽  
pp. 6.1-6.36 ◽  
Author(s):  
I. Gultepe ◽  
A. J. Heymsfield ◽  
P. R. Field ◽  
D. Axisa
Keyword(s):  
Collection Efficiency ◽  
Numerical Models ◽  
Mass Density ◽  
Three Dimensional ◽  
Phase Precipitation ◽  
Microphysical Parameters ◽  
Mass Size ◽  
Ice Water ◽  
Ice Phase

AbstractIce-phase precipitation occurs at Earth’s surface and may include various types of pristine crystals, rimed crystals, freezing droplets, secondary crystals, aggregates, graupel, hail, or combinations of any of these. Formation of ice-phase precipitation is directly related to environmental and cloud meteorological parameters that include available moisture, temperature, and three-dimensional wind speed and turbulence, as well as processes related to nucleation, cooling rate, and microphysics. Cloud microphysical parameters in the numerical models are resolved based on various processes such as nucleation, mixing, collision and coalescence, accretion, riming, secondary ice particle generation, turbulence, and cooling processes. These processes are usually parameterized based on assumed particle size distributions and ice crystal microphysical parameters such as mass, size, and number and mass density. Microphysical algorithms in the numerical models are developed based on their need for applications. Observations of ice-phase precipitation are performed using in situ and remote sensing platforms, including radars and satellite-based systems. Because of the low density of snow particles with small ice water content, their measurements and predictions at the surface can include large uncertainties. Wind and turbulence affecting collection efficiency of the sensors, calibration issues, and sensitivity of ground-based in situ observations of snow are important challenges to assessing the snow precipitation. This chapter’s goals are to provide an overview for accurately measuring and predicting ice-phase precipitation. The processes within and below cloud that affect falling snow, as well as the known sources of error that affect understanding and prediction of these processes, are discussed.

scholarly journals The Effect of Neutron Irradiation on Second Phase Precipitation Processes

1971 ◽  
Vol 11 (5) ◽  
pp. 289-293 ◽  
Author(s):  
Z. E. OSTROVSKY ◽  
G. A. SERNYAEV ◽  
P. P. GRINTCHUK ◽  
S. N. VOTINOV ◽  
V. I. PROKHOROV
Keyword(s):  
Neutron Irradiation ◽  
Second Phase ◽  
Phase Precipitation ◽  
Precipitation Processes

scholarly journals Simulated Kelvin–Helmholtz Waves over Terrain and Their Microphysical Implications

2018 ◽  
Vol 75 (8) ◽  
pp. 2787-2800 ◽  
Author(s):  
Robert Conrick ◽  
Clifford F. Mass ◽  
Qi Zhong
Keyword(s):  
Oscillatory Behavior ◽  
Microphysics Scheme ◽  
Low Level ◽  
Mixing Ratios ◽  
Olympic Mountains ◽  
Arw Model ◽  
Western Washington ◽  
The Impact ◽  
Intense Shear ◽  
Melting Level

Abstract Two Kelvin–Helmholtz (KH) wave events over western Washington State were simulated and evaluated using observations from the Olympic Mountains Experiment (OLYMPEX) field campaign. The events, 12 and 17 December 2015, were simulated realistically by the WRF-ARW Model, duplicating the mesoscale environment, location, and structure of embedded KH waves, which had observed wavelengths of approximately 5 km. In simulations of both cases, waves developed from instability within an intense shear layer, caused by low-level easterly flow surmounted by westerly winds aloft. The low-level easterlies resulted from blocking by the Olympic Mountains in the 12 December case, while in the 17 December event, the easterly flow was produced by the synoptic environment. Simulated microphysics were evaluated for both cases using OLYMPEX observations. When the KH waves were within the melting level, simulated microphysical fields, such as hydrometeor mixing ratios, evinced considerable oscillatory behavior. In contrast, when waves were located below the melting level, the microphysical response was attenuated. Turning off the model’s microphysics scheme and latent heating resulted in weakened KH wave activity, while removing the Olympic Mountains eliminated KH waves in the 12 December event but not the 17 December case. Finally, the impact of several microphysics parameterizations on KH activity was evaluated for both events.

scholarly journals Role of sublimation and riming in the precipitation distribution in the Kananaskis Valley, Alberta, Canada

2019 ◽  
Vol 23 (10) ◽  
pp. 4097-4111
Author(s):  
Émilie Poirier ◽  
Julie M. Thériault ◽  
Maud Leriche
Keyword(s):  
Emergency Services ◽  
Water Cycle ◽  
Vertical Shear ◽  
Atmospheric Conditions ◽  
Phase Precipitation ◽  
Surface Evolution ◽  
Temperature Changes ◽  
Surface Precipitation ◽  
Ice Phase

Abstract. The phase of precipitation and its distribution at the surface can affect water resources and the regional water cycle of a region. A field project was held in March–April 2015 on the eastern slope of the Canadian Rockies to document precipitation characteristics and associated atmospheric conditions. During the project, 60 % of the particles documented were rimed in relatively warm and dry conditions. Rain–snow transitions also occurred aloft and at the surface in sub-saturated conditions. Ice-phase precipitation falling through a saturated atmospheric layer with temperatures > 0 ∘C will start melting. In contrast, if the melting layer is sub-saturated, the ice-phase precipitation undergoes sublimation, which increases the depth of the rain–snow transition. In this context, this study investigates the role of sublimation and riming in precipitation intensity and type reaching the surface in the Kananaskis Valley, Alberta, during March–April 2015. To address this, a set of numerical simulations of an event of mixed precipitation observed at the surface was conducted. This event on 31 March 2015 was documented with a set of devices at the main observation site (Kananaskis Emergency Services, KES), including a precipitation gauge, disdrometer, and micro rain radar. Sensitivity experiments were performed to assess the impacts of temperature changes from sublimation and the role of the production of graupel (riming) aloft in the surface precipitation evolution. A warmer environment associated with no temperature changes from sublimation leads to a peak in the intensity of graupel at the surface. When the formation of graupel is not considered, the maximum snowfall rate occurred at later times. Results suggest that unrimed snow reaching the surface is formed on the western flank and is advected eastward. In contrast, graupel would form aloft in the Kananaskis Valley. The cooling from sublimation and melting by rimed particles increases the vertical shear near KES. Overall, this study illustrated that the presence of graupel influenced the surface evolution of precipitation type in the valley due to the horizontal transport of precipitation particles.

PRELIMINARY FINDINGS OF OIL-SOLIDS INTERACTION IN EIGHT ALASKAN RIVERS

2001 ◽  
Vol 2001 (2) ◽  
pp. 845-849 ◽  
Author(s):  
James McCourt ◽  
Larry Shier
Keyword(s):  
Stream Flow ◽  
Suspended Solids ◽  
Historical Data ◽  
Significant Degree ◽  
South Central ◽  
Yukon River ◽  
Solids Concentration ◽  
High Concentrations ◽  
The Times ◽  
Mineral Aggregates

ABSTRACT The formation of oil-mineral aggregates in rivers with high concentrations of suspended solids could be an important mechanism for transferring oil from a surface slick into the water column. Seven glacier-fed rivers in south-central Alaska were sampled three times in the summer of 1999 and tested to see how suspended solids in the water would interact with crude oil. Oil-mineral aggregates formed with all samples, which lead to the conclusion that similar oil-solids interaction should occur if oil is spilled into other glacier-fed rivers. The amount of oil associated with the solids after mixing was roughly proportional to the concentration of suspended solids in the samples. The oil-loading results ranged between 0.01 and 0.45 g oil/g solid, with most of the measurements falling between 0.03 and 0.24 g oil/g solid. The average loading for all tests was 0.13 g oil/g solid, which is consistent with the findings of a similar study done in 1998 on the Yukon River. This result indicates that the suspended solids in the streams studied—especially the larger Yukon, Copper, and Lowe Rivers—have a large oil-holding capacity and would be capable of scavenging a considerable volume of oil. The exact quantity would depend on several factors, including the volume and dimensions of the slick, concentration of suspended solids, and current velocity of the river. Historical data on stream flow, suspended-solids concentration, and particle-size distribution were gathered and used in conjunction with the laboratory oil-solids interaction results to identify the times of the year when such interaction could occur to a significant degree. This data indicated that oil-mineral aggregates are expected to form in all rivers tested, with the most significant periods being during the summer months.

scholarly journals Winter Precipitation Liquid–Ice Phase Transitions Revealed with Polarimetric Radar and 2DVD Observations in Central Oklahoma

2017 ◽  
Vol 56 (5) ◽  
pp. 1345-1363 ◽  
Author(s):  
Petar Bukovčić ◽  
Dušan Zrnić ◽  
Guifu Zhang
Keyword(s):  
Radar Data ◽  
Winter Precipitation ◽  
Precipitation Event ◽  
Vertical Profiles ◽  
Polarimetric Radar ◽  
Phase Precipitation ◽  
Local Enhancement ◽  
Model Simulations ◽  
Differential Reflectivity ◽  
Ice Phase

AbstractObservations and analysis of an ice–liquid phase precipitation event, collected with an S-band polarimetric KOUN radar and a two-dimensional video disdrometer (2DVD) in central Oklahoma on 20 January 2007, are presented. Using the disdrometer measurements, precipitation is classified either as ice pellets or rain/freezing rain. The disdrometer observations showed fast-falling and slow-falling particles of similar size. The vast majority (>99%) were fast falling with observed velocities close to those of raindrops with similar sizes. In contrast to the smaller particles (<1 mm in diameter), bigger ice pellets (>1.5 mm) were relatively easy to distinguish because their shapes differ from the raindrops. The ice pellets were challenging to detect by looking at conventional polarimetric radar data because of the localized and patchy nature of the ice phase and their occurrence close to the ground. Previously published findings referred to cases in which ice pellet areas were centered on the radar location and showed a ringlike structure of enhanced differential reflectivity ZDR and reduced copolar correlation coefficient ρhv and horizontal reflectivity ZH in PPI images. In this study, a new, unconventional way of looking at polarimetric radar data is introduced: slanted vertical profiles (SVPs) at low (0°–1°) radar elevations. From the analysis of the localized and patchy structures using SVPs, the polarimetric refreezing signature, reflected in local enhancement in ZDR and reduction in ZH and ρhv, became much more evident. Model simulations of sequential drop freezing using Marshall–Palmer DSDs along with the observations suggest that preferential freezing of small drops may be responsible for the refreezing polarimetric signature, as suggested in previous studies.

The influence of riming on the oxygen isotopic composition of ice-phase precipitation

1991 ◽  
Vol 26 (6) ◽  
pp. 463-488 ◽  
Author(s):  
Belay B. Demoz ◽  
Joseph A. Warburton ◽  
Richard H. Stone
Keyword(s):  
Isotopic Composition ◽  
Oxygen Isotopic Composition ◽  
Phase Precipitation ◽  
Oxygen Isotopic ◽  
Ice Phase

scholarly journals Human impact of septic tank effluent on groundwater quality in the rural area of Ain Soltane (Ain Defla), Algieria

2019 ◽  
Vol 7 (2) ◽  
pp. 1-9
Author(s):  
Abdelkader Bouderbala
Keyword(s):  
Groundwater Quality ◽  
Rural Area ◽  
Significant Degree ◽  
Septic Tank ◽  
Septic Tanks ◽  
Groundwater Samples ◽  
Septic Tank Effluent ◽  
Pre Treatment ◽  
High Concentrations ◽  
The Impact

Abstract The impact of individual septic tank effluent on groundwater quality was investigated in the rural area of the Ain Soltane municipality in Algeria. This area has an important number of individual septic tanks, and it is devoid of a drinking water supply and sewerage systems. The septic tank is a pre-treatment solution of sewage by bacteria living without oxygen (anaerobic). The alluvial aquifer in this area is covered by a layer of good permeability on the surface, which can pollute groundwater by vertical transport of pollutants through the soil, including microbial contamination. Groundwater samples were collected from 33 wells in the dry period of 2016. The monitoring of groundwater quality has shown a significant degree of organic and inorganic pollution in the majority of wells, with very high concentrations of sulphate and chloride exceeding 450 mg/l and 250 mg/l respectively. The analyzes also show the presence of bacterial germs in the groundwater of which the origin is faecal (faecal coliform densities are above 10 organisms per 100 ml, and the Total Streptococcus is more than 240 colonies per 100 ml). Monitoring confirms the contamination of these wells from septic tanks and that it was moving into groundwater, which makes it unfit for drinking due to the pathogenic germs. This poses a major problem for public health. This study has identified the effects of septic tank effluent on groundwater quality in this area.

Sign in / Sign up

Export Citation Format

Share Document