Numerical Simulation of the Effects of Varying Ice Crystal Nucleation Rates and Aggregation Processes on Orographic Snowfall

Cotton, William R.; Tripoli, Gregory J.; Rauber, Robert M.; Mulvihill, Elizabeth A.

doi:10.1175/1520-0450(1986)025<1658:nsoteo>2.0.co;2

Cited by 327 publications

(243 citation statements)

References 26 publications

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“…Cloud models specifically need to adequately represent the hydrometeor evolution over a wide variety of conditions to accurately predict the microstructure of cloud systems. Cloud modelers have two options to represent the hydrometeor spectra, explicit bin-resolving (Young, 1974;Hall, 1980;Kogan, 1991;Feingold et al, 1988Feingold et al, , 1994 or bulk microphysical models (Lin et al, 1983;Hobbs, 1983, 1984;Cotton et al, 1986). Bin models divide each hydrometeor category (e.g.…”

Section: Introductionmentioning

confidence: 99%

New RAMS cloud microphysics parameterization. Part II: The two-moment scheme

Meyers

Walko

Harrington

et al. 1997

Atmospheric Research

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This paper is the second in a series of articles describing the new microphysics scheme in the Regional Atmospheric Modeling System (RAMS). In this part, a new two-moment microphysical parameterization is described. The proposed scheme predicts the mixing ratio and number concentration of rain, pristine ice crystals, snow, aggregates, graupel and hail. The general gamma distribution is the basis function used for hydrometeor size in each category. Additional features include: use of stochastic collection for number concentration tendency; breakup of rain droplets formulated into the collection efficiency; diagnosis of ice crystal habit dependent on temperature and saturation; evaporation and melting of each species assuming that the smallest particles completely disappear first; and more complex shedding formulations which take into account the amount of water mass on the coalesced hydrometeor. Preliminary sensitivity testing of the new microphysical scheme in an idealized convective simulation shows that the two-moment prediction scheme allows more flexibility of the size distribution enabling the mean diameter to evolve in contrast to the one-moment scheme. Sensitivity to the prescribed input parameters such as cloud droplet concentrations and the shape parameter v is demonstrated in the model results. © 1997 Elsevier Science B.V.

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Section: Introductionmentioning

confidence: 99%

New RAMS cloud microphysics parameterization. Part II: The two-moment scheme

Meyers

Walko

Harrington

et al. 1997

Atmospheric Research

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435

331

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“…(4b) in according to Cotton et al (1986). This parameterization represents the secondary production of ice splinters within the riming process.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity Experiments on the Orographic Snowfall over the Mountainous Region of Northern Japan

Saitō¹,

Murakami²,

Matsuo

et al. 1996

Journal of the Meteorological Society of Japan

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Numerical experiments on the orographic snowfall over the mountainous region of northern Japan in winter are conducted using a 2-dimensional non-hydrostatic model with a cloud microphysical parameterization which predicts not only the mixing ratio of water species but also the number density of ice species. The orographic effect on the snowfall is investigated by sensitivity tests from cloud microphysical aspects.Modification of air-mass and formation of snow clouds over the Sea of Japan, enhancement of snowfall over the windward slope of the mountainous area and disappearance of clouds on the lee side are simulated by an experiment where a simplified orography and sea-land distribution of northern Japan is given. The snow clouds gradually increase their top heights from sea, off the west coast, to inland, and the number density of cloud ice increases with the decrease of cloud-top temperature. The influence of the differences of roughness and temperature between sea and land on the snowfall distribution is examined as subsidiary factors. According to comparative experiments, the difference of temperature between sea and land contributes to the enhancement of snowfall over the windward side of land area, while the difference of roughness does not have a substantial influence.Forced condensation is evaluated assuming that the air-mass is lifted up by the mountain, and precipitation efficiency is defined as the portion of the forced condensation which converts to precipitation over the land. In the sensitivity experiments on the mountain-top height, the precipitation amount over the land increases significantly when the mountain height exceeds the height of cloud base. The precipitation efficiency is about 40% when the mountain height is below 600m, while it reaches about 80% when the mountain height is greater than 1000m. On the other hand, in the warm-rain experiments, the precipitation amount as well as the precipitation efficiency are only about 1/3 those of the experiments with ice phase, because the greater part of the condensed cloud water goes to the lee of the mountain before it converts to rain. Sensitivity experiments where ice nucleation rates are changed over the land are conducted, and it is shown that the snowfall over the land decreases with the suppression of ice nucleation over the mountain, while it increases with the enhancement of ice nucleation over the land, even without mountain. These experimental results suggest that not only the forced condensation but also the natural seeding over the mountainous area the ice nucleation by the decrease of the temperature in cloud due to the orographic ascent-plays an important role in the orographic enhancement of the snowfall over northern Japan.A seeding experiment in which the ice nucleation rates are enhanced over a specified zone in the Sea of Japan demonstrates the possibility of artificial modification of the snowfall.

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“…Newly incorporated and revised parts of parameterizations are described below, which are mainly based upon Murakami (1990) and Cotton et al (1986). In the following, (L-nn), (CT-nn) and (M-nn) denote the number of equations appearing in Lin et al (1983), Cotton et al (1986) and Murakami (1990), respectively.…”

Section: Eq (20) Inmentioning

confidence: 99%

“…In this list, L-nn, CT-nn and M-nn indicate that these terms are given by the formula "nn" in Lin et al (1983), Cotton et al (1986), and Murakami (1990), respectively. For elementary cloud microphysical production terms, notations are largely followed after Lin et al, and the terms which have the same notation and are evaluated by the same formula as Lin et al, such as Prevp, Psacw, are omitted in this list for simplicity.…”

Section: Appendixmentioning

confidence: 99%

“…Recently, Cotton et al (1986) and Murakami (1990) developed the bulk parameterization schemes of cloud microphysics in which the number concentrations of ice crystals and snow aggregates are predicted in addition to the mixing ratios of water substances. Cotton et al applied the scheme to the simulation of orographic snowfall from stratiform clouds observed in Colorado in winter.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Modeling of the Convective Snow Cloud over the Sea of Japan

Ikawa¹,

Mizuno²,

Matsuo³

et al. 1991

Journal of the Meteorological Society of Japan

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A bulk parameterization scheme of cloud microphysics which predicts not only the number concentrations of cloud ice and snow but also that of graupel, in addition to the mixing ratios of six water species (water vapor, cloud water, rain, cloud ice, ;snow and graupel), is developed. This scheme is applied to the 3-dimensional simulation of the convective snow cloud observed over the Sea of Japan on Feb. 4, 1989, with a cloud top temperature at -20*.In the simulation where conventional parameters are used for Fletcher's deposition/sorption nucleation, Bigg's freezing of cloud droplets and the Hallet-Mossop rime-splinter secondary production of ice crystals, the maximum of number concentration of ice particles is about 5 *104/m3, 1/4 of the observed counterpart (2 *105/m3). Radar reflectivity is larger by 10 dBZ than observation. Other aspects appear to be well reproduced by the model at least qualitatively. Precipitation formation in the simulated cloud is examined, and it is found to be consistent with observational studies.Sensitivity experiments to the amplification of various ice nucleation rates are conducted to simulate the cloud more realistically and to see the effects of the increase of the number concentration of ice crystals on the precipitation formation of the convective cloud. The increase in the number concentration of ice crystals to the value of 105*106/m3 results in the increase of snow in mass and number and the decrease of radar reflectivity. The further increase in the number concentration of ice crystals to the value (107/m3) results in suppression of precipitation, glaciation of cloud with little cloud water and suspension of abundant snow in the air. These experiments give some support to the possibility of suppressing the precipitation by overseeding.Some merits of predicting number concentrations of ice particles are discussed. In the simulation, the intercept parameters of the inverse exponential size distribution functions for snow and graupel, Nos and Nog, are found to be more dependent on the stage of the cloud development than on the precipitation rate. This feature cannot be reproduced by the model with the prescribed Nos and Nog. For a more realistic simulation of clouds, a more reliable knowledge about ice nucleation is crucial.

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Numerical Simulation of the Effects of Varying Ice Crystal Nucleation Rates and Aggregation Processes on Orographic Snowfall

Cited by 327 publications

References 26 publications

New RAMS cloud microphysics parameterization. Part II: The two-moment scheme

New RAMS cloud microphysics parameterization. Part II: The two-moment scheme

Sensitivity Experiments on the Orographic Snowfall over the Mountainous Region of Northern Japan

Numerical Modeling of the Convective Snow Cloud over the Sea of Japan

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