scholarly journals Modeling of the Melting Layer. Part III: The Density Effect

2005 ◽  
Vol 62 (10) ◽  
pp. 3705-3723 ◽  
Author(s):  
I. Zawadzki ◽  
W. Szyrmer ◽  
C. Bell ◽  
F. Fabry
Keyword(s):  
Velocity Ratio ◽  
Cloud Water ◽  
Essential Elements ◽  
Previous Description ◽  
Snow Density ◽  
Physical Processes ◽  
Radar Observations ◽  
Melting Layer ◽  
Small Peak ◽  
Stratiform Precipitation

Abstract A model of the melting snow and its radar reflectivity is presented here. The main addition to previous description of the melting layer is the explicit introduction of snow density as a variable. The model is validated with radar observations. Differences in brightband intensity for comparable precipitation rates are related here to the coexistence of supercooled cloud water (SCW) with snow above the melting level leading to riming and change in snow density. Cases where riming was suspected were selected according to the characteristics of the vertical profile of reflectivity flux above the melting layer and vertical Doppler velocities faster than expected from low-density snow. For stratiform precipitation with a melting layer, high snow-to-rain velocity ratio indicates high-density snow and consequently a small peak-to-rain reflectivity difference is expected. This relationship was computed from the model and confirmed with vertically pointing radar observations. In spite of the complexity of the physical processes present in the melting layer the model appears to capture the essential elements.

scholarly journals The IMPROVE-1 Storm of 1–2 February 2001. Part IV: Precipitation Enhancement across the Melting Layer

2008 ◽  
Vol 65 (3) ◽  
pp. 1087-1092 ◽  
Author(s):  
Christopher P. Woods ◽  
John D. Locatelli ◽  
Mark T. Stoelinga
Keyword(s):  
Model Simulation ◽  
Ambient Air ◽  
Cloud Water ◽  
Precipitation Rate ◽  
Combined Processes ◽  
Melting Snow ◽  
Melting Layer ◽  
Stratiform Precipitation ◽  
Precipitation Enhancement ◽  
Direct Condensation

Abstract Previous model simulations indicate that in stratiform precipitation, the precipitation rate can increase by 7% in the melting layer through direct condensation onto melting snow and the resultant cooled rain. In the present study, a model simulation of stratiform precipitation in a wide cold frontal rainband indicates that the precipitation rate can also increase by 5% in the melting layer through accretion, by melting snow and rain, of additional cloud water produced by the latent cooling of the ambient air associated with melting snow. The contribution of the combined processes, and therefore the additional precipitation gained through the latent cooling of melting snow within the melting layer, may contribute as much as 10% to the precipitation rate in stratiform precipitation.

Climatology of Melting Layer Heights Estimated from Cloud Radar Observations at Various Locations

2021 ◽  
Author(s):  
Jae In Song ◽  
Seong Soo Yum ◽  
Sung‐Hwa Park ◽  
Ki‐Hoon Kim ◽  
Ki‐Jun Park ◽  
...  
Keyword(s):  
Radar Observations ◽  
Melting Layer ◽  
Cloud Radar

scholarly journals Estimation of liquid water path below the melting layer in stratiform precipitation systems using radar measurements during MC3E

2019 ◽  
Vol 12 (7) ◽  
pp. 3743-3759 ◽  
Author(s):  
Jingjing Tian ◽  
Xiquan Dong ◽  
Baike Xi ◽  
Christopher R. Williams ◽  
Peng Wu
Keyword(s):  
Liquid Water ◽  
Department Of Energy ◽  
Cloud Base ◽  
Retrieval Algorithm ◽  
Doppler Velocity ◽  
Liquid Water Path ◽  
Water Path ◽  
Melting Layer ◽  
Stratiform Precipitation ◽  
Cloud Particles

Abstract. In this study, the liquid water path (LWP) below the melting layer in stratiform precipitation systems is retrieved, which is a combination of rain liquid water path (RLWP) and cloud liquid water path (CLWP). The retrieval algorithm uses measurements from the vertically pointing radars (VPRs) at 35 and 3 GHz operated by the US Department of Energy Atmospheric Radiation Measurement (ARM) and National Oceanic and Atmospheric Administration (NOAA) during the field campaign Midlatitude Continental Convective Clouds Experiment (MC3E). The measured radar reflectivity and mean Doppler velocity from both VPRs and spectrum width from the 35 GHz radar are utilized. With the aid of the cloud base detected by a ceilometer, the LWP in the liquid layer is retrieved under two different situations: (I) no cloud exists below the melting base, and (II) cloud exists below the melting base. In (I), LWP is primarily contributed from raindrops only, i.e., RLWP, which is estimated by analyzing the Doppler velocity differences between two VPRs. In (II), cloud particles and raindrops coexist below the melting base. The CLWP is estimated using a modified attenuation-based algorithm. Two stratiform precipitation cases (20 and 11 May 2011) during MC3E are illustrated for two situations, respectively. With a total of 13 h of samples during MC3E, statistical results show that the occurrence of cloud particles below the melting base is low (9 %); however, the mean CLWP value can be up to 0.56 kg m−2, which is much larger than the RLWP (0.10 kg m−2). When only raindrops exist below the melting base, the average RLWP value is larger (0.32 kg m−2) than the with-cloud situation. The overall mean LWP below the melting base is 0.34 kg m−2 for stratiform systems during MC3E.

scholarly journals Turbulence and Wind Shear in Layers of Large Doppler Spectrum Width in Stratiform Precipitation

2009 ◽  
Vol 26 (3) ◽  
pp. 430-443 ◽  
Author(s):  
Valery M. Melnikov ◽  
Richard J. Doviak
Keyword(s):  
Wind Shear ◽  
Weather Radar ◽  
Velocity Fields ◽  
The Other ◽  
Doppler Spectrum ◽  
Weak Turbulence ◽  
Radar Observations ◽  
Spectrum Width ◽  
Stratiform Precipitation ◽  
Radar Resolution

Abstract Weather radar observations of stratiform precipitation often reveal regions having very large measured Doppler spectrum widths, exceeding 7, and sometimes 10, m s−1. These widths are larger than those typically found in thunderstorms; widths larger than 4 m s−1 are associated with moderate or severe turbulence in thunderstorms. In this work, stratiform precipitation has been found to have layers of widths larger than 4 m s−1 in more than 80% of cases studied, wherein the shear of the wind on scales that are large compared to the dimensions of the radar resolution volume is the dominant contributor to spectrum width. Analyzed data show that if width ≤7 m s−1, and if the layers are not wavy or patchy, these layers have weak turbulence. On the other hand, regions having widths >4 m s−1 in patches or in wavelike structures are likely to have moderate to severe turbulence with the potential to be a hazard to safe flight. To separate the contributions to spectrum width from wind shear and turbulence and to evaluate the errors in turbulence estimates, data have been collected with elevation increments much less than a beamwidth. Despite beamwidth limitations, the small elevation increments reveal impressive structures in the fields. For example, the “cat’s eye” structure associated with Kelvin–Helmholtz waves is clearly exhibited in the fields of spectrum width observed at low-elevation angles, but not in the reflectivity or velocity fields. Reflectivity fields in stratiform precipitation are featureless compared to spectrum width fields.

scholarly journals Examining Polarimetric Radar Observations of Bulk Microphysical Structures and Their Relation to Vortex Kinematics in Hurricane Arthur (2014)

2017 ◽  
Vol 145 (11) ◽  
pp. 4521-4541 ◽  
Author(s):  
Anthony C. Didlake ◽  
Matthew R. Kumjian
Keyword(s):  
Tropical Cyclone ◽  
Lower Layer ◽  
Polarimetric Radar ◽  
Arthur Prior ◽  
Radar Observations ◽  
Melting Layer ◽  
Ice Particles ◽  
Planar Crystal ◽  
Differential Reflectivity ◽  
Left Quadrant

Dual-polarization radar observations were taken of Hurricane Arthur prior to and during landfall, providing needed insight into the microphysics of tropical cyclone precipitation. A total of 30 h of data were composited and analyzed by annuli capturing storm features (eyewall, inner rainbands, and outer rainbands) and by azimuth relative to the deep-layer environmental wind shear vector. Polarimetric radar variables displayed distinct signatures indicating a transition from convective to stratiform precipitation in the downshear-right to downshear-left quadrants, which is an organization consistent with the expected kinematic asymmetry of a sheared tropical cyclone. In the downshear-right quadrant, vertical profiles of differential reflectivity ZDR and copolar correlation coefficient ρHV were more vertically stretched within and above the melting layer at all annuli, which is attributed to convective processes. An analysis of specific differential phase KDP indicated that nonspherical ice particles had an increased presence in two layers: just above the melting level and near 8-km altitude. Here, convective updrafts generated ice particles in the lower layer, which were likely columnar crystals, and increased the available moisture in the upper layer, leading to increased planar crystal growth. A sharp transition in hydrometeor population occurred downwind in the downshear-left quadrant where ZDR and ρHV profiles were more peaked within the melting layer. Above the melting layer, these signatures indicated reduced ice column counts and shape diversity owing to aggregation in a predominantly stratiform regime. The rainband quadrants exhibited a sharper transition compared to the eyewall quadrants owing to weaker winds and longer distances that decreased azimuthal mixing of ice hydrometeors.

Modeling melting layer radar observations at GPM frequencies; comparison to measurements

2011 ◽  
Author(s):  
A. von Lerber ◽  
D. Moisseev ◽  
J. Leinonen ◽  
J. Tyynela ◽  
V. Chandrasekar ◽  
...  
Keyword(s):  
Radar Observations ◽  
Melting Layer

scholarly journals Radar-Observed Characteristics of Precipitation in the Tropical High Andes of Southern Peru and Bolivia

2018 ◽  
Vol 57 (7) ◽  
pp. 1441-1458 ◽  
Author(s):  
Jason L. Endries ◽  
L. Baker Perry ◽  
Sandra E. Yuter ◽  
Anton Seimon ◽  
Marcos Andrade-Flores ◽  
...  
Keyword(s):  
Diurnal Cycle ◽  
Amazon Basin ◽  
Vertical Structure ◽  
Radar Data ◽  
Doppler Velocity ◽  
Tropical Andes ◽  
La Paz ◽  
Melting Layer ◽  
Southern Peru ◽  
Stratiform Precipitation

AbstractThis study used the first detailed radar measurements of the vertical structure of precipitation obtained in the central Andes of southern Peru and Bolivia to investigate the diurnal cycle and vertical structure of precipitation and melting-layer heights in the tropical Andes. Vertically pointing 24.1-GHz Micro Rain Radars in Cusco, Peru (3350 m MSL, August 2014–February 2015), and La Paz, Bolivia (3440 m MSL, October 2015–February 2017), provided continuous 1-min profiles of reflectivity and Doppler velocity. The time–height data enabled the determination of precipitation timing, melting-layer heights, and the identification of convective and stratiform precipitation features. Rawinsonde data, hourly observations of meteorological variables, and satellite and reanalysis data provided additional insight into the characteristics of these precipitation events. The radar data revealed a diurnal cycle with frequent precipitation and higher rain rates in the afternoon and overnight. Short periods with strong convective cells occurred in several storms. Longer-duration events with stratiform precipitation structures were more common at night than in the afternoon. Backward air trajectories confirmed previous work indicating an Amazon basin origin of storm moisture. For the entire dataset, median melting-layer heights were above the altitude of nearby glacier termini approximately 17% of the time in Cusco and 30% of the time in La Paz, indicating that some precipitation was falling as rain rather than snow on nearby glacier surfaces. During the 2015–16 El Niño, almost half of storms in La Paz had melting layers above 5000 m MSL.

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