Radar Observations and Modelling of Warm Rain Initiation

Caylor, I. J.; Illingworth, Anthony J.

doi:10.1002/qj.49711347806

Cited by 47 publications

(24 citation statements)

References 23 publications

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“…In the middle to lower part of the cloud, the ZDR signal was characteristic of raindrops with diameters between 1 and 3 mm. These studies confirmed and extended earlier work of Caylor and Illingworth (1987), Illingworth et al (1987), and Illingworth (1988) that used ZDR to show that low concentrations of large raindrops are present simultaneously with the early weak radar reflectivity echoes in cumulus. In each of these studies, the authors hypothesized that these early large raindrops were a result of growth on GN.…”

Section: ϫ3supporting

confidence: 88%

Radar Analysis of Precipitation Initiation in Maritime versus Continental Clouds near the Florida Coast: Inferences Concerning the Role of CCN and Giant Nuclei

Göke

Ochs

Rauber

2007

Journal of the Atmospheric Sciences

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A method of analyzing radar data is developed and applied to determine whether the X-band radar reflectivity evolution of clouds observed during summertime on the northeast Florida coast during the Small Cumulus Microphysics Study (SCMS) shows distinct differences in precipitation development that can be associated with the clouds' maritime or continental characteristics. For this study, the entire National Center for Atmospheric Research CP2 radar dataset from SCMS was examined, and 38 clouds were used. For these clouds the evolution in X-band radar reflectivity, from the clouds' earliest detection through precipitation, was clearly documented and met specific requirements concerning the clouds' location relative to the coastline and direction of movement. Since cloud condensation nuclei (CCN) and giant and ultragiant nuclei (GN) measurements were not available for the specific clouds used in this study, proxies were used to partition the clouds into four groups based on the cloud location and direction of movement. Specifically, it was assumed that clouds forming over the ocean during onshore flow had maritime characteristics (group 1: low CCN, high GN), clouds forming over land during onshore flow would have modified maritime characteristics (group 2: high CCN, high GN), clouds forming over land during offshore flow would have continental characteristics (group 3: high CCN, low GN), and clouds forming over the ocean during offshore flow would have modified continental characteristics (group 4: high CCN, high GN). These assumptions are based on past measurements presented by Sax and Hudson. Then, these populations were statistically compared using the nonparametric multiresponse permutation procedure developed by Mielke et al. A comparison of groups 1 and 2 provided a test of the role of CCN concentrations in precipitation development in these cloud populations. A comparison of groups 3 and 4 provided a test of the role of GN concentrations in precipitation development in these cloud populations. The two cloud populations that were disjoint at a statistically significant level were groups 1 and 2. For these groups, the analysis showed that the median characteristic total water content of the truly maritime clouds (group 1) was about half that of the modified maritime clouds (group 2) at the time of precipitation formation. The characteristic time to precipitation formation was about 60% smaller for the truly maritime clouds. Thus, the characteristic reflectivity threshold for precipitation development was reached at a much lower altitude above cloud base in a much faster time in the truly maritime clouds. This result supports the conclusions of Hudson and Yum that precipitation development in the SCMS clouds was primarily controlled by CCN concentrations rather than GN concentrations.

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Section: ϫ3supporting

confidence: 88%

Radar Analysis of Precipitation Initiation in Maritime versus Continental Clouds near the Florida Coast: Inferences Concerning the Role of CCN and Giant Nuclei

Göke

Ochs

Rauber

2007

Journal of the Atmospheric Sciences

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“…The Z DR columns in their study were transient features, with lifetimes of less than 10 min. Caylor and Illingworth (1987) concluded that the only tenable hypothesis for the anomalously large Z DR values was the presence of large drops (they focused mainly on the lower portions of the Z DR columns). They suggested that ultragiant nuclei could serve to grow such large drops, and they developed a model to test their suggestion.…”

Section: A Observations Of Z Dr Columnsmentioning

confidence: 97%

The Anatomy and Physics of ZDR Columns: Investigating a Polarimetric Radar Signature with a Spectral Bin Microphysical Model

Kumjian

Хаин

Benmoshe

et al. 2014

Journal of Applied Meteorology and Climatology

157

127

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Polarimetric radar observations of deep convective storms frequently reveal columnar enhancements of differential reflectivity Z DR . Such ''Z DR columns'' can extend upward more than 3 km above the environmental 08C level, indicative of supercooled liquid drops being lofted by the updraft. Previous observational and modeling studies of Z DR columns are reviewed. To address remaining questions, the Hebrew University Cloud Model, an advanced spectral bin microphysical model, is coupled with a polarimetric radar operator to simulate the formation and life cycle of Z DR columns in a deep convective continental storm. In doing so, the mechanisms by which Z DR columns are produced are clarified, including the formation of large raindrops in the updraft by recirculation of smaller raindrops formed aloft back into the updraft at low levels. The internal hydrometeor structure of Z DR columns is quantified, revealing the transition from supercooled liquid drops to freezing drops to hail with height in the Z DR column. The life cycle of Z DR columns from early formation, through growth to maturity, to demise is described, showing how hail falling out through the weakening or ascending updraft bubble dominates the reflectivity factor Z H , causing the death of the Z DR column and leaving behind its ''ghost'' of supercooled drops. In addition, the practical applications of Z DR columns and their evolution are explored. The height of the Z DR column is correlated with updraft strength, and the evolution of Z DR column height is correlated with increases in Z H and hail mass content at the ground after a lag of 10-15 min.

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“…Several earlier studies showed the time evolution of the averaged Z dr versus Z hh from the early growth phase to the mature phase of convective cells (e.g., Caylor and Illingworth 1987;Illingworth 1988;Bringi et al 1991). In their studies, the initial stages of the cloud were characterized by low Z hh and unusually large Z dr implying a very low number concentration of large raindrops developed through a warm rain process.…”

Section: Raindrop Sizes Near the Surfacementioning

confidence: 98%

Characteristics of Polarimetric Radar Variables in Three Types of Rainfalls in a Baiu Front Event over the East China Sea

Shusse

Nakagawa

Takahashi

et al. 2009

Journal of the Meteorological Society of Japan

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Characteristics of polarimetric radar variables in three rainfall types in a Baiu front event over the East China Sea observed on 1 June 2004 were studied and compared using a C-band polarimetric radar, the CRL Okinawa bistatic polarimetric radar (COBRA). The selected rainfalls are common types in the Baiu season in this area: (1) stratiform type (ST), (2) isolated convective type (ICT) and (3) embedded convective type (ECT). ST was characterized by an obvious bright band in the field of radar reflectivity (Z hh ). ICT and ECT had almost the same 30-dBZ echo-top height of about 5.5 km, and their strong echo region (Z hh > 40 dBZ) did not exceed the 0 C level (4.4 km altitude) even in their mature stages. Around the 0 C level, overall decrease in correlation coe‰cient between horizontal and vertical polarization signals (r hv ) and increase in di¤erential reflectivity (Z dr ) were observed in ST and ECT, which indicated the presence of a layer of mixed-phase precipitation. By contrast, significant decrease in r hv and increase in Z dr were not found in ICT. At lower levels, Z dr ranged from 0 to 1.5 dB and most of r hv were higher than 0.98 in ST and ECT. The values of Z dr and r hv had wider variations in ICT. The characteristics of the vertical profiles of Z dr and r hv in ECT are consequently more similar to those in ST rather than to those in ICT, although their echo-top heights of 30 dBZ and maximum Z hh near the surface were almost equal.Corresponding author and current a‰liation: Yukari Shusse, Hydrospheric Atmospheric Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan. E-mail: shusse@rain.hyarc.nagoya-u.ac.jp 6 2009, Meteorological Society of Japan Near the surface, su‰ciently below the 0 C level, ICT had larger Z dr and lower r hv than ECT in the region with Z hh stronger than 45 dBZ. This indicates that larger raindrops were more dominant in ICT than in ECT at the same Z hh in the intense rainfall regions. This di¤erence of dominant raindrop sizes appears to reflect the difference in precipitation growth processes between ICT and ECT.

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Radar Observations and Modelling of Warm Rain Initiation

Cited by 47 publications

References 23 publications

Radar Analysis of Precipitation Initiation in Maritime versus Continental Clouds near the Florida Coast: Inferences Concerning the Role of CCN and Giant Nuclei

Radar Analysis of Precipitation Initiation in Maritime versus Continental Clouds near the Florida Coast: Inferences Concerning the Role of CCN and Giant Nuclei

The Anatomy and Physics of ZDR Columns: Investigating a Polarimetric Radar Signature with a Spectral Bin Microphysical Model

Characteristics of Polarimetric Radar Variables in Three Types of Rainfalls in a Baiu Front Event over the East China Sea

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