High ice water content at low radar reflectivity near deep convection – Part 1: Consistency of in situ and remote-sensing observations with stratiform rain column simulations

Fridlind, A. M.; Ackerman, Andrew S.; Grandin, Alice; Dezitter, Fabien; Weber, Marc André; Strapp, J. W.; Korolev, Alexei; Williams, C. R.

doi:10.5194/acp-15-11713-2015

Cited by 29 publications

(21 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These ice crystals form in convective updrafts reaching heights of~10-12 km and are then advected both forward and backward relative to the squall line movement, forming a typical forward and trailing anvils that are known to be part of the squall-line phenomena. Such high concentrations of small ice at the tops of both maritime and especially continental deep convective clouds have been observed previously (Fridlind et al, 2015;Heymsfield et al, 2009;Leroy et al, 2017;Rosenfeld & Woodley, 2000;Strapp et al, 2016). Very high concentrations of small ice crystals above the homogeneous freezing level in midlatitude deep convection also have been observed by polarimetric radar (A. Ryzhkov, July 2018, personal comunication).…”

Section: Overall Microphysical Properties and Convective Intensitysupporting

confidence: 74%

Simulating a Mesoscale Convective System Using WRF With a New Spectral Bin Microphysics: 1: Hail vs Graupel

et al. 2019

View full text Add to dashboard Cite

A modified Fast Spectral Bin Microphysics scheme (FSBM‐2) embedded into the Weather Research and Forecasting (WRF) model is used to simulate a mesoscale deep convective system observed during the Midlatitude Continental Convective Clouds Experiment (MC3E). FSBM‐2 uses modified source codes as compared to the current FSBM (FSBM‐1). In contrast to FSBM‐1, FSBM‐2 can simulate hail of several centimeters in diameter and includes additional processes such as spontaneous breakup of raindrops and aerosol regeneration by drop evaporation. It is shown that allowing large hail particles of diameters exceeding about 1 cm substantially increases the agreement between the simulated and observed squall‐line structures in both the convective and stratiform regions. In contrast, if graupel particles are used to represent high‐density hydrometeors in convective areas, the ratio of convective‐to‐stratiform areas diverges from the ratio seen in observations and maximum radar reflectivities are substantially underestimated. Analysis of snow size distributions in the stratiform area shows an important link between the ice crystals formed by homogeneous freezing in the convective area to ice particle number concentration in the stratiform region. Simulated raindrop size distributions in the stratiform area below the melting level from FSBM‐2 show a good agreement with observations. The regeneration of cloud condensational nuclei (CCN) by droplet evaporation and detrainment of these CCN to the stratiform region increases the concentration of CCN there up to 8‐ to 9‐km altitude; the additional CCN penetrate clouds and produce new droplets, leading to some convection intensification.

show abstract

Section: Overall Microphysical Properties and Convective Intensitysupporting

confidence: 74%

Simulating a Mesoscale Convective System Using WRF With a New Spectral Bin Microphysics: 1: Hail vs Graupel

et al. 2019

View full text Add to dashboard Cite

show abstract

“…For the baseline and strong updraft, the PSDs overlap with the hint of an upturn in the Airbus PSD envelope at the small end of the PSD measurements, suggesting that this smaller mode, if real and not a shattering artifact, could correspond to homogeneously frozen water drops, which would be expected to be more favored in stronger updrafts. As noted above, there is observational evidence for homogeneous freezing in strong updrafts (e.g., Khain et al, 2012;Gayet et al, 2014;Stith et al, 2014). In these simplified simulations, the size of homogeneously frozen drops best matches observations for the strong updraft.…”

Section: Homogeneous Freezingmentioning

confidence: 89%

High ice water content at low radar reflectivity near deep convection – Part 2: Evaluation of microphysical pathways in updraft parcel simulations

et al. 2015

Self Cite

View full text Add to dashboard Cite

Abstract. The aeronautics industry has established that a threat to aircraft is posed by atmospheric conditions of substantial ice water content (IWC) where equivalent radar reflectivity (Ze) does not exceed 20–30 dBZ and supercooled water is not present; these conditions are encountered almost exclusively in the vicinity of deep convection. Part 1 (Fridlind et al., 2015) of this two-part study presents in situ measurements of such conditions sampled by Airbus in three tropical regions, commonly near 11 km and −43 °C, and concludes that the measured ice particle size distributions are broadly consistent with past literature with profiling radar measurements of Ze and mean Doppler velocity obtained within monsoonal deep convection in one of the regions sampled. In all three regions, the Airbus measurements generally indicate variable IWC that often exceeds 2 g m-3 with relatively uniform mass median area-equivalent diameter (MMDeq) of 200–300 μm. Here we use a parcel model with size-resolved microphysics to investigate microphysical pathways that could lead to such conditions. Our simulations indicate that homogeneous freezing of water drops produces a much smaller ice MMDeq than observed, and occurs only in the absence of hydrometeor gravitational collection for the conditions considered. Development of a mass mode of ice aloft that overlaps with the measurements requires a substantial source of small ice particles at temperatures of about −10 °C or warmer, which subsequently grow from water vapor. One conceivable source in our simulation framework is Hallett–Mossop ice production; another is abundant concentrations of heterogeneous ice freezing nuclei acting together with copious shattering of water drops upon freezing. Regardless of the production mechanism, the dominant mass modal diameter of vapor-grown ice is reduced as the ice-multiplication source strength increases and as competition for water vapor increases. Both mass and modal diameter are reduced by entrainment and by increasing aerosol concentrations. Weaker updrafts lead to greater mass and larger modal diameters of vapor-grown ice, the opposite of expectations regarding lofting of larger ice particles in stronger updrafts. While stronger updrafts do loft more dense ice particles produced primarily by raindrop freezing, we find that weaker updrafts allow the warm rain process to reduce competition for diffusional growth of the less dense ice expected to persist in convective outflow.

show abstract

“…The IWC calculation scheme utilized by this study was simplistic but represents a good first-order estimation of IWC that when used as the LMD proxy matched the dual-Doppler divergence profiles (Mullendore et al, 2009). There has been a significant amount of research into ice-phase microphysics and further development of complex IWC calculation schemes and their evaluation (e.g., Fridlind et al, 2015;Hogan et al, 2006;Leroy et al, 2016Leroy et al, , 2017Sayres et al, 2008). If the vertical spacing of the radar data is improved, if data from different wavelength radars is incorporated, or if more parameters are included, more complex IWC calculation schemes can be incorporated to improve the identification of the LMD.…”

Section: Limitationsmentioning

confidence: 99%

Retrievals of Convective Detrainment Heights Using Ground‐Based Radar Observations

2020

View full text Add to dashboard Cite

To better constrain model simulations, more observations of convective detrainment heights are needed. For the first time, ground‐based S band radar observations are utilized to create a comprehensive view of irreversible convective transport over a 7‐year period for the months of May and July across the United States. The radar observations are coupled with a volumetric radar echo classification scheme and a methodology that uses the convective anvil as proxy for convective detrainment to determine the level of maximum detrainment (LMD) for deep moist convection. The LMD height retrievals are subset by month (i.e., May and July), by morphology (i.e., mesoscale convective system, MCS, and quasi‐isolated strong convection, QISC), and region (i.e., northcentral, southcentral, northeast, and southeast). Overall, 135,890 deep convective storms were successfully sampled and had a mean LMD height of 8.6 km or tropopause‐relative mean LMD height of −4.3 km; however, LMD heights were found to extend up to 2 km above the tropopause. May storms had higher mean tropopause‐relative LMD heights, but July storms contained the highest overall LMD heights that more commonly extended above the tropopause. QISC had higher mean tropopause‐relative LMD heights and more commonly had LMD heights above the tropopause while only a few MCSs had LMD heights above the tropopause. The regional analysis showed that northern regions have higher mean LMD heights due to large amounts of diurnally driven convection being sampled in the southern regions. By using the anvil top, the highest possible convective detrainment heights extended up to 6 km above the tropopause.

show abstract

High ice water content at low radar reflectivity near deep convection – Part 1: Consistency of in situ and remote-sensing observations with stratiform rain column simulations

Cited by 29 publications

References 57 publications

Simulating a Mesoscale Convective System Using WRF With a New Spectral Bin Microphysics: 1: Hail vs Graupel

Simulating a Mesoscale Convective System Using WRF With a New Spectral Bin Microphysics: 1: Hail vs Graupel

High ice water content at low radar reflectivity near deep convection – Part 2: Evaluation of microphysical pathways in updraft parcel simulations

Retrievals of Convective Detrainment Heights Using Ground‐Based Radar Observations

Contact Info

Product

Resources

About