A Satellite‐Based Estimate of Convective Vertical Velocity and Convective Mass Flux: Global Survey and Comparison with Radar Wind Profiler Observations

2020 ◽  
Author(s):  
Jeyavinoth Jeyaratnam ◽  
Zhengzhao Johnny Luo ◽  
Scott E. Giangrande ◽  
Dié Wang ◽  
Hirohiko Masunaga
Keyword(s):  
Vertical Velocity ◽  
Mass Flux ◽  
Wind Profiler ◽  
Global Survey ◽  
Convective Mass Flux

Measuring the variability of the shallow convective mass flux profiles in the tropical trade wind region

2020 ◽  
Author(s):  
Marcus Klingebiel ◽  
Heike Konow ◽  
Bjorn Stevens
Keyword(s):  
Boundary Layer ◽  
Vertical Velocity ◽  
Mass Flux ◽  
Doppler Radar ◽  
Cloud Fraction ◽  
Cloud Base ◽  
Trade Wind ◽  
Geophysical Research ◽  
Wind Region ◽  
Convective Mass Flux

<p>Mass flux is a key parameter to represent shallow convection in global circulation models. To estimate the shallow convective mass flux as accurately as possible, observations of this parameter are necessary. Prior studies from Ghate et al. (2011) and Lamer et al. (2015) used Doppler radar measurements over a few months to identify a typical shallow convective mass flux profile based on cloud fraction and vertical velocity. In this study, we extend their observations by using long term remote sensing measurements at the Barbados Cloud Observatory (13° 09’ N, 59° 25’ W) over a time period of 30 months and check a hypothesis by Grant (2001), who proposed that the cloud base mass flux is just proportional to the sub-cloud convective velocity scale. Therefore, we analyze Doppler radar and Doppler lidar measurements to identify the variation of the vertical velocity in the cloud and sub-cloud layer, respectively. Furthermore, we show that the in-cloud mass flux is mainly influenced by the cloud fraction and provide a linear equation, which can be used to roughly calculate the mass flux in the trade wind region based on the cloud fraction.</p><p> </p><p>References:<br>Ghate,  V.  P.,  M.  A.  Miller,  and  L.  DiPretore,  2011:   Vertical  velocity structure of marine boundary layer trade wind cumulus clouds. Journal  of  Geophysical  Research: Atmospheres, 116  (D16), doi:10.1029/2010JD015344.</p><p>Grant,  A.  L.  M.,  2001:   Cloud-base  fluxes  in  the  cumulus-capped boundary layer. Quarterly Journal of the Royal Meteorological Society, 127 (572), 407–421, doi:10.1002/qj.49712757209.</p><p>Lamer, K., P. Kollias, and L. Nuijens, 2015:  Observations of the variability  of  shallow  trade  wind  cumulus  cloudiness  and  mass  flux. Journal of Geophysical Research: Atmospheres, 120  (12), 6161–6178, doi:10.1002/2014JD022950.</p>

scholarly journals Estimating the Shallow Convective Mass Flux from the Subcloud-Layer Mass Budget

2020 ◽  
Vol 77 (5) ◽  
pp. 1559-1574 ◽  
Author(s):  
Raphaela Vogel ◽  
Sandrine Bony ◽  
Bjorn Stevens
Keyword(s):  
Vertical Velocity ◽  
Diurnal Cycle ◽  
Mass Flux ◽  
Large Scale ◽  
Cloud Base ◽  
Entrainment Rate ◽  
Field Campaign ◽  
Mass Budget ◽  
Convective Mixing ◽  
Convective Mass Flux

Abstract This paper develops a method to estimate the shallow-convective mass flux M at the top of the subcloud layer as a residual of the subcloud-layer mass budget. The ability of the mass-budget estimate to reproduce the mass flux diagnosed directly from the cloud-core area fraction and vertical velocity is tested using real-case large-eddy simulations over the tropical Atlantic. We find that M reproduces well the magnitude, diurnal cycle, and day-to-day variability of the core-sampled mass flux, with an average root-mean-square error of less than 30% of the mean. The average M across the four winter days analyzed is 12 mm s−1, where the entrainment rate E contributes on average 14 mm s−1 and the large-scale vertical velocity W contributes −2 mm s−1. We find that day-to-day variations in M are mostly explained by variations in W, whereas E is very similar among the different days analyzed. Instead E exhibits a pronounced diurnal cycle, with a minimum of about 10 mm s−1 around sunset and a maximum of about 18 mm s−1 around sunrise. Application of the method to dropsonde data from an airborne field campaign in August 2016 yields the first measurements of the mass flux derived from the mass budget, and supports the result that the variability in M is mostly due to the variability in W. Our analyses thus suggest a strong coupling between the day-to-day variability in shallow convective mixing (as measured by M) and the large-scale circulation (as measured by W). Application of the method to the EUREC4A field campaign will help evaluate this coupling, and assess its implications for cloud-base cloudiness.

scholarly journals Convective cloud vertical velocity and mass‐flux characteristics from radar wind profiler observations during GoAmazon2014/5

2016 ◽  
Vol 121 (21) ◽  
pp. 12,891-12,913 ◽  
Author(s):  
Scott E. Giangrande ◽  
Tami Toto ◽  
Michael P. Jensen ◽  
Mary Jane Bartholomew ◽  
Zhe Feng ◽  
...  
Keyword(s):  
Vertical Velocity ◽  
Mass Flux ◽  
Convective Cloud ◽  
Wind Profiler

scholarly journals The Estimation of Convective Mass Flux from Radar Reflectivities

2016 ◽  
Vol 55 (5) ◽  
pp. 1239-1257 ◽  
Author(s):  
Vickal V. Kumar ◽  
Alain Protat ◽  
Christian Jakob ◽  
Christopher R. Williams ◽  
Surendra Rauniyar ◽  
...  
Keyword(s):  
Vertical Velocity ◽  
Mass Flux ◽  
General Circulation ◽  
General Circulation Models ◽  
Parametric Model ◽  
Training Dataset ◽  
Wind Profiler ◽  
Dual Frequency ◽  
Cumulus Clouds ◽  
Vertical Velocity Profile

AbstractCumulus parameterizations in general circulation models (GCMs) frequently apply mass-flux schemes in their description of tropical convection. Mass flux constitutes the product of the fractional area covered by cumulus clouds in a model grid box and the vertical velocity within the cumulus clouds. The cumulus area fraction profiles can be derived from precipitating radar reflectivity volumes. However, the vertical velocities are difficult to observe, making the evaluation of mass-flux schemes difficult. In this paper, the authors develop and evaluate a parameterization of vertical velocity in convective (cumulus) clouds using only radar reflectivities collected by a C-band polarimetric research radar (CPOL), operating at Darwin, Australia. The parameterization is trained using vertical velocity retrievals from a dual-frequency wind profiler pair located within the field of view of CPOL. The parametric model uses two inputs derived from CPOL reflectivities: the 0-dBZ echo-top height (0-dBZ ETH) and a height-weighted column reflectivity index (ZHWT). The 0-dBZ ETH determines the shape of the vertical velocity profile, while ZHWT determines its strength. The evaluation of these parameterized vertical velocities using (i) the training dataset, (ii) an independent wind-profiler-based dataset, and (iii) 1 month of dual-Doppler vertical velocity retrievals indicates that the statistical representation of vertical velocity is reasonably accurate up to the 75th percentile. However, the parametric model underestimates the extreme velocities. The method allows for the derivation of cumulus mass flux and its variability on current GCM scales based only on reflectivities from precipitating radar, which could be valuable to modelers.

scholarly journals Convective mass-flux from long term radar reflectivities over Darwin, Australia

2021 ◽  
Author(s):  
Alessandro Carlo Maria Savazzi ◽  
Christian Jakob ◽  
Pier Siebesma
Keyword(s):  
Mass Flux ◽  
Convective Mass Flux

scholarly journals Analysis of Convective Transport and Parameter Sensitivity in a Single Column Version of the Goddard Earth Observation System, Version 5, General Circulation Model

2009 ◽  
Vol 66 (3) ◽  
pp. 627-646 ◽  
Author(s):  
L. E. Ott ◽  
J. Bacmeister ◽  
S. Pawson ◽  
K. Pickering ◽  
G. Stenchikov ◽  
...  
Keyword(s):  
Mass Flux ◽  
General Circulation ◽  
Parameter Sensitivity ◽  
Convective Transport ◽  
Trace Gas ◽  
Gas Mixing ◽  
Mixing Ratios ◽  
Mass Fluxes ◽  
Single Column ◽  
Convective Mass Flux

Abstract Convection strongly influences the distribution of atmospheric trace gases. General circulation models (GCMs) use convective mass fluxes calculated by parameterizations to transport gases, but the results are difficult to compare with trace gas observations because of differences in scale. The high resolution of cloud-resolving models (CRMs) facilitates direct comparison with aircraft observations. Averaged over a sufficient area, CRM results yield a validated product directly comparable to output from a single global model grid column. This study presents comparisons of vertical profiles of convective mass flux and trace gas mixing ratios derived from CRM and single column model (SCM) simulations of storms observed during three field campaigns. In all three cases, SCM simulations underpredicted convective mass flux relative to CRM simulations. As a result, the SCM simulations produced lower trace gas mixing ratios in the upper troposphere in two of the three storms than did the CRM simulations. The impact of parameter sensitivity in the moist physics schemes employed in the SCM has also been examined. Statistical techniques identified the most significant parameters influencing convective transport. Convective mass fluxes are shown to be strongly dependent on chosen parameter values. Results show that altered parameter settings can substantially improve the comparison between SCM and CRM convective mass flux. Upper tropospheric trace gas mixing ratios were also improved in two storms. In the remaining storm, the SCM representation of CO2 was not improved because of differences in entrainment and detrainment levels in the CRM and SCM simulations.

Observed Boundary Layer Controls on Shallow Cumulus at the ARM Southern Great Plains Site

2018 ◽  
Vol 75 (7) ◽  
pp. 2235-2255 ◽  
Author(s):  
Neil P. Lareau ◽  
Yunyan Zhang ◽  
Stephen A. Klein
Keyword(s):  
Boundary Layer ◽  
Great Plains ◽  
Vertical Velocity ◽  
Mass Flux ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Southern Great Plains ◽  
Clear Sky ◽  
Shallow Cumulus ◽  
In Situ Sensors

Abstract The boundary layer controls on shallow cumulus (ShCu) convection are examined using a suite of remote and in situ sensors at ARM Southern Great Plains (SGP). A key instrument in the study is a Doppler lidar that measures vertical velocity in the CBL and along cloud base. Using a sample of 138 ShCu days, the composite structure of the ShCu CBL is examined, revealing increased vertical velocity (VV) variance during periods of medium cloud cover and higher VV skewness on ShCu days than on clear-sky days. The subcloud circulations of 1791 individual cumuli are also examined. From these data, we show that cloud-base updrafts, normalized by convective velocity, vary as a function of updraft width normalized by CBL depth. It is also found that 63% of clouds have positive cloud-base mass flux and are linked to coherent updrafts extending over the depth of the CBL. In contrast, negative mass flux clouds lack coherent subcloud updrafts. Both sets of clouds possess narrow downdrafts extending from the cloud edges into the subcloud layer. These downdrafts are also present adjacent to cloud-free updrafts, suggesting they are mechanical in origin. The cloud-base updraft data are subsequently combined with observations of convective inhibition to form dimensionless “cloud inhibition” (CI) parameters. Updraft fraction and liquid water path are shown to vary inversely with CI, a finding consistent with CIN-based closures used in convective parameterizations. However, we also demonstrate a limited link between CBL vertical velocity variance and cloud-base updrafts, suggesting that additional factors, including updraft width, are necessary predictors for cloud-base updrafts.

Horizontal Divergence and Vertical Velocity Retrievals from Doppler Radar and Wind Profiler Observations

1996 ◽  
Vol 13 (5) ◽  
pp. 948-966 ◽  
Author(s):  
Robert Cifelli ◽  
Steven A. Rutledge ◽  
Dennis J. Boccippio ◽  
Thomas Matejka
Keyword(s):  
Vertical Velocity ◽  
Doppler Radar ◽  
Wind Profiler
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