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Title: Tropical continental downdraft characteristics: mesoscale systems versus unorganized convection

Journal Article · · Atmospheric Chemistry and Physics (Online)

Downdrafts and cold pool characteristics for strong mesoscale convective systems (MCSs) and isolated, unorganized deep precipitating convection are analyzed using multi-instrument data from the DOE Atmospheric Radiation Measurement (ARM) GoAmazon2014/5 campaign. Increases in column water vapor (CWV) are observed leading convection, with higher CWV preceding MCSs than for isolated cells. For both MCSs and isolated cells, increases in wind speed, decreases in surface moisture and temperature, and increases in relative humidity occur coincidentally with system passages. Composites of vertical velocity data and radar reflectivity from a radar wind profiler show that the downdrafts associated with the sharpest decreases in surface equivalent potential temperature (θe) have a probability of occurrence that increases with decreasing height below the freezing level. Both MCSs and unorganized convection show similar mean downdraft magnitudes and probabilities with height. Mixing computations suggest that, on average, air originating at heights greater than 3km must undergo substantial mixing, particularly in the case of isolated cells, to match the observed cold pool θe, implying a low typical origin level. Precipitation conditionally averaged on decreases in surface equivalent potential temperature (Δθe) exhibits a strong relationship because the most negative Δθe values are associated with a high probability of precipitation. The more physically motivated conditional average of Δθe on precipitation shows that decreases in θe level off with increasing precipitation rate, bounded by the maximum difference between surface θe and its minimum in the profile aloft. In conclusion, robustness of these statistics observed across scales and regions suggests their potential use as model diagnostic tools for the improvement of downdraft parameterizations in climate models.

Research Organization:
Univ. of California, Los Angeles, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
Grant/Contract Number:
SC0011074
OSTI ID:
1502121
Journal Information:
Atmospheric Chemistry and Physics (Online), Vol. 18, Issue 3; ISSN 1680-7324
Publisher:
European Geosciences UnionCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 29 works
Citation information provided by
Web of Science

References (76)

Convective cloud vertical velocity and mass-flux characteristics from radar wind profiler observations during GoAmazon2014/5 journal November 2016
Simulating deep convection with a shallow convection scheme journal January 2011
Traveling Convective Storms over Venezuela journal July 1977
Deep Convection and Column Water Vapor over Tropical Land versus Tropical Ocean: A Comparison between the Amazon and the Tropical Western Pacific journal October 2016
Non-precipitating cumulus convection and its parameterization journal January 1973
A One-Dimensional Entraining/Detraining Plume Model and Its Application in Convective Parameterization journal December 1990
The Relationship of Surface Pressure Features to the Precipitation and Airflow Structure of an Intense Midlatitude Squall Line journal July 1988
Mesoscale Organization of Springtime Rainstorms in Oklahoma journal March 1990
Numerical Simulations of Convectively Generated Stratospheric Gravity Waves journal August 1992
Organization of Tropical Convection in Low Vertical Wind Shears: The Role of Cold Pools journal July 2001
Mechanisms of convective cloud organization by cold pools over tropical warm ocean during the AMIE/DYNAMO field campaign journal April 2015
Warm Upper-Level Downdrafts Associated with a Squall Line journal October 1993
On the sizes and lifetimes of cold pools: On the Sizes and Lifetimes of Cold Pools journal April 2016
Sensitivity of climate simulations to the parameterization of cumulus convection in the Canadian climate centre general circulation model journal September 1995
Mass-Flux Characteristics of Tropical Cumulus Clouds from Wind Profiler Observations at Darwin, Australia journal May 2015
The MJO Transition from Shallow to Deep Convection in CloudSat/CALIPSO Data and GISS GCM Simulations text January 2012
Orogenic Propagating Precipitation Systems over the United States in a Global Climate Model with Embedded Explicit Convection journal August 2011
Temperature–Moisture Dependence of the Deep Convective Transition as a Constraint on Entrainment in Climate Models journal April 2012
Precipitation and cold air Production in Mesoscale Thunderstorm Systems journal August 1959
A Model of Intense Downdrafts Driven by the Melting and Evaporation of Precipitation journal July 1987
On Trade Wind Cumulus Cold Pools journal January 2012
Mesoscale convective systems journal January 2004
Variability of Midtropospheric Moisture and Its Effect on Cloud-Top Height Distribution during TOGA COARE* journal December 1997
Influence of the Subcloud Layer on the Development of a Deep Convective Ensemble journal September 2012
Vertical Motion Structure in Maritime continent mesoscale Convective Systems: Results from a 50-MHz Profiler journal September 1994
The Role of Organized Unsaturated Convective Downdrafts in the Structure and Rapid Decay of an Equatorial Disturbance journal October 1969
A Lagrangian Study of Precipitation-Driven Downdrafts journal February 2016
Cloud organization and growth during the transition from suppressed to active MJO conditions journal October 2015
On the Theory of Disturbances in a Conditionally Unstable Atmosphere journal January 1960
Multiobjective constraints for climate model parameter choices: Pragmatic P areto fronts in CESM1 journal September 2017
A Comprehensive Mass Flux Scheme for Cumulus Parameterization in Large-Scale Models journal August 1989
A Theory for Strong, Long-Lived Squall Lines journal February 1988
Moisture Vertical Structure, Column Water Vapor, and Tropical Deep Convection journal June 2009
Rainfall evaporation in thunderstorm downdraughts journal October 1966
Non-precipitating cumulus convection and its parameterization journal January 1973
Introduction: Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) journal January 2016
The MJO Transition from Shallow to Deep Convection in CloudSat /CALIPSO Data and GISS GCM Simulations journal June 2012
Kinematic and Precipitation Structure of the 10–11 June 1985 Squall Line journal December 1991
Convective Storm Initiation in a Moist Tropical Environment journal June 2008
Study of diurnal cycle of convective precipitation over Amazonia using a single column model: SCM STUDY OF DIURNAL CYCLE OF PRECIPITATION journal December 2002
Large-eddy simulation of maritime deep tropical convection journal December 2009
The dynamics and simulation of tropical cumulonimbus and squall lines: CUMULONIMBUS AND SQUALL LINES journal April 1976
High-Resolution Simulation of Shallow-to-Deep Convection Transition over Land journal December 2006
ARM: Balloon-borne sounding system (BBSS): Vaisala-processed winds, press., temp, and RH
  • Coulter, Richard; Kyrouac, Jenni; Holdridge, Donna
  • Atmospheric Radiation Measurement (ARM) Archive, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (US); https://doi.org/10.5439/1021460
dataset January 1994
Shifting the diurnal cycle of parameterized deep convection over land: DIURNAL CYCLE OF CONVECTION journal April 2009
Vertical Structure of Thunderstorm Outflows journal November 1976
The Life Cycle of Thunderstorm Gust Fronts as Viewed with Doppler Radar and Rawinsonde Data journal August 1982
Mesoscale Convective Systems book January 2001
Convective cloud downdraft structure: An interpretive survey journal January 1985
Surface Characteristics of Observed Cold Pools journal December 2008
Rainfall evaporation in thunderstorm downdraughts journal April 1968
Characteristics of Isolated Convective Storms book January 1986
The Sensitivity of Intraseasonal Variability in the NCAR CCM3 to Changes in Convective Parameterization journal May 2001
Vertically Velocity Characteristics of Oceanic Convection journal March 1989
Introduction: Observations and Modeling of the Green Ocean Amazon (GoAmazon2014/5) journal January 2015
Subcloud Layer Energetics of Precipitating Convection journal February 1982
Aircraft observations of cold pools under marine stratocumulus journal January 2013
The Transition to Strong Convection journal August 2009
The Computation of Equivalent Potential Temperature journal July 1980
Initiation of Convective Storms at Radar-Observed Boundary-Layer Convergence Lines journal December 1986
Application of Gravity Current Model to Analysis of Squall-Line Gust Front journal February 1974
Impact of convective downdrafts on model simulations: results from aqua-planet integrations journal January 2008
The Thermodynamic Transformation of the Tropical Subcloud Layer by Precipitation and Downdrafts journal June 1976
ARM: AOS: aerosol-based meteorology data
  • Koontz, Annette; Springston, Stephen; Kyrouac, Jenni
  • Atmospheric Radiation Measurement (ARM) Archive, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (US); https://doi.org/10.5439/1025153
dataset January 2010
Downward transport of ozone rich air and implications for atmospheric chemistry in the Amazon rainforest journal January 2016
Mesoscale and Convective–Scale Downdrafts as Distinct Components of Squall-Line Structure journal December 1977
Simulated Convective Invigoration Processes at Trade Wind Cumulus Cold Pool Boundaries journal August 2014
ARM: ECOR: surface vertical fluxes of momentum, sensible heat, and latent heat, 30-min avg
  • Sullivan, Ryan; Cook, David
  • Atmospheric Radiation Measurement (ARM) Archive, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (US); https://doi.org/10.5439/1025039
dataset January 1997
Vertical Velocity Characteristics of Deep Convection over Darwin, Australia journal June 1999
The Formation of Wider and Deeper Clouds as a Result of Cold-Pool Dynamics journal August 2014
Cumulus dynamics: Local compensating subsidence and its implications for cumulus parameterization journal December 1975
Numerical Simulation of a Midlatitude Squall Line in Two Dimensions journal December 1988
Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall journal October 2016
Some Uses of High-Resolution GOES Imagery in the Mesoscale Forecasting of Convection and Its Behavior journal December 1976
Frequency of extreme Sahelian storms tripled since 1982 in satellite observations journal April 2017
Atmospheric Convection book February 1994

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GoAmazon2014/5 campaign points to deep-inflow approach to deep convection across scales journal April 2018
Mesoscale convective systems over the Amazon basin: The GoAmazon2014/5 program journal June 2019
Ongoing Breakthroughs in Convective Parameterization journal April 2019
Multi-year statistical and modeling analysis of submicrometer aerosol number size distributions at a rain forest site in Amazonia journal January 2018
Planetary boundary layer evolution over the Amazon rainforest in episodes of deep moist convection at the Amazon Tall Tower Observatory journal January 2020
Planetary boundary layer evolution over the Amazon rainforest in episodes of deep moist convection at the Amazon Tall Tower Observatory journal January 2020
A Survey of Precipitation-Induced Atmospheric Cold Pools over Oceans and Their Interactions with the Larger-Scale Environment journal November 2017
Moisture Distributions in Tropical Cold Pools From Equatorial Indian Ocean Observations and Cloud-Resolving Simulations journal October 2018
A Survey of Precipitation-Induced Atmospheric Cold Pools over Oceans and Their Interactions with the Larger-Scale Environment book January 2017