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Title: Tropical Convective Transition Statistics and Causality in the Water Vapor–Precipitation Relation

Abstract

Abstract Previous work by various authors has pointed to the role of lower-free-tropospheric humidity in affecting the onset of deep convection in the tropics. Empirical relationships between column water vapor (CWV) and precipitation have been inferred to result from these effects. Evidence from previous work has included deep convective conditional instability calculations for entraining plumes, in which the lower-free-tropospheric environment affects the onset of deep convection due to the differential impact on buoyancy of turbulent entrainment of dry versus moist air. The relationship between deep convection and water vapor is, however, a two-way interaction because convection also moistens the free troposphere. The present study adds an additional line of evidence toward fully establishing the causality of the precipitation–water vapor relationship. Parameter perturbation experiments using the coupled Community Earth System Model (CESM) with high-time-resolution output are analyzed for a set of statistics for the transition to deep convection, coordinated with observational diagnostics for the Green Ocean Amazon (GOAmazon) campaign and tropical western Pacific Atmospheric Radiation Measurement (ARM) sites. For low values of entrainment in the deep convective scheme, these statistics are radically altered and the observed pickup of precipitation with CWV is no longer seen. In addition to helping cement themore » dominant direction of causality in the fast-time-scale precipitation–CWV relationship, the results point to impacts of entrainment on the climatology. Because at low entrainment convection can fire before tropospheric moistening, the climatological values of relative humidity are lower than observed. These findings can be consequential to biases in simulated climate and to projections of climate change.« less

Authors:
 [1];  [1];  [1]
  1. Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, Los Angeles, California
Publication Date:
Research Org.:
Univ. of California, Los Angeles, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI Identifier:
1346277
Alternate Identifier(s):
OSTI ID: 1426863
Grant/Contract Number:  
SC0011074
Resource Type:
Published Article
Journal Name:
Journal of the Atmospheric Sciences
Additional Journal Information:
Journal Name: Journal of the Atmospheric Sciences Journal Volume: 74 Journal Issue: 3; Journal ID: ISSN 0022-4928
Publisher:
American Meteorological Society
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

Kuo, Yi-Hung, Neelin, J. David, and Mechoso, C. Roberto. Tropical Convective Transition Statistics and Causality in the Water Vapor–Precipitation Relation. United States: N. p., 2017. Web. doi:10.1175/JAS-D-16-0182.1.
Kuo, Yi-Hung, Neelin, J. David, & Mechoso, C. Roberto. Tropical Convective Transition Statistics and Causality in the Water Vapor–Precipitation Relation. United States. doi:10.1175/JAS-D-16-0182.1.
Kuo, Yi-Hung, Neelin, J. David, and Mechoso, C. Roberto. Thu . "Tropical Convective Transition Statistics and Causality in the Water Vapor–Precipitation Relation". United States. doi:10.1175/JAS-D-16-0182.1.
@article{osti_1346277,
title = {Tropical Convective Transition Statistics and Causality in the Water Vapor–Precipitation Relation},
author = {Kuo, Yi-Hung and Neelin, J. David and Mechoso, C. Roberto},
abstractNote = {Abstract Previous work by various authors has pointed to the role of lower-free-tropospheric humidity in affecting the onset of deep convection in the tropics. Empirical relationships between column water vapor (CWV) and precipitation have been inferred to result from these effects. Evidence from previous work has included deep convective conditional instability calculations for entraining plumes, in which the lower-free-tropospheric environment affects the onset of deep convection due to the differential impact on buoyancy of turbulent entrainment of dry versus moist air. The relationship between deep convection and water vapor is, however, a two-way interaction because convection also moistens the free troposphere. The present study adds an additional line of evidence toward fully establishing the causality of the precipitation–water vapor relationship. Parameter perturbation experiments using the coupled Community Earth System Model (CESM) with high-time-resolution output are analyzed for a set of statistics for the transition to deep convection, coordinated with observational diagnostics for the Green Ocean Amazon (GOAmazon) campaign and tropical western Pacific Atmospheric Radiation Measurement (ARM) sites. For low values of entrainment in the deep convective scheme, these statistics are radically altered and the observed pickup of precipitation with CWV is no longer seen. In addition to helping cement the dominant direction of causality in the fast-time-scale precipitation–CWV relationship, the results point to impacts of entrainment on the climatology. Because at low entrainment convection can fire before tropospheric moistening, the climatological values of relative humidity are lower than observed. These findings can be consequential to biases in simulated climate and to projections of climate change.},
doi = {10.1175/JAS-D-16-0182.1},
journal = {Journal of the Atmospheric Sciences},
number = 3,
volume = 74,
place = {United States},
year = {2017},
month = {3}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1175/JAS-D-16-0182.1

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Cited by: 2 works
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Works referencing / citing this record:

Campaign datasets for Observations and Modeling of the Green Ocean Amazon (GOAMAZON)
dataset, January 2016

  • Martin, Scot; Mei, Fan; Alexander, Lizabeth
  • ARM, 64 data sets
  • DOI: 10.5439/1346559

Mesoscale convective systems over the Amazon basin: The GoAmazon2014/5 program
journal, June 2019

  • Rehbein, Amanda; Ambrizzi, Tercio; Mechoso, Carlos R.
  • International Journal of Climatology, Vol. 39, Issue 15
  • DOI: 10.1002/joc.6173

Mesoscale convective systems over the Amazon basin: The GoAmazon2014/5 program
journal, June 2019

  • Rehbein, Amanda; Ambrizzi, Tercio; Mechoso, Carlos R.
  • International Journal of Climatology, Vol. 39, Issue 15
  • DOI: 10.1002/joc.6173