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Title: Using the GoAmazon-CHUVA measurements to understand what causes the biases in the onset of the rainy season in Amazonia in climate models

Abstract

The onset of the Amazon rainy season has a large temporal and spatial variability, and strong impact on aerosols, ecosystems, fire, carbon fluxes, dry season length, agriculture, and hydropower. Two major droughts occurred in the region in the last 20 years, and the dry season has increased in length by about one month. These events highlight the urgency for improving our understanding and capability to project the rainy season onset and drought variability. However, global climate models (CMIP3 and CMIP5) appear to underestimate the past variability, and also project virtually no future change of the onset of rainy season over the Amazon even when they are forced by strong greenhouse forcing under the RCP8.5 scenario. Why these models underestimate the variability of the rainy season onset, and whether this bias implies an underestimate of sensitivity of their dry season length to anthropogenic radiative forcing remain unclear. This proposal aims to explore use of the measurements provided by the Atmospheric Radiation Measurement (ARM) Mobile Facilities (AMF)-GoAmazon project and the Cloud processes of the main precipitation systems in Brazil (CHUVA) Field Experiments, along with global and regional model experiments, to explore the sources of the above described uncertainty, in order to improvemore » the US CESM and the Brazilian Eta regional Model and the BESM (Brazilian Earth System Model). Based on previous and our ongoing studies, we hypothesize that the underestimation of changes of the rainy season onset over the Amazon and its climate variability and sensitivity to anthropogenic forcing are in part related to: a) The inadequate representation of the types of convection (i.e., maritime versus continental) and their relationships to aerosols, land surface and atmospheric circulation as represented in climate models, b) Inadequacies of the modeled oceanic variability, land surface processes and their coupling to the atmosphere. To evaluate these hypotheses, we propose to clarify the following questions: a. How would changes of land surface conditions and aerosol influence the intensity and type of the convection over the Amazon? How adequately are these influences represented in NCAR/DOE CESM 1.2/CAM5.3/CLM4.5 climate model and the Eta regional Model and the BESM (Brazilian Earth System Model) as used by the Brazilian National Institute of Space Research (INPE)? b. How would a change of convective type influence the vertical profiles of diabatic heating, surface fluxes and large-scale circulation during the dry to wet season transition? c. What are the relative contributions from uncertainties of the local processes (land surface and aerosols) vs. those of Atlantic and Pacific ITCZ to the underestimation of the variability of the dry season length in CESM and BESM?« less

Authors:
 [1];  [2];  [1]
  1. University of California, Los Angeles
  2. Jackson School of Geosciences
Publication Date:
Research Org.:
Jackson School of Geosciences
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Contributing Org.:
Jet Propulsion Laboratory, California Institute of Technology
OSTI Identifier:
1556997
Report Number(s):
DOE-UTAustin-SC0011117
4046801607
DOE Contract Number:  
SC0011117
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; GoAmazon, aerosols, rainfall

Citation Formats

Fu, Rong, Fu, Rong, and Fu, Rong. Using the GoAmazon-CHUVA measurements to understand what causes the biases in the onset of the rainy season in Amazonia in climate models. United States: N. p., 2019. Web. doi:10.2172/1556997.
Fu, Rong, Fu, Rong, & Fu, Rong. Using the GoAmazon-CHUVA measurements to understand what causes the biases in the onset of the rainy season in Amazonia in climate models. United States. doi:10.2172/1556997.
Fu, Rong, Fu, Rong, and Fu, Rong. Tue . "Using the GoAmazon-CHUVA measurements to understand what causes the biases in the onset of the rainy season in Amazonia in climate models". United States. doi:10.2172/1556997. https://www.osti.gov/servlets/purl/1556997.
@article{osti_1556997,
title = {Using the GoAmazon-CHUVA measurements to understand what causes the biases in the onset of the rainy season in Amazonia in climate models},
author = {Fu, Rong and Fu, Rong and Fu, Rong},
abstractNote = {The onset of the Amazon rainy season has a large temporal and spatial variability, and strong impact on aerosols, ecosystems, fire, carbon fluxes, dry season length, agriculture, and hydropower. Two major droughts occurred in the region in the last 20 years, and the dry season has increased in length by about one month. These events highlight the urgency for improving our understanding and capability to project the rainy season onset and drought variability. However, global climate models (CMIP3 and CMIP5) appear to underestimate the past variability, and also project virtually no future change of the onset of rainy season over the Amazon even when they are forced by strong greenhouse forcing under the RCP8.5 scenario. Why these models underestimate the variability of the rainy season onset, and whether this bias implies an underestimate of sensitivity of their dry season length to anthropogenic radiative forcing remain unclear. This proposal aims to explore use of the measurements provided by the Atmospheric Radiation Measurement (ARM) Mobile Facilities (AMF)-GoAmazon project and the Cloud processes of the main precipitation systems in Brazil (CHUVA) Field Experiments, along with global and regional model experiments, to explore the sources of the above described uncertainty, in order to improve the US CESM and the Brazilian Eta regional Model and the BESM (Brazilian Earth System Model). Based on previous and our ongoing studies, we hypothesize that the underestimation of changes of the rainy season onset over the Amazon and its climate variability and sensitivity to anthropogenic forcing are in part related to: a) The inadequate representation of the types of convection (i.e., maritime versus continental) and their relationships to aerosols, land surface and atmospheric circulation as represented in climate models, b) Inadequacies of the modeled oceanic variability, land surface processes and their coupling to the atmosphere. To evaluate these hypotheses, we propose to clarify the following questions: a. How would changes of land surface conditions and aerosol influence the intensity and type of the convection over the Amazon? How adequately are these influences represented in NCAR/DOE CESM 1.2/CAM5.3/CLM4.5 climate model and the Eta regional Model and the BESM (Brazilian Earth System Model) as used by the Brazilian National Institute of Space Research (INPE)? b. How would a change of convective type influence the vertical profiles of diabatic heating, surface fluxes and large-scale circulation during the dry to wet season transition? c. What are the relative contributions from uncertainties of the local processes (land surface and aerosols) vs. those of Atlantic and Pacific ITCZ to the underestimation of the variability of the dry season length in CESM and BESM?},
doi = {10.2172/1556997},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {8}
}

Works referenced in this record:

Rainforest-initiated wet season onset over the southern Amazon
journal, July 2017

  • Wright, Jonathon S.; Fu, Rong; Worden, John R.
  • Proceedings of the National Academy of Sciences, Vol. 114, Issue 32
  • DOI: 10.1073/pnas.1621516114

Sensitivity of Amazon Regional Climate to Deforestation
journal, January 2017

  • Alves, Lincoln Muniz; Marengo, Jose A.; Fu, Rong
  • American Journal of Climate Change, Vol. 06, Issue 01
  • DOI: 10.4236/ajcc.2017.61005

What controls the interannual variation of the wet season onsets over the Amazon?: Yin et al: Amazonian Wet Season Onset
journal, March 2014

  • Yin, Lei; Fu, Rong; Zhang, Yong-Fei
  • Journal of Geophysical Research: Atmospheres, Vol. 119, Issue 5
  • DOI: 10.1002/2013JD021349

How Do Environmental Conditions Influence Vertical Buoyancy Structure and Shallow-to-Deep Convection Transition across Different Climate Regimes?
journal, June 2018

  • Zhuang, Yizhou; Fu, Rong; Wang, Hongqing
  • Journal of the Atmospheric Sciences, Vol. 75, Issue 6
  • DOI: 10.1175/JAS-D-17-0284.1