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Mülmenstädt J, Nam C, Salzmann M, Kretzschmar J, L’Ecuyer TS, Lohmann U, Ma PL, Myhre G, Neubauer D, Stier P, Suzuki K, Wang M, Quaas J. Reducing the aerosol forcing uncertainty using observational constraints on warm rain processes. Sci Adv 2020; 6:eaaz6433. [PMID: 32523991 PMCID: PMC7259935 DOI: 10.1126/sciadv.aaz6433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 03/30/2020] [Indexed: 06/11/2023]
Abstract
Global climate models (GCMs) disagree with other lines of evidence on the rapid adjustments of cloud cover and liquid water path to anthropogenic aerosols. Attempts to use observations to constrain the parameterizations of cloud processes in GCMs have failed to reduce the disagreement. We propose using observations sensitive to the relevant cloud processes rather than only to the atmospheric state and focusing on process realism in the absence of aerosol perturbations in addition to the process susceptibility to aerosols. We show that process-sensitive observations of precipitation can reduce the uncertainty on GCM estimates of rapid cloud adjustments to aerosols. The feasibility of an observational constraint depends on understanding the precipitation intensity spectrum in both observations and models and also on improving methods to compare the two.
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Affiliation(s)
- Johannes Mülmenstädt
- Institute of Meteorology, Universität Leipzig, Leipzig, Germany
- Atmospheric Sciences & Global Change Division, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Christine Nam
- Institute of Meteorology, Universität Leipzig, Leipzig, Germany
| | - Marc Salzmann
- Institute of Meteorology, Universität Leipzig, Leipzig, Germany
| | - Jan Kretzschmar
- Institute of Meteorology, Universität Leipzig, Leipzig, Germany
| | - Tristan S. L’Ecuyer
- Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, WI, USA
| | - Ulrike Lohmann
- Institute of Atmospheric and Climate Science, ETH Zürich, Zürich, Switzerland
| | - Po-Lun Ma
- Atmospheric Sciences & Global Change Division, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Gunnar Myhre
- CICERO Center for International Climate Research, Oslo, Norway
| | - David Neubauer
- Institute of Atmospheric and Climate Science, ETH Zürich, Zürich, Switzerland
| | - Philip Stier
- Department of Physics, University of Oxford, Oxford, UK
| | - Kentaroh Suzuki
- Atmosphere and Ocean Research Institute, University of Tokyo, Tokyo, Japan
| | - Minghuai Wang
- School of Atmospheric Sciences, Nanjing University, Nanjing, China
| | - Johannes Quaas
- Institute of Meteorology, Universität Leipzig, Leipzig, Germany
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Lebsock MD, L’Ecuyer TS, Pincus R. An Observational View of Relationships Between Moisture Aggregation, Cloud, and Radiative Heating Profiles. Surv Geophys 2017; 38:1237-1254. [PMID: 31997842 PMCID: PMC6956940 DOI: 10.1007/s10712-017-9443-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 10/19/2017] [Indexed: 06/10/2023]
Abstract
Data from several coincident satellite sensors are analyzed to determine the dependence of cloud and precipitation characteristics of tropical regions on the variance in the water vapor field. Increased vapor variance is associated with decreased high cloud fraction and an enhancement of low-level radiative cooling in dry regions of the domain. The result is found across a range of sea surface temperatures and rain rates. This suggests the possibility of an enhanced low-level circulation feeding the moist convecting areas when vapor variance is large. These findings are consistent with idealized models of self-aggregation, in which the aggregation of convection is maintained by a combination of low-level radiative cooling in dry regions and mid-to-upper-level radiative warming in cloudy regions.
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Affiliation(s)
- Matthew D. Lebsock
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 USA
| | | | - Robert Pincus
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309 USA
- Physical Sciences Division, NOAA Earth System Research Lab, Boulder, CO 80305 USA
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Holloway CE, Wing AA, Bony S, Muller C, Masunaga H, L’Ecuyer TS, Turner DD, Zuidema P. Observing Convective Aggregation. Surv Geophys 2017; 38:1199-1236. [PMID: 31997841 PMCID: PMC6956938 DOI: 10.1007/s10712-017-9419-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 06/14/2017] [Indexed: 05/21/2023]
Abstract
Convective self-aggregation, the spontaneous organization of initially scattered convection into isolated convective clusters despite spatially homogeneous boundary conditions and forcing, was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network.
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Affiliation(s)
| | - Allison A. Wing
- Lamont-Doherty Earth Observatory, Columbia University, PO Box 1000, 61 Route 9W, Palisades, NY 10964-1000 USA
- Department of Earth, Ocean and Atmospheric Science, Florida State University, Mail Code 4520, PO Box 3064520, Tallahassee, FL 32306-4520 USA
| | - Sandrine Bony
- Sorbonne University, LMD/IPSL, CNRS, Univ Paris 06, mailbox 99, 4 Place Jussieu, 75252 Paris cedex 05, France
| | - Caroline Muller
- LMD/IPSL, CNRS, École Normale Supérieure, Paris Sciences Et Lettres, 24 rue Lhomond, 75230 Paris cedex 05, France
| | - Hirohiko Masunaga
- Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan
| | - Tristan S. L’Ecuyer
- Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, 1225 West Dayton Street, Madison, WI 53706 USA
| | - David D. Turner
- NOAA/Earth System Research Laboratory, Global Systems Division, 325 Broadway, Boulder, CO 80305-3337 USA
| | - Paquita Zuidema
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149 USA
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