Allison A. Wing, Ph.D.

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Tropical Convection and Climate

Tropical clouds and thunderstorms, known as tropical convection, are often organized into clusters maintaining many individual cells. This organized convection spans a range of scales, from squall lines, to mesoscale convective complexes, to tropical cyclones, to the Madden-Julian Oscillation. Organized convection contributes significantly to tropical rainfall and cloudiness, and, when clouds cluster together more, they change the amount of cloudiness and humidity in the surrounding large-scale environment. Therefore, the behavior of tropical convection and its coupling with circulation is essential to understanding tropical and global climate and climate sensitivity. However, this is a difficult problem, due to the scale separation between large-scale tropical dynamics and convection, models generally must parameterize convection or parameterize or omit large-scale dynamics.

We study several aspects of this problem. Much of our work has focused on better understanding the mechanisms by which tropical convection organizes, by using idealized cloud resolving model simulations as a tool. In particular, we study the physical mechanisms controlling the self-aggregation of convection, in which interactions between the environment and the convection allow the convection to spontaneously organize into one or several clusters. We also investigate the response of clouds, circluation, and climate sensitivity to warming in a model configuration that has both explicit convection and, through the existence of self-aggregation of convection, large-scale circulations. Prof. Wing is leading RCEMIP, an international, coordinated, intercomparison of models configured in radiative-convective equilibrium (RCE), which is a popular idealization of the tropical atmosphere that has long been used to study basic questions in climate science and for understanding the behavior of tropical clouds and convection. Through RCEMIP, we will advance our understanding of the response of clouds to warming, the robustness of self-aggregation of convection across the spectrum of models and the extent to which the degree of aggregation depends on temperature, and the climate sensitivity of the RCE state and the impact of self-aggregation on the climate sensitivity. The first results of RCEMIP are summarized in a recorded presentation from the AGU Fall Meeting in December 2020.

We are also investigating convective organization in observations. ORCESTRA is an international field campaign occuring in August-September 2024 about ORganized Convection and Earthcare Studies over the TRopical Atlantic. The overarching objective of ORCESTRA is to better understand the physical mechanisms that organize tropical convection at the mesoscale, influencing the structure and dynamics of the inter-tropical convergence zone (ITCZ). This includes the interaction of convective organization with tropical waves and air-sea interaction, and the impact of convective organization on climate and the Earth’s radiation budget and processes of tropical cyclogenesis. In addition to advancing understanding of tropical meteorology and atmospheric processes, ORCESTRA observations will help calibrate and validate satellite remote sensing (especially EarthCARE) and a new generation of global ocean-eddy and storm-resolving climate models.

Prof. Wing is leading PICCOLO, the NSF-funded US-component of ORCESTRA. PICCOLO is the Process Investigation of Clouds and Convective Organization over the atLantic Ocean. PICCOLO plans to deploy the SEA-POL radar on the Meteor to investigate the nature, governing mechanisms, and impact of mesoscale organization of precipitating deep convection in the context of the Atlantic ITCZ. The objectives of PICCOLO involve (1) precipitation, humidity, and organization; (2) microphysical characteristics; (3) importance of radiative processes; and (4) the entropy budget. SEA-POL is the Colorado State University Sea-Going Polarimetric Radar, a National Science Foundation (NSF) community facility. SEA-POL is a 5.65 GHz ship-stabilized Doppler radar that operates at C-band to measure dual-polarization. PICCOLO is funded by the US National Science Foundation. For more information about ORCESTRA/PICCOLO see http://orcestra-campaign.org and here.

What does self-aggregation look like?

Self-Aggregation of Tropical Convection from Ryan Abernathey on Vimeo

The movie to the left shows the evolution of clouds and humidity during a cloud resolving model simulation of spontaneous organization of tropical convection, known as “self-aggregation". The simulation uses a framework of non-rotating radiative-convective equilibrium. The white shading is the mixing ratio of total cloud condensate, indicating the presence and amount of clouds, and the colors indicate the water vapor mixing ratio near the surface. Each frame is a 6-hourly snapshot and the simulation runs for 100 days. Thanks to Ryan Abernathey for helping to create this visualization!

Link --> Self-aggregation in a long channel: This movie shows the evolution of aggregation for a long channel simulation; the channel is ~12,000 km long and ~200 km wide. The top subplot shows the cloud-top temperature and the precipitation rate, and the bottom subplot shows the precipitable water. In order to zoom in on the elongated channel, it is divided into quarters and each segment is wrapped left-to-right, as if it were lines of text. Movie from Wing and Cronin (2016).

Link --> Self-aggregation in varied domain geometry: This movie shows a five day period from simulations at four different aspect ratios, to scale (64:1, 16:1, 4:1, and 1:1). The variables plotted are the same as in the previous movie. Movie from Wing and Cronin (2016).

Papers on this topic

Self-Aggregation

Carstens, J.D. and A.A. Wing (2023): Regimes of convective self-aggregation in convection-permitting beta-plane simulations, J. Atmos. Sci., 80, 2187-2205, doi:10.1175/JAS-D-22-0222.1.

Carstens, J.D. and A.A. Wing (2022): A spectrum for convective self-aggregation based on background rotation, J. Adv. Model. Earth Syst., 14, e2021MS002860, doi:10.1029/2021MS002860. [cover article]

Carstens, J. and A.A. Wing, (2020): Tropical cyclogenesis from self-aggregated convection in numerical simulations of rotating radiative-convective equilibrium, J. Adv. Model. Earth Syst., 12, e2019MS002020, doi:10.1029/2019MS002020.

Wing, A. A. (2019): Self-aggregation of deep convection and its implications for climate, Curr. Clim. Change Rep., doi:10.1007/s40641-019-00120-3.

Wing, A.A., K. Emanuel, C.E. Holloway, and C. Muller (2017), Convective self-aggregation in numerical simulations: A review, Surveys in Geophysics, 38, 1173-1197, doi:10.1007/s10712-017-9408-4.

Wing, A.A. and T.W. Cronin (2016), Self-aggregation of convection in long channel geometry, Q.J.R. Meteorol. Soc., 142, 1-15, doi:10.1002/qj.2628.

Emanuel, K., A.A. Wing, and E. Vincent (2014), Radiative-Convective Instability, J. Adv. Model. Earth Sys., 6, 75-90, doi:10.1002/2013MS000270.

Wing, A.A. and K.A. Emanuel (2014), Physical mechanisms controlling self-aggregation of convection in idealized numerical modeling simulations, J. Adv. Model. Earth Sys., 6, 59-74, doi:10.1002/2013MS000269.

Clouds & Climate

Cronin, T.W. and A.A. Wing (2017), Clouds, circulation, and climate sensitivity in a radiative-convective equilibrium channel model, J. Adv. Model. Earth Sys., 9, 2833-2905, doi:10.1002/2017MS001111.

Holloway, C.E., A.A. Wing, S. Bony, C. Muller, H. Masunaga, T.S. L'Ecuyer, D.D. Turner, P. Zuidema (2017), Observing convective aggregation, Surveys in Geophysics, 38, 1199-1236, doi:10.1007/s10712-017-9419-1.

RCEMIP

Wing, A. A., Reed, K. A., Satoh, M., Stevens, B., Bony, S., and Ohno, T. (2018): Radiative-Convective Equilibrium Model Intercomparison Project, Geosci. Model Dev., 11, 793-813, doi:10.5194/gmd-11-793-2018.

Wing, A.A., C.L. Stauffer, T. Becker, K.A. Reed, M.-S. Ahn, N.P. Arnold, S. Bony, M. Branson, G.H. Bryan, J.-P. Chaboureau, S.R. de Roode, K. Gayatri, C. Hohenegger, I.-K. Hu, F. Jansson, T.R. Jones, M. Khairoutdinov, D. Kim, Z.K. Martin, S. Matsugishi, B. Medeiros, H. Miura, Y. Moon, S.K. Müller, T. Ohno, M. Popp, T. Prabhakaran, D. Randall, R. Rios-Berrios, N. Rochetin, R. Roehrig, D.M. Romps, J.H. Ruppert, Jr., M. Satoh, L.G. Silvers, M.S. Singh, B. Stevens, L. Tomassini, C.C. van Heerwaarden, S. Wang, and M. Zhao (2020): Clouds and convective self-aggregation in a multi-model ensemble of radiative-convective equilibrium simulations, J. Adv. Model. Earth Syst., 12, e2020MS002138, doi:10.1029/2020MS002138.

Becker, T. and A.A. Wing (2020): Understanding the extreme spread in climate sensitivity within the Radiative-Convective Equilibrium Model Intercomparison Project, J. Adv. Model. Earth Syst., 12, e2020MS002165, doi:10.1029/2020MS002165.

Reed, K.A., L.G. Silvers, A.A. Wing, I.-K. Hu, and B. Medeiros (2021): Using radiative convective equilibrium to explore clouds and climate in the Community Atmosphere Model, J. Adv. Model. Earth Syst., 13, e2021MS002539, doi:10.1029/2021MS002539.

Stauffer, C.L. and A.A. Wing (2022): Properties, Changes, and Controls of Deep-Convecting Clouds in Radiative-Convective Equilibrium, J. Adv. Model. Earth Syst., 14, e2021MS002917, doi:10.1029/2021MS002917.

Silvers, L.G., K.A. Reed, and A.A. Wing (2023): The response of the large-scale tropical circulation to warming, J. Adv. Model. Earth Syst., 15, e2021MS002966, doi:10.1029/2021MS002966.

Stauffer, C.L. and A.A. Wing (2023): Explicitly Resolved Cloud Feedbacks in the Radiative-Convective Equilibrium Model Intercomparison Project, J. Adv. Model. Earth Syst., 15, e2023MS003738, doi:10.1029/2023MS003738.

Wing, A.A. and M.S. Singh (2024): Control of Stability and Relative Humidity in the Radiative-Convective Equilibrium Model Intercomparison Project, J. Adv. Model. Earth Syst., 16, e2023MS003914, doi:10.1029/2023MS003914.

Stauffer, C.L. and A.A. Wing: How Does Organized Convection Impact Explicitly Resolved Cloud Feedbacks in the Radiative-Convective Equilibrium Model Comparison Project, J. Adv. Model. Earth Syst., in review.

Wing, A.A., L.G. Silvers, and K.A. Reed: RCEMIP-II: Mock-Walker Simulations as Phase II of the Radiative-Convective Equilibrium Model Intercomparison Project, Geosci. Model Dev. Discuss. [preprint], doi:10.5194/gmd-2023-235, in review.