Energy Gain Kernel for Climate Feedbacks. Part I: Formulation and Physical Understanding

Ming Cai aDepartment of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL, USA

Search for other papers by Ming Cai in
Current site
Google Scholar
PubMed
Close
,
Xiaoming Hu bSchool of Atmospheric Sciences, Sun Yat-sen University and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, P. R. China
cGuangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Zhuhai, P. R. China

Search for other papers by Xiaoming Hu in
Current site
Google Scholar
PubMed
Close
,
Jie Sun aDepartment of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL, USA

Search for other papers by Jie Sun in
Current site
Google Scholar
PubMed
Close
,
Feng Ding dDepartment of Atmospheric and Oceanic Sciences, Peking University, Beijing, P. R. China

Search for other papers by Feng Ding in
Current site
Google Scholar
PubMed
Close
, and
Jing Feng eAtmospheric and Oceanic Sciences Program, Princeton University, Princeton, NJ, USA

Search for other papers by Jing Feng in
Current site
Google Scholar
PubMed
Close
Open access

Abstract

This paper introduces a climate feedback kernel, referred to as the “energy gain kernel” (EGK). EGK allows for separating the net longwave radiative energy perturbations given by a Planck feedback matrix explicitly into thermal energy emission perturbations of individual layers, and thermal radiative energy flux convergence perturbations at individual layers resulting from the coupled atmosphere-surface temperature changes in response to the unit forcing in individual layers. The former is represented by the diagonal matrix of a Planck feedback matrix and the latter by EGK. Elements of EGK are all positive, representing amplified energy perturbations at a layer where forcing is imposed and energy gained at other layers, both of which are achieved through radiative thermal coupling within an atmosphere-surface column.

Applying EGK to input energy perturbations, whether external or internal due to responses of non-temperature feedback processes to external energy perturbations, such as water vapor and albedo feedbacks, yields their total energy perturbations amplified through radiative thermal coupling within an atmosphere-surface column.

As the strength of EGK depends exclusively on climate mean states, it offers a solution for effectively and objectively separating control climate state information from climate perturbations for climate feedback studies. Given that an EGK comprises critical climate mean state information on mean temperature, water vapor, clouds, and surface pressure, we envision that the diversity of EGK across different climate models could provide insight into the inquiry of why, under the same anthropogenic greenhouse gas increase scenario, different models yield varying degrees of global mean surface warming.

© 2024 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Ming Cai, mcai@fsu.edu

Abstract

This paper introduces a climate feedback kernel, referred to as the “energy gain kernel” (EGK). EGK allows for separating the net longwave radiative energy perturbations given by a Planck feedback matrix explicitly into thermal energy emission perturbations of individual layers, and thermal radiative energy flux convergence perturbations at individual layers resulting from the coupled atmosphere-surface temperature changes in response to the unit forcing in individual layers. The former is represented by the diagonal matrix of a Planck feedback matrix and the latter by EGK. Elements of EGK are all positive, representing amplified energy perturbations at a layer where forcing is imposed and energy gained at other layers, both of which are achieved through radiative thermal coupling within an atmosphere-surface column.

Applying EGK to input energy perturbations, whether external or internal due to responses of non-temperature feedback processes to external energy perturbations, such as water vapor and albedo feedbacks, yields their total energy perturbations amplified through radiative thermal coupling within an atmosphere-surface column.

As the strength of EGK depends exclusively on climate mean states, it offers a solution for effectively and objectively separating control climate state information from climate perturbations for climate feedback studies. Given that an EGK comprises critical climate mean state information on mean temperature, water vapor, clouds, and surface pressure, we envision that the diversity of EGK across different climate models could provide insight into the inquiry of why, under the same anthropogenic greenhouse gas increase scenario, different models yield varying degrees of global mean surface warming.

© 2024 American Meteorological Society. This is an Author Accepted Manuscript distributed under the terms of the default AMS reuse license. For information regarding reuse and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Ming Cai, mcai@fsu.edu
Save