Graeme Stephens | Colorado State University (original) (raw)

Papers by Graeme Stephens

Research paper thumbnail of Uncertainties in Space-Based Estimates of Clouds and Precipitation: Implications for Deriving Global Diabatic Heating

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Research paper thumbnail of Terminal versus transient cumulus congestus: A CloudSat perspective

Geophysical Research Letters, 2009

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Research paper thumbnail of Earth’s Energy Imbalance Measured From Space

IEEE Transactions on Geoscience and Remote Sensing, 2019

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Research paper thumbnail of The Super Greenhouse effect in a changing climate

Journal of Climate, 2016

In all outputs of the 1% yr−1 increase in CO2 climate model experiments archived under the World ... more In all outputs of the 1% yr−1 increase in CO2 climate model experiments archived under the World Climate Research Programme’s (WCRP) phase 5 of the Coupled Model Intercomparison Project (CMIP5), regions exist in the low latitudes where both the clear-sky and all-sky OLR decrease with surface warming. These are identified as regions of positive longwave feedback and are regions of a super greenhouse effect (SGE). These SGE regions are identified from feedback analysis of the 4 × CO2 abrupt experiments of CMIP5, and despite their existence, there is little agreement across models as to the magnitude of the effect. The general effects of clouds on the SGE are to amplify the clear-sky SGE, but there is also poor agreement on the magnitude of the amplification that varies by an order of magnitude across models. Sensitivity analyses indicate that localized SGE regions are spatially aligned with a large moistening of the upper troposphere. The reduction in clear-sky OLR arises from a reduc...

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Research paper thumbnail of Improved ice content, radiation, precipitation and low-level circulation over the tropical pacific from ECMWF ERA-interim to ERA5

Environmental Research Communications

This study evaluates changes in simulated Pacific climate between two ECMWF re-analyses; the ERA ... more This study evaluates changes in simulated Pacific climate between two ECMWF re-analyses; the ERA Interim (ERAI) and the newest ERA5. Changes in the Integrated Forecasting System (IFS) and possibly sea surface temperature result in greatly reduced discrepancies in ERA5’s ice water path (IWP), radiative fluxes and precipitation relative to satellite-based observational products. IWP shows the largest percentage change, increasing by over 300% from ERAI to ERA5, due to inclusion of falling ice (snow) that impacts radiative calculation. ERAI to ERA5 changes in high-cloud fraction are generally anticorrelated as expected with outgoing longwave radiation, with ERA5 having smaller longwave discrepancies versus CERES observations compared with ERAI. Reflected shortwave discrepancies are similarly reduced from ERAI to ERA5, which appears to be due to changes in both cloud fraction and optical depth. Finally, ERA5 also reduces a longstanding precipitation excess relative to the GPCP observati...

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Research paper thumbnail of On the combination of active and passive measurements in the study of clouds and precipitation

IGARSS 2001. Scanning the Present and Resolving the Future. Proceedings. IEEE 2001 International Geoscience and Remote Sensing Symposium (Cat. No.01CH37217)

Presents an approach that combines millimetric radar measurements and radiometer measurements for... more Presents an approach that combines millimetric radar measurements and radiometer measurements for deriving the water contents of clouds and precipitation and does so within the context of the CloudSat satellite mission

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Research paper thumbnail of Monitoring of Geoengineering Effects and their Natural and Anthropogenic Analogues

A number of climate intervention concepts, referred to as “geoengineering,” are being considered ... more A number of climate intervention concepts, referred to as “geoengineering,” are being considered as a potential additional approach (beyond mitigation of greenhouse gas emissions) to manage climate change. However, before governments go down the path of attempting deliberate climate intervention including precursor field-experiments, it is essential that the scientific community take the necessary steps to validate our understanding that underpins any of the proposed intervention concepts in order to understand all likely consequences and put in place the necessary strategies for monitoring the expected and unintended consequences of such intervention. The Keck Institute for Space Studies (KISS) has sponsored a project to identify specific priorities for improved scientific understanding and focused efforts to address selected priorities. This project does not advocate the deployment of geoengineering, outdoor geoengineering experiments, or monitoring systems for such proposed geoen...

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Research paper thumbnail of The Useful Pursuit of Shadows The study of clouds has profoundly influenced science and human culture and stands poised to lead climate science forward again

Howard, a London pharmacist and amateur meteorologist, aired his ideas about the classification o... more Howard, a London pharmacist and amateur meteorologist, aired his ideas about the classification of clouds. These ideas were presented to a small gathering of young science-minded intellectuals who called themselves The Askesian Society. Howard's lecture on that evening was titled " On the Modification of Clouds " and opened as follows: My talk this evening concerns itself with what may strike some as an uncharacteristically impractical subject: it is concerned with the modification of clouds. Since the increased attention which has been given to meteorology, the studies of various appearances of water suspended in the atmosphere has become an interesting and even necessary branch of that pursuit. If clouds were the mere result of condensation of vapour in the masses of the atmosphere which they occupy, if their variations were produced by the movements of the atmosphere alone, then indeed might the study be deemed a useless pursuit of shadows.… This was a historic lect...

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Research paper thumbnail of What is the Role of GEWEX in R 2 O and O 2 R ?

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Research paper thumbnail of The cooling of light rains in a warming world

Nature Climate Change

Recent changes to how clouds are represented in global models, especially over the Southern Ocean... more Recent changes to how clouds are represented in global models, especially over the Southern Ocean, resulted in increased climate warming. Correcting rain processes in a model shows improved cloud representation but leads to a greatly enhanced negative feedback, offsetting documented increases in model climate sensitivity.

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Research paper thumbnail of Applying Search Algorithms to the Temperature Inversion problem

Several inverse problems exist in the atmospheric sciences that are computationally costly when u... more Several inverse problems exist in the atmospheric sciences that are computationally costly when using traditional gradient based methods. Unfortunately, many standard evolutionary algorithms do not perform well on these problems. This paper investigates why the temperature inversion problem is so difficult for heuristic search. We show that algorithms imposing smoothness constraints find more competitive solutions. Additionally, a new algorithm is presented that addresses the difficulties of this problem and finds approximate solutions fast.

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Research paper thumbnail of The Impacts of Bias in Cloud-Radiation-Dynamics Interactions on Central Pacific Seasonal and El Niño Simulations in Contemporary GCMs

Earth and Space Science

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Research paper thumbnail of Earth's water reservoirs in a changing climate

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

Progress towards achieving a quantitative understanding of the exchanges of water between Earth&#... more Progress towards achieving a quantitative understanding of the exchanges of water between Earth's main water reservoirs is reviewed with emphasis on advances accrued from the latest advances in Earth Observation from space. These exchanges of water between the reservoirs are a result of processes that are at the core of important physical Earth-system feedbacks, which fundamentally control the response of Earth's climate to the greenhouse gas forcing it is now experiencing, and are therefore vital to understanding the future evolution of Earth's climate. The changing nature of global mean sea level (GMSL) is the context for discussion of these exchanges. Different sources of satellite observations that are used to quantify ice mass loss and water storage over continents, how water can be tracked to its source using water isotope information and how the waters in different reservoirs influence the fluxes of water between reservoirs are described. The profound influence of...

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Research paper thumbnail of Revisiting the Entrainment Relationship of Convective Plumes: A Perspective From Global Observations

Geophysical Research Letters

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Research paper thumbnail of Earth's water reservoirs in a changing climate

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Apr 1, 2020

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Research paper thumbnail of The Emerging Technological Revolution in Earth Observations

Bulletin of the American Meteorological Society

A technology revolution in Earth observation sensor design is occurring. This revolution in part ... more A technology revolution in Earth observation sensor design is occurring. This revolution in part is associated with the emergence of CubeSat platforms that have forced a de facto standardization on the volume and power into which sensors have to fit. The extent that small sensors can indeed provide similar or replacement capabilities compared to larger and more expensive counterparts has barely been demonstrated and any loss of capability of smaller systems weighed against the gains in costs and new potential capabilities offered by implementing them with a more distributed observing strategy also has not yet been embraced. This paper provides four examples of observations made with prototype miniaturized observing systems, including from CubeSats, that offer a glimpse of this emerging sensor revolution and a hint at future observing system design.

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Research paper thumbnail of A Distributed Small Satellite Approach for Measuring Convective Transports in the Earth's Atmosphere

IEEE Transactions on Geoscience and Remote Sensing

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Research paper thumbnail of Conditional Generative Adversarial Networks (cGANs) for Near Real-Time Precipitation Estimation from Multispectral GOES-16 Satellite Imageries—PERSIANN-cGAN

Remote Sensing

In this paper, we present a state-of-the-art precipitation estimation framework which leverages a... more In this paper, we present a state-of-the-art precipitation estimation framework which leverages advances in satellite remote sensing as well as Deep Learning (DL). The framework takes advantage of the improvements in spatial, spectral and temporal resolutions of the Advanced Baseline Imager (ABI) onboard the GOES-16 platform along with elevation information to improve the precipitation estimates. The procedure begins by first deriving a Rain/No Rain (R/NR) binary mask through classification of the pixels and then applying regression to estimate the amount of rainfall for rainy pixels. A Fully Convolutional Network is used as a regressor to predict precipitation estimates. The network is trained using the non-saturating conditional Generative Adversarial Network (cGAN) and Mean Squared Error (MSE) loss terms to generate results that better learn the complex distribution of precipitation in the observed data. Common verification metrics such as Probability Of Detection (POD), False Al...

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Research paper thumbnail of Cloud Physics from Space

Quarterly Journal of the Royal Meteorological Society

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Research paper thumbnail of A stochastic formation of radiative transfer in clouds

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Research paper thumbnail of Uncertainties in Space-Based Estimates of Clouds and Precipitation: Implications for Deriving Global Diabatic Heating

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Terminal versus transient cumulus congestus: A CloudSat perspective

Geophysical Research Letters, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Earth’s Energy Imbalance Measured From Space

IEEE Transactions on Geoscience and Remote Sensing, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The Super Greenhouse effect in a changing climate

Journal of Climate, 2016

In all outputs of the 1% yr−1 increase in CO2 climate model experiments archived under the World ... more In all outputs of the 1% yr−1 increase in CO2 climate model experiments archived under the World Climate Research Programme’s (WCRP) phase 5 of the Coupled Model Intercomparison Project (CMIP5), regions exist in the low latitudes where both the clear-sky and all-sky OLR decrease with surface warming. These are identified as regions of positive longwave feedback and are regions of a super greenhouse effect (SGE). These SGE regions are identified from feedback analysis of the 4 × CO2 abrupt experiments of CMIP5, and despite their existence, there is little agreement across models as to the magnitude of the effect. The general effects of clouds on the SGE are to amplify the clear-sky SGE, but there is also poor agreement on the magnitude of the amplification that varies by an order of magnitude across models. Sensitivity analyses indicate that localized SGE regions are spatially aligned with a large moistening of the upper troposphere. The reduction in clear-sky OLR arises from a reduc...

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Research paper thumbnail of Improved ice content, radiation, precipitation and low-level circulation over the tropical pacific from ECMWF ERA-interim to ERA5

Environmental Research Communications

This study evaluates changes in simulated Pacific climate between two ECMWF re-analyses; the ERA ... more This study evaluates changes in simulated Pacific climate between two ECMWF re-analyses; the ERA Interim (ERAI) and the newest ERA5. Changes in the Integrated Forecasting System (IFS) and possibly sea surface temperature result in greatly reduced discrepancies in ERA5’s ice water path (IWP), radiative fluxes and precipitation relative to satellite-based observational products. IWP shows the largest percentage change, increasing by over 300% from ERAI to ERA5, due to inclusion of falling ice (snow) that impacts radiative calculation. ERAI to ERA5 changes in high-cloud fraction are generally anticorrelated as expected with outgoing longwave radiation, with ERA5 having smaller longwave discrepancies versus CERES observations compared with ERAI. Reflected shortwave discrepancies are similarly reduced from ERAI to ERA5, which appears to be due to changes in both cloud fraction and optical depth. Finally, ERA5 also reduces a longstanding precipitation excess relative to the GPCP observati...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of On the combination of active and passive measurements in the study of clouds and precipitation

IGARSS 2001. Scanning the Present and Resolving the Future. Proceedings. IEEE 2001 International Geoscience and Remote Sensing Symposium (Cat. No.01CH37217)

Presents an approach that combines millimetric radar measurements and radiometer measurements for... more Presents an approach that combines millimetric radar measurements and radiometer measurements for deriving the water contents of clouds and precipitation and does so within the context of the CloudSat satellite mission

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Monitoring of Geoengineering Effects and their Natural and Anthropogenic Analogues

A number of climate intervention concepts, referred to as “geoengineering,” are being considered ... more A number of climate intervention concepts, referred to as “geoengineering,” are being considered as a potential additional approach (beyond mitigation of greenhouse gas emissions) to manage climate change. However, before governments go down the path of attempting deliberate climate intervention including precursor field-experiments, it is essential that the scientific community take the necessary steps to validate our understanding that underpins any of the proposed intervention concepts in order to understand all likely consequences and put in place the necessary strategies for monitoring the expected and unintended consequences of such intervention. The Keck Institute for Space Studies (KISS) has sponsored a project to identify specific priorities for improved scientific understanding and focused efforts to address selected priorities. This project does not advocate the deployment of geoengineering, outdoor geoengineering experiments, or monitoring systems for such proposed geoen...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The Useful Pursuit of Shadows The study of clouds has profoundly influenced science and human culture and stands poised to lead climate science forward again

Howard, a London pharmacist and amateur meteorologist, aired his ideas about the classification o... more Howard, a London pharmacist and amateur meteorologist, aired his ideas about the classification of clouds. These ideas were presented to a small gathering of young science-minded intellectuals who called themselves The Askesian Society. Howard's lecture on that evening was titled " On the Modification of Clouds " and opened as follows: My talk this evening concerns itself with what may strike some as an uncharacteristically impractical subject: it is concerned with the modification of clouds. Since the increased attention which has been given to meteorology, the studies of various appearances of water suspended in the atmosphere has become an interesting and even necessary branch of that pursuit. If clouds were the mere result of condensation of vapour in the masses of the atmosphere which they occupy, if their variations were produced by the movements of the atmosphere alone, then indeed might the study be deemed a useless pursuit of shadows.… This was a historic lect...

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Research paper thumbnail of What is the Role of GEWEX in R 2 O and O 2 R ?

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The cooling of light rains in a warming world

Nature Climate Change

Recent changes to how clouds are represented in global models, especially over the Southern Ocean... more Recent changes to how clouds are represented in global models, especially over the Southern Ocean, resulted in increased climate warming. Correcting rain processes in a model shows improved cloud representation but leads to a greatly enhanced negative feedback, offsetting documented increases in model climate sensitivity.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Applying Search Algorithms to the Temperature Inversion problem

Several inverse problems exist in the atmospheric sciences that are computationally costly when u... more Several inverse problems exist in the atmospheric sciences that are computationally costly when using traditional gradient based methods. Unfortunately, many standard evolutionary algorithms do not perform well on these problems. This paper investigates why the temperature inversion problem is so difficult for heuristic search. We show that algorithms imposing smoothness constraints find more competitive solutions. Additionally, a new algorithm is presented that addresses the difficulties of this problem and finds approximate solutions fast.

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Research paper thumbnail of The Impacts of Bias in Cloud-Radiation-Dynamics Interactions on Central Pacific Seasonal and El Niño Simulations in Contemporary GCMs

Earth and Space Science

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Earth's water reservoirs in a changing climate

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

Progress towards achieving a quantitative understanding of the exchanges of water between Earth&#... more Progress towards achieving a quantitative understanding of the exchanges of water between Earth's main water reservoirs is reviewed with emphasis on advances accrued from the latest advances in Earth Observation from space. These exchanges of water between the reservoirs are a result of processes that are at the core of important physical Earth-system feedbacks, which fundamentally control the response of Earth's climate to the greenhouse gas forcing it is now experiencing, and are therefore vital to understanding the future evolution of Earth's climate. The changing nature of global mean sea level (GMSL) is the context for discussion of these exchanges. Different sources of satellite observations that are used to quantify ice mass loss and water storage over continents, how water can be tracked to its source using water isotope information and how the waters in different reservoirs influence the fluxes of water between reservoirs are described. The profound influence of...

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Research paper thumbnail of Revisiting the Entrainment Relationship of Convective Plumes: A Perspective From Global Observations

Geophysical Research Letters

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Earth's water reservoirs in a changing climate

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Apr 1, 2020

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Research paper thumbnail of The Emerging Technological Revolution in Earth Observations

Bulletin of the American Meteorological Society

A technology revolution in Earth observation sensor design is occurring. This revolution in part ... more A technology revolution in Earth observation sensor design is occurring. This revolution in part is associated with the emergence of CubeSat platforms that have forced a de facto standardization on the volume and power into which sensors have to fit. The extent that small sensors can indeed provide similar or replacement capabilities compared to larger and more expensive counterparts has barely been demonstrated and any loss of capability of smaller systems weighed against the gains in costs and new potential capabilities offered by implementing them with a more distributed observing strategy also has not yet been embraced. This paper provides four examples of observations made with prototype miniaturized observing systems, including from CubeSats, that offer a glimpse of this emerging sensor revolution and a hint at future observing system design.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Distributed Small Satellite Approach for Measuring Convective Transports in the Earth's Atmosphere

IEEE Transactions on Geoscience and Remote Sensing

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Conditional Generative Adversarial Networks (cGANs) for Near Real-Time Precipitation Estimation from Multispectral GOES-16 Satellite Imageries—PERSIANN-cGAN

Remote Sensing

In this paper, we present a state-of-the-art precipitation estimation framework which leverages a... more In this paper, we present a state-of-the-art precipitation estimation framework which leverages advances in satellite remote sensing as well as Deep Learning (DL). The framework takes advantage of the improvements in spatial, spectral and temporal resolutions of the Advanced Baseline Imager (ABI) onboard the GOES-16 platform along with elevation information to improve the precipitation estimates. The procedure begins by first deriving a Rain/No Rain (R/NR) binary mask through classification of the pixels and then applying regression to estimate the amount of rainfall for rainy pixels. A Fully Convolutional Network is used as a regressor to predict precipitation estimates. The network is trained using the non-saturating conditional Generative Adversarial Network (cGAN) and Mean Squared Error (MSE) loss terms to generate results that better learn the complex distribution of precipitation in the observed data. Common verification metrics such as Probability Of Detection (POD), False Al...

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Research paper thumbnail of Cloud Physics from Space

Quarterly Journal of the Royal Meteorological Society

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Research paper thumbnail of A stochastic formation of radiative transfer in clouds

Bookmarks Related papers MentionsView impact