Observation‐Based Radiative Kernels From CloudSat/CALIPSO

Kramer, Ryan J.; Matus, Alexander V.; Soden, Brian J.; L’Ecuyer, Tristan

doi:10.1029/2018jd029021

Cited by 39 publications

(56 citation statements)

References 36 publications

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“…To convert changes in the noncloud variables to a radiative response, we multiply each time series of anomalies by radiative kernels derived from CloudSat/CALIPSO observations (Kramer et al., 2019). Following common practice, we separately diagnose radiative responses due to uniform temperature change (Planck effect) and due to departures from the uniform temperature change (lapse rate response).…”

Section: Methodsmentioning

confidence: 99%

“…(b) Time series of the tropical‐mean Δ N observed from CERES (thick solid line) and reconstructed from kernel radiative calculations (thin solid line; Equation ). Also reported are the radiative contributions due to I o r g anomalies (in red) and to EIS anomalies (in blue) inferred from kernel calculations (Kramer et al., 2019). Note that the two reconstitutions of Δ N reported on panels (a) and (b) correspond to two distinct approximations: In (a) it is assumed that N depends only on I o r g and EIS, while in (b) it is assumed that N can be reconstructed from the variations in temperature, humidity, etc., which are congruent with I o r g and EIS variations.…”

Section: Convective Organization Versus Lower‐tropospheric Stabilitymentioning

confidence: 99%

“…By using radiative kernels (Kramer et al., 2019; section 2.3), the total TOA flux anomalies can be decomposed into contributions from changes in temperature, water vapor, surface albedo, and clouds:

Δ N = \sum_{x = T, R H, A} K_{x} Δ x + Δ N_{C} = \sum_{x = T, R H, A, C} Δ N_{x} .

…”

Section: Decomposition Of Radiative Anomaliesmentioning

confidence: 99%

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Observed Modulation of the Tropical Radiation Budget by Deep Convective Organization and Lower‐Tropospheric Stability

et al. 2020

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This study analyzes the observed monthly deseasonalized and detrended variability of the tropical radiation budget and suggests that variations of the lower-tropospheric stability and of the spatial organization of deep convection both strongly contribute to this variability. Satellite observations show that on average over the tropical belt, when deep convection is more aggregated, the free troposphere is drier, the deep convective cloud coverage is less extensive, and the emission of heat to space is increased; an enhanced aggregation of deep convection is thus associated with a radiative cooling of the tropics. An increase of the tropical-mean lower-tropospheric stability is also coincident with a radiative cooling of the tropics, primarily because it is associated with more marine low clouds and an enhanced reflection of solar radiation, although the free-tropospheric drying also contributes to the cooling. The contributions of convective aggregation and lower-tropospheric stability to the modulation of the radiation budget are complementary, largely independent of each other, and equally strong. Together, they account for more than sixty percent of the variance of the tropical radiation budget. Satellite observations are thus consistent with the suggestion from modeling studies that the spatial organization of deep convection substantially influences the radiative balance of the Earth. This emphasizes the importance of understanding the factors that control convective organization and lower-tropospheric stability variations, and the need to monitor their changes as the climate warms. Plain Language Summary Anomalies of the tropically averaged radiative balance determine the time variations of the tropical climate. The stability of the lower atmosphere has been shown to influence this balance because increased stability favors the formation of low-level clouds and the reflection of solar radiation to space. Modeling studies have suggested that the spatial distribution of deep convection, especially the degree of clustering of deep clouds, could also impact humidity and cloud coverage, and thus the radiative balance of the Earth system. However, the relationships between cloud clustering, humidity, and the radiation budget have never been observed at the scale of the tropics. By analyzing long time series of satellite observations, we show that monthly variations of lower-atmospheric stability and convective clustering are both strongly correlated with variations of the radiative cooling of the tropics and that their contributions to the modulation of the radiation budget are complementary and equally important. These observational results thus confirm modeling inferences and emphasize that to predict the future of our climate, it will be necessary to determine how the stability and the clustering of deep convection will change with warming.

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Section: Methodsmentioning

confidence: 99%

Section: Convective Organization Versus Lower‐tropospheric Stabilitymentioning

confidence: 99%

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Observed Modulation of the Tropical Radiation Budget by Deep Convective Organization and Lower‐Tropospheric Stability

et al. 2020

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“…5 in ref. 27 ), atmospheric cooling is particularly sensitive to temperature change in the boundary layer. Interestingly, the rapid adjustment terms, and particularly the strong cloud adjustment, for CFCs are similar to the adjustment terms for the strongly absorbing black carbon aerosol (Fig.…”

Section: Changes In Temperature Humidity and Cloudsmentioning

confidence: 99%

The effect of rapid adjustments to halocarbons and N2O on radiative forcing

et al. 2020

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Rapid adjustments occur after initial perturbation of an external climate driver (e.g., CO2) and involve changes in, e.g. atmospheric temperature, water vapour and clouds, independent of sea surface temperature changes. Knowledge of such adjustments is necessary to estimate effective radiative forcing (ERF), a useful indicator of surface temperature change, and to understand global precipitation changes due to different drivers. Yet, rapid adjustments have not previously been analysed in any detail for certain compounds, including halocarbons and N2O. Here we use several global climate models combined with radiative kernel calculations to show that individual rapid adjustment terms due to CFC-11, CFC-12 and N2O are substantial, but that the resulting flux changes approximately cancel at the top-of-atmosphere due to compensating effects. Our results further indicate that radiative forcing (which includes stratospheric temperature adjustment) is a reasonable approximation for ERF. These CFCs lead to a larger increase in precipitation per kelvin surface temperature change (2.2 ± 0.3% K−1) compared to other well-mixed greenhouse gases (1.4 ± 0.3% K−1 for CO2). This is largely due to rapid upper tropospheric warming and cloud adjustments, which lead to enhanced atmospheric radiative cooling (and hence a precipitation increase) and partly compensate increased atmospheric radiative heating (i.e. which is associated with a precipitation decrease) from the instantaneous perturbation.

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“…The radiative kernel for a feedback variable x is defined as K x = ∂R/∂x, in which R is the net top-of-atmosphere (TOA) flux, and x is an individual radiative state variable (e.g., temperature, water vapor, clouds, or surface albedo). The radiative kernel is derived from CloudSat/CALIPSO measurements 37,38 .…”

Section: Methodsmentioning

confidence: 99%

Enhanced hydrological cycle increases ocean heat uptake and moderates transient climate sensitivity

Liu¹,

Vecchi²,

Soden³

et al. 2020

Preprint

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The large-scale moistening of the atmosphere in response to the greenhouse gas increases tends to amplify the existing patterns of precipitation minus evaporation (P-E) which, in turn, amplifies the spatial contrast in sea surface salinity (SSS). We propose that subtropical surface salinification due to the intensified hydrological cycle provides a buoyancy sink that increases the rate of ocean heat uptake and moderates transient climate sensitivity. We quantify the impact of these SSS changes in a series of CO2 doubling experiments using two configurations of a coupled climate model: a standard configuration and a modified one in which SSS is held constant by restoring it back to its seasonally-varying climatology from the control run. In response to CO2-induced warming, dry conditions (P-E < 0) over the subtropical oceans are amplified due to an enhanced hydrological cycle, increasing the SSS in salty regions. There is an increased rate of ocean heat uptake in the standard CO2 doubling experiment relative to the fixed-SSS version. The largest increase in ocean heat content (OHC) for the standard run occurs in the southern subtropical Pacific and the tropical and subtropical Atlantic Ocean, where SSS shows the largest increase, highlighting the role of salinification in accelerating heat uptake. The weakening of the Atlantic Meridional Overturning Circulation in response to high latitude freshening and warming also plays a role in modulating the OHC. Consistent with a smaller rate of ocean heat uptake, the fixed-SSS version produces a transient climate response approximately 0.4K greater than the standard run. Observed multidecadal changes in subsurface temperature and salinity resembles those simulated, indicating that anthropogenically-forced changes in salinity are likely enhancing the rate of ocean heat uptake.

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Observation‐Based Radiative Kernels From CloudSat/CALIPSO

Cited by 39 publications

References 36 publications

Observed Modulation of the Tropical Radiation Budget by Deep Convective Organization and Lower‐Tropospheric Stability

Observed Modulation of the Tropical Radiation Budget by Deep Convective Organization and Lower‐Tropospheric Stability

The effect of rapid adjustments to halocarbons and N2O on radiative forcing

Enhanced hydrological cycle increases ocean heat uptake and moderates transient climate sensitivity

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