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In this study, we evaluated the performance of machine learning (ML) models (XGBoost) in predicting low‐cloud fraction (LCF), compared to two generations of the community atmospheric model (CAM5 and CAM6) and ERA5 reanalysis data, each having a different cloud scheme. ML models show a substantial enhancement in predicting LCF regarding root mean squared errors and correlation coefficients. The good performance is consistent across the full spectrums of atmospheric stability and large‐scale vertical velocity. Employing an explainable ML approach, we revealed the importance of including the amount of available moisture in ML models for representing spatiotemporal variations in LCF in the midlatitudes. Also, ML models demonstrated marked improvement in capturing the LCF variations during the stratocumulus‐to‐cumulus transition (SCT). This study suggests ML models' great potential to address the longstanding issues of "too few" low clouds and "too rapid" SCT in global climate models. Plain Language Summary: Low clouds impose a strong radiative cooling effect on Earth's climate. Predicting low‐cloud fraction (LCF) is, however, challenging in global climate models (GCMs), partly due to some deficiencies in cloud parameterization schemes. Machine learning (ML) models might fill this gap as it is recognized as an efficient, economical, and accurate method to make predictions. In this study, we find that ML models (XGBoost) exhibit superior proficiency in predicting LCF regarding root mean squared errors and correlation coefficients compared to two generations of the community atmospheric model (CAM5 and CAM6) and ERA5 reanalysis data, each having a different cloud scheme. This improvement helps address one important issue of "too few" low clouds in GCMs. Furthermore, ML models demonstrate marked improvement in representing LCF variations when stratocumulus clouds transition to cumulus clouds, as opposed to too rapid decreases in LCF simulated by two CAMs and ERA5. Such findings testify to the unique role of ML models in refining the parameterization of LCF within GCMs. Key Points: Machine learning (ML) models substantially improve "too few" low‐cloud problems in the subtropics compared to traditional cloud schemesThey also show marked improvement in representing low‐cloud fraction (LCF) variations during the stratocumulus‐to‐cumulus transitionIncluding the effect of moisture source in ML models is crucial to representing spatiotemporal variations in LCF in the midlatitudes [ABSTRACT FROM AUTHOR]

To enhance our understanding of cloud simulations over land, this study provides the first assessment of coupling between cloud and land surface in the Large‐Eddy Simulation (LES) Atmospheric Radiation Measurement Symbiotic Simulation and Observation (LASSO) activity for the shallow convection scenario. The analysis of observation data reveals a diurnal cycle of cloud‐land coupling, which co‐varies with surface fluxes. However, coupled (or decoupled) cumulus clouds are inadequately simulated, manifesting as a too‐high (or low) occurrence frequency during the afternoon. This discrepancy is mirrored by the overestimated cloud liquid water path and cloud‐top height. These overestimations are linked to the overpredicted boundary‐layer development and the easier trigger of shallow convection misrepresented in LES runs. Our study underscores the need to improve the representations of boundary‐layer processes and cloud‐land interactions within LES to better simulate shallow clouds in the future. Plain Language Summary: Cloud‐surface coupling is crucial in weather and climate predictions, yet its processes, particularly over the land surface, remain poorly understood. This study examined the evolution of coupled cloud occurrence frequency and cloud macro‐physical properties [e.g., cloud fraction, liquid water path (LWP), and cloud‐top height (CTH)] in LASSO Large‐Eddy Simulations (LESs) for 77 shallow convection case days against observations. We found that LES runs erroneously simulate a too‐high occurrence frequency of coupled cumulus clouds during the afternoon. In accord with that, shallow convection development is also markedly overestimated during the same period, manifested by overestimated cloud LWP and CTH. These errors are possibly linked to the misrepresentation of a key physical process, namely, the shallow convective trigger, which needs to be improved to achieve more accurate cloud simulations. Key Points: Observed cloud‐land coupling has notable diurnal variations but is inadequately simulated by Large‐Eddy Simulations (LESs)LESs overestimate the frequency and vertical extent of coupled cumuli in the afternoonThese overestimations by LESs are related to the misrepresentation of triggering shallow convection [ABSTRACT FROM AUTHOR]

This study leveraged a Lagrangian framework to examine the evolution of stratocumulus clouds under cold and warm advections (CADV and WADV) in the Community Earth System Model 2 (CESM2) against observations. We found that CESM2 simulates a too rapid decline in low‐cloud fraction (LCF) and cloud liquid water path (CLWP) under CADV conditions, while it better aligns closely with observed LCF under WADV conditions but overestimates the increase in CLWP. Employing an explainable machine learning approach, we found that too rapid decreases in LCF and CLWP under CADV conditions are related to overestimated drying effects induced by sea surface temperature, whereas the substantial increase in CLWP under WADV conditions is associated with the overestimated moistening effects due to free‐tropospheric moisture and surface winds. Our findings suggest that overestimated drying effects of sea surface temperature on cloud properties might be one of crucial causes for the high equilibrium climate sensitivity in CESM2. Plain Language Summary: Stratocumulus clouds have extensive coverage over the oceans and modulate the climate system by efficiently reflecting incoming solar radiation back to space. However, their simulations in climate models are challenging due to complex meteorological controls, in which temperature advection is one of the most uncertain controlling factors. To enhance our understanding, we examine the stratocumulus evolution influenced by cold‐advection (CADV) and warm‐advection (WADV) in the midlatitudes in a climate model, CESM2. A too rapid decrease in low‐cloud fraction (LCF) and cloud liquid water path (CLWP) is erroneously simulated under CADV conditions, while an increase in CLWP is substantially overestimated under WADV conditions. Using an explainable machine learning approach, these errors are found to be caused by the amplified drying or moistening effects due to improper treatments of meteorological controls on clouds in CESM2. This study suggests that these misrepresentations of cloud physics in the midlatitudes should be imperatively improved to reduce climate prediction uncertainties. Key Points: Community Earth System Model 2 simulates a too rapid decline in low‐cloud fraction and cloud liquid water path when clouds experience cold‐air advectionIt substantially overestimates increases in cloud liquid water path when clouds experience warm‐air advectionUtilizing an explainable machine learning methodology, the effects of meteorological factors on cloud evolution are assessed [ABSTRACT FROM AUTHOR]

An initially well‐mixed stratocumulus deck can remain overcast for several tens of hours under warm‐advection conditions, although moisture supply is cut off from the ocean due to surface‐atmosphere decoupling (stabilization of the surface‐atmosphere interface). In this study, a set of idealized large‐eddy simulations were performed to investigate the physical mechanism of how warm‐air advection impacts the evolution of a pre‐existing stratocumulus deck. To mimic warm‐air advection, we decrease the sea surface temperature linearly over time in a doubly periodic domain. Given the same initial conditions, the stratocumulus deck is more persistent when experiencing warm‐air advection than cold‐air advection. This persistence is caused by reduced cloud‐top entrainment drying due to decoupling, a process more influential than the decoupling‐induced cutoff of moisture supply. This mechanism is more notable when the free troposphere becomes more humid. The relevance of the mechanism to previous observations of less low‐level cloudiness under warm‐advection conditions is discussed. Plain Language Summary: Marine stratocumulus clouds exert strong radiative cooling on Earth's climate because they reflect much solar radiation back to space. It is important to understand what factors control the cloud properties, or cloud‐controlling factors. Among all cloud‐controlling factors, the least understood is warm‐air advection, meaning winds mobilizing clouds from over warm water to over cold water. A high‐resolution numerical model was used to investigate the response of the stratocumulus evolution to warm‐air advection. A stratocumulus deck was found to persist longer under warm‐advection conditions than its cold counterpart, inconsistent with the decoupling‐induced dissipation mechanism. This persistence is primarily due to the weaker mixing of clouds with the overlying dry air when the atmosphere become decoupled from the sea surface, a consequence of warm‐air advection. This work revises our conventional understanding of how clouds respond to changes in temperature advection that might change as the planet warms, contributing to a more confident projection of future climates. Key Points: A preexisting stratocumulus deck is more persistent when experiencing warm‐air advection than cold‐air advectionThis persistence is due to reduced entrainment drying as a result of decoupling, which outweighs decreased cloud‐base moisture transportThe mechanism is more notable when free‐tropospheric humidity is higher [ABSTRACT FROM AUTHOR]

Due to surface heating, the morning boundary layer transits from stable to neutral or convective conditions, exerting critical influences on low tropospheric thermodynamics. Low clouds closely interact with the boundary layer development, yet their interactions bear considerable uncertainties. Our study reveals that cloud‐surface coupling alters the morning transition from stable to unstable boundary layer and thus notably affects the diurnal variation of the boundary layer. Specifically, due to the reduction in surface fluxes, decoupled clouds can delay the process of eroding nocturnal inversion by 0.8‐hr and even prevent the transition of the boundary layer from happening for 12% of decoupled cases, keeping the boundary layer in a stable state during the noontime. On the other hand, when clouds are coupled with the surface, cloud‐top radiative cooling can directly cool the upper boundary layer to facilitate sub‐cloud convection, leading to an unstable boundary layer in the earlier morning. Plain Language Summary: Low clouds closely interact with the planetary boundary layer, yet their interactions bear considerable uncertainties. Our study reveals that cloud‐surface coupling plays an important role in regulating the diurnal variation of boundary layer. In particular, cloud‐surface coupling affects the energy budget of the land‐atmosphere system and further alters the transition from the stable boundary layer to the unstable boundary layer during the morning. Due to the reduction in surface fluxes, decoupled clouds can notably delay the process of eroding nocturnal inversion, keeping the boundary layer in a relatively stable state. On the other hand, when clouds are coupled with the surface, cloud‐top radiative cooling can directly cool the upper boundary layer to facilitate convection, leading to an unstable boundary layer in the earlier morning. Key Points: Decoupled clouds can notably delay the process of eroding nocturnal inversion by suppressing surface fluxesCloud‐top radiative cooling caused by coupled clouds facilitates the formation of the unstable boundary layer in the earlier morningCloud‐surface coupling notably affects the diurnal variation of the boundary layer by altering the phase transition of the boundary layer [ABSTRACT FROM AUTHOR]

The states of coupling between clouds and surface or boundary layer have been investigated much more extensively for marine stratocumulus clouds than for continental low clouds, partly due to more complex thermodynamic structures over land. A manifestation is a lack of robust remote sensing methods to identify coupled and decoupled clouds over land. Following the idea for determining cloud coupling over the ocean, we have generalized the concept of coupling and decoupling to low clouds over land, based on potential temperature profiles. Furthermore, by using ample measurements from lidar and a suite of surface meteorological instruments at the U.S. Department of Energy's Atmospheric Radiation Measurement Program's Southern Great Plains site from 1998 to 2019, we have developed a method to simultaneously retrieve the planetary boundary layer (PBL) height (PBLH) and coupled states under cloudy conditions during the daytime. The new lidar-based method relies on the PBLH, the lifted condensation level, and the cloud base to diagnose the cloud coupling. The coupled states derived from this method are highly consistent with those derived from radiosondes. Retrieving the PBLH under cloudy conditions, which has been a persistent problem in lidar remote sensing, is resolved in this study. Our method can lead to high-quality retrievals of the PBLH under cloudy conditions and the determination of cloud coupling states. With the new method, we find that coupled clouds are sensitive to changes in the PBL with a strong diurnal cycle, whereas decoupled clouds and the PBL are weakly related. Since coupled and decoupled clouds have distinct features, our new method offers an advanced tool to separately investigate them in climate systems. [ABSTRACT FROM AUTHOR]

We explore the decoupling physics of a stratocumulus-topped boundary layer (STBL) moving over cooler water, a situation mimicking warm-air advection (WADV). We simulate an initially well-mixed STBL over a doubly periodic domain with the sea surface temperature decreasing linearly over time using the System for Atmospheric Modeling large-eddy model. Due to the surface cooling, the STBL becomes increasingly stably stratified, manifested as a near-surface temperature inversion topped by a well-mixed cloud-containing layer. Unlike the stably stratified STBL in cold-air advection (CADV) that is characterized by cumulus coupling, the stratocumulus deck in the WADV is unambiguously decoupled from the sea surface, manifested as weakly negative buoyancy flux throughout the subcloud layer. Without the influxes of buoyancy from the surface, the convective circulation in the well-mixed cloud-containing layer is driven by cloud-top radiative cooling. In such a regime, the downdrafts propel the circulation, in contrast to that in CADV regime for which the cumulus updrafts play a more determinant role. Such a contrast in convection regime explains the difference in many aspects of the STBLs including the entrainment rate, cloud homogeneity, vertical exchanges of heat and moisture, and lifetime of the stratocumulus deck, with the last being subject to a more thorough investigation in Part II. Finally, we investigate under what conditions a secondary stratus near the surface (or fog) can form in the WADV. We found that weaker subsidence favors the formation of fog whereas a more rapid surface cooling rate does not. Significant Statement: The low-lying blanketlike clouds, called stratocumulus (Sc), reflect much incoming sunlight, substantially modulating Earth's temperature. While much is known about how the Sc evolves when it moves over warmer water, few studies examine the opposite situation of Sc moving over colder water. We used a high-resolution numerical model to simulate such a case. When moving over cold water, the Sc becomes unambiguously decoupled from the water surface, distinctive from its warm counterpart in which the Sc interacts with the water surface via intermittent cauliflower-like clouds called cumulus clouds. Such decoupling influences many aspects of the Sc–sea surface system, which combine to alter the ability of the Sc to reflect sunlight, thereby influencing the climate. This work laid the foundation for future work that quantifies the contribution of such a decoupled Sc regime to Earth's radiative budget and climate change. [ABSTRACT FROM AUTHOR]

A one‐year's worth of near‐global marine shallow single‐layer cloud top radiative cooling (CTRC) is derived from a radiative transfer model with inputs from the satellite cloud retrievals and reanalysis sounding. The mean cloud top radiative flux divergence is 61 Wm−2, decomposed into the longwave and shortwave components of 73 and −11 W m−2, respectively. Equatorward of 30°N/S, the CTRC is largely a reflection of free‐atmospheric specific humidity distribution: a dry atmosphere enhances CTRC by reducing downward thermal radiation. Consequently, the cooling minimizes in the "wet" tropics and maximizes in the "dry" eastern subtropics. Poleward of 30°N/S, the CTRC decreases slightly due to the colder clouds that emit less effectively. The CTRC exhibits distinctive seasonal cycles with stronger cooling in the winter and has amplitudes of order 10–20 Wm−2 in stratocumulus‐rich regions. The datasets were used to train a machine‐learning model that substantially speeds up the retrieval. Plain Language Summary: Marine low‐lying clouds cool by emitting thermal radiation. The cooling is known as cloud top radiative cooling (CTRC). A change in CTRC can influence the properties of marine clouds via many avenues, ranging from altering the vertical motions of the clouds to changing the clouds' ability to reflect sunlight. Despite the importance of CTRC to the climate system, its climatological characteristics, namely how it varies with space and time, remain unknown. This work fills this knowledge gap. We generate the product of the CTRC over the global ocean using a novel satellite methodology developed in our previous work. Analyses of the data show that the spatial and temporal distributions of the CTRC are largely reflections of the atmospheric humidity: the drier the atmosphere, the stronger the cooling. As a result, the CTRC is weakest in the wet tropics and strongest in the dry eastern subtropical oceans, such as the west of California coast. We also use the CTRC data to train a machine‐learning algorithm that can substantially speed up the calculation of CTRC. Key Points: A one‐year's worth of global marine shallow single‐layer cloud top radiative cooling (CTRC) is derived from satellite and reanalysis dataSpatial and seasonal variations of CTRC are largely reflections of changes in free‐tropospheric humidity and cloud top temperatureA neural network model for the CTRC was trained, which substantially speeds up the retrieval while maintaining good accuracy [ABSTRACT FROM AUTHOR]

Most prior studies on decoupling of a stratocumulus‐topped boundary layer (STBL) are focused on subtropics where cold air advection with moderate strength is dominant. This study expands across a wider spectrum of temperature advection spanning from moderately strong warm air advection to extremely strong cold air advection. A STBL undergoing warm advection is found to be more mixed than a STBL undergoing cold advection. This finding is consistent with the cold advection facilitating turbulent mixing in the boundary layer. When cold advection becomes sufficiently strong (<−5 K/day), the STBL becomes more stably stratified again because of emergence of the cumulus‐coupled STBL regime induced by the "deepening‐warming" mechanism. Such a "deepening‐warming" induced STBL decoupling, however, is still much weaker than that caused by warm advection flows (even weak ones), suggesting that the direction and strength of temperature advection must be considered for any STBL decoupling studies. Key Points: The coupling state of a stratocumulus‐topped boundary layer (STBL) is sensitive to the strength and direction of temperature advectionGround observations from three DOE/ASR marine campaigns suggest that a STBL is more coupled in cold advection than in warm advectionWhen cold advection becomes extremely strong, a STBL becomes more decoupled again, but still more coupled than that in warm advection [ABSTRACT FROM AUTHOR]

Cloud top radiative cooling rate (CTRC) is the leading term in the energy budget of a marine boundary layer capped by stratocumulus. It plays a significant role in the formation, evolution, and maintenance of the stratocumulus cloud system. This study demonstrates the feasibility of estimating the CTRC, with high accuracy, from passive satellite data only. The estimation relies on a radiative transfer model with inputs from satellite‐retrieved cloud parameters in combination with reanalysis sounding that is revised, in a physically coherent way, by satellite data. The satellite‐based estimates CTRC agree with ground‐based ones to within ~10%. The high accuracy largely benefits from the good capability of satellite data in constraining parameters of most influence to the CTRC such as free‐tropospheric sounding, cloud top temperature, and cloud optical depth. Applying this technique, we generate a climatology of CTRC during summer over the Southern Hemisphere tropical and subtropical oceans. Plain Language Summary: Everything cools radiatively. For marine low‐lying clouds, the radiative cooling at the cloud top makes the ambient air heavier and sink and, equivalently, the underlying air lighter and float. This forms a vertical mixing process that brings moisture from the underlying sea surfaces upward to feed the clouds, preventing them from dissipation. Therefore, the cloud top radiative cooling rate (CTRC) is one of the most important variables for understanding the behaviors of marine low clouds and their interactions with the Earth's climate system. Despite its significance, the CTRC has rarely been retrieved, with good accuracy, from satellite, the only observational tool that offers global coverage. This study fills this gap by developing a novel remote sensing method to estimate the CTRC from satellite data at an accuracy of 10%. This new capability will help advance our understanding of many poorly understood behaviors of marine low clouds over regions with scarce observations (e.g., middle‐ and high‐latitude oceans). More broadly, the new remote sensing products will improve the accuracy with which the future climate is predicted because our climate system is sensitive to the low cloud mixing process that is regulated by the CTRC. Key Points: Cloud top radiative cooling rate (CTRC) is a fundamental physical variable for understanding many essential behaviors of marine low cloudsMore accurate retrieval of CTRC is feasible from satellite with a retrieval uncertainty of 10% demonstrated by comparing them with "ground truth"A single summertime climatology of CTRC over the Southern Hemisphere oceans is generated, showing physically coherent results [ABSTRACT FROM AUTHOR]

Detailed airborne measurements were carried out to explore aerosol-cloud interactions and cloud microphysical properties in a drizzling marine stratocumulus cloud deck over eastern China. Results show that the collision-coalescence of cloud droplets, the condensation of small droplets, and the collision-induced break-up of drizzle were the dominant microphysical processes in the sampled water cloud parcel. The region in the vicinity of the cloud's lateral boundary was spatially divided into sub-regions to better understand aerosol and droplet interactions. Relationships between the relative dispersion (ε) and the cloud''s microphysical and dynamical characteristics were also examined. A negative relation was found between ε and the cloud droplet number concentration, with ε showing a close relationship with the liquid water content (LWC) and updraft velocity. When LWC was greater than ~0.75 g kg−1, the range of ε values narrowed, and updrafts dominated. By introducing ε in the cloud droplet effect radius (R e) parameterization, we find that ε can further affect indirect forcing by changing the R e distribution for the cloud examined in this study. The dispersion effect (DE) was estimated using the effective radius ratio and the specific cloud water content. An in-depth analysis indicates that DE may offset the Twomey effect by ~12%. Two different methods of estimating the indirect effect (IE) yielded close values (0.084 and 0.077), suggesting that introducing DE into the estimation had a small influence on the IE calculation in the drizzling marine stratocumulus cloud of this study. Note that the estimated IE has a large uncertainty, given the large biases in the cloud properties measured. • The dispersion effect was first calculated in a drizzling marine stratocumulus by aircraft measurement over eastern China. • The primary microphysical processes of the case study cloud were discussed through a detailed analysis on cloud parameters. • In the core region of the mature cumulus, the updrafts and LWC reach their maximum and ε varies in a very narrow range. • Considering the uncertainty of IE estimation, a positive dispersion effect was calculated in this study. [ABSTRACT FROM AUTHOR]

The decoupling degree of stratocumulus (Sc) decks is an important quantity dictating evolutions of Sc. In subtropical oceans, the Sc decoupling is a key intermediate process of the Sc‐to‐cumulus transitions, a persistent phenomenon that is not fully understood. This study introduces a new approach for estimating the degree of decoupling of subtropical Sc decks using passive satellite sensors. This method is limited to regions where Sc decks are advected over progressively warmer water. This is most common in the subtropics. The estimation concept is that decoupled Sc clouds under cold‐advection conditions are fed by spreading of the tops of cumulus clouds that are coupled. The cumulus clouds constitute a much larger liquid water path over small areas, which is identified by a positive skewness of the liquid water path, a quantity measurable from high‐resolution satellite data. The decoupling degree here is defined as the difference between the Sc cloud‐base height and lifting condensation level that is the cumulus cloud‐base height under cold‐advection conditions. This concept and the satellite‐based estimations are supported by ship measurements over the Northeast Pacific. One‐year climatology of the satellite‐inferred decoupling degree was generated over the same region, revealing a coherent pattern of offshore decoupling, consistent with previous theory and field‐campaign observations. Plain Language Summary: Our climate system is considerably sensitive to marine low clouds that reflect a great amount of incoming solar radiation and cool the earth. These marine clouds are intimately coupled with the underlying sea surfaces that feed moisture and energy to the clouds for sustaining them. The degree of the surface‐cloud coupling (SCC) considerably influences the cloud properties, which in turn modulates the temperature of our climate system. Despite its significance to climate, the SCC degree has never been measured from satellite, the only observational tool that offers global coverage. This study addresses this long‐lasting issue by developing an innovative method to estimate the SCC degree using satellite data. The validity of this method is demonstrated by validating the SCC degree estimated by this new method against ground truth measurements over the Northeast Pacific. This method offers unprecedentedly new geophysical information, namely, the SCC degree that is crucial for the understanding of behavior of marine low clouds and its interactions with our climate system. This will eventually improve the accuracy with which future climate change is projected. Key Points: A new satellite‐based method for inferring the decoupling degree of Sc decks over subtropical oceans is proposedThis method is based on an empirically found relationship between the decoupling degree and the satellite‐derived skewness of liquid water pathThis method is not expected to be valid in regions where clouds are decoupled due to low‐level warm advection to colder waters [ABSTRACT FROM AUTHOR]

Cloud top radiative cooling (CTRC) drives turbulence in marine boundary layers (MBLs) topped by stratocumulus clouds. This study examines the role of CTRC in regulating the surface‐cloud coupling, surface latent heat fluxes, and cloud base height by exploiting a 6‐month worth of shipborne observations over the subtropical northeast Pacific in combination with geostationary satellite data. We find that owning to the prevailing equatorward flow that advects stratocumulus clouds over warmer sea surfaces, the vast majority of the decoupled stratocumulus decks are fed by divergence from the tops of underlying cumulus, forming cumulus‐coupled MBL. The cumulus‐coupled and well‐mixed MBL dominate the subtropical MBL regimes. We find that strong CTRC favors greater (smaller) occurrence frequency of well‐mixed (cumulus‐coupled) MBLs. In well‐mixed MBLs, strong CTRC enhances entrainment of dry free‐tropospheric air, desiccates the MBL, increases the surface latent heat fluxes, and elevates the cloud‐base height. This is demonstrated by the observed covariabilities between the CTRC rate and surface latent heat fluxes and cloud‐base height. The relationships are more statistically significant in conditions where the inversion strength is relatively weak, and thus, the entrainment is more effective. In cumulus‐coupled MBLs, however, the influence of CTRC in regulating the surface moisture is not detected by the ship observations. The much greater latent heat fluxes than the CTRC rate in cumulus‐coupled MBLs suggest stronger surface forcing, which substantially tames the footprint of CTRC. Key Points: The vast majority of decoupled stratocumulus are coupled with the surfaces by cumulus convection in subtropical northeast PacificCloud top radiative cooling of stratocumulus regulates surface latent heat fluxes and cloud‐base height in well‐mixed boundary layersThe strong surface forcing in cumulus‐coupled boundary layers dominate the signature of the cloud top radiative cooling in influencing surface energetics [ABSTRACT FROM AUTHOR]

Atmospheric temperature inversions, i.e., temperatures increasing with altitude, modulate both radiative and buoyancy fluxes in the atmosphere. A temperature inversion layer often occurs immediately above a cloud layer that cools radiatively and thereby strengthens the capping temperature inversion. This study aims to investigate the characteristics of temperature inversions above clouds and their relationships with cloud-top radiative cooling. Using a 17-year (January 2001 to December 2017) high-quality and continuous radiosonde dataset collected at the Atmospheric Radiation Measurement Southern Great Plains Central Facility site, key temperature inversion parameters, namely, the occurrence frequency (d p), depth (d z), temperature difference (d T), and gradient (d T /d z), are derived for single- and double-layer clouds (SLC and DLC, respectively). The occurrence frequency of temperature inversions above single-layer clouds decreases dramatically as cloud tops rise from low to high altitudes. When an overlying higher cloud layer is present, the inversion becomes less frequent, shallower, and weaker than without it. This may be because higher clouds weaken the cloud-top radiative cooling of the underneath clouds by enhancing downwelling infrared radiation. This is supported by radiative transfer simulations. There are distinctive seasonal cycles of cloud-top radiative cooling for high clouds that are primarily driven by variations in shortwave heating. Distinctive seasonal cycles of temperature inversions also occurred regardless of the cloud regime (SLC or DLC) and altitude (low or high clouds). They appear to be driven by the seasonal cycle of cloud coverage (i.e., a greater amount of clouds undergoes stronger area-mean radiative cooling) although the shortwave heating seasonal cycle also plays a role for high clouds. Cloud radiative cooling cannot explain the diurnal cycle of temperature inversions. • Temperature inversions above clouds and their relationships with cloud-top radiative cooling were investigated. • Higher clouds weaken the cloud-top radiative cooling of the underneath clouds by enhancing downwelling infrared radiation. • Distinctive seasonal cycles of cloud-top radiative cooling for high clouds were revealed. • The occurrence frequency of temperature inversions above single-layer clouds decreases dramatically as cloud tops rise. [ABSTRACT FROM AUTHOR]