The atmospheric energy budget associated with the heating and cooling of the atmosphere on daily time scales across the globe is analyzed using a fixed atmospheric mass calculation of the instantaneous atmospheric heat flux convergence. The heating and moistening of the atmospheric column during a typical heating event requires of order 1000 W m-2 of energy input to the atmosphere. The required energy input is predominantly provided by the atmospheric heat transport convergence. In contrast, the temporal variability of energy inputs by surface turbulent fluxes and radiation are an order of magnitude smaller. This result suggests that the atmospheric temperature variability is set by the magnitude of variability in lateral energy fluxes in the atmosphere, limited by the heat capacity of the atmosphere, and provides a framework for understanding the controls on heat wave intensity. To relate the magnitude of atmospheric heating to the intensity of heat waves measured by the variance of surface temperature additional considerations are made for (i) the temporal duration of heating events, (ii) the fraction of atmospheric energy input that goes into moistening versus warming the atmosphere, and (iii) the vertical structure of temperature changes during heating events. Of these factors, surface heat wave intensity is damped by the moisture storage contribution by a factor of four in the tropics and amplified by the vertical structure of temperature by almost an order of magnitude over extratropical landmasses as compared to the ocean.

Outside the tropics, extratropical cyclones account for most of the poleward atmospheric heat transport, and extreme heat transport events are known to occur in their vicinity. Yet, it remains unclear how individual cyclones contribute to heat transport over the course of their lifetime and whether the seasonal heat transport - viewed from a zonally integrated standpoint - is determined by their number. This study adopts a cyclone-centered perspective to quantify in detail the relationship between poleward heat transport and the life cycle characteristics of extratropical cyclones in Southern Hemispheric winter. Specifically, objectively identified surface cyclone tracks derived from ERA5 data (1981-2021) are combined with a moist static energy (MSE) framework involving an eddy-mean decomposition of the meridional MSE flux.It is found that the local transient eddy MSE flux maximizes during the cyclone intensification phase and is largest in the warm sector with a secondary maximum in the cold sector. A considerable fraction of the flux in the warm sector is located well equatorward of the cyclone and thus outside the cyclonic region identified by the tracking algorithm. This leads to a latitudinal shift between maxima in cyclone frequency and transient eddy MSE fluxes. To bridge the gap between zonally integrated MSE flux and contributions from individual cyclones, local vertically integrated transient eddy MSE flux events are attributed to cyclones based on spatial overlap with the identified cyclone area. Poleward of 50 degrees S, the cyclones that become most intense are the ones that exhibit the largest zonally integrated cyclone-attributed MSE flux while the strongly intensifying cyclones dominate equatorward thereof. Although both of these sets of cyclones contribute disproportionally to the cyclone-attributed transient eddy MSE fluxes, the relationship between their seasonal number and the seasonal mean poleward transient eddy MSE flux is sensitive to the choice of the eddy-mean decomposition method. This result indicates that low wavenumber background flows mask the influence of cyclone intensities and intensification rates in the vertical, zonal, and seasonal integral. Notably, at 50 degrees S the relationship between the overall cyclone number and total MSE flux shows a peak. Further research on the interplay between synoptic and planetary MSE fluxes in the vicinity of cyclones is needed to understand to which extent the cyclone number may be constrained by the global energy imbalance.

Global warming results from anthropogenic greenhouse gas emissions which upset the delicate balance between the incoming sunlight, and the reflected and emitted radiation from Earth. The imbalance leads to energy accumulation in the atmosphere, oceans and land, and melting of the cryosphere, resulting in increasing temperatures, rising sea levels, and more extreme weather around the globe. Despite the fundamental role of the energy imbalance in regulating the climate system, as known to humanity for more than two centuries, our capacity to observe it is rapidly deteriorating as satellites are being decommissioned.

Global mean temperature rapidly warmed during 2023, making 2023 the second warmest year on record at 1.45°C above pre‐industrial climate, and 2024 became the first year on record to surpass 1.5°C. Here we explore the likelihood, mechanisms, and predictability of the rapid warming during 2023 with CMIP simulations and a fully‐coupled forecast ensemble initialized on 1 November 2022. The year‐to‐year (Y2Y) warming for the second half of 2023 of 0.49°C equaled the largest on record since 1850, and is simulated as a 1 in 6,000 years event. The forecast ensemble‐mean predicts about 75% of the observed warming during 2023. The remaining 25% of the warming lies within the forecast spread, with members that forecast a strong 2023 El Niño and positive absorbed shortwave anomalies more likely to forecast the entirety of the observed warming. The forecast ensemble succesfully predicts 2024 to be the first year on record above 1.5°C.

The meridional atmospheric heat transport (AHT) represents the net energy moved by winds across a latitude circle and is constrained to balance the global atmospheric energy budget. This balance statement provides two strategies for calculating AHT: (i) the dynamic estimate from the vertical and zonal integral of the energy flux calculated from high-frequency atmospheric reanalysis/models and (ii) the energetic estimate calculated as the integral (accumulation) of the net energy input into the atmosphere from one pole to the other. To date, estimates of AHT mainly rely on the dynamic approach due to the historic inability to accurately observe the atmospheric energy budget. We challenge this notion by examining the consistency of AHT calculated using the dynamic approach with atmospheric reanalysis products and the energetic approach using several observation-based estimates of the atmospheric energy balance. There is good agreement in the annual-mean AHT in the Southern Hemisphere between most products (within 15%). However, Northern Hemisphere annual-mean AHT is substantially (up to 40%) lower in the observed products, attributable to reduced poleward atmospheric heating gradients from observed surface turbulent heat fluxes compared to reanalysis. While the mean state differs between calculations, monthly AHT variance has agreement, with correlations of up to 0.8 and 0.5 in the midlatitudes and tropics, respectively. However, nonstationarity in the observed AHT record may restrict long-term assessment of trends. Uncertainty in the surface turbulent heat flux remains as a leading constraint on observing the atmospheric energy budget and consequently AHT.

We investigate the linear trends in meridional atmospheric heat transport (AHT) since 1980 in atmospheric reanalysis datasets, coupled climate models, and atmosphere-only climate models forced with historical sea surface temperatures. Trends in AHT are decomposed into contributions from three components of circulation: (i) transient eddies, (ii) stationary eddies, and (iii) the mean meridional circulation. All reanalyses and models agree on the pattern of AHT trends in the Southern Ocean, providing confidence in the trends in this region. There are robust increases in transient-eddy AHT magnitude in the Southern Ocean in the reanalyses, which are well replicated by the atmosphere-only models, while coupled models show smaller magnitude trends. This suggests that the pattern of sea surface temperature trends contributes to the transient-eddy AHT trends in this region. In the tropics, we find large differences between mean-meridional circulation AHT trends in models and the reanalyses, which we connect to discrepancies in tropical precipitation trends. In the Northern Hemisphere, we find less evidence of large-scale trends and more uncertainty, but note several regions with mismatches between models and the reanalyses that have dynamical explanations. Throughout this work we find strong compensation between the different components of AHT, most notably in the Southern Ocean where transient-eddy AHT trends are well compensated by trends in the mean-meridional circulation AHT, resulting in relatively small total AHT trends. This highlights the importance of considering AHT changes holistically, rather than each AHT component individually.

Atmospheric heat transport (AHT) is an important piece of our climate system but has primarily been studied at monthly or longer time scales. We introduce a new method for calculating zonal-mean meridional AHT using instantaneous atmospheric fields. When time averaged, our calculations closely reproduce the climatological AHT used elsewhere in the literature to understand AHT and its trends on long time scales. In the extratropics, AHT convergence and atmospheric heating are strongly temporally correlated suggesting that AHT drives the vast majority of zonal-mean atmospheric temperature variability. Our AHT methodology separates AHT into two components (eddies and the mean meridional circulation) which we find are negatively correlated throughout most of the mid- to high latitudes. This negative correlation reduces the variance in the total AHT compared to eddy AHT. Last, we find that the temporal distribution of the total AHT at any given latitude is approximately symmetric.

The observed partitioning of poleward heat transport between atmospheric and oceanic heat transports (AHT and OHT) is compared to that in coupled climate models. Poleward OHT in the models is biased low in both hemispheres, with the largest biases in the Southern Hemisphere extratropics. Poleward AHT is biased high in the Northern Hemisphere, especially in the vicinity of the peak AHT near 40$^\circ$N. The significant model biases are persistent across three model generations (CMIP3, CMIP5, CMIP6) and are insensitive to the satellite radiation and atmospheric reanalyses products used to derive observational estimates of AHT and OHT. Model biases in heat transport partitioning are consistent with biases in the spatial structure of energy input to the ocean and atmosphere. Specifically, larger than observed model evaporation in the tropics adds excess energy to the atmosphere that drives enhanced poleward AHT at the expense of weaker OHT

Atmospheric heat transport (AHT) moderates spatial gradients in surface temperature, and its efficiency (hereinafter referred to as diffusivity) shapes the distribution of moist static energy and the hydrological cycle. Using a linear downgradient rule for AHT, we diagnose zonal-mean diffusivity using observational and model data. We find it varies two- to threefold with season and latitude, but is nearly invariant across different climate states. We then employ a moist energy balance model (MEBM) to explore the impacts of changing the magnitude and spatial pattern of diffusivity on the climatology and climate response to forcing. Spatial anomalies in diffusivity in the extra-tropics have a larger impact on temperature and hydrology than diffusivity anomalies in the tropics. We demonstrate that compensating dynamical adjustments in the MEBM act to mute the impact of changing diffusivity patterns on the resulting climate. We isolate the impacts of spatial patterns of forcing, ocean heat uptake, radiative feedbacks, and diffusivity on the spatial pattern of climate change; and find that the pattern of climate change is least sensitive to the detailed pattern of diffusivity. Overall, these results suggest that although diffusivity is far from spatially invariant, understanding the climatology and spatial patterns of climate change does not depend on a detailed characterization of the spatial pattern of diffusivity.

A study of prompt $\Xi_{c}^{+}$ production in proton-lead collisions is performed with the LHCb experiment at a centre-of-mass energy per nucleon pair of 8.16 TeV in 2016 in $p$Pb and Pb$p$ collisions with an estimated integrated luminosity of approximately 12.5 and 17.4 nb$^{-1}$, respectively. The $\Xi_{c}^{+}$ production cross-section, as well as the $\Xi_{c}^{+}$ to $\Lambda_{c}^{+}$ production cross-section ratio, are measured as a function of the transverse momentum and rapidity and compared to latest theory predictions. The forward-backward asymmetry is also measured as a function of the $\Xi_{c}^{+}$ transverse momentum.

Global warming is expected to cause significant changes in the pattern of precipitation minus evaporation ( P − E ), which represents the net flux of water from the atmosphere to the surface or, equivalently, the convergence of moisture transport within the atmosphere. In most global climate model simulations, the pattern of P − E change resembles an amplification of the historical pattern—a tendency known as “wet gets wetter, dry gets drier.” However, models also predict significant departures from this approximation that are not well understood. Here, we introduce a new method of decomposing the pattern of P − E change into contributions from various dynamic and thermodynamic mechanisms and use it to investigate the response of P − E to global warming within the CESM1 Large Ensemble. In contrast to previous decompositions of P − E change, ours incorporates changes not only in the monthly means of atmospheric winds and moisture, but also in their temporal variability, allowing us to isolate the hydrologic impacts of changes in the mean circulation, transient eddies, relative humidity, and the spatial and temporal distributions of temperature. In general, we find that changes in the mean circulation primarily control the P − E response in the tropics, while temperature changes dominate at higher latitudes. Although the relative importance of specific mechanisms varies by region, at the global scale departures from the wet-gets-wetter approximation over land are primarily due to changes in the temperature lapse rate, while changes in the mean circulation, relative humidity, and horizontal temperature gradients play a secondary role.

Abstract Arctic warming under increased CO2 peaks in winter, but is influenced by summer forcing via seasonal ocean heat storage. Yet changes in atmospheric heat transport into the Arctic have mainly been investigated in the annual mean or winter, with limited focus on other seasons. We investigate the full seasonal cycle of poleward heat transport modeled with increased CO2 or with individually applied Arctic sea‐ice loss and global sea‐surface warming. We find that a winter reduction in dry heat transport is driven by Arctic sea‐ice loss and warming, while a summer increase in moist heat transport is driven by sub‐Arctic warming and moistening. Intermodel spread in Arctic warming controls spread in seasonal poleward heat transport. These seasonal changes and their intermodel spread are well‐captured by down‐gradient diffusive heat transport. While changes in moist and dry heat transport compensate in the annual‐mean, their opposite seasonality may support non‐compensating effects on Arctic warming.

Abstract At most latitudes, the seasonal cycle of zonal‐mean surface air temperature is notably asymmetric: the length of the warming season is not equal to the length of the cooling season. The asymmetry varies spatially, with the cooling season being ∼40 days shorter than the warming season in the subtropics and the warming season being ∼100 days shorter than the cooling season at the poles. Furthermore, the asymmetry differs between the Northern Hemisphere and the Southern Hemisphere. Here, we show that these observed features are broadly captured in a simple model for the evolution of temperature forced by realistic insolation. The model suggests that Earth's orbital eccentricity largely determines the hemispheric contrast, and obliquity broadly dictates the meridional structure. Clouds, atmospheric heat flux convergence, and time‐invariant effective surface heat capacity have minimal impacts on seasonal asymmetry. This simple, first‐order picture has been absent from previous discussions of the surface temperature seasonal cycle.

Abstract An unprecedented heatwave impacted East Antarctica in March 2022, peaking at 39°C above climatology, the largest temperature anomaly ever recorded globally. We investigate the causes of the heatwave, the impact of climate change, and a climate model's ability in simulating such an event. The heatwave, which was skillfully forecast, resulted from a highly anomalous large‐scale circulation pattern that advected an Australian airmass to East Antarctica in 4 days and produced record atmospheric heat fluxes. Southern Ocean sea surface temperatures anomalies had a minimal impact on the heatwave's amplitude. Simulations from a climate model fail to simulate such a large temperature anomaly mostly due to biases in its large‐scale circulation variability, showcasing a pathway for future model improvement in simulating extreme heatwaves. The heatwave was made 2°C warmer by climate change, and end of 21st century heatwaves may be an additional 5–6°C warmer, raising the prospect of near‐melting temperatures over the interior of East Antarctica.

Evaporation adds moisture to the atmosphere, while condensation removes it. Condensation also adds thermal energy to the atmosphere, which must be removed from the atmosphere by radiative cooling. As a result of these two processes, there is a net flow of energy driven by surface evaporation adding energy and radiative cooling removing energy from the atmosphere. Here, we calculate the implied heat transport of this process to find the atmospheric heat transport in balance with the surface evaporation. In modern-day Earth-like climates, evaporation varies strongly between the equator and the poles, while the net radiative cooling in the atmosphere is nearly meridionally uniform, and as a consequence, the heat transport governed by evaporation is similar to the total poleward heat transport of the atmosphere. This analysis is free from cancellations between moist and dry static energy transports, which greatly simplifies the interpretation of atmospheric heat transport and its relationship to the diabatic heating and cooling that governs the atmospheric heat transport. We further demonstrate, using a hierarchy of models, that much of the response of atmospheric heat transport to perturbations, including increasing CO2 concentrations, can be understood from the distribution of evaporation changes. These findings suggest that meridional gradients in surface evaporation govern atmospheric heat transport and its changes.

Abstract Given the key role that atmospheric heat transport plays in Earth's climate system, efforts to document its changes over the satellite era are valuable. Clark et al. (2022, https://doi.org/10.1029/2022GL098822) calculated trends in atmospheric heat transport among four reanalysis data sets and found substantial disagreements between data sets. However, after accounting for the lack of mass‐conservation in reanalysis data sets, we find much smaller magnitude trends, with much better agreement among reanalyses. This highlights the importance of mass corrections when calculating atmospheric heat transport.

Microbial communities are found throughout the biosphere, from human guts to glaciers, from soil to activated sludge. Understanding the statistical properties of such diverse communities can pave the way to elucidate the common mechanisms ...Multiple ecological forces act together to shape the composition of microbial communities. Phyloecology approaches—which combine phylogenetic relationships between species with community ecology—have the potential to disentangle such forces but are often ...