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Variability and Trends in Cloud Properties Over 17 Years From CALIPSO Space Lidar Observations
No full textInternational audienceIn this paper we search for fingerprints of cloud changes over 17 years (2006–2023) within the record of cloud properties collected by the CALIPSO space lidar. Indeed, climate model projections suggest that clouds are rising up in altitude, shrinking in cover and changing rapidly in the Arctic under the influence of human induced climate warming. We describe how changes in CALIPSO space lidar operations over the mission have impacted the stability of the cloud detection. Removing contaminated data reduces the record to 11 full years (2008–2018). For these 11 years, we analyze de‐seasonalized anomalies of cloud cover, altitude, emissivity and vertical profile, to identify trends at global scale and in specific latitude bands. Results show a decrease in opaque cloud cover and a rise in opaque cloud altitude, consistent in sign with climate model projected changes, but statistically insignificant in the observations. Observed changes do not extend beyond the natural variability in any statistically significant way. This suggests that if cloud changes exist, the CALIPSO record might be too short in time or not precise enough to detect them with confidence. This study underscores the need for extending the cloud record from space lidars and building a harmonized record from observations made by successive space lidars
The Distributional Effects of Oil Shocks
No full textInternational audienceNegative oil supply shocks since the 1980s have increased German inflation and reduced aggregate economic activity and prompted moderate monetary tightening to counter these inflationary effects. Using 45 years of high-frequency German administrative data, we find that these shocks disproportionally harm low-income individuals: their earnings growth falls by two percentage points two years after a 10-percent exogenous oil price rise, while high-income individuals are largely unaffected. Job-finding probabilities for low-income workers also decline significantly. This contrasts with the distributional effects of monetary policy shocks, which, while also stronger at the bottom, primarily impact job-separation probabilities. To understand the role of monetary policy in shaping these outcomes, we analyze counterfactual scenarios of policy non-response. Because the actual policy response to oil shocks involves an initial rate rise followed by a fall, a fully anticipated non-response (estimated following McKay and Wolf 2023) leaves the oil shock’s aggregate and distributional effects little changed. When monetary policy repeatedly surprises by not reacting (following Sims and Zha 2006), in contrast, the implied initial monetary loosening dominates, boosting activity, inflation, and particularly employment prospects for low-income individuals
Decadal responses of global land monsoon to two surface thermal modes in the last millennium
No full textInternational audienceThis study investigates the influence of natural external forcing over the last millennium (950–1850) on global land monsoon variability at decadal scale. Two major players operate through changes in global mean surface temperature (GMST) and in the tropical Pacific temperature gradient (TPTG). They modulate precipitation, either individually or jointly in the form of cool-GMST and weak-TPTG episodes. A diagnostic with moisture budget decomposition is performed to separate dynamic and thermodynamic contributions leading to monsoon precipitation. Cool-GMST primarily suppresses the summer precipitation via thermodynamic contributions, with a complex winter response featuring competing thermodynamic gains and evaporation losses. In contrast, weak-TPTG involves significant dynamic adjustments, driving an inter-hemispheric dipole for the summer land monsoon precipitation: decreases in the Northern Hemisphere via anomalous subsidence, and increases in the Southern Hemisphere via the thermodynamic contributions and evaporation. The enhanced winter monsoon precipitation (especially in the Southern Hemisphere) in the case of weak-TPTG is largely driven by the dynamics and evaporation. Under compound conditions, the overall monsoon intensity response can be largely interpreted as a linear superposition of the individual drivers. Summer precipitation is substantially reduced, primarily due to cooling-induced thermodynamic suppression, with additional dynamic contributions. The winter response shows a distinct inter-hemispheric pattern, with precipitation increasing in the Southern Hemisphere and slightly decreasing in the Northern Hemisphere, reflecting different controls by cool-GMST and weak-TPTG. This study provides a valuable framework for interpreting the past monsoon variability and projecting its future variation
Four-dimensional variational data assimilation with a sea-ice thickness emulator
No full textInternational audienceDeveloping operational data assimilation systems for sea-ice models is challenging, especially using a variational approach due to the absence of adjoint models. NeXtSIM, a sea-ice model based on a brittle rheology paradigm, enables high-fidelity simulations of sea-ice dynamics at mesoscale resolution (∼10 km) but lacks an adjoint. By training a neural network as an Arctic-wide emulator for sea-ice thickness based on mesoscale simulations with neXtSIM, we gain access to an adjoint. Building on this emulator and its adjoint, we introduce a four-dimensional variational (4D–Var) data assimilation system to correct the emulator's bias and to better position the marginal ice zone (MIZ). Firstly, we perform twin experiments to demonstrate the capabilities of this 4D–Var system and to evaluate two approximations of the background covariance matrix. These twin experiments demonstrate that the assimilation improves the positioning of the MIZ and enhances the forecast quality, achieving an average reduction in sea-ice thickness root-mean-squared error of 0.8 m compared to the free run. Secondly, we assimilate real CS2SMOS satellite retrievals with this system. While the assimilation of these rather smooth retrievals amplifies the loss of small-scale information in our system, it effectively corrects the forecast bias. The forecasts of our 4D–Var system achieve a similar performance as the operational sea-ice forecasting system neXtSIM-F. These results pave the way to the use of deep learning-based emulators for 4D–Var systems to improve sea-ice modeling
Unpacking Household Engel Curves
No full textInternational audienceAcknowledging that decision making does not happen at the household but at the individual level, can house- hold Engel curves be safely estimated based solely on household-level data? Answering this question requires considering the intra-household Engel curves (IECs) and assessing how estimates of such IECs relate to standard household Engel curves estimates. Aggregating the IECs to the household level reveals confounding factors in standard household Engel curves, including intra-household inequality. A unique data set for Senegal is used to estimate IECs. Large discrepancies are found between the standard estimates of Engel curves and the con- sistently aggregated IECs. The main source of the discrepancy is a household fixed effect on intra-household spending behavior, which is only partially offset by differences in intra-household inequality. Results suggest that income elasticity of food consumption might be overestimated by as much as 43 percent by the standard household Engel curve estimation
A turbulence-informed parameterization of phase partitioning in stratiform mixed-phase clouds for the ICOLMDZ model
No full textHigh-latitude clouds, present over the Arctic Ocean, the Southern Ocean and the Antarctic continent, are very often. Despite being essential for the climate of the poles, they remain a major modelling challenge for climate models. In this study, we present a new cloud phase partitioning parameterization developed for the ICOLMDZ atmospheric model. This parameterization is based on the theory of the evolution of supersaturation in a turbulent environment and is inspired by previous theoretical and modelling works. This scheme completely abandons the standard temperature dependent phase partitioning used in the model to predict the amount of supercooled liquid water in clouds as a function of turbulent kinetic energy, resolved vertical velocity and pre-existing ice crystal properties. This new scheme is evaluated over the Southern Ocean with observation from the MARCUS campaign and results show an improvement in the simulation of the cloud phase spatial variability. The sensitivity to the crystal number concentration determined by a prescribed concentration of ice nucleating particles is also assessed. A second evaluation is performed in the Arctic region with observations collected in mid-level frontal during the RALI-Thinice campaign and a perturbed parameter ensemble experiment is conducted to assess the parametric sensitivity. The new scheme suppresses the systematic overestimation of liquid far from cloud top and shows the ability to simulate patches and thin layers of supercooled liquid water as commonly observed in polar frontal clouds.</div
Climbing the Ladder? How Latin Americans See Their Economic Mobility
No full textThis paper investigates intergenerational economic mobility in 18 Latin American countries using highly comparable data on self-reported economic status (SRES) from 2000 to 2020. Persistence estimates based on this new measure show a similar order of magnitude to income elasticities, indicating that subjective assessments capture meaningful transmission of advantage across generations.Results show that mobility in the region is both low and uneven. A clear hierarchy emerges, with countries in Central America displaying the lowest mobility. For most countries, persistence has remained broadly stable over time, except for Chile and Peru, where it has risen sharply. A complementary cohort analysis confirms this pattern, as younger cohorts tend to display higher persistence conditional on age
Activation of deformation mechanisms in natural salt rock: A microscale investigation using digital image correlation
No full textInternational audienceThis study examines the deformation behaviour of two natural salt rocks during uniaxial compression, observed by high-definition optical imaging. In-plane local strain maps were analysed at different loading stages using Digital Image Correlation (DIC), revealing intense localization and strong heterogeneities in relation with the microstructures of the materials. Combined with microstructural characterization via Electron Backscatter Diffraction (EBSD), three key deformation mechanisms were identified: crystal slip plasticity (CSP), grain boundary sliding (GBS), and intra-crystalline cracking. The interaction of these mechanisms is evident in the localization of deformation bands within certain large grains and relative movement at grain boundaries. Quantitative analysis on the relative dominance of CSP and GBS and the heterogeneity of strain fields reveals the influence of microstructure on the complex interaction of micro-mechanisms