Earth Observation Data Group

Abstract:

Abstract Reducing uncertainty in anthropogenic climate forcing requires improved observational constraints on aerosol and cloud properties. This study demonstrates how hyperspectral observations with exceptionally low radiometric uncertainty, exemplified by the proposed Traceable Radiometry Underpinning Terrestrial and Helio Studies (TRUTHS)-like configuration, can strengthen these constraints relative to Plankton, Aerosol, Cloud, and ocean Ecosystem (PACE) Ocean Color Instrument (OCI)-like configuration. Using forward radiative transfer simulations, we quantify the influence of radiometric uncertainty on spectral sensitivity to aerosol and cloud properties, including idealised layered aerosol–cloud configurations, with a focus on the O 2 A-band. At ±0.3% radiometric uncertainty, TRUTHS-like observations distinguish changes of ∼0.4 in cloud optical thickness (COT), ∼2 km in cloud top height, and ∼3 μm in effective radius (CER), approximately 0.01 in aerosol optical depth (AOD) and 0.02 in both single-scattering albedo and Ångström exponent (AE), demonstrating greater spectral sensitivity than the ±1.5% of PACE OCI-like uncertainty assumption. Lower radiometric uncertainty preserves subtle spectral differences between clean and aerosol-influenced clouds, enhancing discrimination among marine, continental, desert, and urban aerosol types under idealised within- and above-cloud configurations. A joint optimal-estimation information-content analysis across an ensemble of 100 simulated scenes shows that these spectral sensitivity differences translate into stronger simultaneous constraints on COT-CER and AOD-AE. Relative to PACE OCI-like observations, TRUTHS-like observations reduce mean posterior uncertainty by 46.97% (COT), 74.22% (CER), 24.39% (AOD), and 58.35% (AE), while mean degrees of freedom for signal (DFS) increase from 1.48 to 1.94 for clouds and from 1.29 to 1.57 for aerosols, with positive DFS differences across all scenes. Improved COT-CER constraints would underpin more accurate estimation of cloud droplet number concentration though that is not explored here. These results highlight the potential of low-radiometric-uncertainty hyperspectral observations to increase the information available to constrain aerosol and cloud properties, with implications for space-based aerosol–cloud characterisation, climate-model evaluation, and radiative-forcing assessments.

Abstract:

The Earth’s middle atmosphere spans the deep region from the upper troposphere/lower stratosphere at around 10 km altitude to the mesosphere/lower thermosphere at around 100 km altitude. It is being increasingly recognized for its role in driving extreme surface weather and regional climate change. Climate models predict large ongoing and future changes in the middle atmosphere composition and circulation. However, the observations needed to detect, attribute and understand these changes and their impacts, to test predictions, and thereby to improve our models, are lacking. Here we show the capacity of infrared limb-imaging tomography to provide the needed observations. This evaluation is based on studies performed within a recent satellite mission concept – the Changing-Atmosphere Infrared Tomography Explorer, CAIRT. Observing thermal infrared emissions simultaneously from the middle troposphere at about 4 km up to the lower thermosphere at about 115 km altitude this technique provides observations of temperature and an extensive range of trace gases with unprecedented spatial resolution of about 50 by 50 km horizontally and about 1 km vertically. We show how these observations would (a) help to quantify the changing atmospheric circulation, (b) allow characterization and quantification of the gravity waves that are critical in driving this circulation, (c) reveal how variability in solar radiation and energetic particles propagate downward to affect regional climate at the surface, (d) detect how volcanic eruptions and wildfires impact the middle atmosphere and climate, and (e) resolve how stratosphere-troposphere exchange affects ozone and water vapor in the crucial and climate-relevant tropopause region.

Abstract:

Abstract UK summer heatwaves are dictated by the polar jet stream position and sea surface temperature (SST) variability, affecting the Summer North Atlantic Oscillation (SNAO) index. The SNAO can determine and influence the Central England Precipitation (CEP) and Central England Temperature (CET). A strong and significant negative correlation ( r  = −0.63) is found between the SNAO and CEP, but a weaker correlation for the CET. Summers with highly positive SNAO (i.e. 1976 and 2018) are among the driest and warmest on record. In this study, we highlight the roles of large‐scale atmospheric circulations and use of Met Office‐defined weather regimes in understanding UK heatwave characteristics.

Abstract:

The global energy transition depends on solar photovoltaic (PV) power displacing fossil fuels to deliver projected climate and air quality benefits. However, aerosol pollution from co-located coal plants actively suppresses PV energy production. Here a global, facility-level dataset shows that aerosols reduced global PV generation by 5.8% in 2023 (111 TWh). From 2017 to 2023, annual aerosol-induced PV energy losses from existing systems were, on average, equivalent to one-third of the energy added by new PV installations. In China, aerosols caused the largest PV energy losses worldwide, reducing national PV generation by 7.7% in 2023. The corresponding annual loss-to-growth ratio averaged 38% and frequently exceeded 50%. Despite continued coal expansion, PV energy losses have declined by 1.4% yr−1 since 2017 owing to stricter emission controls. By contrast, the USA, where co-location of solar and coal plants is limited, experienced only 3.1% aerosol-induced PV loss. Given the slow pace of global coal phase-out, these results reveal a constraint on solar performance that, if unaccounted for, could lead to a systematic overestimation of the transition’s contribution to climate and air quality goals.