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Evaluation of CMIP6 model simulations of PM2.5 and its components over China
Fangxuan Ren, Jintai Lin, Chenghao Xu, Jamiu A. Adeniran, Jingxu Wang, Randall V. Martin, Aaron van Donkelaar, Melanie S. Hammer, Larry W. Horowitz, Steven T. Turnock, Naga Oshima, Jie Zhang, Susanne Bauer, Kostas Tsigaridis, Øyvind Seland, Pierre Nabat, David Neubauer, Gary Strand, Twan van Noije, Philippe Le Sager, and Toshihiko Takemura
Geosci. Model Dev., 17, 4821–4836, https://doi.org/10.5194/gmd-17-4821-2024, 2024
We evaluate the performance of 14 CMIP6 ESMs in simulating total PM2.5 and its 5 components over China during 2000–2014. PM2.5 and its components are underestimated in almost all models, except that black carbon (BC) and sulfate are overestimated in two models, respectively. The underestimation is the largest for organic carbon (OC) and the smallest for BC. Models reproduce the observed spatial pattern for OC, sulfate, nitrate and ammonium well, yet the agreement is poorer for BC.

Abstract

Land monsoon rainfall has a distinct annual cycle. Under global warming, whether the phase and amplitude of this annual cycle would be changed is still unclear. Here, a global investigation is conducted using 34 CMIP6 and 34 CMIP5 models under a high emission scenario. Seasonal delays would occur in the Southern Hemisphere (SH) American (3.43 days), Northern Hemisphere (NH) African (5.98 days) and SH African (3.76 days) monsoon regions, while no robust signal is found in other monsoon regions. Except NH American monsoon, amplitude is enhanced in all the monsoon regions. Compared to amplitude, the phase changes dominate the future changes of precipitation in the SH American, NH African and SH African monsoon regions. In these phase-dominated regions, atmospheric energetic framework is proved to be reliable at regional scale and the enhanced effective atmospheric heat capacity is found to be the dominant factor.

Abstract

Rapid intensification (RI) of tropical cyclones (TCs) not only plays a crucial role in the development of major TCs but also poses great challenges to operational forecasting. Previous studies predominantly focused on RI over 24-hr periods, overlooking the potential for extended durations with intermittent moments. Here, we investigate the actual duration of RI and show that, when considering the interruption and intermittent moments, the longest RI can persist for up to 90 hr. Declines and resurgences in maximum potential intensity (MPI) and tropical cyclone heat potential (TCHP) are associated with the interruption of RI process. Given that the error in TC track prediction is much lower compared with that in intensity prediction, such a local minimum in MPI and TCHP could be better forecasted and potentially assist the prediction of RI, ultimately reducing TC-related hazards.

Abstract

The dynamics shaping the El Niño-Southern Oscillation's (ENSO) response to present and future climate change remain unclear, partly due to limited paleo-ENSO records spanning past abrupt climate events. Here, we measure Mg/Ca ratios on individual foraminifera to reconstruct east Pacific subsurface temperature variability, a proxy for ENSO variability, across the last 25,000 years, including the millennial-scale events of the last deglaciation. Combining these data with proxy system model output reveals divergent ENSO responses to Northern Hemisphere stadials: enhanced variability during Heinrich Stadial 1 (H1) and reduced variability during the Younger Dryas (YD), relative to the Holocene. H1 ENSO likely intensified through meltwater-induced changes to ocean/atmospheric circulation, a response observed in models, but the lack of a similar response during the YD challenges model simulations. We suggest the tropical Pacific mean state during H1 primed ENSO for larger fluctuations under meltwater forcing, whereas the YD mean state likely buffered against it.

Abstract

We investigate the role of ocean heat transport (OHT) in driving the decadal variability of the Arctic climate by analyzing the pre-industrial control simulation of a high-resolution climate model. While the OHT variability at 65°N is greater in the Atlantic, we find that the decadal variability of Arctic-wide surface temperature and sea ice area is much better correlated with Bering Strait OHT than Atlantic OHT. In particular, decadal Bering Strait OHT variability causes significant changes in local sea ice cover and air-sea heat fluxes, which are amplified by shortwave feedbacks. These heat flux anomalies are regionally balanced by longwave radiation at the top of the atmosphere, without compensation by atmospheric heat transport (Bjerknes compensation). The sensitivity of the Arctic to changes in OHT may thus rely on an accurate representation of the heat transport through the Bering Strait, which is difficult to resolve in coarse-resolution ocean models.

Abstract

Understanding how changing seasonal precipitation will affect ecosystems and water resources can benefit from understanding how precipitation from different seasons contributes to runoff versus evapotranspiration (ET). We use stable-isotope data from 23 National Ecological Observatory Network watersheds to quantify the fractions of winter and summer precipitation that supply ET, and the fractions of ET supplied by summer versus winter precipitation. Across 20 watersheds, 34%–101% of summer precipitation supplied ET, with 8%–105% of ET supplied by summer precipitation; these end-member-splitting solutions were poorly constrained in the other three watersheds. These precipitation partitioning fractions were significantly correlated with many topographic, climatic, and vegetation metrics. This first empirical study of seasonal precipitation partitioning fractions across diverse ecoregions demonstrates that they can be well-constrained in many locations using existing public data sets, and that partitioning-fraction variations are largely explained by climate variations.

Abstract

This study investigates boreal spring events of Pacific Meridional Mode (PMM) from 1950 to 2022, revealing that cold PMM is more effective in triggering subsequent La Niña compared to warm PMM's induction of following El Niño. This asymmetry stems from the varying origins and sub-efficacies of PMM groups. The cold PMM is primarily initiated by pre-existing La Niña, while the warm PMM is comparably activated by pre-existing El Niño and internal atmospheric dynamics. PMMs initiated by pre-existing El Niño or La Niña play a crucial role in determining the efficacies of PMMs in triggering subsequent El Niño-Southern Oscillation (ENSO). The strong discharge of pre-existing El Niño hampers warm PMM's induction of subsequent El Niño, whereas weak recharge from pre-existing La Niña enhances the efficacy of cold PMM in inducing subsequent La Niña. Comprehending not only the PMM phase but also its origin is crucial for ENSO research and prediction.

Abstract

We report in situ observation of magnetic reconnection between magnetic flux rope (MFR) and magnetic hole (MH) in the magnetosheath by the Magnetospheric Multiscale mission. The MFR was rooted in the magnetopause and could be generated by magnetopause reconnection therein. A thin current sheet was generated due to the interaction between MFR and MH. The sub-Alfvénic ion bulk flow and the Hall field were detected inside this thin current sheet, indicating an ongoing reconnection. An elongated electron diffusion region characterized by non-frozen-in electrons, magnetic-to-particle energy conversion, and crescent-shaped electron distribution was detected in the reconnection exhaust. The observation provides a mechanism for the dissipation of MFRs and thus opens a new perspective on the evolution of MFRs at the magnetopause. Our work also reveals one potential fate of the MHs in the magnetosheath which could reconnect with the MFRs and further merge into the magnetopause.

Abstract

Martian CO2 ice clouds are intriguing features, representing a rare occurrence of atmospheric condensation of a major component. These clouds play a crucial role due to their radiative properties, interactions with surface, and coupling with microphysical cycles of aerosols. Observations have been limited, prompting modeling studies to understand their formation and dynamics. Here, we present the first high-resolution 3D simulations of CO2 ice clouds using a Large-Eddy Simulation (LES) model incorporating CO2 microphysics. We investigate cloud formation in idealized temperature perturbations in the polar night. A reference simulation with a −2K perturbation demonstrates that the formed CO2 ice cloud possesses a convective potential, leading to its ascent in the troposphere. We determine the timescales and orders of magnitude of various phenomena involved in the lifecycle of a CO2 ice cloud. Sensitivity tests show that convection can be inhibited or intensified by the thermodynamic and microphysical conditions of the simulated environment.

Abstract

Deciphering how modern precipitation patterns became established in monsoon-dominated East Asia and the arid interior Asia is crucial for predicting future precipitation trends under accelerated global warming and increased climate extremes. However, this effort is hindered by a scarcity of quantitative paleo-precipitation data in this region. Here we reconstruct the pattern of Middle to Late Miocene paleo-precipitation across an east-to-west transect from the summer monsoon-dominated East Asian region through the transition zone and into interior Asia. Our work is based on a newly established precipitation calculation equation and quantitative pollen-based precipitation conversion. Analysis indicates a common trend of precipitation across the studied region prior to ca, 11 Ma, followed by a clear divergence of precipitation variations between East and interior Asia since at least 11–9 Ma. This divergence is characterized by increasing precipitation in East Asia, but a coeval decrease in rainfall in the transition zone and interior Asia. The timing of this precipitation divergence was contemporaneous with intense tectonic activity in the northern Tibetan Plateau, which differentially affected the efficacy of water vapor transport into East and interior Asia. Modeling work using different topographic settings corroborates this tectonic influence. Our study demonstrates the early establishment of modern-like precipitation patterns in East-interior Asia at least in the early Late Miocene.

Abstract

We report a citizen science-motivated study on the cause of an unusually bright red aurora as witnessed from Hokkaido, Japan during a magnetic storm on 1 December 2023. The auroral brightness of 5 kR is unusual for the Dst index peak of only −107 nT. In spite of the moderate storm amplitude, the extremely high solar wind density of >50/cc and dynamic pressure of >25 nPa caused the aurora oval extension to 53 magnetic latitudes (L = 2.8). We discuss that the drift loss of the ring current particles across the small-size magnetopause is important, and Hokkaido was at the right position to see the direct effect of the large particle injection of the storm-time substorm.

Abstract

Changes in precipitation and its causes under future warming scenarios in Northwest China are of great concern. Based on the dynamical downscaling results of the Weather Research and Forecasting model (WRF), this study quantitatively identified the contribution of local evaporation and external moisture transport to future precipitation changes in western and eastern Northwest China (WNWC and ENWC) by calculating the precipitation recycling ratio (PRR). The results showed that the WRF could reasonably reproduce the observed spatial and temporal distribution of precipitation and evaporation during the historical reference period of 1985–2014. Under the 1.5 and 2.0°C stabilized warming scenarios from 2071 to 2100, there is a stronger precipitation growth in WNWC than in ENWC, and the PRR generally increases in WNWC and decreases in ENWC. Further analysis indicates that external moisture transport is the dominant contributor to the increased precipitation in all cases with its contribution exceeding 70%, while the difference of precipitation growth in two sub-regions arises from the summer moisture transport at the southern boundary as the inflow in WNWC and outflow in ENWC. Compared to the negligible contribution of evaporation in ENWC (less than 7%), evaporation contributes more than 23% to the precipitation increase in WNWC under future warming scenarios, which may be related to the strong land-atmosphere coupling there. Furthermore, an additional warming of 0.5°C leads to an increase in precipitation for both sub-regions, which is mainly due to the contribution of external moisture transport.

Science, Volume 384, Issue 6702, June 2024.

Science, Volume 384, Issue 6702, June 2024.

Science, Volume 385, Issue 6705, Page 168-174, July 2024.

Science, Volume 384, Issue 6702, Page 1292-1298, June 2024.

Science, Volume 384, Issue 6702, Page 1318-1323, June 2024.

Science, Volume 384, Issue 6702, Page 1330-1335, June 2024.

Science, Volume 384, Issue 6702, Page 1335-1339, June 2024.

Science, Volume 384, Issue 6702, Page 1340-1344, June 2024.