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The reconstruction of paleo‐elevation serves a dual purpose to enhance our comprehension of geodynamic processes affecting terrestrial landforms and to contribute significantly to the interpretation of atmospheric circulation and biodiversity. The oxygen (δ18Ow) and deuterium (δDw) isotopes in atmospheric precipitation are systematically depleted with the increase of altitude, which are typical and widely applicated paleo‐altimeters. The utilization of hydrogen isotope of hydrous silicate minerals within the shear zone system, volcanic glass, and plant leaf wax alkanes offers valuable insights for addressing evaporation and diagenesis. In this paper, we review the principle, application conditions, and influencing factors of the hydrogen isotope paleo‐altimeter. In addition, we discuss the feasibility of utilizing this technique for quantitatively estimating the paleo‐elevation of the southeastern Tibetan Plateau, where multiple shear zones extend over hundred kilometers parallel to the topographic gradient. [ABSTRACT FROM AUTHOR]

The effects of small‐scale topography‐induced land surface heterogeneity are not well represented in current Earth System Models (ESMs). In this study, a new topography‐based subgrid structure referred to as topographic units (TGU) designed to better capture subgrid topographic effects, and methods to downscale atmospheric forcing to the land TGUs have been implemented in the Energy Exascale Earth System Model (E3SM) Land Model (ELM). Effects of the subgrid scheme and downscaling methods on ELM simulated land surface processes are evaluated over the conterminous United States (CONUS). For this purpose, ELM simulations are performed using two configurations without (NoD ELM) and with (D ELM) downscaling, both using TGUs derived for the 0.5‐degree grids and the same land surface parameters. Simulations using the two ELM configurations are compared over the CONUS domain, regional levels, and at observational sites (e.g., SNOTEL). The CONUS‐level results suggest that D ELM simulates more snowfall and snow water equivalent (SWE), higher runoff, and less ET during spring and summer. Regional‐level results suggest more pronounced impacts of downscaling over regions dominated by higher elevation TGUs and regions with maximum precipitation occurring during cool seasons. Results at the SNOTEL sites suggest that D ELM has superior capability of reproducing the observed SWE at 83% of the sites, with more pronounced performance over topographically heterogeneous TGUs with their maximum precipitation occurring during cool seasons. The results highlight the importance of improving representation of small‐scale surface heterogeneity in ESMs and motivate future research to understand their effects on land‐atmosphere interactions, streamflow, and water resources management over mountainous regions. Plain Language Summary: Current global Earth System Models (ESMs) used in climate simulation and projection represent the land surface using coarse grids with limited ability to resolve the surface variability within the grid. This study introduced a new subgrid structure and methods to downscale atmospheric variables such as precipitation and temperature from the atmosphere grid to the land subgrid units in the Energy Exascale Earth System Model (E3SM) Land Model (ELM) to improve its ability of representing the effects of topography induced subgrid surface variability on land surface processes. Effects of the new developments on simulations of land surface processes are evaluated using the conterminous United States (CONUS) as a case study. ELM simulations with the new developments generally yield higher snowfall, snow water equivalent and runoff over CONUS. Effects of the new developments are found to be larger over regions dominated by higher elevation landscapes and regions receiving their maximum precipitation during cool seasons. Also, the new developments improved ELM's ability to reproduce observed snow water equivalent at the SNOTEL sites. The new developments have important implications for streamflow modeling and water resources management dependent on hydrologic processes in mountainous regions. Key Points: A topography‐based subgrid scheme and downscaling of atmospheric forcing have been implemented in the E3SM Land Model componentThese new methods have more pronounced effects in high subgrid elevation areas that receive their major precipitation during cool seasonsThe new methods improve model capability to reproduce the observed snow water equivalent at 83% of the SNOTEL sites [ABSTRACT FROM AUTHOR]

The Northeast United States (NEUS) has faced the most rapidly increasing occurrences of extreme precipitation within the US in the past few decades. Understanding the physics leading to long‐term trends in regional extreme precipitation is essential but the progress is limited partially by the horizontal resolution of climate models. The latest fully coupled 25‐km GFDL (Geophysical Fluid Dynamics Laboratory) SPEAR (Seamless system for Prediction and EArth system Research) simulations provide a good opportunity to study changes in regional extreme precipitation and the relevant physical processes. Here, we focus on the contributions of changes in synoptic‐scale events, including atmospheric rivers (AR) and tropical cyclone (TC)‐related events, to the trend of extreme precipitation in the fall season over the Northeast US in both the recent past and future projections using the 25‐km GFDL‐SPEAR. In observations, increasing extreme precipitation over the NEUS since the 1990s is mainly linked to TC‐related events, especially those undergoing extratropical transitions. In the future, both AR‐related and TC‐related extreme precipitation over the NEUS are projected to increase, even though the numbers of TCs in the North Atlantic are projected to decrease in the SPEAR simulations using the SSP5‐8.5 projection of future radiative forcing. Factors such as enhancing TC intensity, strengthening TC‐related precipitation, and/or westward shift in Atlantic TC tracks may offset the influence of declining Atlantic TC numbers in the model projections, leading to more frequent TC‐related extreme precipitation over the NEUS. Plain Language Summary: In recent decades, the densely populated Northeast United States has faced the most rapid increase in the frequency of extreme rainfall within the US. Here, we examine the causes of the increase in extreme rainfall over the Northeast US in both current and future climates. We find that the surge in extreme rainfall since the 1990s is primarily linked to events associated with tropical cyclones. In a future warming climate, based on projections from a high‐resolution climate model, our research shows that we can expect more frequent occurrences of extreme rainfall related to both atmospheric rivers and tropical cyclones. However, the increase in extreme rainfall linked to atmospheric rivers is projected to outpace that associated with tropical cyclones. Given the distinct spatial patterns of extreme rainfall resulting from atmospheric rivers and tropical cyclones, changes in their relative contributions could have profound implications for flood prevention and mitigation strategies. Key Points: The autumn extreme precipitation trend over the Northeast US is primarily attributed to tropical cyclone‐related events since the 1990sIn future projections, extreme precipitation linked to atmospheric rivers increases faster than that associated with tropical cyclonesDespite fewer projected tropical cyclones in the future, extreme precipitation associated with them is projected to increase [ABSTRACT FROM AUTHOR]