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1. Below-surface water mediates the response of African forests to reduced rainfall

   https://doi.org/10.1088/1748-9326/ab724a  

   Madani, Nima; Kimball, John S; Parazoo, Nicholas C; Ballantyne, Ashley P; Tagesson, Torbern; Jones, Lucas A; Reichle, Rolf H; Palmer, Paul I; Velicogna, Isabella; Bloom, A Anthony; et al (March 2020, Environmental Research Letters)
2. Biocrusts enhance non-rainfall water deposition and alter its distribution in dryland soils

   https://doi.org/10.1016/j.jhydrol.2021.126050  

   Li, Shenglong; Bowker, Matthew A.; Xiao, Bo (April 2021, Journal of Hydrology)
3. Indian Monsoon Rainfall

   https://doi.org/10.14379/iodp.proc.353.2016  

   Clemens, S.C.; Kuhnt, W.; LeVay, L.J. (July 2016, Proceedings of the International Ocean Discovery Program)

   null (Ed.)

   International Ocean Discovery Program (IODP) Expedition 353 drilled six sites in the Bay of Bengal, recovering 4280 m of sediments during 32.9 days of on-site drilling. The primary objective of Expedition 353 is to reconstruct changes in Indian monsoon circulation since the Miocene at tectonic to centennial timescales. Analysis of the sediment sections recovered will improve our understanding of how monsoonal climates respond to changes in forcing external to the Earth’s climate system (i.e., insolation) and changes in forcing internal to the Earth’s climate system, including changes in continental ice volume, greenhouse gas concentrations, sea level, and the ocean-atmosphere exchange of energy and moisture. All of these mechanisms play critical roles in current and future climate change in monsoonal regions. The primary signal targeted is the exceptionally low salinity surface waters that result, in roughly equal measure, from both direct summer monsoon precipitation above the Bay of Bengal and runoff from the numerous large river basins that drain into the Bay of Bengal. Changes in rainfall and surface ocean salinity are captured and preserved in a number of chemical, physical, isotopic, and biological components of sediments deposited in the Bay of Bengal. Expedition 353 sites are strategically located in key regions where these signals are the strongest and best preserved. 

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4. Conservation of Dry Air, Water, and Energy in CAM and Its Potential Impact on Tropical Rainfall

   https://doi.org/10.1175/JCLI-D-21-0512.1  

   Harrop, Bryce E.; Pritchard, Michael S.; Parishani, Hossein; Gettelman, Andrew; Hagos, Samson; Lauritzen, Peter H.; Leung, L. Ruby; Lu, Jian; Pressel, Kyle G.; Sakaguchi, Koichi (May 2022, Journal of Climate)

   Abstract For the Community Atmosphere Model version 6 (CAM6), an adjustment is needed to conserve dry air mass. This adjustment exposes an inconsistency in how CAM6’s energy budget incorporates water—in CAM6 water in the vapor phase has energy, but condensed phases of water do not. When water vapor condenses, only its latent energy is retained in the model, while its remaining internal, potential, and kinetic energy are lost. A global fixer is used in the default CAM6 model to maintain global energy conservation, but locally the energy tendency associated with water changing phase violates the divergence theorem. This error in energy tendency is intrinsically tied to the water vapor tendency, and reaches its highest values in regions of heavy rainfall, where the error can be as high as 40 W m −2 annually averaged. Several possible changes are outlined within this manuscript that would allow CAM6 to satisfy the divergence theorem locally. These fall into one of two categories: 1) modifying the surface flux to balance the local atmospheric energy tendency and 2) modifying the local atmospheric tendency to balance the surface plus top-of-atmosphere energy fluxes. To gauge which aspects of the simulated climate are most sensitive to this error, the simplest possible change—where condensed water still does not carry energy and a local energy fixer is used in place of the global one—is implemented within CAM6. Comparing this experiment with the default configuration of CAM6 reveals precipitation, particularly its variability, to be highly sensitive to the energy budget formulation. Significance Statement This study examines and explains spurious regional sources and sinks of energy in a widely used climate model. These energy errors result from not tracking energy associated with water after it transitions from the vapor phase to either liquid or ice. Instead, the model used a global fixer to offset the energy tendency related to the energy sources and sinks associated with condensed water species. We replace this global fixer with a local one to examine the model sensitivity to the regional energy error and find a large sensitivity in the simulated hydrologic cycle. This work suggests that the underlying thermodynamic assumptions in the model should be revisited to build confidence in the model-simulated regional-scale water and energy cycles. 

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5. Ecosystem-scale rainfall manipulation in a Pinon-Juniper Woodland: Volumetric Water Content (VWC) Profile Data (2009-2013 )

   https://doi.org/10.6073/pasta/d93ddafe0eacd6b475a4f21894f2a61a  

   Pockman, William; McDowell, Nathan (January 2015, Environmental Data Initiative)

   Climate models predict that water limited regions around the world will become drier and warmer in the near future, including southwestern North America. We developed a large-scale experimental system that allows testing of the ecosystem impacts of precipitation changes. Four treatments were applied to 1600 m2 plots (40 m × 40 m), each with three replicates in a piñon pine (Pinus edulis) and juniper (Juniper monosperma) ecosystem. These species have extensive root systems, requiring large-scale manipulation to effectively alter soil water availability.  Treatments consisted of: 1) irrigation plots that receive supplemental water additions, 2) drought plots that receive 55% of ambient rainfall, 3) cover-control plots that receive ambient precipitation, but allow determination of treatment infrastructure artifacts, and 4) ambient control plots. Our drought structures effectively reduced soil water potential and volumetric water content compared to the ambient, cover-control, and water addition plots. Drought and cover control plots experienced an average increase in maximum soil and air temperature at ground level of 1-4° C during the growing season compared to ambient plots, and concurrent short-term diurnal increases in maximum air temperature were also observed directly above and below plastic structures. Our drought and irrigation treatments significantly influenced tree predawn water potential, sap-flow, and net photosynthesis, with drought treatment trees exhibiting significant decreases in physiological function compared to ambient and irrigated trees.  Supplemental irrigation resulted in a significant increase in both plant water potential and xylem sap-flow compared to trees in the other treatments. This experimental design effectively allows manipulation of plant water stress at the ecosystem scale, permits a wide range of drought conditions, and provides prolonged drought conditions comparable to historical droughts in the past – drought events for which wide-spread mortality in both these species was observed. 

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