Evaluation of climate and hydrological models for impact projections in the Upper Indus basin

Ph. D. ThesisWater resources in the Indus basin are under acute and growing stress. How climate change will affect this situation in the coming decades depends substantially on responses in the datasparse mountains of the upper basin. However, model projections of changes in the cryosphere-dominated hydrology here are highly uncertain. Integral to this uncertainty are challenges in: characterising near-surface climate fields needed for model input; selecting appropriate model structures to balance process fidelity with data availability; and understanding the wide spread in climate model projections used in impact assessments. As such, this thesis aims to identify pathways for refined hydrological projections in the upper Indus basin through in-depth evaluation of climate, cryospheric and hydrological models. Firstly, using the High Asia Refined Analysis (HAR), the study assesses how relatively high resolution regional climate modelling can help describe spatiotemporal variability in nearsurface climate. The HAR exhibits substantial skill in many respects, but particularly in capturing the complex patterns of precipitation in the basin. Some seasonally varying biases in temperature and incoming radiation suggest deficiencies in snow and cloud representations that are likely resolvable. Secondly, the Factorial Snowpack Model (FSM) is driven with the HAR to examine the feasibility and required structure of process-based snowpack modelling. Model correspondence with local observations and remote sensing is good for a subset of FSM configurations using a prognostic albedo parameterisation, as well as a representation of liquid water retention, drainage and melt/refreezing cycles in the snowpack. The multiphysics approach additionally highlights the inputs and processes needing further investigation, which include the atmospheric stability adjustment. Thirdly, using an adapted FSM program and TOPKAPI-ETH, simplified representations of cryospheric processes are compared with more process-based approaches. This helps to identify where systematic differences in hydrological response occur and their connection with spatial and temporal scales. It is found that an enhanced temperature index (ETI) model exhibits behaviour and climate sensitivity more akin to energy balance formulations than a classical temperature index model. However, there may be structural limits to the fidelity of the ETI formulation under cloudy conditions, while further attention is needed on the translation of surface melt to runoff, especially at high elevations. ii The study then moves to examine controls on regional trends and variability simulated by climate models, focusing on temperature in CMIP5 GCMs. While the models partly reproduce key regional atmospheric circulation influences, variation in summer temperature responses depends on differing snow and albedo representations. Ultimately this may offer some potential to constrain temperature projections. Finally, using CMIP5 and HAPPI GCM outputs, the study explores climate and hydrological projections under selected global warming stabilisation scenarios. This shows that shifts in the timing of runoff are discernible even for low warming targets. Overall water availability may depend particularly on natural variability in precipitation, but in dry years the pressures on water resources in the basin could worsen in future. Further efforts to constrain the range of projections using observations and process-based reasoning are required, but effective water resources management in the basin is likely to depend on increasing resilience to a wide range of climatic and hydrological variability

Atomic Resonance and Scattering

Contains research objectives, summary of research and reports on four research projects.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DAAB07-71-C-0300National Science Foundation (Grant GP-28679)National Bureau of Standards (Grant NBS2-9011)U. S. Air Force - Office of Scientific Research (Contract F44620-72-C-0057

Colloids versus crystalloids for fluid resuscitation in critically ill people

Background Critically ill people may lose fluid because of serious conditions, infections (e.g. sepsis), trauma, or burns, and need additional fluids urgently to prevent dehydration or kidney failure. Colloid or crystalloid solutions may be used for this purpose. Crystalloids have small molecules, are cheap, easy to use, and provide immediate fluid resuscitation, but may increase oedema. Colloids have larger molecules, cost more, and may provide swifter volume expansion in the intravascular space, but may induce allergic reactions, blood clotting disorders, and kidney failure. This is an update of a Cochrane Review last published in 2013. Objectives To assess the effect of using colloids versus crystalloids in critically ill people requiring fluid volume replacement on mortality, need for blood transfusion or renal replacement therapy (RRT), and adverse events (specifically: allergic reactions, itching, rashes). Search methods We searched CENTRAL, MEDLINE, Embase and two other databases on 23 February 2018. We also searched clinical trials registers. Selection criteria We included randomised controlled trials (RCTs) and quasi‐RCTs of critically ill people who required fluid volume replacement in hospital or emergency out‐of‐hospital settings. Participants had trauma, burns, or medical conditions such as sepsis. We excluded neonates, elective surgery and caesarean section. We compared a colloid (suspended in any crystalloid solution) versus a crystalloid (isotonic or hypertonic). Data collection and analysis Independently, two review authors assessed studies for inclusion, extracted data, assessed risk of bias, and synthesised findings. We assessed the certainty of evidence with GRADE. Main results We included 69 studies (65 RCTs, 4 quasi‐RCTs) with 30,020 participants. Twenty‐eight studied starch solutions, 20 dextrans, seven gelatins, and 22 albumin or fresh frozen plasma (FFP); each type of colloid was compared to crystalloids. Participants had a range of conditions typical of critical illness. Ten studies were in out‐of‐hospital settings. We noted risk of selection bias in some studies, and, as most studies were not prospectively registered, risk of selective outcome reporting. Fourteen studies included participants in the crystalloid group who received or may have received colloids, which might have influenced results. We compared four types of colloid (i.e. starches; dextrans; gelatins; and albumin or FFP) versus crystalloids. Starches versus crystalloids We found moderate‐certainty evidence that there is probably little or no difference between using starches or crystalloids in mortality at: end of follow‐up (risk ratio (RR) 0.97, 95% confidence interval (CI) 0.86 to 1.09; 11,177 participants; 24 studies); within 90 days (RR 1.01, 95% CI 0.90 to 1.14; 10,415 participants; 15 studies); or within 30 days (RR 0.99, 95% CI 0.90 to 1.09; 10,135 participants; 11 studies). We found moderate‐certainty evidence that starches probably slightly increase the need for blood transfusion (RR 1.19, 95% CI 1.02 to 1.39; 1917 participants; 8 studies), and RRT (RR 1.30, 95% CI 1.14 to 1.48; 8527 participants; 9 studies). Very low‐certainty evidence means we are uncertain whether either fluid affected adverse events: we found little or no difference in allergic reactions (RR 2.59, 95% CI 0.27 to 24.91; 7757 participants; 3 studies), fewer incidences of itching with crystalloids (RR 1.38, 95% CI 1.05 to 1.82; 6946 participants; 2 studies), and fewer incidences of rashes with crystalloids (RR 1.61, 95% CI 0.90 to 2.89; 7007 participants; 2 studies). Dextrans versus crystalloids We found moderate‐certainty evidence that there is probably little or no difference between using dextrans or crystalloids in mortality at: end of follow‐up (RR 0.99, 95% CI 0.88 to 1.11; 4736 participants; 19 studies); or within 90 days or 30 days (RR 0.99, 95% CI 0.87 to 1.12; 3353 participants; 10 studies). We are uncertain whether dextrans or crystalloids reduce the need for blood transfusion, as we found little or no difference in blood transfusions (RR 0.92, 95% CI 0.77 to 1.10; 1272 participants, 3 studies; very low‐certainty evidence). We found little or no difference in allergic reactions (RR 6.00, 95% CI 0.25 to 144.93; 739 participants; 4 studies; very low‐certainty evidence). No studies measured RRT. Gelatins versus crystalloids We found low‐certainty evidence that there may be little or no difference between gelatins or crystalloids in mortality: at end of follow‐up (RR 0.89, 95% CI 0.74 to 1.08; 1698 participants; 6 studies); within 90 days (RR 0.89, 95% CI 0.73 to 1.09; 1388 participants; 1 study); or within 30 days (RR 0.92, 95% CI 0.74 to 1.16; 1388 participants; 1 study). Evidence for blood transfusion was very low certainty (3 studies), with a low event rate or data not reported by intervention. Data for RRT were not reported separately for gelatins (1 study). We found little or no difference between groups in allergic reactions (very low‐certainty evidence). Albumin or FFP versus crystalloids We found moderate‐certainty evidence that there is probably little or no difference between using albumin or FFP or using crystalloids in mortality at: end of follow‐up (RR 0.98, 95% CI 0.92 to 1.06; 13,047 participants; 20 studies); within 90 days (RR 0.98, 95% CI 0.92 to 1.04; 12,492 participants; 10 studies); or within 30 days (RR 0.99, 95% CI 0.93 to 1.06; 12,506 participants; 10 studies). We are uncertain whether either fluid type reduces need for blood transfusion (RR 1.31, 95% CI 0.95 to 1.80; 290 participants; 3 studies; very low‐certainty evidence). Using albumin or FFP versus crystalloids may make little or no difference to the need for RRT (RR 1.11, 95% CI 0.96 to 1.27; 3028 participants; 2 studies; very low‐certainty evidence), or in allergic reactions (RR 0.75, 95% CI 0.17 to 3.33; 2097 participants, 1 study; very low‐certainty evidence). Authors' conclusions Using starches, dextrans, albumin or FFP (moderate‐certainty evidence), or gelatins (low‐certainty evidence), versus crystalloids probably makes little or no difference to mortality. Starches probably slightly increase the need for blood transfusion and RRT (moderate‐certainty evidence), and albumin or FFP may make little or no difference to the need for renal replacement therapy (low‐certainty evidence). Evidence for blood transfusions for dextrans, and albumin or FFP, is uncertain. Similarly, evidence for adverse events is uncertain. Certainty of evidence may improve with inclusion of three ongoing studies and seven studies awaiting classification, in future updates

Atomic Resonance and Scattering

Contains research objectives and summary of research on eight research projects.National Science Foundation (Grant PHY75-15421-A01)U. S. Air Force - Office of Scientific Research (Grant AFOSR 76-2972)Joint Services Electronics Program (Contract DAAB07-76-C-1400)U. S. Air Force - Office of Scientific Research (Contract F44620-72-C-0057

Atomic Resonance and Scattering

Contains reports on nine research projects.U.S. Energy Research and Development Administration (Contract EG-77-S-02-4370)U. S. Air Force - Office of Scientific Research (Contract F44620-72-C-0057)Joint Services Electronics Program (Contract DAAB07-76-C-1400)National Science Foundation (Grant PHY75-15421-AO1)National Science Foundation (Grant PHY77-09155)National Science Foundation (Grant CHE76-81750)U. S. Air Force - Office of Scientific Research (Grant AFOSR-76-2972A

Atomic Resonance and Scattering

Contains reports on eight research projects.National Science Foundation (Grant PHY77-09155)Joint Services Electronics Program (Contract DAAG29-78-C-0020)U. S. Department of Energy (Grant EG-77-S-02-4370)National Science Foundation (Grant DMR 77-10084)National Aeronautics and Space Administration (Grant NSG-1551)U. S. Air Force - Office of Scientific Research (Grant AFOSR-76-2972)National Science Foundation (Grant CHE76-81750

Shrub expansion modulates belowground impacts of changing snow conditions in alpine grasslands

Climate change is disproportionately impacting mountain ecosystems, leading to large reductions in winter snow cover, earlier spring snowmelt and widespread shrub expansion into alpine grasslands. Yet, the combined effects of shrub expansion and changing snow conditions on abiotic and biotic soil properties remains poorly understood. We used complementary field experiments to show that reduced snow cover and earlier snowmelt have effects on soil microbial communities and functioning that persist into summer. However, ericaceous shrub expansion modulates a number of these impacts and has stronger belowground effects than changing snow conditions. Ericaceous shrub expansion did not alter snow depth or snowmelt timing but did increase the abundance of ericoid mycorrhizal fungi and oligotrophic bacteria, which was linked to decreased soil respiration and nitrogen availability. Our findings suggest that changing winter snow conditions have cross-seasonal impacts on soil properties, but shifts in vegetation can modulate belowground effects of future alpine climate change

Shrub expansion modulates belowground impacts of changing snow conditions in alpine grasslands

From Wiley via Jisc Publications RouterHistory: received 2021-05-03, rev-recd 2021-06-18, accepted 2021-10-06, pub-electronic 2021-10-27Article version: VoRPublication status: PublishedFunder: Natural Environment Research Council; Id: http://dx.doi.org/10.13039/501100000270; Grant(s): NE/N009452/1Funder: Biotechnology and Biological Sciences Research Council; Id: http://dx.doi.org/10.13039/501100000268; Grant(s): BB/S010661/1Abstract: Climate change is disproportionately impacting mountain ecosystems, leading to large reductions in winter snow cover, earlier spring snowmelt and widespread shrub expansion into alpine grasslands. Yet, the combined effects of shrub expansion and changing snow conditions on abiotic and biotic soil properties remains poorly understood. We used complementary field experiments to show that reduced snow cover and earlier snowmelt have effects on soil microbial communities and functioning that persist into summer. However, ericaceous shrub expansion modulates a number of these impacts and has stronger belowground effects than changing snow conditions. Ericaceous shrub expansion did not alter snow depth or snowmelt timing but did increase the abundance of ericoid mycorrhizal fungi and oligotrophic bacteria, which was linked to decreased soil respiration and nitrogen availability. Our findings suggest that changing winter snow conditions have cross‐seasonal impacts on soil properties, but shifts in vegetation can modulate belowground effects of future alpine climate change

Climate change disrupts the seasonal coupling of plant and soil microbial nutrient cycling in an alpine ecosystem

The seasonal coupling of plant and soil microbial nutrient demands is crucial for efficient ecosystem nutrient cycling and plant production, especially in strongly seasonal alpine ecosystems. Yet, how these seasonal nutrient cycling processes are modified by climate change and what the consequences are for nutrient loss and retention in alpine ecosystems remain unclear. Here, we explored how two pervasive climate change factors, reduced snow cover and shrub expansion, interactively modify the seasonal coupling of plant and soil microbial nitrogen (N) cycling in alpine grasslands, which are warming at double the rate of the global average. We found that the combination of reduced snow cover and shrub expansion disrupted the seasonal coupling of plant and soil N-cycling, with pronounced effects in spring (shortly after snow melt) and autumn (at the onset of plant senescence). In combination, both climate change factors decreased plant organic N-uptake by 70% and 82%, soil microbial biomass N by 19% and 38% and increased soil denitrifier abundances by 253% and 136% in spring and autumn, respectively. Shrub expansion also individually modified the seasonality of soil microbial community composition and stoichiometry towards more N-limited conditions and slower nutrient cycling in spring and autumn. In winter, snow removal markedly reduced the fungal:bacterial biomass ratio, soil N pools and shifted bacterial community composition. Taken together, our findings suggest that interactions between climate change factors can disrupt the temporal coupling of plant and soil microbial N-cycling processes in alpine grasslands. This could diminish the capacity of these globally widespread alpine ecosystems to retain N and support plant productivity under future climate change

Atomic Resonance and Scattering

Contains reports on nine research projects.National Science Foundation (Grant PHY79-09743)National Science Foundation (Grant PHY82-10486)Joint Services Electronics Program (Contract DAAG29-83-K-0003)U.S. Navy - Office of Naval Research (Contract N00014-79-C-0183)National Bureau of Standards (Grant NB83-NAHA-4058)National Science Foundation (Grant CHE79-02967-A04)National Science Foundation (Grant PHY83-07172)Joint Services Electronics Program (Grant DAAG29-83-K-0003