Hydrological responses to dynamically and statistically downscaled climate model output

Daily rainfall and surface temperature series were simulated for the Animas River basin, Colorado using dynamically and statistically downscaled output from the National Center for Environmental Prediction/ National Center for Atmospheric Research (NCEP/NCAR) re-analysis. A distributed hydrological model was then applied to the downscaled data. Relative to raw NCEP output, downscaled climate variables provided more realistic simulations of basin scale hydrology. However, the results highlight the sensitivity of modeled processes to the choice of downscaling technique, and point to the need for caution when interpreting future hydrological scenarios.This article is from Geophysical Research Letters 27 (2000): 1199-1202, doi:10.1029/1999GL006078. Posted with permission.</p

Hydrological responses to dynamically and statistically downscaled climate model output

Abstract. Daily rainfall and surface temperature series were simulated for the Animas River basin, Colorado using dynamically and statistically downscaled output from the Regional climate models simulate sub-GCM grid scale climate features dynamically at resolutions of 20-50 kilometres given time-varying atmospheric conditions National Center for Environmental Prediction / National supplied by the GCM bounding a specified domain (see Center for Atmospheric Research (NCEP/NCAR) re-analysis. reviews by McGregor, 1997; Giorgi and Mearns, 1999). The A distributed hydrological model was then applied to the main advantage of RCMs is their ability to respond in downscaled data. Relative to raw NCEP output, downscaled physically consistent ways to different external forcings (such climate variables provided more realistic simulations of basin as land-surface or atmospherichemistry changes). RCMs can scale hydrology. However, the results highlight the sensitivity also resolve important atmospheric processes such as of modeled processes to the choice of downscaling technique, orographic precipitation better than the driving GCM (Jones and point to the need for caution when interpreting future hydrological scenarios. et al., 1995). However, RCMs are computationally demanding and require orders of magnitude more computer time than SDS to compute equivalent scenarios. Ultimately the realism of both SDS and RCM scenario

Head of bed elevation in pediatric patients with severe traumatic brain injury.

OBJECTIVE: Head of bed (HOB) elevation to 30° after severe traumatic brain injury (TBI) has become standard positioning across all age groups. This maneuver is thought to minimize the risk of elevated ICP in the hopes of decreasing cerebral blood and fluid volume and increasing cerebral venous outflow with improvement in jugular venous drainage. However, HOB elevation is based on adult population data due to a current paucity of pediatric TBI studies regarding HOB management. In this prospective study of pediatric patients with severe TBI, the authors investigated the role of different head positions on intracranial pressure (ICP), cerebral perfusion pressure (CPP), and cerebral venous outflow through the internal jugular veins (IJVs) on postinjury days 2 and 3 because these time periods are considered the peak risk for intracranial hypertension. METHODS: Patients younger than 18 years with a Glasgow Coma Scale score ≤ 8 after severe TBI were prospectively recruited at a single quaternary pediatric intensive care unit. All patients had an ICP monitor placed, and no other neurosurgical procedure was performed. On the 2nd and 3rd days postinjury, the degree of HOB elevation was varied between 0° (head-flat or horizontal), 10°, 20°, 30°, 40°, and 50° while ICP, CPP, and bilateral IJV blood flows were recorded. RESULTS: Eighteen pediatric patients with severe TBI were analyzed. On each postinjury day, 13 of the 18 patients had at least 1 optimal HOB position (the position that simultaneously demonstrated the lowest ICP and the highest CPP). Six patients on each postinjury day had 30° as the optimal HOB position, with only 2 being the same patient on both postinjury days. On postinjury day 2, 3 patients had more than 1 optimal HOB position, while 5 patients did not have an optimal position. On postinjury day 3, 2 patients had more than 1 optimal HOB position while 5 patients did not have an optimal position. Interestingly, 0° (head-flat or horizontal) was the optimal HOB position in 2 patients on postinjury day 2 and 3 patients on postinjury day 3. The optimal HOB position demonstrated lower right IJV blood flow than a nonoptimal position on both postinjury days 2 (p = 0.0023) and 3 (p = 0.0033). There was no significant difference between optimal and nonoptimal HOB positions in the left IJV blood flow. CONCLUSIONS: In pediatric patients with severe TBI, the authors demonstrated that the optimal HOB position (which decreases ICP and improves CPP) is not always at 30°. Instead, the optimal HOB should be individualized for each pediatric TBI patient on a daily basis

Accelerating advances in continental domain hydrologic modeling

In the past, hydrological modeling of surface water resources has mainly focused on simulating the hydrologic cycle at local to regional catchment modeling domains. There now exists a level of maturity amongst the catchment, global water security, and land surface modeling communities such that these communities are converging towards continental domain hydrologic models. This commentary, written from a catchment hydrology community perspective, provides a review of progress in each community towards this achievement, identifies common challenges the communities face, and details immediate and specific areas in which these communities can mutually benefit one another from the convergence of their research perspectives. Those include: (1) creating new incentives and infrastructure to report and share model inputs, outputs, and parameters in data services and open access, machine-independent formats for model replication or re-analysis; (2) ensuring that hydrologic models have: sufficient complexity to represent the dominant physical processes and adequate representation of anthropogenic impacts on the terrestrial water cycle, a process-based approach to model parameter estimation, and appropriate parameterizations to represent large-scale fluxes and scaling behaviour; (3) maintaining a balance between model complexity and data availability as well as uncertainties and (4) quantifying and communicating significant advancements towards the modeling goals