[1] Thirty-three snowpack models of varying complexity and purpose were evaluated across a wide range of hydrometeorological and forest canopy conditions at five Northern Hemisphere locations, for up to two winter snow seasons. Modeled estimates of snow water equivalent (SWE) or depth were compared to observations at forest and open sites at each location. Precipitation phase and duration of above-freezing air temperatures are shown to be major influences on divergence and convergence of modeled estimates of the subcanopy snowpack. When models are considered collectively at all locations, comparisons with observations show that it is harder to model SWE at forested sites than open sites. There is no universal ''best'' model for all sites or locations, but comparison of the consistency of individual model performances relative to one another at different sites (and vice versa). Calibration of models at forest sites provides lower errors than uncalibrated models at three out of four locations. However, benefits of calibration do not translate to subsequent years, and benefits gained by models calibrated for forest snow processes are not translated to open conditions.

Improving the accuracy of estimates of forest carbon exchange is a central priority for understanding ecosystem response to increased atmospheric CO levels and improving carbon cycle modelling. However, the spatially continuous parameterization of photosynthetic capacity (Vcmax) at global scales and appropriate temporal intervals within terrestrial biosphere models (TBMs) remains unresolved. This research investigates the use of biochemical parameters for modelling leaf photosynthetic capacity within a deciduous forest. Particular attention is given to the impacts of seasonality on both leaf biophysical variables and physiological processes, and their interdependent relationships. Four deciduous tree species were sampled across three growing seasons (2013-2015), approximately every 10 days for leaf chlorophyll content (Chl ) and canopy structure. Leaf nitrogen (N ) was also measured during 2014. Leaf photosynthesis was measured during 2014-2015 using a Li-6400 gas-exchange system, with A-Ci curves to model Vcmax. Results showed that seasonality and variations between species resulted in weak relationships between Vcmax normalized to 25°C (Vcmax25) and N (R = 0.62, P < 0.001), whereas Chl demonstrated a much stronger correlation with Vcmax25 (R = 0.78, P < 0.001). The relationship between Chl and N was also weak (R = 0.47, P < 0.001), possibly due to the dynamic partitioning of nitrogen, between and within photosynthetic and nonphotosynthetic fractions. The spatial and temporal variability of Vcmax25 was mapped using Landsat TM/ETM satellite data across the forest site, using physical models to derive Chl . TBMs largely treat photosynthetic parameters as either fixed constants or varying according to leaf nitrogen content. This research challenges assumptions that simple N -Vcmax25 relationships can reliably be used to constrain photosynthetic capacity in TBMs, even within the same plant functional type. It is suggested that Chl provides a more accurate, direct proxy for Vcmax25 and is also more easily retrievable from satellite data. These results have important implications for carbon modelling within deciduous ecosystems.

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Abstract. This paper describes ESM-SnowMIP, an international coordinated modelling effort to evaluate current snow schemes, including snow schemes that are included in Earth system models, in a wide variety of settings against local and global observations. The project aims to identify crucial processes and characteristics that need to be improved in snow models in the context of local- and global-scale modelling. A further objective of ESM-SnowMIP is to better quantify snow-related feedbacks in the Earth system. Although it is not part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6), ESM-SnowMIP is tightly linked to the CMIP6-endorsed Land Surface, Snow and Soil Moisture Model Intercomparison (LS3MIP).

Abstract:Snow accumulation and melt were observed at shrub tundra and tundra sites in the western Canadian Arctic. End of winter snow water equivalent (SWE) was higher at the shrub tundra site than the tundra site, but lower than total winter snowfall because snow was removed by blowing snow, and a component was also lost to sublimation. Removal of snow from the shrub site was larger than expected because the shrubs were bent over and covered by snow during much of the winter. Although SWE was higher at the shrub site, the snow disappeared at a similar time at both sites, suggesting enhanced melt at the shrub site. The Canadian Land Surface Scheme (CLASS) was used to explore the processes controlling this enhanced melt. The spring-up of the shrubs during melt had a large effect on snowmelt energetics, with similar turbulent fluxes and radiation above the canopy at both sites before shrub emergence and after the snowmelt. However, when the shrubs were emerging, conditions were considerably different at the two sites. Above the shrub canopy, outgoing shortwave radiation was reduced, outgoing longwave radiation was increased, sensible heat flux was increased and latent flux was similar to that at the tundra site. Above the snow surface at this site, incoming shortwave radiation was reduced, incoming longwave radiation was increased and sensible heat flux was decreased. These differences were caused by the lower albedo of the shrubs, shading of the snow, increased longwave emission by the shrub stems and decreased wind speed below the shrub canopy. The overall result was increased snowmelt at the shrub site. Although this article details the impact of shrubs on snow accumulation and melt, and energy exchanges, additional research is required to consider the effect of shrub proliferation on both regional hydrology and climate.

PurposeThis paper seeks to investigate the links between different types of visibility, joint initiatives and business performance using the concepts of transparency as a measure of visibility in supply chains. The prognosis that increased supply chain visibility can be achieved through suppliers and customers working on joint initiative(s), the deployment of which leads to collaborative successes, is tested.Design/methodology/approachLamming et al.'s transparency concept was used as a basis for the development of a framework for assessing the visibility gaps between the focal company – Rolls‐Royce (RR) – and their suppliers. The framework was applied to a particular supplier to identify visibility gaps; subsequently a joint initiative was launched across the supply chain and the benefits measured and assessed. A case study approach was followed due to the contemporary nature of the work undertaken.FindingsThe supply chain's performance vis‐à‐vis schedule adherence was significantly improved as a result of the initiative launched. Additionally, there were improvements in visibility across capacity planning, material ordering and inventory management.Practical implicationsThe study demonstrated the value of using the developed transparency framework in a structured manner to generate improvements in the supply chain. RR will look to extend its use across other supply chains; the approach could also be extended out to other sectors.Originality/valueThe development and application of the transparency frameworks in the aerospace sector are unique and have shown the value of the approach. The work has demonstrated tangibly that the exchange of high‐quality information as part of an improvement initiative does lead to significant improvements in the overall performance of the supply chain.

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