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Gardiner T.,National Physical Laboratory United Kingdom | Madonna F.,CNR Institute of Methodologies for Environmental analysis | Wang J.,NCAR Earth Observing Laboratory | Whiteman D.N.,NASA | And 4 more authors.
AIP Conference Proceedings | Year: 2013

The GCOS Reference Upper Air Network (GRUAN) is an international reference observing network, designed to meet climate requirements and to fill a major void in the current global observing system. Upper air observations within the GRUAN network will provide long-term high-quality climate records, will be used to constrain and validate data from space based remote sensors, and will provide accurate data for the study of atmospheric processes. The network covers measurements of a range of key climate variables including temperature. Implementation of the network has started, and as part of this process a number of scientific questions need to be addressed in order to establish a viable climate reference upper air network, in addition to meeting the other objectives for the network measurements. These include quantifying collocation issues for different measurement techniques including the impact on the overall uncertainty of combined measurements; change management requirements when switching between sensors; assessing the benefit of complementary measurements of the same variable using different measurement techniques; and establishing the appropriate sampling strategy to determine long-term trends. This paper reviews the work that is currently underway to address these issues.

Lowenthal D.H.,Desert Research Institute | Borys R.D.,Desert Research Institute | Cotton W.,Colorado State University | Saleeby S.,Colorado State University | And 2 more authors.
Atmospheric Environment | Year: 2011

Oxygen isotopic ratios (δ18O) and sulfate concentrations were measured in cloud water and snow collected at Storm Peak Laboratory (SPL) during winter, 2007. The rimed mass fraction (RMF) was estimated as the ratio of sulfate concentration in snow to that in cloud water. A sharp increase in the RMF at mean droplet diameters above 10μm confirmed the expected relationship between riming efficiency and cloud droplet size. The mass-weighted altitude of snow formation was inferred from δ18O in cloud water and snow and did not exceed 300m above SPL. The mass-weighted altitude of snow growth by vapor deposition alone was no higher than 900m above SPL. The results suggest that snow crystals nucleated under water-sub-saturated conditions at higher elevations attained a significant fraction of their water content as they grew by riming and vapor deposition in transit through the low-level orographic cloud near the mountain crest. This approach provides a direct means of validating model simulations of snow growth processes in cold mountain clouds. © 2010 Elsevier Ltd.

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