High and Dry: New Observations of Tropospheric and Cloud Properties above the Greenland Ice Sheet

Cloud and atmospheric properties strongly influence the mass and energy budgets of the Greenland Ice Sheet (GIS). To address critical gaps in the understanding of these systems, a new suite of cloud- and atmosphere-observing instruments has been installed on the central GIS as part of the Integrated Characterization of Energy, Clouds, Atmospheric State, and Precipitation at Summit (ICECAPS) project. During the first 20 months in operation, this complementary suite of active and passive ground-based sensors and radiosondes has provided new and unique perspectives on important cloud?atmosphere properties. High atop the GIS, the atmosphere is extremely dry and cold with strong near-surface static stability predominating throughout the year, particularly in winter. This low-level thermodynamic structure, coupled with frequent moisture inversions, conveys the importance of advection for local cloud and precipitation formation. Cloud liquid water is observed in all months of the year, even the particularly cold and dry winter, while annual cycle observations indicate that the largest atmospheric moisture amounts, cloud water contents, and snowfall occur in summer and under southwesterly flow. Many of the basic structural properties of clouds observed at Summit, Greenland, particularly for low-level stratiform clouds, are similar to their counterparts in other Arctic regions. The ICECAPS observations and accompanying analyses will be used to improve the understanding of key cloud?atmosphere processes and the manner in which they interact with the GIS. Furthermore, they will facilitate model evaluation and development in this data-sparse but environmentally unique region

The IPWG satellite precipitation validation effort

The estimation of precipitation (rainfall and snowfall) across the Earth’s surface is important for both science and user applications, ranging from understanding and improving our knowledge of the global energy and water cycle, to water resources and hydrological modelling, and to societal applications such as water availability and monitoring of waterborne diseases (see Kirschbaum DB, Huffman GJ, Adler RF, Braun S, Garrett K, Jones E, McNally A, Skofronick-Jackson G, Stocker E, Wu H, Zaitchik BF, Bull Am Meteorol Soc 98:1169–1194, 2017). The global mapping of precipitation through conventional means is essentially limited to land areas due to the reliance upon rain (and snow) gauges and/or radar (see Kidd C, Becker A, Huffman GJ, Muller CL, Joe P, Skofronick-Jackson G, Kirschbaum DB, Bull Am Meteorol Soc 98:69–78, 2017a). For truly global precipitation mapping satellite observations must be used. A range of techniques, algorithms and schemes have been developed to exploit these satellite observations and generate quantitative precipitation products, many with (quasi-) global coverage. Alongside these techniques, there is a need for the inter-comparison, verification, and validation of such products in order to quantify their accuracy and performance (and consistency) for both developers and users. The International Precipitation Working Group (IPWG) has supported a long-term effort to inter-compare and validate precipitation products through the exploitation of large-scale regional surface reference data sets. Here, we present the current and future validation efforts of the IPWG together with examples of satellite-surface inter-comparisons