Note: Intro -- Contents -- Foreword: International Space Science Institute (ISSI) Workshop on the Earth's Hydrological Cycle -- References -- Review of Understanding of Earth's Hydrological Cycle: Observations, Theory and Modelling -- Abstract -- Introduction -- Clouds and Precipitation -- Soil Moisture -- Evapotranspiration -- Ground Water Observations -- Water Extent and Levels -- Vegetation Stage -- Water Vapour -- Snow -- Permafrost -- Glaciers and Ice Caps -- Ice Sheet -- Sea Ice -- Sea Level -- Sea-surface Salinity -- Freshwater Discharge for Large Mid-Latitude and Tropical Rivers -- Conclusions and Observational Needs for the Future -- Acknowledgments -- References -- Challenges and Opportunities in Water Cycle Research: WCRP Contributions -- Abstract -- Introduction -- The WCRP -- The Global Water Budget and Hydrological Cycle -- Grand Challenges -- Grand Challenge on Water Resources -- Grand Challenge on Water Extremes -- Conclusions -- Acknowledgments -- References -- Physically Consistent Responses of the Global Atmospheric Hydrological Cycle in Models and Observations -- Abstract -- Introduction -- Constraints upon Global Mean Precipitation Responses -- Simple Model of Global Precipitation -- Transient Response in Global Precipitation in CMIP5 Models -- Current Changes in the Global Atmospheric Water Cycle -- Water Vapor and Regional Constraints on Precipitation -- Moisture Flux into Tropical Wet Regions -- Precipitation Response in the Wet and Dry Regions of the Tropics -- Extremes of Precipitation -- Influence of Dynamical Changes on Precipitation and Its Extremes -- Conclusions -- Acknowledgments -- References -- Quantifying and Reducing Uncertainty in the Large-Scale Response of the Water Cycle -- Abstract -- Introduction -- Scientific Challenges in Modelling the Global Water Cycle -- Global Water Budget -- The Role of Model Resolution. , Influence of Resolution on Global Precipitation -- Resolved Versus Parametrised Processes in Models -- Representing Hydrological Processes and Phenomena -- Clouds, Humidity and Radiation -- Model Representations of Cloud and Precipitation and Their Evaluation -- Diurnal Cycle of Clouds and Precipitation -- Precipitation in Mid-latitude Cyclones -- Land--Atmosphere Interactions -- Ocean--Atmosphere Processes and Interactions -- The Role of the Cryosphere -- Global Monsoons -- Summary -- Acknowledgments -- References -- Connecting Satellite Observations with Water Cycle Variables Through Land Data Assimilation: Examples Using the NASA GEOS-5 LDAS -- Abstract -- Introduction -- Data and Methods -- GEOS-5 Land Data Assimilation System -- Assimilated Observations -- Validation Data and Approach -- Results -- Assimilation of Sparse and Coarse-Scale Observations -- Partitioning of Terrestrial Water Storage Observations -- Microwave Radiative Transfer Models for Radiance Data Assimilation -- Warm-Season, L-Band Radiative Transfer Modeling -- Predicting Microwave Brightness Temperatures over Snow -- Observation Selection for a Root Zone Soil Moisture Analysis -- Using Precipitation Observations -- Assimilating Surface Soil Moisture Retrievals -- Combining Precipitation Observations and Surface Soil Moisture Retrievals -- Summary and Discussion -- Conclusions and Outlook -- Acknowledgments -- References -- Initialisation of Land Surface Variables for Numerical Weather Prediction -- Abstract -- Introduction -- Snow Analysis -- Snow Forecast Models -- Snow Observations -- Snow Analysis Methods -- Results -- Soil Moisture Analysis -- History of Soil Moisture Analysis for NWP -- Comparison Between the OI and EKF Soil Moisture Analyses -- Use of Satellite Data to Analyse Soil Moisture -- Conclusion -- Acknowledgments -- References. , Closing the Gaps in Our Knowledge of the Hydrological Cycle over Land: Conceptual Problems -- Abstract -- Introduction -- Observations of the Hydrological Cycle -- Models of the Hydrological Cycle -- Data Assimilation of the Hydrological Cycle -- Introduction -- Data Assimilation Methods -- Representation of Errors -- Advantages and Disadvantages of Assimilation Methods -- Example of a Land Data Assimilation System -- Data Assimilation Research Applications -- Single-column Applications -- Distributed Applications -- Towards Operational Land Data Assimilation -- Conceptual Problems and Key Challenges -- Assimilated Observations -- Forward and Retrieval Models, with Particular Reference to Radiances and Backscatter Processes -- Land Surface Models -- Data Assimilation Challenges -- Validation -- Conclusions -- Acknowledgments -- Appendix: Sensor acronyms -- References -- Toward Improved Estimation of the Dynamic Topography and Ocean Circulation in the High Latitude and Arctic Ocean: The Importance of GOCE -- Abstract -- Introduction -- Ocean Dynamic Topography -- Surface Circulation -- Volume Transport -- Summary -- Acknowledgments -- References -- Sea Surface Salinity Observations from Space with the SMOS Satellite: A New Means to Monitor the Marine Branch of the Water Cycle -- Abstract -- Introduction -- Data -- SMOS SSS Data -- Ocean Surface Currents -- Rain, Evaporation and River Discharge Data -- Ocean Color Products -- In Situ Data -- SMOS Monitoring of the Major Tropical Atlantic River Plumes -- Amazon and Orinoco River Plume Monitoring -- Eastern Tropical Atlantic Freshwater Pools Monitoring -- Precipitation Signatures in SSS Data from Space -- SSS Temporal Variability Associated with Rain Events -- Systematically Fresher Skin SSS in Rainy Regions -- SSS as a Tracer of the Evaporation--Precipitation Budget in the Oceanic Mixed Layer. , Large-scale SSS Interannual Variability in Tropical Indian and Pacific Oceans -- Fresh Pool Interactions with Wind-driven Processes -- An Example of Fresh Pool Erosion by Wind-driven Upwelling -- Fresh Pool Interactions with Tropical Cyclones -- Conclusions and Perspectives -- Acknowledgments -- References -- Role of Ocean in the Variability of Indian Summer Monsoon Rainfall -- Abstract -- Introduction -- Monsoon Onset Over India -- Active--Break Cycle of Monsoon -- Inter-annual and Decadal Variability of Monsoon -- Rapid Warming of the Indian Ocean -- Summary and Conclusions -- References -- Perspectives in Modelling Climate--Hydrology Interactions -- Abstract -- Introduction -- Impact of Anthropogenic Land Use, Especially Irrigation, on Climate -- Impact of Irrigation on the South Asian Summer Monsoon (SASM) -- Conclusions and Perspectives for the Impact of Irrigation on Climate -- Permafrost -- Basic Hydrological Processes in Permafrost Areas -- Representation of Permafrost Processes in ESMs -- Wetlands -- Concluding Remark -- Acknowledgments -- References -- Downscaling Satellite Precipitation with Emphasis on Extremes: A Variational ell1-Norm Regularization in the Derivative Domain -- Abstract -- Introduction -- Precipitation Downscaling as a Regularized Inverse Problem -- Basic Concepts in the Continuous Space -- Discrete Representation -- Geometrical Versus Statistical Interpretation of the ell1-Norm Regularized Downscaling -- Working with an Unknown Downgrading Operator (H) -- Results from a Case Study -- Concluding Remarks -- Acknowledgments -- References -- Global Snow Mass Measurements and the Effect of Stratigraphic Detail on Inversion of Microwave Brightness Temperatures -- Abstract -- Introduction -- Current Snow Mass Estimation -- General Circulation Models and Reanalyses -- Products Which Prioritise Snow -- Surface Observations Only. , Land Surface Models Assimilating In Situ Observations -- Remote Sensing of Snow Mass -- Assimilation of Passive Microwave Observations to Improve Snow Mass Estimation -- Assimilation of Passive Microwave Brightness Temperatures -- Globsnow -- Methodology -- Limitations of Globsnow -- Methods -- The Cold Land Processes Experiment (CLPX) Resampled Snowpits -- Comparison: Layered HUT Scene Simulation Versus Observations -- Comparison: N-layer Versus Fewer Layers of Stratigraphic Information -- Results and Analysis -- Snow Properties at CLPX Sites -- Simulated Scene Brightness Temperatures -- Differences Due to Layering Detail -- Discussion and Conclusions -- Acknowledgments -- References -- Glaciers in the Earth's Hydrological Cycle: Assessments of Glacier Mass and Runoff Changes on Global and Regional Scales -- Abstract -- Introduction -- Assessing glacier mass balance on regional and global scales -- Assessments by in situ mass-balance measurements -- Assessments by geodetic method -- Assessments using satellite gravimetry -- Assessments by other approaches -- AAR method -- Multi-method approach -- Modeling glacier mass balance on regional and global scales -- Models based on mass-balance sensitivity -- Models of surface mass balance -- Model limitations -- Glacier runoff -- Effects of glaciers on streamflow -- What is glacier runoff? -- Assessing global-scale impacts of glaciers on the hydrological cycle -- Synthesis and discussion -- Conclusions -- Acknowledgments -- References -- Observing Global Surface Water Flood Dynamics -- Abstract -- Introduction: Surface Water Floods in the Earth System -- Observing Global Flood Dynamics -- Remote Measurements of Floodplain Topography -- Remote Measurements of Inundation Extent -- Remote Measurements of Water Elevation -- Remote Measurements of Water Storage -- The Proposed SWOT Satellite Mission. , Inferring Remaining Unknown Variables Using DA.