Radiometric sensitivity computation in aperture synthesis interferometric radiometry

This paper is concerned with the radiometric sensitivity computation of an aperture synthesis interferometric radiometer devoted to Earth observation. The impact of system parameters and the use of simultaneous redundant measurements are analyzed. The interferometric radiometer uncertainty principle is presented; it quantifies the relationship between radiometric sensitivity and angular resolution.Peer Reviewe

Radiometric Sensitivity Computation in Aperture Synthesis Interferometric Radiometry

This paper is concerned with the radiometric sensitivity computation of an aperture synthesis interferometric radiometer devoted to Earth observation. The impact of system parameters and the use of simultaneous redundant measurements are analyzed. The interferometric radiometer uncertainty principle is presented; it quantifies the relationship between radiometric sensitivity and angular resolution.Peer Reviewe

Development and Evaluation of a Multi-Year Fractional Surface Water Data Set Derived from Active/Passive Microwave Remote Sensing Data

abstract: The sensitivity of Earth’s wetlands to observed shifts in global precipitation and temperature patterns and their ability to produce large quantities of methane gas are key global change questions. We present a microwave satellite-based approach for mapping fractional surface water (FW) globally at 25-km resolution. The approach employs a land cover-supported, atmospherically-corrected dynamic mixture model applied to 20+ years (1992–2013) of combined, daily, passive/active microwave remote sensing data. The resulting product, known as Surface WAter Microwave Product Series (SWAMPS), shows strong microwave sensitivity to sub-grid scale open water and inundated wetlands comprising open plant canopies. SWAMPS’ FW compares favorably (R[superscript 2] = 91%–94%) with higher-resolution, global-scale maps of open water from MODIS and SRTM-MOD44W. Correspondence of SWAMPS with open water and wetland products from satellite SAR in Alaska and the Amazon deteriorates when exposed wetlands or inundated forests captured by the SAR products were added to the open water fraction reflecting SWAMPS’ inability to detect water underneath the soil surface or beneath closed forest canopies. Except for a brief period of drying during the first 4 years of observation, the inundation extent for the global domain excluding the coast was largely stable. Regionally, inundation in North America is advancing while inundation is on the retreat in Tropical Africa and North Eurasia. SWAMPS provides a consistent and long-term global record of daily FW dynamics, with documented accuracies suitable for hydrologic assessment and global change-related investigations.The final version of this article, as published in Remote Sensing, can be viewed online at: http://www.mdpi.com/2072-4292/7/12/1584

Models of macro-scale hydrology for use in global change research: Tests on two tropical river systems

The subject of this dissertation is the terrestrial water cycle and development of tools to study the issue of global hydrologic change. A rationale is developed to study the water cycle at regional and continental scales using macro-scale hydrology models coupled to Geographic Information Systems (GIS). A linked Water Balance/Water Transport Model (WBM/WTM) was constructed and tested as part of this research. The model was applied to two tropical river systems, the Amazon River in South America and the Zambezi River in southern Africa. The WBM/WTM is a distributed parameter model, operating at 0.5\sp\circ(latitude x longitude) spatial scale and with monthly timesteps. The WBM transforms spatially complex data on climate, vegetation, soils and topography into predictions of soil moisture, evapotranspiration and runoff. The WTM uses computed runoff, information on fluvial topology, linear transfer through river channels and a simple representation of floodplain storage to generate monthly discharge for any cell within a simulated catchment. For the Amazon, WBM/WTM results were checked against established data sources and found to be in good agreement. The Zambezi simulation was more problematic. This study identified and corrected errors in the precipitation, potential evapotranspiration, and soil water capacity data sets, and demonstrated the importance of checking such calculations against reliable discharge data. Simulations with data from the Amazon and Zambezi River systems identified fluvial transport parameters which best matched observed discharge. Similar parameters captured the dynamics of river flow in these strikingly different river systems. This suggests that large tropical rivers may have convergent properties that can be modeled using simple algorithms. This work produced a set of calibrated, macro-scale hydrology models for two large rivers prior to significant anthropogenic disturbance. Such simulations are prerequisites to the study of hydrologic change. The major impacts of such change, from shifting land use, climate change, and water resources management, can be simulated using macro-scale hydrology models. The dissertation offers a strategy to accomplish this goal

Spatial variability of Arctic sea ice algae

The most pronounced effects of global climate change have been experienced in the Arctic region. In particular, Arctic sea ice decline and volume loss have emphasized the impeding threat of continued climate change, and have been center stage in the public eye for over a decade. Many of the observed changes in the Arctic are related to the physical system because these parameters, such as sea ice extent and thickness, are more easily observed from space and airborne platforms. The linkage between ecosystem function and its physical environment is clear from all well investigated systems. This undoubtedly means that the observed changes to the physical system have had an equally dramatic impact on the Arctic ecosystem. Our understanding of the Arctic marine ecosystem, however, is severely limited due to the methodological and logistical constraints of monitoring ecological properties. This has caused significant seasonal and geographical knowledge gaps, particularly in the high (> 80ºN) and central Arctic Ocean. Over the past decades a disproportional emphasis has been put on the importance of primary production (PP) and the availability of food in the water column. Observations have indicated an overall increase in Arctic-wide net primary production (NPP) as a result of a thinning and declining sea ice cover, and increasing duration of the phytoplankton growth season. This increased biomass may suggest a corresponding increase in the biomass of consumers and higher trophic levels. This premise, however, neglects the rather important role that the sea ice environment and sea ice algae play in the Arctic food web. The timing, duration and spatial availability of ice algae are drastically different compared to pelagic phytoplankton. Therefore, it is only by first gaining a better understanding of the base of the Arctic food web that we can start to understand the rest of the food web. Throughout this thesis, we aimed to assess how sea ice algae biomass availability and habitat will be affected by continued changes to the sea ice habitat, and what consequences can be expected for the Arctic food web. This was accomplished by developing novel methodologies and approaches to characterize and quantify the spatial variability of sea ice algae-biomass, -primary production and – habitat. Subsequently, we used this toolset to assess the implications of a rapidly changing sea ice habitat in relation to spatial variability of sea ice algae carbon availability and carbon demand by iceassociated organisms. In Chapter 2, we developed a methodological toolbox to process environmental sensor array observations acquired from under-ice profiling platforms (e.g., Remotely Operated Vehicle – ROV, and the Surface and Under-Ice Trawl – SUIT), which included novel mathematical and statistical approaches to representatively capture the spatial variability of sea ice and under-ice physicalbiological properties. We showed that our developed approaches produced observations, which could capture the spatial variability better than traditional point location characterizations of environmental properties. Specifically, the insufficient spatial representativeness of sea ice-algal biomass can cause biases in large-scale ice algal biomass and PP estimates. In Chapter 3, we further developed upon Chapter 2 methodologies by introducing a new approach to estimate primary production on floe-scales (meters to kilometers), further justifying the need for representative ice-algae biomass and PP estimates. We also showed that the sea ice environment and under-ice water properties played an important role in structuring the under-ice community. Furthermore, we indicated that ecological key species of the central Arctic Ocean thrived significantly on carbon synthesized by ice algae. These results highlighted the key role of sea ice as a habitat and as a feeding ground within the Arctic Ocean. In Chapter 4, we aimed to compare the physical-biological properties of multi-year sea ice (MYI) and first-year sea ice (FYI) to provide some insight into how the Arctic will change with the continued replacement of MYI by FYI. We developed and confirmed the hypothesis that thick MYI hummocks do have the potential to host substantial ice algae biomass and identified hummocks as common and permanent features, which represent a reliable habitat for sea ice algae due to the typically thin or absent snow cover. We developed key physical-biological relationships to classify the springtime spatial variability of sea ice algae habitat for both FYI and MYI. We applied this classification to pan- Arctic ice thickness and snow observations, and showed that MYI is substantially under-estimated in terms of suitable habitat. Furthermore, we identified thick sea ice features, such as MYI hummocks and sea ice ridges, as potentially high biomass regions with great ecological value. We also indicated that the thicker sea ice, which remains in late-summer, has reduced melt-induced algal losses. In conclusion, we developed a robust and novel approach to representatively quantify sea ice environmental properties, and sea ice algae biomass and PP at floe-scales. These estimates resulted in more accurate estimates of overall carbon biomass availability and production, which we used to improve the spatial variability of the ice-algae derived carbon budget. We concluded that there was a large mis-match between ice-algal primary produced carbon and ice-algal carbon demand by dominant species. This mis-match was also accompanied by large regional variability. This was expected during our sampling period since production was shutting down. Taking a different approach, we showed that the standing stocks of ice-algal carbon were quite substantial. These results suggest that during late-summer, when primary production shuts down, the remaining ice-algal biomass in high latitude regions may represent a crucial food source to sustain ice associated organisms during the onset of polar night. Altogether, the continued thinning and loss of thicker sea ice features may result in the loss of a reliable carbon supply, in the form of sea ice algae carbon, at key times of the year when other carbon sources are severely limited

Development and Evaluation of a Multi-Year Fractional Surface Water Data Set Derived from Active/Passive Microwave Remote Sensing Data

The sensitivity of Earth’s wetlands to observed shifts in global precipitation and temperature patterns and their ability to produce large quantities of methane gas are key global change questions. We present a microwave satellite-based approach for mapping fractional surface water (FW) globally at 25-km resolution. The approach employs a land cover-supported, atmospherically-corrected dynamic mixture model applied to 20+ years (1992–2013) of combined, daily, passive/active microwave remote sensing data. The resulting product, known as Surface WAter Microwave Product Series (SWAMPS), shows strong microwave sensitivity to sub-grid scale open water and inundated wetlands comprising open plant canopies. SWAMPS’ FW compares favorably (R2 = 91%–94%) with higher-resolution, global-scale maps of open water from MODIS and SRTM-MOD44W. Correspondence of SWAMPS with open water and wetland products from satellite SAR in Alaska and the Amazon deteriorates when exposed wetlands or inundated forests captured by the SAR products were added to the open water fraction reflecting SWAMPS’ inability to detect water underneath the soil surface or beneath closed forest canopies. Except for a brief period of drying during the first 4 years of observation, the inundation extent for the global domain excluding the coast was largely stable. Regionally, inundation in North America is advancing while inundation is on the retreat in Tropical Africa and North Eurasia. SWAMPS provides a consistent and long-term global record of daily FW dynamics, with documented accuracies suitable for hydrologic assessment and global change-related investigations

Proceedings of the Third Workshop on 'The Okhotsk Sea and adjacent areas'

Foreword SESSION 1 Evidence and Consequences of Decadal-Scale Climate Variation in the Okhotsk Sea and Northwestern Pacific Ocean SESSION 2 Physical and Chemical Processes in the Okhotsk Sea and Northwestern Pacific Ocean SESSION 3 Biological Variability: Evidence and Consequences SESSION 4 Anthropogenic Impacts on the Okhotsk Sea Ecosystem(s) (265 page document

Remote Sensing Applications in Coastal Environment

Coastal regions are susceptible to rapid changes, as they constitute the boundary between the land and the sea. The resilience of a particular segment of coast depends on many factors, including climate change, sea-level changes, natural and technological hazards, extraction of natural resources, population growth, and tourism. Recent research highlights the strong capabilities for remote sensing applications to monitor, inventory, and analyze the coastal environment. This book contains 12 high-quality and innovative scientific papers that explore, evaluate, and implement the use of remote sensing sensors within both natural and built coastal environments

Tropical cyclones in the South-West Indian Ocean : intensity changes, oceanic interaction and impacts

Includes abstract.Includes bibliographical references (p. 229-253).This study investigates the climatology, intensification and ocean atmosphere interaction in relation to the passage of tropical cyclones (TCs) in the South-West Indian Ocean (SWIO). A Climatology of TCs in the SWIO including landfall in the area of Mozambique and Madagascar was developed for the 1952-2007 and 1980-2007 periods