The Chandler Wobble (CW) period is considered a single time-invariable constant, ~1.2 years, but the possible time-variability has not been examined using modern space-geodetic data. We first examined whether the Chandler period could vary with time on the assumption of minimum excitation power. Unexpectedly, the estimated Chandler period has been shortened by more than 60 days since about 2005. Moreover, by simple least-squares modeling, we found that CW started to be weaker in 2005 and almost disappeared in 2015. We interpret these results in both excitation and wobble domains as caused by the absence of CW for the first time in the observation history. Assuming no excitations of CW since 2005, the rather abrupt damping suggests the Q-value is below 25. Meanwhile, the analyses of the available atmospheric and oceanic angular momentum (AAM/OAM) functions indicate the significant amplitude of CW even after 2005, implying that the AAM/OAM functions are incomplete.

Ionospheric response to sudden stratospheric warming (SSW) are not well understood. During the 2013 SSW, ionospheric disturbances were observed in eighteen stations on three meridional chains of 100°E, 110°E and 120°E ranging from 19.03°N to 49.21°N at latitudes over East Asia region. The TEC response showed evident semi-diurnal disturbance that enhancement in the morning and depletion in the afternoon. The maximum TEC increased by more than 220% on the chain 120°E. In addition, the semi-diurnal disturbance of TEC were enhanced and indicated evident latitudinal and longitudinal dependence. The wavelet spectra of semi-diurnal disturbance in TEC presented quasi-16 day planetary wave-like oscillations at middle latitudes and quasi-10 day planetary wave-like oscillations at low latitudes. Meanwhile, the zonal winds and meridional winds at altitudes of 92-100 km showed quasi-16 day planetary wave at Mohe located middle latitude and quasi-10 day planetary wave at Sanya located low latitude, which are agree with semi-diurnal disturbance of TEC. Especially, the 12-hour component of TEC showed a quasi-16 day periodic component at middle latitude and a quasi-10 day periodic component at low latitude, indicating that the modulated semi-diurnal tides may transmit these 10 day and 16 day planetary wave-like oscillations to the ionosphere. The coupling between the atmosphere and ionosphere may be strengthened by the quasi-16 day waves at middle latitude and quasi-10 day waves at low latitude. This can further confirm the PW-tide interaction theory during the 2013 SSW and it is of significance in the middle and low latitude ionospheric response to SSW.

This paper examines the radar penetration into a rough soil surface with a vertical moisture profile. Numerical analysis shows that the penetration depth decreases exponentially with increasing frequency, and the difference between H- and V- polarization reduces. For the incident angle dependence, the variation of penetration depth is somehow complex. For incident angle larger than 20o, the penetration depth decreases at H polarization, but increases first and then decreases at V polarization. As for soil surface dependence, the topsoil moisture content has a greater impact on the penetration depth than the surface roughness. Of the two roughness parameters, the rms height has a more significant influence on the penetration depth than the correlation length. The dependence of penetration depth on the wave polarization moderates when the surface becomes rougher. Results suggest that the penetration depth is sensitive to the inhomogeneity of moisture profiles due to the temporal evaporation process, indicating that the penetration depth is difficult to measure and an equivalent model to estimate it may be inappropriate, or at least it is difficult to establish.

Quantification of river flow is a significant component of water resource management needed to develop infrastructure, prepare for drought or flood, and ensure equitable resource use. Yet, these data have often been deficient in rural regions generally dependent on smaller river systems, especially in low- and middle- income countries, and in places where no remote gaging capabilities currently exist. A relationship between river flow and width has been previously demonstrated in attempts to record and monitor flow with only satellite-based measurements; however, those methods have focused on rivers with a width of > 30m and have shown extreme errors when compared to historical gaging records. A new technique for monitoring river flow remotely is presented here, which uses Manning’s equation for open channel flow coupled with width measurements from satellites. This technique allows for the creation of a remotely-sensed historical river flow record and uses the minimum number of ground-based measurements for the calibration of Manning’s equation. Cross-river depth profile, discharge, and slope are necessary for initial calibration. This method used four-band satellite images with 3m-resolution for width measurements, with images being adjusted for the Normalized Difference Water Index (NDWI) for better delineation of the water’s edge. Buffalo Creek, in Freeport, Pennsylvania and the Mutale River, in the Limpopo Province of South Africa, were used as study locations. An estimation of flow at each site was obtained using every available satellite image of those transects. Preliminary results indicated successful calibration of Manning’s equation for the individual river transects, and verification of this method yielded flow estimation with an average of 74% error at Buffalo Creek and 48% error at the Mutale River, when compared to historical data from gages present near the study sites. The primary challenge of using this method on smaller rivers is the determination of width from the satellite images. Automated techniques to delineate the water’s edge are presented as recommendations to increase accuracy. This method may be used as an additional tool in river flow monitoring for water resource management.

A hybrid Linear Programming (LP) and Nonlinear Programming (NLP) optimization model is developed for California’s hydropower operations. Built on top of Pyomo library, a high optimization modeling language in Python, the model can connect to several freely available, state-of-the-art solvers. In this model, fast evaluation of LP and detailed model representation of NLP are fully utilized. The hybrid model solves the same problem with linear approximation (a simplified objective function representation) and with NLP solver, where no simplification is made to objective function. Outputs from LP model are used as initial values (warmstart) for NLP model’s decision variables, which reduce number of iterations for convergence and so runtime. The model is capable of representing large network of hydropower plants that are in serial or parallel, or fixed and variable head plants. The model is used to evaluate effects of increased solar photovoltaic (PV) generation in California. California has a goal of generating electricity from renewable resources at least 33% by 2020, and 50% by 2030, and solar PV generation supplies most of renewable generation portfolio during daytime. This expanded use of solar PV changes generation pattern from one daily peak system to two daily peak system. Due to excess generation of solar PV, negative prices can occur during daytime. Therefore, evaluating effects of solar PV on hydropower operations and adapting to new conditions are essential.

Based on a large database of Wideband Imaging Camera (WIC), which is a part of Far Ultraviolet (FUV) instrument, onboard the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite during 5 years between 2000 and 2005, we found a new morphological type of transpolar arcs (TPAs), which are identified as “nightside distorted TPAs”. The nightside ends of the dawnside (duskside) TPAs got distorted toward pre- (post-) midnight sector; These TPAs look like the shape of an alphabetical letter of “J” or “L”. We identified 17 nightside distorted TPAs from our database. The 12 events out of 17 nightside distorted TPA events were the dawnside TPA with the nightside end distorted toward the pre-midnight sector (“J”-shaped TPA), and the TPAs in the duskside, whose nightside parts got distorted toward the post-midnight sector, were found in the remnant 5 events (“L”-shaped TPA). Statistically, the nightside distorted TPAs can dominantly be found under the northward Interplanetary Magnetic Field (IMF) conditions. Furthermore, when the IMF-By component pointed to the dawnward (duskward) direction, the “J” (“L”)-shaped TPAs were dominantly observed, suggesting that the relation between the IMF-Bz and By orientations, and the locations of the nightside distorted TPAs is consistent with that between the IMF conditions and regular TPA previously reported. We also followed the time sequence of the nightside distorted TPA evolution with the IMAGE FUV-WIC imager and additional Polar UVI data. In most cases, the “J” and “L”-shaped TPAs started to grow from the nightside main auroral oval, and protruded to the dayside region with being distorted. In this presentation, we will introduce several selected cases of the nightside distorted TPA among our database, and discuss why and how the nightside end of the TPA became distorted toward pre- or post-midnight sectors based on the in-situ satellite nightside plasma sheet observations and the electron drift velocity distribution calculated utilizing a simple electromagnetic field model in magnetotail, together with the auroral imager data.

Mangrove forests, occupying tropical and subtropical coastal areas, serve as coast protector, water filter, spot of attraction and an exceptional carbon reservoir. Despite these extraordinary ecological and economic functions, our understanding of the mangroves is limited because field survey is hard to conduct in the intertidal mangrove habitats. While satellite remote sensing provides good spatial and temporal coverages globally, data availability at the tropical latitudes is limited due to frequent cloud contamination. The quickly emerging unmanned aerial vehicle (UAV) technique enables data collection under almost all weather conditions, thus provides new opportunities. By mounting light detection and ranging (LiDAR) sensors on UAVs, the 3D structure of mangroves can be accurately characterized even at individual tree level. The basic tree parameters such as tree height and crown size can be easily extracted, which then enables the estimation of biomass, carbon stock and other important ecological indices. This study uses high density (>100 pt/m2) UAV-LiDAR data collected at four consecutive years to detect the growth rate and pattern of mangroves. The change detection is done at individual tree level. The dependence of mangrove growth pattern on tree species and clumpingness are analyzed. The output will allow scientists and environment managers to know mangroves better and to manage them effectively and efficiently.

Land use/land cover (LULC) change could adversely affect watershed health by elevating nutrients and sediment levels and intensifying the risk of flooding. In this study, a spatially-explicit LULC change modeling framework was coupled with the Chesapeake Bay Watershed Model (CBWM) to investigate the impact of LULC change on nutrients (total nitrogen and total phosphorous), sediment and runoff volume in the watersheds surrounding Virginia’s Shenandoah National Park, U.S. Four stakeholder-informed scenarios alongside a Recent Trends LULC change scenario were studied. The stakeholder-informed LULC change scenarios, which differed in consideration of future planning and population growth, were developed through several meetings with stakeholders. To develop the Recent Trends, the historical LULC trend from 2001 to 2011 was analyzed. Using 2011 as a baseline scenario, the spatio-temporal patterns of LULC change were estimated as influenced by physiographic and socio-economic drivers 50 years in the future (2061). The projected LULCs were fed into the CBWM to predict the change in average annual loading of nutrients, sediment and runoff volume. While the changes in loads at the full study area were not substantial (< 0.9%), changes became more pronounced at finer spatial scales. Expectedly, the LULC change scenario with ad-hoc planning and high population growth resulted in the largest increase in runoff volume. However, the scenario with ad-hoc planning and low population growth showed the largest increase in the simulated pollutants. This was because while this scenario projected less development, it projected more increases in agricultural LULCs that export more nutrients and sediment than other changing LULCs. This implied that sole land use planning based on urban development is not sufficient for watershed protection and agricultural LULCs need to be incorporated in concert in our future planning. This further suggested that land use planning plays a more critical role than population growth rate in water quality management. The results have implications for the Chesapeake Bay total maximum daily load and could help well-informed future land use planning and watershed protection by incorporating the impact of future LULC change on water quality and quantity.

The International Satellite Cloud Climatology Project (ISCCP)’s Convection Tracking (CT) database was designed to track the evolution of deep convective cloud systems throughout their life cycle. The database is produced in 3 steps. The first step determines whether a particular image pixel is cloudy and determines the cloud top temperature and optical thickness. The second step clusters up all adjacent cold IR pixels with brightness temperature (TBIR)< 245 K and stores the summary information about cloud structural and radiative properties. Such clusters are referred to as Convective Systems (CSs). A further test identifies Convective Clusters (CCs) as adjacent cloud pixels with TBIR < 220 K. The third step tracks each individual CS over time to form families and produces the CT database. Previous version of the CT data covered the period from 1983-2008 and treated one geostationary satellite at a time. Recently, we started producing a new version of CT data that are built upon the new, H-version ISCCP data (HXG). Improvements from this new CT data include: 1) globally uniform coverage, 2) higher spatial sampling/resolution (from 30 km down to 10 km), and 3) longer data record (1983-2015). This presentation will introduce the new ISCCP CT database and show some preliminary results including comparison with the old CT data and some essential global statistics of deep convective cloud systems.

Large increases in joint heat-humidity extremes are a robust feature of climate projections, more so than increases in either variable independently. The wet-bulb temperature threshold of 35°C is considered particularly important, corresponding to the level at which it is impossible for the human body to maintain homeostasis. Our analysis of more than 7500 global weather stations from HadISD reveals that instances of 35°C have already been briefly but reliably recorded in some cities of the coastal Middle East. Additionally, South Asia and coastal areas throughout the subtropics regularly experience values perilously close to this threshold. Station and ERA-Interim reanalysis data both indicate that the most extreme heat-humidity combinations have increased significantly over the 1979-2017 period. We develop and employ a generalized-extreme-value model to estimate that the 30-year return value of global-maximum wet-bulb temperature at ERA-Interim resolution will exceed 35°C when global-mean temperature has risen between 1.5°C and 2.0°C above the pre-industrial, masking even higher values at smaller spatial scales. The occurrence in the coming decades of such severe heat and humidity over large populated regions represents a situation never before experienced. We also present observational evidence that these wet-bulb temperature extremes are fostered by locally high SSTs as well as modulated by regional dynamics such as monsoons. Large-scale climate modes of variability, such as ENSO, lead to highly correlated interannual variability between the number of global exceedances of different wet-bulb temperature thresholds. Overall, our results show that the wet-bulb temperature ‘safety margin’ between currently reported values and 35°C is both smaller than previously understood and rapidly shrinking, presenting a serious challenge to human survival in the hottest and most humid places on Earth.

How does climate change affect the production of native Grains of America? There is an impact of climate change on rain-fed crops productivity and its association with alimentary security. This study analyzes how events such as global warming, unsustainable agriculture or intense droughts caused by lack of water, affects the production of quinoa in Bolivia and maize in Mexico. Our estimates suggest that climate variability will modify agriculture yields (of maize and quinoa) per hectare depending on the agricultural season, the municipality and the ensemble model used to project climate change scenarios. The study indicates tremendous heterogeneity in areas and regionally. Based on the cobweb phenomena approach, it is suggested that the producers base their decisions for their future production on the assumption that present prices will continue. If this is not the case, rigid price expectations may produce irreversible supply conditions in the short run. These prices are set by the available supply of the grains. Their production is completely determined by the producers’ response to price, under conditions of pure competition.

The Coastal Range in the Mediterranean segment of Chile is a soil mantled landscape with potential to store valuable supplies of fresh water and support a biodiverse native forest. Nevertheless, human intervention has been increasing soil erosion for ~ 200 yr, with  intensive management of exotic tree plantations during the last ~ 45 yr. At the same time, this landscape has been affected by a prolonged megadrought, and is not yet well understood how the combined effect of anthropogenic disturbances and hydrometeorologic trends affect sediment transport at the catchment scale.In this study we calculate a decadal-scale catchment erosion rate from suspended sediment loads and compare it with a 104-year-scale catchment denudation rate estimated from detritic 10Be. We then contrast these rates against the effects of discrete anthropogenic disturbances and hydroclimatic trends. Erosion/denudation rates are similar on both time scales, i.e. 0.018 ± 0.005 mm/yr and 0.024 ± 0.004 mm/yr, respectively. Recent human-made disturbances include logging operations during each season and a dense network of forestry roads, which increase structural sediment connectivity. Other disturbances include two widespread wildfires (2015 and 2017) and one Mw 8.8 earthquake (2010).We observe a decrease in suspended sediment load during the wet seasons for the period 1986-2018 coinciding with declines in streamflow, baseflow and rainfall. The low 104-year denudation rate agrees with a landscape dominated by slow diffusive soil creep. However, the low 10-year-scale erosion rate and the decrease in suspended sediments are not in agreement with the expected effect of intensive anthropogenic disturbances and increased structural (sediment) connectivity. These paradox suggest that, either suspended sediment loads and, thus, catchment erosion, are underestimated, and/or that decennial sediment detachment and transport were smeared by decreasing rainfall and streamflow. Our findings indicate that human-made disturbances and hydrometeorologic trends may result in opposite, partially offsetting effects on recent erosion, but both contribute to the landscape degradation.

Over 33,000 flash flood events recorded by the NOAA National Weather Service (NWS) between 2006 and 2017, after polygon warnings replaced county-wide warnings, are analyzed in terms of NEXRAD (Next Generation Weather Radar) radar coverage in two ways. Events are binned in two large categories according to whether the starting point of an event falls inside or outside the range implied by the 6 kft AGL bottom-of-the-beam altitude, accounting for beam clutter and beam obstructions. Separately, events are classified according to the percentage surface area covered under the 6 kft beam height for each NWS Weather Forecast Office (WFO) or state. Emphasis is on unwarned events associated with fatalities, injuries and property damage and their relationship to WFO-area NEXRAD coverage. Significant property damage is defined in terms of the mean damage per event of about $411k. There is parity in the ratio of events warned or unwarned inside the inside/outside distance bins except for injury-event ratios. The linear fits to the traditional metrics of warned ratio (WR), false alarm ratio (FAR) and critical success index (CSI) are statistically significant and improve with more radar coverage. A stronger sensitivity is found for the WR as a function of the total number of events. New metrics are also evaluated, such as the mean flash flood partial event warning (PEW) and the ratios of unwarned to all events per WFO have statistically significant variations with radar coverage, improving with higher coverage. This is unlike the linear fits to the ratios of unwarned fatal-to-all-fatal events, which is marginally significant. Unwarned fatal-to-all-fatal, unwarned injury-to-all events and unwarned significant damage-to-nonzero damage event ratios are both not statistically significant to the 95% level of significance. The large scatter in the data results in very low coefficients of determination, and is interpreted to mean that radar coverage alone is not necessarily the primary driver though there is sensitivity to variations in such coverage.

The lunar surface consists of a regolith layer, i.e., fragmental and unconsolidated rock material of highly varied character, which covers the underlying bedrock. Understanding the structure and composition of the lunar regolith and the underlying bedrock is very important to reveal geologic features of the Moon, explore natural resources humans can exploit, and obtain valuable information regarding the history of the solar system. Electromagnetic radiations from the surface of the Moon at microwave frequencies depends on the physical, chemical, and electrical properties of the regolith layer and the bedrock. Moreover, the electromagnetic penetration depth changes with frequency which allows wideband microwave radiometers operating below 50 GHz to conveniently profile these properties versus depth to characterize the lunar regolith and bedrock with wide spatial coverage. Combining current models of depth-dependent physical and chemical properties with simple electromagnetic forward radiation models, surface emissions over the Apollo sites were simulated and compared with Chinese Chang’E-1 and Chang’E-2 multi-frequency microwave radiometer measurements. Potential sources of the differences between the simulations and measurements have been identified as the temperature dependence of the electrical properties of the regolith, bedrock type, surface and bedrock roughness, as well as density fluctuations, scattering due to inhomogeneities, and coherent interference of electromagnetic fields within the regolith. However, many of these subjects have been studied thoroughly for the remote sensing of the cryosphere; thus leveraging this experience with the rapid developments in radiometer designs, wideband microwave radiometers promise valuable scientific returns in future lunar missions.

Dense polymorphs of silica have been demonstrated experimentally to incorporate from 1.5% to as much as 11.6% weight percent H2O as OH groups, with implications for the hydrogen budgets of Earth and other planets. This OH is thought to enter the SiO2 structure via a charge-balanced substitution in which silicon vacancies (VSi) are compensated by protonating four of the surrounding six oxygen atoms, often referred to as a hydrogarnet-type defect. There are many possible configurations for this defect structure in dense silica, but the nature of these configurations and whether they can be distinguished experimentally is unknown. We present here density functional theory (DFT) calculations that systematically assess the possible configurations of a hydrogarnet-type defect in stishovite (rutile-type SiO2), with direct comparisons to experimental vibrational spectroscopy data. We predict that stishovite synthesized at 450 K and 10 GPa quenched to room temperature is dominated by a single defect type with tetrahedral geometry. This leads to OH stretching modes (2500-3000 cm-1) and SiOH bending modes (~1400 to 1450 cm-1) largely consistent with experimentally observed modes. One remaining issue is that our calculations produce results compatible with experimental data on H to D exchange, but do not explain why a considerable fraction of the 1420 cm-1 mode shifts by only 40 cm-1 in deuterated samples. At elevated pressures and temperatures, we find that a second square planar defect configuration also becomes favorable, leading to modes that should allow differentiation from the tetrahedral configuration.

Index Terms: 1622: Earth system modeling; 1630: Land/atmosphere interactions; 1800: Hydrology; 1836 Hydrological cycles and budgets; 1840 Hydrometeorology; 1855: Remote sensing; 1996 Web Services; 4305: Space weather; 6334: Regional Planning This work addresses a key objective of SERVIR-Mekong Project related to integrating geospatial information in government decision-making, planning, and communication for societal good. The SERVIR-Mekong is a partnership between the U.S. Agency for International Development (USAID) and the U.S. National Aeronautics and Space Agency (NASA) formed to help regional organizations in the Lower Mekong Region to use information provided by Earth observing satellites and geospatial technologies in managing climate risks. Our work integrated multiple satellite-based earth observation systems, in-situ station data and spatial data with the Soil & Water Assessment Tool (SWAT) hydrologic model employed in the Mekong River Basin region to develop a Lower Mekong River Basin region’s hydrological decision support system. Simulated hydrological fluxes of streamflow, soil moisture, and evapotranspiration at the Lower Mekong River Basin were presented utilizing our developed hydrological decision support system. Our work results have been presented via multiple Tethys platforms, Tethys is an easily customizable platform that hosts web applications, that facilitate accessing NASA satellite-based earth observation systems as well as the Lower Mekong River Basin region’s hydrological decision support system. Earth observations data has provided solutions to assist people in the Lower Mekong River Basin to overcome various obstacles experienced in enhancing hydrological decisions that are related to difficult access and incompleteness, inconsistency, scarcity, as well as poor spatial representation of in situ data products.

We attempt, for the first time, to estimate the surface carbon flux by the method of automatic differentiation. The atmospheric transport model is developed using a deep learning framework and is validated against standard approaches. Depends on the built-in automatic differentiation feature of the deep learning framework, the system derivatives/gradients are readily available without any extra effort. We then formulate the surface carbon flux estimation as an inverse problem using the variational approach, driven by back-propagated objective gradients. The feasibility of the automatic differentiation method is demonstrated in identical-twin observing system simulation experiments (OSSEs). The proposed framework shows favorable accuracy and great efficiency in both fully and partially observable scenarios. The present study establishes a link between machine learning frameworks and general data assimilation or inverse modeling problems, and the promising results encourage more investigations in incorporating machine learning techniques in inverse carbon modeling.

Spacecraft charge mitigation is critical for a host of space plasma measurement techniques. However, charge mitigation in tenuous space plasmas can be a difficult problem. It is especially difficult and essential during active experiments that feature ion or electron beams, as collection from the ambient plasma is often insufficient to balance the beam emission current. For electron emission experiments, the use of a plasma contactor that emits an ionized gas is the only practical option. A series of parametric chamber experiments were completed to address how spacecraft charge mitigation using a plasma contactor may scale in tenuous space plasmas. Experiments focus on how spacecraft potential scales with beam emission current, contactor current (the rate at which the contactor generates quasi-neutral plasma), and contactor expellant mass (ion mass). These experimental results are compared to scaling laws derived via Curvilinear Particle-In-Cell (CPIC) simulations for further validation and physical insights. Implications for improving space plasma measurements and enabling future active experiments such as the Connections Explorer (CONNEX) mission are discussed.