By Mahta Moghaddam et al.
Although multiple efforts have been made to model global navigation satellite system (GNSS)-reflectometry (GNSS-R) delay-Doppler maps (DDMs) over land, there is still a need for models that better represent the signals over land and can enable reliable retrievals of the geophysical variables. Our paper presents improvements to an existing GNSS-R DDM model by accounting for short-wave diffraction due to small-scale ground surface roughness and signal attenuation due to vegetation. This is a step forward in increasing the model fidelity. Our model, called the improved geometric optics with topography (IGOT), predicts GNSS-R DDM over land for the purpose of retrieving geophysical parameters, including soil moisture. Validation of the model is carried out using DDMs from the Cyclone GNSS (CYGNSS) mission over two validation sites with in situ soil moisture sensors: Walnut Gulch, AZ, USA, and the Jornada Experimental Range, NM, USA. Both the peak reflectivity and the DDM shape are studied. The results of the study show that the IGOT model is able to accurately predict CYGNSS DDMs at these two validation sites.
By Mahta Moghaddam et al.
IEEE Antennas and Wireless Propagation Letters
2023
A new quad-band tapered patch transmit-receive antenna array designed for a multistatic microwave imaging cavity system is presented. The reverberating cube-shaped chamber is filled with a matching fluid emulsion and encompasses 64 antenna elements mounted on its sidewalls (16 per panel). Four resonant frequencies that lie in the range of 0.5−3 GHz are achieved. The design procedure is provided based on system constraints and performance requirements that need to be taken into account: (1) the near-field nature of the electromagnetic wave in the presence of a shielded chamber and (2) the propagation of waves into the immersion fluid within the imaging domain. The antenna array design was numerically verified, and its prototype was fabricated. Results show good agreement between measurements and simulations, achieving antenna system performance requirements.
By Mahta Moghaddam et al.
Journal of Spacecraft and Rockets
2023
In early satellite mission design, requirements are not yet fixed, cost is sometimes negotiable, and designs are relatively unconstrained. During this period of design freedom, multi-objective optimization can provide a useful lens into the design space by showing theoretical performance limits and illuminating design tradeoffs. This work optimizes a radar constellation for a potential soil moisture mission. Several different optimization cases with different variables are considered and contrasted. The optimization of the instrument and constellation parameters is considered jointly and separately to better understand the effect of coupling on the optimization performance. A science-driven optimization based on soil moisture retrieval error is compared with a performance-metric-driven optimization. Pareto analysis and association rule mining are performed on the generated designs to provide insight into driving features. Design recommendations are made for several cost caps. Results show that optimization that considers the instrument and constellation design together find superior revisit metrics than treating instrument and constellation separately. The use of the science value metric as an optimization objective shows that while cost may always be increased to improve instrument and constellation performance, the difference in science value may be negligible. These findings can inform tradespace exploration studies for similar problems.
By Mahta Moghaddam et al.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
2023
Surface soil organic carbon (SOC) content is among the first-order controls on the rate and extent of Arctic permafrost thaw. There is a large discrepancy in current SOC estimates in Arctic tundra, where sparse measurements are unable to capture SOC complexity over the vast tundra region. Synthetic aperture radar (SAR) data are sensitive to surface vegetation, roughness, and moisture conditions, and may provide useful information on surface SOC properties. Here, we investigated the potential of multitemporal Sentinel-1 C-band SAR data for regional SOC mapping in the Arctic tundra through principal component analysis (PCA). Multiple in situ SOC datasets in the Alaska North Slope were assembled to generate a consistent surface (0–10 cm) SOC and bulk density dataset ( n = 97). The radar VV backscatter shows a strong correlation with surface SOC, but the correlation varies greatly with surface snow, moisture, and freeze/thaw conditions. However, the first principal component (PC1) of radar backscatter time series from different years shows spatial consistency representing dominant and persistent surface backscatter behavior. The PC1 also shows a strong linear correlation with surface SOC concentration ( R = 0.65, p <0.01), and an exponential relationship with bulk density ( R = −0.65, p <0.01). The resulting predicted SOC maps show much lower soil bulk density and higher SOC concentration in the southern shrub tundra area than in the northern coastal region, consistent with in situ data. Our analysis shows that it is possible to separate the effects of different factors on the radar backscatter response using PCA and multitemporal SAR data, which may lead to more effective satellite-based methods for Arctic SOC mapping.
By Burcin Becerik-Gerber et al.
Building and Environment
2023
We regularly face stress during our everyday activities, to the extent that stress is recognized by the World Health Organization as the epidemic of the 21st century. Stress is how humans respond physically and psychologically to adjustments, experiences, conditions, and circumstances in their lives. While there are many reasons for stress, work and job pressure remain the main cause. Thus, companies are increasingly interested in creating healthier, more comfortable, and stress-free offices for their workers. The indoor environment can induce environmental stress when it cannot satisfy the individual needs for health and comfort. In fact, office environmental conditions (e.g., thermal, and indoor air conditions, lighting, and noise) and interior design parameters (e.g., office layout, colors, furniture, access to views, distance to window, personal control and biophilic design) have been found to affect office workers’ stress levels. A line of research based on the stress recovery theory offers new insights for establishing offices that limit environmental stress and help with work stress recovery. To that end, this paper answers ten questions that explore the relation between the indoor office-built environment and stress levels among workers. The answers to the ten questions are based on an extensive literature review to draw conclusions from what has been achieved to date. Thus, this study presents a foundation for future environmental stress related research in offices.
By Wändi Bruine de Bruine et al.
American Journal of Preventive Medicine
2023
Food insecurity affects 1 in 10 Americans in a typical year; recent U.S. Department of Agriculture data show that this food insecurity rate was stable from 2019 to 2021. However, data from Los Angeles County and other U.S. regions show that food insecurity spiked during the early months of the COVID-19 pandemic. One reason for this discrepancy may be that food insecurity measures assess experiences over different time frames. This study investigated the discrepancies in food insecurity rates by comparing past-week and past-year food insecurity measures and explored the role of recall bias.
By Wändi Bruine de Bruine et al.
Environmental Science and Technology
2023
Water safety refers to the quality of one’s drinking water and whether it lacks dangerous contaminants. Limited access to safe water is projected to impact approximately 5 billion people worldwide by 2050. Climate change and worsening severe weather events pose increasing threats to global water safety. However, people may not perceive links between climate change and water safety, potentially undermining their willingness to implement behaviors that improve water safety. Existing studies on water safety risk perceptions have mostly been conducted in single-country contexts, which limits researchers’ ability to make cross-national comparisons. Here, we assessed the extent to which people’s severe weather concern and climate change concern predict their water safety concern. Our analyses used survey data from the 142-country 2019 Lloyd’s Register Foundation World Risk Poll, including 21 low-income and 34 lower-middle-income countries. In mixed-effects models, severe weather concern was significantly more predictive of water safety concern than was climate change concern, although both resulted in positive associations. Worldwide, this finding was robust, insensitive to key model specifications and countries’ varying protection against unsafe drinking water. We suggest communicators and policymakers improve messaging about water safety and other environmental threats by explaining how they are impacted by worsening severe weather.
By Rob McConnell et al.
Science of the Total Environment
2023
Higher ambient temperature and air pollution may contribute to increased risk of behaviors harmful to oneself or to others; however, quantitative evidence is limited. We examined the relationship of deaths due to suicide and homicide with temperature and air pollution in California—a state prone to high levels of both exposures.
