Adjusting for desert-dust-related biases in a climate data record of sea surface temperature

Atmospheric desert-dust aerosol, primarily from north Africa, causes negative biases in remotely sensed climate data records of sea surface temperature (SST). Here, large-scale bias adjustments are deduced and applied to the v2 climate data record of SST from the European Space Agency Climate Change Initiative (CCI). Unlike SST from infrared sensors, SST measured in situ is not prone to desert-dust bias. An in-situ-based SST analysis is combined with column dust mass from the Modern-Era Retrospective analysis for Research and Applications, Version 2 to deduce a monthly, large-scale adjustment to CCI analysis SSTs. Having reduced the dust-related biases, a further correction for some periods of anomalous satellite calibration is also derived. The corrections will increase the usability of the v2 CCI SST record for oceanographic and climate applications, such as understanding the role of Arabian Sea SSTs in the Indian monsoon. The corrections will also pave the way for a v3 climate data record with improved error characteristics with respect to atmospheric dust aerosol

Pixel centroid characterization with laser speckle and application to the Nancy Grace Roman Space Telescope detector arrays

The Nancy Grace Roman Space Telescope will use its wide-field instrument to carry out a suite of sky surveys in the near infrared. Several of the science objectives of these surveys, such as the measurement of the growth of cosmic structure using weak gravitational lensing, require exquisite control of instrument-related distortions of the images of astronomical objects. Roman will fly 4kx4k Teledyne H4RG-10 infrared detector arrays. This paper investigates whether the pixel centroids are located on a regular grid by projecting laser speckle patterns through a double slit aperture onto a non-flight detector array. We develop a method to reconstruct the pixel centroid offsets from the stochastic speckle pattern. Due to the orientation of the test setup, only x-offsets are measured here. We test the method both on simulations, and by injecting artificial offsets into the real images. We use cross-correlations of the reconstructions from different speckle realizations to determine how much of the variance in the pixel offset maps is signal (fixed to the detector) and how much is noise. After performing this reconstruction on 64x64 pixel patches, and fitting out the best-fit linear mapping from pixel index to position, we find that there are residual centroid offsets in the x (column) direction from a regular grid of 0.0107 pixels RMS (excluding shifts of an entire row relative to another, which our speckle patterns cannot constrain). This decreases to 0.0097 pix RMS if we consider residuals from a quadratic rather than linear mapping. These RMS offsets include both the physical pixel offsets, as well as any apparent offsets due to cross-talk and remaining systematic errors in the reconstruction. We comment on the advantages and disadvantages of speckle scene measurements as a tool for characterizing the pixel-level behavior in astronomical detectors.Comment: 24 pages, 9 figures, to be submitted to PAS

Eliminating bias in satellite retrievals of sea surface temperature

Sea surface temperature (SST) is a critical parameter for climate research, and needs to be measured with an absolute accuracy of ~0.3 K (average over ~100 km scale on a weekly to monthly time scale) and with a long term stability of 0.1 K per decade. These stringent requirements present a formidable challenge to satellite based SST measurement. The most promising satellite radiometer is the ATSR (and successors), but bias and spurious trends have arisen in the ATSR SST retrieval process. Eliminating such retrieval bias is the focus of this thesis. SSTs derived from the ATSR using the prelaunch retrieval scheme are biased by up to -1.5 K by stratospheric aerosol from the eruption of Mount Pinatubo shortly before launch. An "aerosol-robust" retrieval scheme is derived which has no detectable aerosol- related bias. Another bias of up to 0.5 K arising from a deficiency of the radiative transfer model used to develop the prelaunch retrieval scheme is resolved by implementing an updated parameterisation of water vapour continuum absorption. The new SSTs are shown to have an accuracy better than 0.3 K (error in a single retrieval over a -20 km spatial scale) and to be robust to aerosol effects, by a validation exercise against buoys measuring SST in situ. The validation data consist of 620 satellite-buoy coincidences in the tropical Pacific between September 1991 and May 1992, a region and period associated with high loadings of stratospheric aerosol and tropospheric water vapour. This is the first validation exercise to correct for the effects of the difference between bulk SSTs (measured by buoys) and skin SSTs (measured radiometrically). The factor now limiting accuracy is residual cloud contamination. The new retrieval scheme has been adopted for the reprocessing of all archived ATSR data to SST

Current and Shot Noise Measurements in a Carbon Nanotube-Based Spin Diode

Low-temperature measurements of asymmetric carbon nanotube (CNT) quantum dots are reported. The CNTs are end-contacted with one ferromagnetic and one normal-metal electrode. The measurements show a spin-dependent rectification of the current caused by the asymmetry of the device. This rectification occurs for gate voltages for which the normal-metal lead is resonant with a level of the quantum dot. At the gate voltages at which the current is at the maximum current, a significant decrease in the current shot noise is observed

Effects of Diffusion on Photocurrent Generation in Single-Walled Carbon Nanotube Films

We have studied photocurrent generation in large carbon nanotube (CNT) films using electrodes with different spacings. We observe that the photocurrent depends strongly on the position of illumination, with maximum observed response occurring upon illumination at the electrode edges. The rate of change of the response decays exponentially, with the fastest response occurring for samples with the smallest electrode spacing. We show that the time response is due to charge carrier diffusion in low-mobility CNT films

The effects of emerging adulthood on stress and depression

Many historical theories of development have evolved based on the premise that a person\u27s identity is formed during adolescence. Upon reaching the age of 18, that person is identified as an adult and expected to have achieved a healthy identity. More recent studies suggest that a person continues to develop their identity well into their twenties. This age range is characterized by constant change, instability, and exposure to life stress events. Additional data shows that some people in this cohort do not consider themselves to be an adult, a se if-classification that creates stress and decreased mental health. Researchers are now considering this age range to be an extended period of development termed emerging adulthood. Individuals who perceive themselves to still be developing during this stage (perceived emerging adults) are at higher risk of identity crisis, stress levels, and depression. In order to advance interventions and treatment plans for individuals in this cohort, it is important to understand the impact that this developmental period has on stress and depression. The purpose of this thesis was to investigate the impact that perceived emerging adult status had on mental health. Fifty adults (age 18-25) were surveyed on self-classification as an adult, life stress events, identity status, and depressive symptoms. It was found that there was a significant relationship between perceived adult status and certain life events, such as having children, being married, or living outside the parents \u27 home. No significant relationship was found between emerging adult status and identity status. Additionally, it was found that age and life stress was negatively correlated for emerging adults but not for perceived adults, indicating that life stress eased with age. Finally, for emerging adults but not perceived adults, stress level was positively correlated with depression

Worldwide alteration of lake mixing regimes in response to climate change

Lakes hold much of Earth’s accessible liquid freshwater, support biodiversity and provide key ecosystem services to people around the world. However, they are vulnerable to climate change, for example through shorter durations of ice cover, or through rising lake surface temperatures. Here we use a one-dimensional numerical lake model to assess climate change impacts on mixing regimes in 635 lakes worldwide. We run the lake model with input data from four state-of-the-art model projections of twenty-first-century climate under two emissions scenarios. Under the scenario with higher emissions (Representative Concentration Pathway 6.0), many lakes are projected to have reduced ice cover; about one-quarter of seasonally ice-covered lakes are projected to be permanently ice-free by 2080–2100. Surface waters are projected to warm, with a median warming across lakes of about 2.5 °C, and the most extreme warming about 5.5 °C. Our simulations suggest that around 100 of the stud- ied lakes are projected to undergo changes in their mixing regimes. About one-quarter of these 100 lakes are currently clas- sified as monomictic—undergoing one mixing event in most years— and will become permanently stratified systems. About one-sixth of these are currently dimictic—mixing twice per year—and will become monomictic. We conclude that many lakes will mix less frequently in response to climate change

Datasets related to in-land water for limnology and remote sensing applications: distance-to-land, distance-to-water, water-body identifier and lake-centre co-ordinates

Datasets containing information to locate and identify water bodies have been generated from data locating static-water-bodies with resolution of about 300 m (1/360 deg) recently released by the Land Cover Climate Change Initiative (LC CCI) of the European Space Agency. The LC CCI water-bodies dataset has been obtained from multi-temporal metrics based on time series of the backscattered intensity recorded by ASAR on Envisat between 2005 and 2010. The new derived datasets provide coherently: distance to land, distance to water, water-body identifiers and lake-centre locations. The water-body identifier dataset locates the water bodies assigning the identifiers of the Global Lakes and Wetlands Database (GLWD), and lake centres are defined for in-land waters for which GLWD IDs were determined. The new datasets therefore link recent lake/reservoir/wetlands extent to the GLWD, together with a set of coordinates which locates unambiguously the water bodies in the database. Information on distance-to-land for each water cell and the distance-to-water for each land cell has many potential applications in remote sensing, where the applicability of geophysical retrieval algorithms may be affected by the presence of water or land within a satellite field of view (image pixel). During the generation and validation of the datasets some limitations of the GLWD database and of the LC CCI water-bodies mask have been found. Some examples of the inaccuracies/limitations are presented and discussed. Temporal change in water-body extent is common. Future versions of the LC CCI dataset are planned to represent temporal variation, and this will permit these derived datasets to be updated

Literature Review on Aquaponics as Commercial Food Production and suggestions for improvements to the Matthaei Aquaponics system

This paper is a review of the body of literature related to the implementation of commercial aquaponics. This review was conducted after issues with an experimental aquaponics system developed into an interest in the relationship between the issues identified with the aquaponics system in the experiment and the issues identified with commercial aquaponics in the literature in the literature. Previous research on the development and commercialization of aquaponics does exists and overs a diversity of topics. This research is gaining in its importance as the FAO has identified a need to improve the sustainability of the methods used to produce fish products. Commercial aquaponics if developed properly could fill this need in the food system. In this analysis the review was conducted using Citation Network Explorer and Visualization of Similarities Viewer which allowed the researchers to narrow in on the literature within the aquaponics field specifically focused on commercial aquaponics systems. It was found that there is broad coverage of the issues related to commercial aquaponics; however, the technology remains complex and expensive, there is little cross pollination of research within the field focused on commercialization, and there is a lack of understanding of both consumer and producer priorities which limits the applicability of the system designs in the food system. Developing solutions aimed at reducing the complexity and costs of commercial systems, integrating research from all of the identified areas of interest, and identifying consumer and producer priorities could be used to develop more appropriate system designs, increase ethe adoption of commercial aquaponics, and increase the resilience of the production systems.Master of ScienceSchool for Environment and SustainabilityUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/167261/1/Merchant_Christopher_Practicum.pd