New developments in the representation of Saharan dust sources in the aerosol–climate model ECHAM6-HAM2

In the aerosol–climate model ECHAM6-HAM2, dust source activation (DSA) observations from Meteosat Second Generation (MSG) satellite are proposed to replace the original source area parameterization over the Sahara Desert. The new setup is tested in nudged simulations for the period 2007 to 2008. The evaluation is based on comparisons to dust emission events inferred from MSG dust index imagery, Aerosol Robotic Network (AERONET) sun photometer observations, and satellite retrievals of aerosol optical thickness (AOT).<br><br>The model results agree well with AERONET measurements especially in terms of seasonal variability, and a good spatial correlation was found between model results and MSG-SEVIRI (Spinning-Enhanced Visible and InfraRed Imager) dust AOT as well as Multi-angle Imaging SpectroRadiometer (MISR) AOT. ECHAM6-HAM2 computes a more realistic geographical distribution and up to 20 % higher annual Saharan dust emissions, using the MSG-based source map. The representation of dust AOT is partly improved in the southern Sahara and Sahel. In addition, the spatial variability is increased towards a better agreement with observations depending on the season. Thus, using the MSG DSA map can help to circumvent the issue of uncertain soil input parameters.<br><br>An important issue remains the need to improve the model representation of moist convection and stable nighttime conditions. Compared to sub-daily DSA information from MSG-SEVIRI and results from a regional model, ECHAM6-HAM2 notably underestimates the important fraction of morning dust events by the breakdown of the nocturnal low-level jet, while a major contribution is from afternoon-to-evening emissions

Does STEM Integration in High School Mathematics Classes in Underserved Schools Benefit Students\u27 Standardized Testing Outcomes?

STEM education in Indiana has become increasingly popular with, among many other factors, the recent focus by the Indiana Department of Education on the STEM workforce pipeline and school STEM certification (IDoE, 2023b). Some previous research has shown that integrating STEM into science classes and afterschool spaces has helped students from low-income communities catch up to their higher-income peers on assessments like high-stakes standardized testing (Bartell et al., 2008; Hurley, 2001; Weissglass, 2011). However, regarding STEM integration into mathematics classes, it can be more challenging than integration into other classes like science (Walker, 2016) and large gaps remain in the research of STEM integration into mathematics courses (English, 2016) . This study looks specifically at high school mathematics classrooms in a low-income community in Indiana. Mathematics-focused lessons with varying degrees of STEM components integrated were taught an average of one lesson every two weeks over an entire school year in a 9th grade Algebra classroom. Pre- and post- ACT Aspire scores were analyzed for growth, comparing students who received the STEM-integrated mathematics lessons and students who took the same course at the same school but received traditional, non-STEM mathematics courses. While the students who received the STEM integration improved on the ACT Aspire at a higher rate than the other students, the growth was not statistically significant. This study ends with suggestions for improving the methods for this specific study and other next steps in investigating the benefits of STEM integration in mathematics courses in schools from underserved communities

Field lab: equity research on Adidas AG

Despite significant increases of Adidas’ share price throughout the past years, the following report concludes that the stock is still undervalued. Based on an extensive analysis of Adidas’ past performance and actions, the company’s position within the industry, as well as current industry trends, the report concludes that Adidas is well set for the future with revenues that are expected to increase with a CAGR of 7.0% until 2025. The main drivers are the expansion of middle-class population in Asian economies, a shift towards more sustainable sportswear products, and increasing sports participation globally

Cannabis sativa L.

https://thekeep.eiu.edu/herbarium_specimens_byname/19997/thumbnail.jp

Uniformity correction for a scanned long wavelength infrared focal plane array

This paper presents an alternative approach in providing uniformity correction for an infrared focal plane array by utilizing analog MOSFET circuitry. This technology is compatible with modern VLSI production and is capable of enhanced operation at cryogenic temperatures. The method presented here is a potential contribution to the growing list of special analog circuit configurations which may be incorporated for on-chip signal processing, inside the cryogenic dewar assembly. Electronic packaging of current thermal systems could be significantly reduced in size and weight by trading some of the cumbersome digital algorithms and complex post-processing circuitry for implementation in VLSI form. The proposed method employs capacitor storage of the thermal reference voltages to correct for the Responsivity and Bias of each detector channel. This compensation for gain and level can be achieved in real operating time using a background subtraction technique and feedback which features pulse-width modulation of the detector\u27s elemental integration period

Orographic Effects and Evaporative Cooling along a Subtropical Cold Front: The Case of the Spectacular Saharan Dust Outbreak of March 2004

On 2 March 2004 a marked upper-level trough and an associated surface cold front penetrated into the Sahara. High winds along and behind this frontal system led to an extraordinary, large-scale, and long-lived dust out reak, accompanied by significant precipitation over parts of Algeria, Tunisia, and Libya. This paper uses sensitivity simulations with the limited-area model developed by the Consortium for Small-Scale Modeling (COSMO) together with analysis data and surface observations to test several hypotheses on the dynamics of this case proposedin previous work. It is demonstrated that air over central Algeria is cooled by evaporation of frontal precipitation, substantially enhancing winds at the leading edge of the cold front. This process is supported by very drylow-level air in the lee of the Atlas Mountains associated with a foehn situation. Flattening the mountain chain in a sensitivity experiment, however, has complex effects on the wind. While reduced evaporative cooling weakens the front, the elimination of the orographic blocking accelerates its penetration into the Sahara. The simulations also indicate high winds associated with a hydraulic jump at the southern slopes of the Tell Atlas. Feedingthe simulated winds into a dust emission parameterization reveals reduced emissions on the order of 20%-30% for suppressed latent heating and even more when effects of the increased precipitation on soil moisture are considered. In the experiment with the Atlas removed, effects of the overall increase in high winds are compensated by an increase in precipitation. The results suggest that a realistic representation of frontal precipitation is an important requisite to accurately model dust emission in such situations

Considerations for Testing Full-Scale Wind Turbine Nacelles with Hardware-in-the-Loop

Full-scale wind turbine nacelle testing with Hardware-In-the-Loop (HIL) configuration allows full operational certification testing with native nacelle controllers, as opposed to open-loop testing which requires significant modification of the controller to bypass missing subsystems when the nacelle is mounted on the test bench. Implementation of Hardware-In-the-Loop testing involves running a real-time simulation of a full turbine model in parallel with the test bench in order to account for the missing rotor, tower, platform, and actuators. For successful implementation of this method, first, the simulation model should be able to capture the dynamic characteristics of the turbine accurately while also meeting the real-time requirements. Second, the deviations resulting from the different boundary conditions between the drivetrain in a full turbine and the test bench environment should be mitigated. In the first part of the study, a sensitivity analysis is performed using a baseline wind turbine model to determine the minimum drivetrain fidelity level necessary to capture the dynamics with a focus on the torsional characteristics that are crucial for performing electro-mechanical certification tests. The results show that the torsional dynamics are dominated by the flexibility of the main shaft and the gearbox supports. The rest of the components can be significantly simplified thereby reducing the total number of modes and degrees of freedom for real-time execution. In the second part of the study, the reduced drivetrain model is utilized in a comparative analysis to quantify the deviations in torsional dynamics resulting from the rigid connections and test bench components (motor, reduction gearbox, and the load application unit) replacing the tower and rotor, respectively. It is found that the different mechanical interfaces can shift the first torsional mode of the drivetrain by as much as 19% which can significantly impact electro-mechanical responses. The feasibility of exploiting the test bench speed controller to introduce virtual inertia, damping, and stiffness and compensating for such differences is studied. It is demonstrated that the controller can be tuned to perform pole placement and match the torsional frequencies between the coupled test bench-nacelle and the full turbine. Finally, the performance of the tuned controller is verified using two case studies: a) free response to characterize the torsional responses in a low voltage ride through scenario, and b) forced response to evaluate its ability to track a highly dynamic speed profile resulting from a turbulent wind profile

Harmattan, Saharan heat low, and West African monsoon circulation: modulations on the Saharan dust outflow towards the North Atlantic

The outflow of dust from the northern African continent towards the North Atlantic is stimulated by the atmospheric circulation over North Africa, which modulates the spatio-temporal distribution of dust source activation and consequently the entrainment of mineral dust into the boundary layer, as well as the transport of dust out of the source regions. The atmospheric circulation over the North African dust source regions, predominantly the Sahara and the Sahel, is characterized by three major circulation regimes: (1) the harmattan (trade winds), (2) the Saharan heat low (SHL), and (3) the West African monsoon circulation. The strength of the individual regimes controls the Saharan dust outflow by affecting the spatio-temporal distribution of dust emission, transport pathways, and deposition fluxes. This study aims at investigating the atmospheric circulation pattern over North Africa with regard to its role favouring dust emission and dust export towards the tropical North Atlantic. The focus of the study is on summer 2013 (June to August), during which the SALTRACE (Saharan Aerosol Long-range TRansport and Aerosol-Cloud interaction Experiment) field campaign also took place. It involves satellite observations by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) flying on board the geostationary Meteosat Second Generation (MSG) satellite, which are analysed and used to infer a data set of active dust sources. The spatio-temporal distribution of dust source activation frequencies (DSAFs) allows for linking the diurnal cycle of dust source activations to dominant meteorological controls on dust emission. In summer, Saharan dust source activations clearly differ from dust source activations over the Sahel regarding the time of day when dust emission begins. The Sahara is dominated by morning dust source activations predominantly driven by the breakdown of the nocturnal low-level jet. In contrast, dust source activations in the Sahel are predominantly activated during the second half of the day, when downdrafts associated with deep moist convection are the major atmospheric driver. Complementary to the satellite-based analysis on dust source activations and implications from their diurnal cycle, simulations on atmosphere and dust life cycle were performed using the mesoscale atmosphere–dust model system COSMO-MUSCAT (COSMO: COnsortium for Small-scale MOdelling; MUSCAT: MUltiScale Chemistry Aerosol Transport Model). Fields from this simulation were analysed regarding the variability of the harmattan, the Saharan heat low, and the monsoon circulation as well as their impact on the variability of the Saharan dust outflow towards the North Atlantic. This study illustrates the complexity of the interaction among the three major circulation regimes and their modulation of the North African dust outflow. Enhanced westward dust fluxes frequently appear following a phase characterized by a deep SHL. Ultimately, findings from this study contribute to the quantification of the interannual variability of the atmospheric dust burden