Analysis of long-term observations of NOx and CO in megacities and application to constraining emissions inventories

Long-term atmospheric NOx/CO enhancement ratios in megacities provide evaluations of emission inventories. A fuel-based emission inventory approach that diverges from conventional bottom-up inventory methods explains 1970–2015 trends in NOx/CO enhancement ratios in Los Angeles. Combining this comparison with similar measurements in other U.S. cities demonstrates that motor vehicle emissions controls were largely responsible for U.S. urban NOx/CO trends in the past half century. Differing NOx/CO enhancement ratio trends in U.S. and European cities over the past 25 years highlights alternative strategies for mitigating transportation emissions, reflecting Europe's increased use of light-duty diesel vehicles and correspondingly slower decreases in NOx emissions compared to the U.S. A global inventory widely used by global chemistry models fails to capture these long-term trends and regional differences in U.S. and Europe megacity NOx/CO enhancement ratios, possibly contributing to these models' inability to accurately reproduce observed long-term changes in tropospheric ozone

Aperture Coupled Microstrip Antenna Design and Analysis

A linearly-polarized aperture coupled patch antenna design is characterized and optimized using HFSS antenna simulation software. This thesis focuses on the aperture coupled patch antenna due to the lack of fabrication and tuning documentation for the design of this antenna and its usefulness in arrays and orthogonally polarized communications. The goal of this thesis is to explore dimension effects on aperture coupled antenna performance, to develop a design and tuning procedure, and to describe performance effects through electromagnetic principles. Antenna parameters examined in this study include the dimensions and locations of the substrates, feed line, ground plane coupling slot, and patch. The operating frequency, input VSWR, percent bandwidth, polarization ratio, and broadside gain are determined for each antenna configuration. The substrate material is changed from RT Duroid (material in nominal HFSS design) to FR4 due to lower cost and availability. The operating frequency is changed from 2.3GHz (specified in nominal HFSS design) to 2.4GHz for wireless communication applications. Required dimensional adjustments when changing substrate materials and operating frequencies for this antenna are non-trivial and the new design procedure is used to tune the antenna. The antenna is fabricated using 59mil thick double and single sided FR4 boards joined together with double sided 45mil thick acrylic tape. The antenna is characterized in an anechoic chamber and experimental results are compared to theoretical predictions. The results show that the new design procedure can be successfully applied to aperture coupled antenna design

Analysis of long-term observations of NO x and CO in megacities and application to constraining emissions inventories

Abstract Long-term atmospheric NO x /CO enhancement ratios in megacities provide evaluations of emission inventories. A fuel-based emission inventory approach that diverges from conventional bottom-up inventory methods explains 1970-2015 trends in NO x /CO enhancement ratios in Los Angeles. Combining this comparison with similar measurements in other U.S. cities demonstrates that motor vehicle emissions controls were largely responsible for U.S. urban NO x /CO trends in the past half century. Differing NO x /CO enhancement ratio trends in U.S. and European cities over the past 25 years highlights alternative strategies for mitigating transportation emissions, reflecting Europe's increased use of light-duty diesel vehicles and correspondingly slower decreases in NO x emissions compared to the U.S. A global inventory widely used by global chemistry models fails to capture these long-term trends and regional differences in U.S. and Europe megacity NO x /CO enhancement ratios, possibly contributing to these models' inability to accurately reproduce observed long-term changes in tropospheric ozone

The application of long-term observations of NO_x and CO to constrain a global emissions inventory

International audienceAccurate knowledge of tropospheric ozone is important for understanding its current and future effects on human health, air quality, and climate. However, global chemistry- climate models generally have problems reproducing tropospheric ozone concentrations, seasonal cycles and interannual trends. Successful tropospheric ozone simulations require high quality information on the emissions of ozone precursors, including nitrogen oxides (NOx), carbon monoxide (CO) and volatile organic compounds (VOCs).We analyzed CO and NOx measurements from four megacities (Los Angeles, New York City, London, and Paris). It has been shown that CO and VOC emissions are highly correlated in urban areas. However, CO is more extensively measured than VOCs. Therefore, we compared the long-term evolution of the measured NOx/CO enhancement ratio in each city to the ratio of the emissions of these two pollutants reported by the MACCity global emissions inventory at the inventory grid points nearest the city. The longest available measurement record (~50 years) is from Los Angeles, where the measured NOx/CO ratios are consistently smaller than the emission ratio in the MACCity inventory and the slope of the long-term trend in measured NOx/CO ratios is of significantly larger magnitude than for MACCity. The other three cities do not have as long of a data record, but the evolution of their NOx/CO ratios also implies that the MACCity NOx/CO emissions trends are not steep enough. However, the agreement between the measured and inventory ratios is better for the shorter time period where measurements are available in these three cities.Comparisons of MACCity with fuel-based emission estimates for Los Angeles (for the 1990s and 2000s) suggest that the CO emissions are underestimated in the inventory, which results in the higher inventory NOx/CO ratios