Tropospheric ozone and El Niño–Southern Oscillation: Influence of atmospheric dynamics, biomass burning emissions, and future climate change

We investigate how El Niño Southern Oscillation (ENSO) influences tropospheric ozone and its precursors in a coupled climate-chemistry model. As shown in similar studies, tropospheric column ozone (TCO) decreases in the central and east Pacific and increases in the west Pacific/Indonesia in response to circulation and convective changes during El Niño conditions. Simulated changes in TCO for “peak” El Niño events in the central and east Pacific are in good agreement but are underestimated in the west Pacific compared to previous observational and modeling studies for October 1997. Tropospheric column-average NOx decreases over Indonesia and generally over South America as a result of suppressed convection and lightning over these land regions. NOx and HOx changes during El Niño modify ozone chemical production and destruction. When we include annually varying biomass burning emissions in our model simulations we find that these emissions peak over Indonesia 1–2 months in advance of the peak elevated sea-surface temperatures (SSTs) and hence the “meteorological” El Niño. We underestimate the strength of the TCO increase due to El Niño–related dry conditions over Indonesia in October 1997 compared to observations. We also examine how future mean and variability changes in ENSO, as simulated in the HadCM3 climate model, impacts tropospheric ozone. A mean future El Niño–like state is simulated in the tropical Pacific in HadCM3, but this has no discernable impact on the future TCO trend in this region. However, we do simulate increased variability in precipitation and TCO related to ENSO in the future

Seasonal variation of carbon monoxide in northern Japan: Fourier transform IR measurements and source-labeled model calculations

Tropospheric carbon monoxide (CO) was measured throughout 2001 using groundbased Fourier transform IR (FTIR) spectrometers at Moshiri 44.4N and Rikubetsu 43.5N) observatories in northern Japan, which are separated by 150 km. Seasonal and day-to-day variations of CO are studied using these data, and contributions from various CO sources are evaluated using three-dimensional global chemistry transport model (GEOS-CHEM) calculations. Seasonal maximum and minimum FTIR-derived tropospheric CO amounts occurred in April and September, respectively. The ratio of partial column amounts between the 0–4 and 0–12 km altitude ranges is found to be slightly greater in early spring. The GEOS-CHEM model calculations generally reproduce these observed features. Source-labeled CO model calculations suggest that the observed seasonal variation is caused by seasonal contributions from various sources, in addition to a seasonal change in chemical CO loss by OH. Changes in meteorological fields largely control the relative importance of various source contributions. The contributions from fossil fuel (FF) combustion in Asia and photochemical CO production have the greatest yearly averaged contribution at 1 km among the CO sources (31% each). The Asian FF contribution increases from winter to summer, because weak southwesterly wind in summer brings more Asian pollutants to the observation sites. The seasonal variation from photochemical CO production is small (±17% at 1 km), likely because of concurrent increases (decreases) of photochemical production and loss rates in summer (winter), with the largest contribution between August and December. The contribution from intercontinental transport of European FF combustion CO is found to be comparable to that of Asian FF sources in winter. Northwesterly wind around the Siberian high in this season brings pollutants from Europe directly to Japan, in addition to southward transport of accumulated pollution from higher latitudes. The influences are generally greater at lower altitudes, resulting in a vertical gradient in the CO profile during winter. The model underestimates total CO by 12–14% between March and June. Satellite-derived fire-count data and the relationship between FTIR-derived HCN and CO amounts are generally consistent with biomass burning influences, which could have been underestimated by the model calculations

Vertical transport of surface fire emissions observed from space

We use optimal estimation to infer the vertical distribution of surface emissions lofted from boreal and tropical biomass burning during June-October (JJASO) 2006. We use satellite observations of CO, a tracer of incomplete combustion, at thermal infrared and microwave wavelengths from Aura Tropospheric Emission Spectrometer (TES) and Microwave Limb Sounder (MLS), respectively. TES and MLS together typically provide two to three pieces of information. We use a maximum a posteriori (MAP) methodology to estimate emitted CO mass in five vertical regions spanning the troposphere and lower stratosphere, equivalent to estimating surface emissions. Correlations between neighboring vertical regions, due to vigorous mixing induced by surface heating, reduce the inversion to the information content provided by the data. We use a total of 1785 TES profile measurements, of which 672 are colocated with MLS. We define an injection height based on MAP statistics. We find that 10%-20% of boreal and tropical fire emissions, depending on the region, reach the free and upper troposphere during JJASO 2006. Our injection height estimates during two key pyroconvective events, Siberia (July) and Indonesia (October), qualitatively agree with measurements of aerosol index and attenuated backscatter from Aura Ozone Monitoring Instrument (OMI) and CALIPSO, respectively. Surface emissions inferred from our mass estimates agree with the Global Fire Emission Database biomass burning emission inventory to within +/-10%. The small percentage of emissions injected above the boundary layer result in disproportionate changes in CO concentrations of more than 2-25 ppb and 15-160 ppb over boreal and tropical regions, respectively.</p

The career development experiences of first-generation students in the health sciences

This study sought to gain insight into the benefits, barriers, and supports that first-generation (or first-gen) students experienced in their career development by answering these questions: (1) How did first-generation students who are juniors and seniors engage with the career development programming offered at the University of Missouri College of Health Sciences? (2) How did they perceive the benefits of career development programming offered by their college? (3) What were the barriers that reduced their access to career development opportunities? (4) What other support systems do first-generation students rely upon for their career development? This embedded qualitative case study recruited 12 first-generation junior/seniors to create a visual map and participate in a semi-structured interview. Using open and axial coding, the identified themes were academic, career planning, institutional, financial, mental health and disability support, and other support systems. The data highlighted important findings: that faculty members are critical partners in promoting career services and its programming. First-gen students understand career services to be expansive, more than just the office titled "career services" Peripheral resources help students to know they have additional resources that provide support. Overall participants found value in career services and were prompted to engage when a career-related action was required, such as updating their resume or the need to find an internship. Aspects such as navigating college, the need to work, building a network, and managing personal health were barriers students shared and sometimes these barriers delayed students entering their career due to the necessity of taking a bridge year or 2 to work or to save money, for instance. Participants overwhelmingly shared that their families were a significant source of support. These findings provide insight and actionable steps to minimize barriers experienced by first-generation students in accessing career services within the health sciences.Includes bibliographical references

Global inventory of nitrogen oxide emissions constrained by space-based observations of NO2 columns

sions (37.7 Tg N yr #1 ) agrees closely with the GEIAbased a priori (36.4) and with the EDGAR 3.0 bottom-up inventory (36.6), but there are significant regional differences. A posteriori NO x emissions are higher by 50 -- 100% in the Po Valley, Tehran, and Riyadh urban areas, and by 25 -- 35% in Japan and South Africa. Biomass burning emissions from India, central Africa, and Brazil are lower by up to 50%; soil NO x emissions are appreciably higher in the western United States, the Sahel, and southern Europe

Fire emissions from C-3 and C-4 vegetation and their influence on interannual variability of atmospheric CO2 and delta (CO2) - C- 13

Measurements of atmospheric trace gases provide evidence that fire emissions increased during the 1997/1998 El Niño event and these emissions contributed substantially to global C