Bernhard Rappenglück

• Professor
• Professor at University of Houston

The dominant fraction of anthropogenic volatile organic compound (VOC) emissions shifted from transportation fuels to volatile chemical products (VCP) in Los Angeles (LA) in 2010. This shift in VOC composition raises the question about the importance of VCP emissions for ozone (O3) formation. In this study, O3 chemistry during the CalNex 2010 was m...

Volatile organic compounds (VOCs) are major ingredients of photochemical smog. It is essential to know the spatial and temporal variation of VOC emissions. In this study, we used the Positive Matrix Factorization (PMF) model for VOC source apportionment in Mexico City. We first analyzed a data set collected during the ozone season from March–May 20...

Nitrophenols (NPs) have significant impacts on human health, climate, and atmospheric chemistry. Despite numerous measurements of particulate NPs, still little is known about their gaseous atmospheric abundances, sources, and fate. Here, four gaseous NPs [2,4-dinitrophenol (2,4-DNP), 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), and 2-Methyl-4-nitrop...

In this study we analyze an air quality data set, which was collected in the vicinity of the center of Mexico City during the ozone season from March to May 2016. It includes 33 volatile organic compounds (VOCs), nitrogen oxide (NO), nitrogen dioxide (NO2), the sum of nitrogen oxides (NOx), carbon monoxide (CO), sulfur dioxide (SO2) and particle ma...

The COVID-19 pandemic altered the human mobility and economic activities immensely, as authorities enforced unprecedented lock down regulations. In order to reduce the spread of COVID-19, a complete lockdown was observed between 24 March - 31 May 2020 in Pakistan. This paper aims at investigating the PM2.5, AOD and column amounts of six trace gases...

Volatile organic compounds (VOCs) data in conjunction with other inorganic pollutants, surface meteorological data and continuous measurement of the Planetary Boundary Layer height (PBLH) at an urban site in Mexico City were performed from 6 to 18 March 2016. Positive Matrix Factorization (PMF) identified four emission source factors of VOCs along...

Ground-level ozone is an important pollutant regarding air quality and climate. Mexico City frequently experiences severe ozone episodes due to a combination of strong ozone precursor emissions and its specific topographical environment which critically impacts meteorological conditions. High ozone levels during these episodes cause harmful effects...

We studied the seasonal variations of volatile organic compounds (VOCs) in the Houston metropolitan area in the summertime and wintertime of 2018. The analysis of hourly measurements obtained from the automated gas chromatograph (auto-GC) network showed the total VOC average concentrations of 28.68 ppbC in the summertime and 33.81 ppbC in the winte...

The planetary boundary layer (PBL) height plays a major role in air quality and weather forecast studies. However, it cannot be directly measured as it can only be determined from the measured profiles of atmospheric parameters such as., temperature, moisture, and aerosol backscatter based on different retrieval mechanisms. This paper presents the...

A commixture of gasphase compounds including carbon monoxide (CO), sulphur dioxide (SO2), volatile organic compounds (VOCs) and trace metals were collected at a site located at the urban/industrial interface in Houston, Texas. Positive Matrix Factorization (PMF) analysis yielded nine factors: gas/crude oil (21.3±5.5%), isoprene emission (17.0±7.1%)...

Anthropogenic secondary organic aerosol (ASOA), formed from anthropogenic emissions of organic compounds, constitutes a substantial fraction of the mass of submicron aerosol in populated areas around the world and contributes to poor air quality and premature mortality. However, the precursor sources of ASOA are poorly understood, and there are lar...

The seasonal variations of volatile organic compounds (VOCs) was studied in the Houston metropolitan area in the summertime and wintertime of 2018. The analysis of hourly measurements obtained from the automated gas chromatograph (auto-GC) network showed the total VOC average concentrations of 28.68 ppbC in the summertime and 33.92 ppbC in the wint...

Total OH reactivity was measured during the California Research at the Nexus of Air Quality and Climate Change field campaign at the Pasadena ground site using a turbulent flow tube reactor with laser‐induced fluorescence detection of the OH radical. Collocated measurements of volatile organic compounds (VOCs), inorganic species, and meteorological...

There has been an alarming increase in the frequency of major flooding events along the Gulf Coast over the last three decades, primarily due to events of unprecedented, or extreme, rainfall. Using data from 63 rain gauges maintained by the Harris County Flood Control District's Flood Warning System (HCFCD FWS), this study examines the changes in d...

Air quality policies based on scientific and technical information are effective for controlling air pollution and protecting public health. Analysis of observations from periodic intensive field studies combined with updated emission inventories, air quality monitoring and numerical modelling can be used to address the causes that trigger air poll...

The diurnal evolution of the planetary boundary layer (PBL) is crucial to air quality studies as it impacts the exchange and distribution of pollutants close to the surface. This paper reports continuous detection of the daytime convective boundary layer height, the stable boundary layer height, and the residual layer height as estimated from the v...

Despite the central role of reactive organic carbon (ROC) in the formation of secondary species that impact global air quality and climate, our assessment of ROC abundance and impacts is challenged by the diversity of species that contribute to it. We revisit measurements of ROC species made during two field campaigns in the United States: the 2013...

Anthropogenic secondary organic aerosol (ASOA), formed from anthropogenic emissions of organic compounds, constitutes a substantial fraction of the mass of submicron aerosol in populated areas around the world and contributes to poor air quality and premature mortality. However, the precursor sources of ASOA are poorly understood, and there are lar...

The main emission source in Central and Southern Chilean cities is biomass combustion from residential heating and cooking due to old combustion technologies that are still widely utilized. In order to improve our understanding of biomass burning pollution and how it ages in the atmosphere, emissions from a pellet and wood stoves were studied with...

The role of the sea/bay breeze in the planetary boundary layer evolution and air quality during a high ozone event day in the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER‐AQ) Texas 2013 campaign was examined. Data from surface air quality monitoring network stations, a...

United States Environmental Protection Agency guidance on the use of photochemical models for assessing the efficacy of an emissions control strategy for ozone requires that modeling be used in a relative sense. Consequently, testing a modeling system's ability to predict changes in ozone resulting from emission changes is critical. We evaluate mod...

In this study, we performed meteorological and chemical sensitivity studies employing two different Weather Research and Forecasting model with Chemistry (WRF-Chem) simulations: one with the standard Planetary Boundary Layer (PBL) Yonsei scheme (YSU), and one with a modified YSU PBL scheme proposed in a previous work. The WRF-Chem results were comp...

We implemented the Weather Research and Forecast (WRF) model and WRF Large-Eddy Simulation (WRF–LES), focusing on calculations for the planetary boundary layer (PBL), and compared the results against a data set of a well-documented campaign, in the Houston–Galveston area, Texas, in summer 2006. A methodology using WRF in a mesoscale and LES was imp...

This study investigated the causes behind the nighttime ozone biases in southeast Texas, including background ozone, the land use/land cover (LULC) change and the minimum nighttime eddy diffusivity coefficient (Kzmin) setting. It also tried to shed light on a historical issue of large ozone biases by tracing the history of Community Multiscale Air...

We analyze an expanded data set of oxygenated volatile organic compounds (OVOCs) in air measured by several instruments at a surface site in Pasadena near Los Angeles during the NOAA California Nexus study in 2010. The contributions of emissions, chemical formation and removal are quantified for each OVOC using CO as a tracer of emissions and the O...

In the present study, the well-known case of day 33 of the Wangara experiment is resimulated using the Weather Research and Forecasting (WRF) model in an idealized single-column mode to assess the performance of a frequently used planetary boundary layer (PBL) scheme, the Yonsei University PBL scheme. These results are compared with two large eddy...

Three algorithms for estimating the boundary layer heights are assessed: an aerosol gradient method, a cluster analysis method, and a Haar wavelet method. Over 40 daytime clear-sky radiosonde profiles are used to compare aerosol backscatter boundary layer heights retrieved by a Vaisala CL31 ceilometer. Overall good agreement between radiosonde- and...

Formaldehyde (HCHO) is the most important carcinogen in outdoor air among the 187 hazardous air pollutants (HAPs) identified by the US Environmental Protection Agency (EPA), not including ozone and particulate matter. However, surface observations of HCHO are sparse and the EPA monitoring network could be prone to positive interferences. Here we us...

Three algorithms for estimating the boundary layer heights are assessed: an aerosol gradient method, a cluster analysis method, and a Haar wavelet method. Over 40 daytime radiosonde profiles are used to compare aerosol backscatter boundary layer heights retrieved by a Vaisala CL31 ceilometer. Overall good agreement between radiosonde and aerosol de...

Measurements of hydroxyl (OH) and hydroperoxy (HO2*) radical concentrations were made at the Pasadena ground site during the CalNex-LA 2010 campaign using the Laser-Induced Fluorescence - Fluorescence Assay by Gas Expansion (LIF-FAGE) technique. The measured concentrations of OH and HO2* exhibited a distinct weekend effect, with higher radical conc...

Unique in-situ measurements of CO, O3, SO2, CH4, NO, NOx, NOy, VOC, CN, and rBC were carried out with the German DLR-Falcon aircraft in Central U.S. thunderstorms during the Deep Convective Clouds and Chemistry (DC3) experiment in summer 2012. Fresh and aged anvil outflow (9-12 km) from supercells, mesoscale convective systems, mesoscale convective...

Four different literature parameterizations for the formation and evolution of urban secondary organic aerosol (SOA) frequently used in 3-D models are evaluated using a 0-D box model representing the Los Angeles metropolitan region during the California Research at the Nexus of Air Quality and Climate Change (CalNex) 2010 campaign. We constrain the...

Formic acid (HCOOH) is one of the most abundant carboxylic acids in the atmosphere. However, current photochemical models cannot fully explain observed concentrations and in particular secondary formation of formic acid across various environments. In this work, formic acid measurements made at an urban receptor site (Pasadena) in June-July 2010 du...

1,3-butadiene is an important pollutant in terms of public health and important driver for photochemical processes influencing ozone formation in the area of Houston. Ambient levels of 1,3-butadiene were simulated with the Community Multiscale Air Quality model (CMAQ) including the SAPRC99-extended mechanism and the results were compared to spatial...

Dust storms are considered to be a natural hazard over the Arabian Peninsula, since they occur all year round with maximum intensity and frequency in Spring and Summer. The Regional Climate Model version 4 (RegCM4) has been used to study the climatology of atmospheric dust over the Arabian Peninsula from 1999 to 2012. This relatively long simulatio...

Four different parameterizations for the formation and evolution of secondary organic aerosol (SOA) are evaluated using a 0-D box model representing the Los Angeles Metropolitan Region during the CalNex 2010 field campaign. We constrain the model predictions with measurements from several platforms and compare predictions with particle and gas-...

In August 2013, the Qatar Environment and Energy Research Institute (QEERI), was the first to launch temporally highly resolved ozonesondes in the Middle East region. The data from 20 launches consistently show changes in meteorological parameters at about 5.5 km above the surface, which are more pronounced following a change in synoptic conditions...

A WRF–SMOKE–CMAQ modeling system was used to simulate vertical profiles of ozone, temperature and wind as well as surface ozone and meteorology during the Study of Houston Atmospheric Radical Precursors (SHARP) in May 2009. WRF and CMAQ sensitivity studies were conducted to define a proper combination of model configurations. With objective analysi...

Air quality forecasting requires atmospheric weather models to generate accurate meteorological conditions, one of which is the development of the planetary boundary layer (PBL). An important contributor to the development of the PBL is the land–air exchange captured in the energy budget as well as turbulence parameters. Standard and surface energy...

With over 6 million inhabitants the Houston metropolitan area is the fourth-largest in the United States. Ozone concentration in this southeast Texas region frequently exceeds the National Ambient Air Quality Standard (NAAQS). For this reason our study employed the Weather Research and Forecasting model with Chemistry (WRF/Chem) to quantify meteoro...

Formic acid (HCOOH) is one of the most abundant carboxylic acids in the atmosphere. However, current photochemical models cannot fully explain observed concentrations and in particular secondary formation of formic acid across various environments. In this work, formic acid measurements made at an urban receptor site in June–July of 2010 during Cal...

Because of the importance of HONO as a radical reservoir, consistent and accurate measurements of its concentration are needed. As part of SHARP (Study of Houston Atmospheric Radical Precursors), time series of HONO were obtained by six different measurement techniques on the roof of the Moody Tower (MT) at the University of Houston. Techniques use...

Air quality model simulations are performed and evaluated for Houston using the Community Multiscale Air Quality (CMAQ) model. The simulations use two different emissions estimates: the EPA 2005 National Emissions Inventory (NEI) and the Texas Commission on Environmental Quality (TCEQ) Emissions Inventory. A comparison of predictions with observed...

During recent years, elevated ozone (O3) values have been observed repeatedly in the Upper Green River basin (UGRB), Wyoming, during wintertime. This paper presents an analysis of high ozone days in late winter 2011 (1 h average up to 166 ppbv – parts per billion by volume). Intensive operational periods (IOPs) of ambient monitoring were performed,...

[1] A sensitive Mobile DOAS system with real-time evaluation capability and HCHO detection limit of 3 ppb over 100 m has been developed. The system was operated together with a Solar Occultation Flux (SOF) system for large-scale vertical flux measurements of HCHO, NO2, SO2 and VOCs in the Houston-Galveston-Brazoria area (HGB) during two studies, in...

Air quality forecasting requires atmospheric weather models to generate accurate meteorological conditions, one of which is the development of the planetary boundary layer (PBL). An important contributor to the development of the PBL is the land-air exchange captured in the energy budget as well as turbulence parameters. Standard and surface energy...

The Study of Houston Atmospheric Radical Precursors (SHARP) was a field campaign developed by the Houston Advanced Research Center (HARC) on behalf of the Texas Environmental Research Consortium (TERC). SHARP capitalized on previous research associated with the Second Texas Air Quality Study (TexAQS II) and the development of the State Implementati...

[1] A mobile platform for flux measurements of VOCs (alkanes and alkenes), SO2 and NO2 emissions using the Solar Occultation Flux method and Mobile DOAS was used in four different studies to measure industrial emissions. The studies were carried out in several large conglomerates of oil refineries and petrochemical industries in Southeast and East...

NOx emissions and O3 chemistry in the Los Angeles (L.A.) Basin during the CalNex-2010 field campaign (May-June 2010) have been evaluated by analyzing O3 and NOy (NO, NO2, HNO3, PAN) observations using a regional air quality model (WRF-Chem). Model simulations were conducted at 4-km spatial resolution over the basin using the Carbon-Bond Mechanism v...

Nitrous acid (HONO) and formaldehyde (HCHO) are important precursors for radicals and are believed to favor ozone formation significantly. Traffic emission data for both compounds are scarce and mostly outdated. A better knowledge of today's HCHO and HONO emissions related to traffic is needed to refine air quality models. Here the authors report r...

Air quality simulations were performed for the Houston‐Galveston‐Brazoria area for springtime conditions in May and June of 2009. Meteorological parameters predicted by Weather Research and Forecasting (WRF) model, for which data assimilation with recursive objective analysis was performed, are well simulated most of the time. The Community Multisc...

Ozone (O3) and secondary fine particles come from the atmospheric oxidation chemistry that involves the hydroxyl radical (OH) and hydroperoxyl radical (HO2), which are together called HOx. Radical precursors such as nitrous acid (HONO) and formaldehyde (HCHO) significantly affect the HOx budget in urban environments. These chemical processes connec...

Organic aerosols (OA) in Pasadena are characterized using multiple measurements from the CalNex campaign. Five OA components are identified using positive matrix factorization including hydrocarbon-like OA (HOA), and two types of oxygenated OA (OOA). The Pasadena OA elemental composition when plotted as H:C versus O:C follows a line less steep than...

During the CalNex (California Research at the Nexus of Air Quality and Climate Change) field study in May–June 2010, measurements of volatile organic compounds (VOCs) were performed in the Los Angeles (LA) basin onboard a NOAA research aircraft and at a ground site located in Pasadena. A weekday‐weekend effect in ozone, caused by lower NO x emissio...

The fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5) and the Weather Research and Forecasting Model (WRF) have been employed to predict troposphere temperatures for atmospheric study and operational decision making with positive results. Temperature bias in MM5 and WRF has been noted in p...

Attributing observed CO2 variations to human or natural cause is critical to deducing and tracking emissions from observations. We have used in situ CO2, CO, and planetary boundary layer height (PBLH) measurements recorded during the CalNex-LA (CARB et al., 2008) ground campaign of 15 May-15 June 2010, in Pasadena, CA, to deduce the diurnally varyi...

Over the last years elevated ozone values have been observed repeatedly in the Upper Green River Basin, Wyoming during wintertime. Here we will report results from the Upper Green Winter Ozone Study (UGWOS) 2011. This campaign included comprehensive in-situ measurements of O3, NO, NO2, NOx, NOy, HNO3, HONO, HCHO, CH4 and speciated VOC canister and...

This study extends the work of Baumgardner et al. (2009) in which measurements of trace gases and particles, at a remote, high altitude mountain site, 60 km from Mexico City were analyzed with respect to the origin of the air masses. In the current evaluation, the temperature, water vapor mixing ratio (WMR), ozone (O3), carbon monoxide (CO), sulfur...

Nitrous acid (HONO) mixing ratios for the Houston metropolitan area were simulated with the Community Multiscale Air Quality (CMAQ) Model for an episode during the Texas Air Quality Study (TexAQS) II in August/September 2006 and compared to in-situ MC/IC (mist-chamber/ion chromatograph) and long path DOAS (Differential Optical Absorption Spectrosco...

To achieve more accurate meteorological inputs than was used in the daily forecast for studying the TexAQS 2006 air quality, retrospective simulations were conducted using objective analysis and 3D/surface analysis nudging with surface and upper observations. Model ozone using the assimilated meteorological fields with improved wind fields shows be...

Particulate matter was measured during August and September of 2006 in Houston as part of the Texas Air Quality Study II Radical and Aerosol Measurement Project. Aerosol size and composition were determined using an Aerodyne quadrupole aerosol mass spectrometer. Aerosol was dominated by sulfate (4.1 ± 2.6 μg m−3) and organic material (5.5 ± 4.0 μg...

This study extends the work of Baumgardner et al. (2009) in which measurements of trace gases and particles, at a remote, high altitude mountain site, 60 km from Mexico City were analyzed with respect to the origin of the air masses. In the current evaluation, the temperature, water vapor, ozone (O₃), carbon monoxide (CO), acyl peroxy ni...

Nitrous acid (HONO) mixing ratios for the Houston metropolitan area were simulated with the Community Multiscale Air Quality (CMAQ) model for an episode during the Texas Air Quality Study (TexAQS) II in August/September 2006 and compared to in-situ MC/IC (mist-chamber/ion chromatograph) and long path DOAS (Differential Optical Absorption Spectrosco...

Attributing observed CO2 variations to human or natural cause is critical to deducing and tracking emissions from observations. We have used in situ CO2, CO, and planetary boundary layer height (PBLH) measurements recorded during the CalNex-LA (CARB et al., 2008) ground campaign of 15 May–15 June 2010, in Pasadena, CA, to deduce the diurnally varyi...

Recent field studies reveal large formation of secondary organic aerosol (SOA) under urban polluted ambient conditions, while SOA formation in biomass burning smoke appears to be variable but sometimes substantial. To study this formation in real-time, a Potential Aerosol Mass (PAM) photooxidation reactor was deployed with submicron aerosol size an...

Atmospheric aerosols impact climate and health, but their sources and composition are poorly understood. To address this knowledge gap, a high-resolution aerosol mass spectrometer (AMS) and complementary instrumentation were deployed during the 2010 CalNex campaign to characterize aerosol composition in the Los Angeles (LA) area. Total mass concent...

Total hydroxyl radical reactivity, which is the inverse of the chemical lifetime of the hydroxyl radical (OH), is an important quantity for investigations of OH and VOC chemistry. Total OH reactivity measurements are often used as an experimental test of theoretical OH budgets. Under certain conditions, total OH reactivity can be used to estimate t...

Volatile organic compounds (VOCs) are critical components in the photochemical production of ozone (O3) and secondary organic aerosol (SOA). During the CalNex 2010 field campaign, an extensive set of VOCs were measured at the Pasadena ground site, and aboard the NOAA WP-3D aircraft and the WHOI Research Vessel Atlantis. The measurements from each p...

Hydroxyl (OH) and hydroperoxy (HO2) radicals are key species in the atmosphere driving the oxidation of organic trace gases leading to the production of ozone and secondary organic aerosols. Previous measurements of these radicals in urban environments have shown similarities and differences across sites due to differing levels of nitrogen oxides (...

In May-July 2010, the Calnex field study was conducted by National Oceanic and Atmospheric Administration (NOAA), California Air Resources Board (CARB), and other partners to answer important scientific questions about emissions, chemical transformations, climate processes, transport, and meteorology in California. The study provided a rich dataset...

More than half of the world's population now lives in urban areas, contributing large fluxes of greenhouse gas to the atmosphere. Quantifying the spatiotemporal distribution of these emissions is critical for providing independent verification of future mitigation activities. We have used high precision measurements of CO2 and CO to determine the c...

We present quantitative, fast time response measurements of formaldehyde (HCHO) onboard an aircraft using a Proton-Transfer-Reaction Mass-Spectrometry (PTR-MS) instrument. The HCHO measurement by PTR-MS is strongly humidity dependent and therefore airborne measurements are difficult and have not been reported. The PTR-MS instrument was run in the n...

a b s t r a c t Gradients of HONO, NO x (NO þ NO 2) and O 3 were measured during an early summer campaign on a high-rise building in downtown Santiago de Chile. Distinct gradients of decreasing concentrations with altitude were observed for HONO and NO x , while O 3 concentrations were found to increase with altitude. From the observed daytime maxi...

We present quantitative, fast time response measurements of formaldehyde (HCHO) onboard an aircraft using a Proton-Transfer-Reaction Mass-Spectrometry (PTR-MS) instrument. The HCHO measurement by PTR-MS is strongly humidity dependent and therefore airborne measurements are difficult and have not been reported. The PTR-MS instrument was run in the n...

Performance of an air quality prediction may suffer with problems due to uncertainties in meteorological forecasts, lack of event-based real-life emissions variations such as forest fires, and inaccurate dynamic boundary conditions representing effects of long-range transport events. The main objective of this article is to demonstrate the combined...

Nitrous acid (HONO) often plays an important role in tropospheric photochemistry as a major precursor of the hydroxyl radical (OH) in early morning hours and potentially during the day. However, the processes leading to formation of HONO and its vertical distribution at night, which can have a considerable impact on daytime ozone formation, are cur...

We combine aircraft measurements (Second Texas Air Quality Study, Megacity Initiative: Local and Global Research Observations, Intercontinental Chemical Transport Experiment: Phase B) over the United States, Mexico, and the Pacific with a 3-D model (GEOS-Chem) to evaluate formaldehyde column (ΩHCHO) retrievals from the Ozone Monitoring Instrument (...

Nitrous acid (HONO) and formaldehyde (HCHO) are supposed to be important precursors for radicals and are believed to favor ozone formation significantly. So far only scarce traffic emissions data is available which includes both compounds. However, this knowledge is needed to further refine and validate air quality modeling. Here we will report mea...

Photochemical modeling of ozone formation in the Houston area generally underestimates the concentrations of free radical precursors contributing to ozone formation. There are unresolved questions about the quantitative contribution of direct emissions and of atmospheric reaction products to the formation of compounds that are related to the free r...

Submicron atmospheric aerosols impact climate and human health, but their sources and composition are poorly understood. To address this knowledge gap, high-resolution time-of-flight aerosol mass spectrometry (AMS) [DeCarlo et al. Anal. Chem. 2006] and other advanced instrumentation were deployed during the CalNex field campaign in May and June 201...