Engineering topics
Iraci, Laura T.
Publications and source records attributed to Iraci, Laura T..
AJAX CABOTS Data
The Alpha Jet Atmospheric eXperiment (AJAX) airborne science project based out of NASA Ames Research Center performed eight science flights in coordination with the California Baseline Ozone Transport Study (CABOTS) campaign. Many of these flights included a series of vertical profiles (~ 0-5 km) distributed roughly along either a North/South or East/West transect. Some flights also connected the fixed-location measurements at Visalia (TOPAZ ozone lidar) and Bodega Bay (ozonesondes). AJAX measured ozone, carbon dioxide, methane, water vapor, and 3-D winds on each flight, and those in situ measurements are the basis of the data sets collected here. Trace gas data sets including time and aircraft position have been delivered as comma-separated-value text files. Meteorological data (temperature, pressure and 3-dimensional winds) are provided at 1 Hz in ICARTT-compliant text files.
Testing and Improving a UAV-Based System Designed for Wetland Methane Source Measurements
Wetlands are the single highest emitting methane source category, but the magnitude of wetland fluxes remains difficult to fully characterize due to their large spatial extent and heterogeneity. Fluxes can vary with land surface conditions, vegetation type, and seasonal changes in environmental conditions. Unmanned aerial vehicles (UAVs) are an emerging platform to better characterize spatial variability in these natural ecosystems. While presenting some advantages over traditional techniques like towers and flux chambers, in that they are mobile vertically and horizontally, their use is still challenging, requiring continued improvement in sensor technology and field measurement approaches. In this work, we employ a small, fast response laser spectrometer on a Matrice 600 hexacopter. The system was previously deployed successfully for 40 flights conducted in a four-day period in 2018 near Fairbanks, Alaska. These flights revealed several potential areas for improvement, including: vertical positioning accuracy, the need for sensor health indicators, and approaches to deal with low wind speeds. An additional set of flights was conducted this year near Antioch in California. Flights were conducted several meters above ground up to 15-25 m in a curtain pattern. These curtains were flown both upwind and downwind of a tower site, allowing us to calculate a mass balance methane flux estimate that can be compared to eddy covariance fluxes from the tower. Testing will better characterize the extent to which altitude drifts in-flight and how GPS values compare with measurements from the onboard LIDAR, as well as the agreement between two-dimensional wind speed and direction on the ground versus measured onboard the UAV. Hardware improvements to the sensor and GPS are being considered to help reduce these sources of uncertainty. Results of this testing and how system performance relates to needs for quantifying wetland fluxes, will be presented.
Laboratory Investigations of Cloud Particle Formation and Sublimation on Titan, Mars, and Earth
Microphysical modeling of cloud formation and growth relies on fundamental measurements of the properties of condensable gases which form cloud particles. NASA's Ames Chemistry Laboratory has the capability to measure vapor pressures and heterogeneous nucleation conditions for a variety of gases found in the atmospheres of solar system bodies. Highlights from work for Earth, Mars, and Titan demonstrate the range of conditions and atmospheres studied to date.
Four Years of Airborne Measurements of Wildfire Emissions in California, with a Focus on the Evolution of Emissions During the Soberanes Megafire
Biomass burning is an important source of trace gases and particles which can influence air quality on local, regional, and global scales. With wildfire events increasing due to changes in land use, increasing population, and climate change, characterizing wildfire emissions and their evolution is vital. In this work we report in situ airborne measurements of carbon dioxide (CO2), methane (CH4), water vapor (H2O), ozone (O3), and formaldehyde (HCHO) from nine wildfire events in California between 2013 and 2016, which were sampled as part of the Alpha Jet Atmospheric eXperiment (AJAX) based at NASA Ames Research Center. One of those fires, the Soberanes Megafire, began on 22 July 2016 and burned for three months. During that time, five flights were executed to sample emissions near and downwind of the Soberanes wildfire. In situ data are used to determine enhancement ratios (ERs), or excess mixing ratio relative to CO2, as well as assess O3 production from the fire. Changes in the emissions as a function of fire evolution are explored. Air quality impacts downwind of the fire are addressed using ground-based monitoring site data, satellite smoke products, and the Community Multiscale Air Quality (CMAQ) photochemical grid model.
Outcomes of 7 Years of Airborne Trace Gas Measurements over California and Nevada: The Alpha Jet Atmospheric eXperiment (AJAX)
The Alpha Jet Atmospheric eXperiment (AJAX) has been flying a scientific payload since January 2011 measuring ozone, carbon dioxide, methane, formaldehyde and meteorological parameters up to 9 kilometers. AJAX is located and operated from the San Francisco Bay Area and has flown a total of 229 flights, on a regular basis (approximately 3 per month) over all seasons cataloguing a long-term record of trace gas concentrations over California and Nevada. The AJAX project focuses on science questions which benefit from routine, frequent observations with flexible scheduling. This presentation will provide an overview of AJAX activities including a discussion of airborne measurements for: Long-Range Transport (LRT) and Stratosphere-to-Troposphere Transport (STT). Regular sampling by AJAX has aided identification of LRT and evidence of STT, which during spring and summer months are visible as elevated O3 laminae within airborne profiles. Some laminae have the ability to impact surface level air quality; Satellite validation - Regular AJAX missions include flights to Railroad Valley, NV in coordination with GOSAT (Greenhouse Gases Observing Satellite) and OCO-2 (Carbon Observatory-2) observations, and more recently to provide coincident measurements under TROPOMI (TROPOspheric Monitoring Instrument); The AJAX project is uniquely flexible to incorporate specialized flights with limited planning notice, such as sampling emissions from California wildfires. Nine wildfires have been sampled, with some more than once allowing to observe emission changes as the fire progresses; Pandora validation - Future work will include development of flight strategies for validation of ground based Pandora spectrometers.
Improved retrievals of carbon dioxide from Orbiting Carbon Observatory-2 with the version 8 ACOS algorithm
Since September 2014, NASA's Orbiting Carbon Observatory-2 (OCO-2) satellite has been taking measurements of reflected solar spectra and using them to infer atmospheric carbon dioxide levels. This work provides details of the OCO-2 retrieval algorithm, versions 7 and 8, used to derive the column-averaged dry air mole fraction of atmospheric CO 2 ( X CO 2 ) for the roughly 100 000 cloud-free measurements recorded by OCO-2 each day. The algorithm is based on the Atmospheric Carbon Observations from Space (ACOS) algorithm which has been applied to observations from the Greenhouse Gases Observing SATellite (GOSAT) since 2009, with modifications necessary for OCO-2. Because high accuracy,better than 0.25 %, is required in order to accurately infer carbon sources and sinks from X CO 2 , significant errors and regional-scale biases in the measurements must be minimized. We discuss efforts to filter out poor-quality measurements, and correct the remaining good-quality measurements to minimize regional-scale biases. Updates to the radiance calibration and retrieval forward model in version 8 have improved many aspects of the retrieved data products. The version 8 data appear to have reduced regional-scale biases overall, and demonstrate a clear improvement over the version 7 data. In particular, error variance with respect to TCCON was reduced by 20 % over land and 40 % over ocean between versions 7 and 8, and nadir and glint observations over land are now more consistent. While this paper documents the significant improvements in the ACOS algorithm, it will continue to evolve and improve as the CO 2 data record continues to expand.
Characterization of Wildfire Emissions in California: Analysis of Airborne Measurements of Trace Gases from 2013 to 2016
Biomass burning, which includes wildfires, prescribed, and agricultural fires, is an important source of trace gases and particles, and can influence air quality on a local, regional, and global scale. Biomass burning emissions are an important source of several key trace gases including carbon dioxide (CO2) and methane (CH4). With the threat of wildfire events increasing due to changes in land use, increasing population, and climate change, the importance of characterizing wildfire emissions is vital. In this work we characterize trace gas emissions from 9 wildfire events in California between 2013 – 2016, in some cases with multiple measurements performed during different burn periods of a specific wildfire. During this period airborne measurements of CO2, CH4, water vapor (H2O), ozone (O3), and formaldehyde (HCHO) were made by the Alpha Jet Atmospheric eXperiment (AJAX). Located in the Bay Area of California, AJAX is a joint effort between NASA Ames Research Center and H211, LLC. AJAX makes in-situ airborne measurements of trace gases 2-4 times per month, resulting in 229 flights to date since 2011. Results presented include emission ratios (ER) of trace gases measured by AJAX during fire flights, and comparisons of ERs are made for each fire, which differ in time, location, burning intensity, and fuel type. We also use our airborne measurements to compare with photochemical grid model results to assess model approximations of plume transport and chemical evolution from select wildfires.
Southern California Megacity CO2, CH4, and CO Flux Estimates Using Ground- and Space-Based Remote Sensing and a Lagrangian Model
We estimate the overall CO2, CH4, and CO flux from the South Coast Air Basin using an inversion that couples Total Carbon Column Observing Network (TCCON) and Orbiting Carbon Observatory-2 (OCO-2) observations, with the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and the Open-source Data Inventory for Anthropogenic CO2 (ODIAC). Using TCCON data we estimate the direct net CO2 flux from the So-CAB to be 104±26 Tg CO2 yr(exp -1) for the study period of July 2013–August 2016. We obtain a slightly higher estimate of 120±30 Tg CO2 yr(exp -1) using OCO-2 data. These CO2 emission estimates are on the low end of previous work. Our net CH4 (360±90 Gg CH4 y(exp -1)) flux estimate is in agreement with central values from previous top-down studies going back to 2010 (342–440 Gg CH4 yr(exp -1)). CO emissions are estimated at 487±122 Gg CO yr(exp -1), much lower than previous top-down estimates (1440 Gg CO yr(exp -1)). Given the decreasing emissions of CO, this finding is not unexpected. We perform sensitivity tests to estimate how much errors in the prior, errors in the covariance, different inversion schemes, or a coarser dynamical model influence the emission estimates. Overall, the uncertainty is estimated to be 25%, with the largest contribution from the dynamical model. Lessons learned here may help in future inversions of satellite data over urban areas.
Quantifying Methane Leak Emissions by Fused Airborne Imaging Spectroscopy with in Situ Surface Mobile and Airborne Observations of a California Producing Oil Field
Methane (CH4) emission budgets remain uncertain and are projected to grow as oil and gas production from short-lived wells increases and their subsequent transport through aging gas distribution networks. Orders-of-magnitude variations in temporal, spatial, and emission scales present a key challenge to leak detection and quantification. Also, the probability distributions for large and stochastic, leaky systems such as geological reservoirs (by natural migration-seeps) and petroleum production from those reservoirs remain largely unknown, needed to address current approach limitations. The scale of many petroleum systems favors remote sensing, but the sensitivity of such systems often precludes detection of weak emissions. Consequently, an accurate evaluation requires that the relative contribution from the emission "tails" of small leaks also be quantified, which is best carried out using high-sensitivity in situ methods. Fusion of remote sensing and in situ approaches leverages complementary capabilities to address these limitations. We show results from mobile surface (AMOG) and airborne in situ (AJAX) and thermal-infrared (TIR) hyperspectral imaging spectroscopy (Mako) data applied to a producing oil field in the California Central Valley near Bakersfield. AMOG is an automobile-based mobile lab that measures 13 trace gases, aerosol size distributions and vertical profiles, 3D winds and other meteorology, and atmospheric column measurements by solar spectroscopy at highway speeds. AJAX measures 5 trace gases and 3D winds at ~140 m/s. Mako is a broad-area TIR imaging spectrometer that can discriminate multiple gases present in each pixel acquired. In situ-derived, total field emissions were 31±16 Gg/yr CH4. This was compared with Mako-derived emissions from all plumes identified across the study site. We found that super-emitters were not the dominant emissions mode and the spatial pattern of plume locations from production infrastructure was correlated to geological structures.
Proposed Trace Gas Measurements Over the Western United States for TROPOMI Validation
The Alpha Jet Atmospheric eXperiment (AJAX), located in the Bay Area of California, is a joint effort between NASA Ames Research Center and H211, LCC. AJAX makes in-situ airborne measurements of trace gases 2-4 times per month, resulting in over 216 flights since 2011. Current measurements include ozone (O3), carbon dioxide (CO2), methane (CH4), water (H2O), formaldehyde (HCHO), and meteorological measurements (i.e., ambient pressure, temperature, and 3D winds). Currently, the AJAX team is working to incorporate nitrogen dioxide (NO2) measurements with a Cavity Attenuated Phase Shift Spectrometer (CAPS). Successful science flights coincident with satellite overpasses have been performed since 2011 by the Alpha Jet, with more than 40 flights under the Greenhouse Observing SATellite (GOSAT) and several flights under the Orbiting Carbon Observatory-2 (OCO-2). Results from these flights, which have covered a range of different surfaces and seasonal conditions, will be presented. In-situ vertical profiles of O3, CO2, CH4, H2O, HCHO, and NO2 from the surface to 28,000 feet made by AJAX will also be valuable for satellite validation of data products obtained from the TROPOspheric Montoring Instrument (TROPOMI). TROPOMI is on board the Copernicus Sentinel-5 precursor (S5p) satellite, with level 2 products including O3, CO, CH4, HCHO, NO2, and aerosols.
A New Non-Resonant Laser-Induced Fluorescence Instrument for the Airborne in Situ Measurement of Formaldehyde
A new in situ instrument for gas-phase formaldehyde (HCHO), COmpact Formaldehyde FluorescencE Experiment (COFFEE), is presented. COFFEE utilizes nonresonant laser-induced fluorescence (NR-LIF) to measure HCHO, with 300 mW of 40 kHz 355 nm laser output exciting multiple HCHO absorption features. The resulting HCHO fluorescence is collected at 5 ns resolution, and the fluorescence time profile is fit to yield the ambient HCHO mixing ratio. Typical 1 sigma precision at approximately 0 pptv HCHO is 150 pptv for 1 s data. The compact instrument was designed to operate with minimal in-flight operator interaction and infrequent maintenance (1-2 times per year). COFFEE fits in the wing pod of the Alpha Jet stationed at the NASA Ames Research Center and has successfully collected HCHO data on 27 flights through 2017 March. The frequent flights, combined with a potentially long-term data set, makes the Alpha Jet a promising platform for validation of satellite-based column HCHO.
Lower-tropospheric CO 2 from near-infrared ACOS-GOSAT observations
We present two new products from near-infrared Greenhouse Gases Observing Satellite (GOSAT) observations: lowermost tropospheric (LMT, from 0 to 2.5 km) and upper tropospheric–stratospheric ( U , above 2.5 km) carbon dioxide partial column mixing ratios. We compare these new products to aircraft profiles and remote surface flask measurements and find that the seasonal and year-to-year variations in the new partial column mixing ratios significantly improve upon the Atmospheric CO 2 Observations from Space (ACOS) and GOSAT (ACOS-GOSAT) initial guess and/or a priori, with distinct patterns in the LMT and U seasonal cycles that match validation data. For land monthly averages, we find errors of 1.9, 0.7, and 0.8 ppm for retrieved GOSAT LMT, U , and X CO 2 ; for ocean monthly averages, we find errors of 0.7, 0.5, and 0.5 ppm for retrieved GOSAT LMT, U , and X CO 2 . In the southern hemispheric biomass burning season, the new partial columns show similar patterns to MODIS fire maps and MOPITT multispectral CO for both vertical levels, despite a flat ACOS-GOSAT prior, and a CO–CO 2 emission factor comparable to published values. The difference of LMT and U , useful for evaluation of model transport error, has also been validated with a monthly average error of 0.8 (1.4) ppm for ocean (land). LMT is more locally influenced than U , meaning that local fluxes can now be better separated from CO 2 transported from far away.
Investigating Sources of Ozone over California Using AJAX Airborne Measurements and Models: Assessing the Contribution from Long Range Transport
High ozone (O3) concentrations at low altitudes (1.5e4 km) were detected from airborne Alpha Jet Atmospheric eXperiment (AJAX) measurements on 30 May 2012 off the coast of California (CA). We investigate the causes of those elevated O3 concentrations using airborne measurements and various models. GEOS-Chem simulation shows that the contribution from local sources is likely small. A back trajectory model was used to determine the air mass origins and how much they contributed to the O3 over CA. Low-level potential vorticity (PV) from Modern Era Retrospective analysis for Research and Applications 2 (MERRA-2) reanalysis data appears to be a result of the diabatic heating and mixing of airs in the lower altitudes, rather than be a result of direct transport from stratospheric intrusion. The Q diagnostic, which is a measure of the mixing of the air masses, indicates that there is sufficient mixing along the trajectory to indicate that O3 from the different origins is mixed and transported to the western U.S.The back-trajectory model simulation demonstrates the air masses of interest came mostly from the mid troposphere (MT, 76), but the contribution of the lower troposphere (LT, 19) is also significant compared to those from the upper troposphere/lower stratosphere (UTLS, 5). Air coming from the LT appears to be mostly originating over Asia. The possible surface impact of the high O3 transported aloft on the surface O3 concentration through vertical and horizontal transport within a few days is substantiated by the influence maps determined from the Weather Research and Forecasting Stochastic Time Inverted Lagrangian Transport (WRF-STILT) model and the observed increases in surface ozone mixing ratios. Contrasting this complex case with a stratospheric-dominant event emphasizes the contribution of each source to the high O3 concentration in the lower altitudes over CA. Integrated analyses using models, reanalysis, and diagnostic tools, allows high ozone values detected by in-situ measurements to be attributed to multiple source processes.
Cloud and Sun-Glint Statistics Derived from GOES and MODIS Observations Over the Intra-Americas Sea for GEO-CAPE Mission Planning
Knowledge of cloud cover, frequency, and duration is not only important to study cloud dynamics, but also critical in determining when and where to take ocean measurements from geostationary orbits such as the Geostationary Coastal and Air Pollution Events (GEO-CAPE) mission due to the challenges in achieving complete hemispheric coverage of coastal oceans, estuaries, and inland waters at hourly frequency. Using GOES hourly measurements at 4 km nadir resolution between 2006 and 2011, the number of cloud-free hourly observations per day (N(sub cf)) for solar zenith angle Theta(sub 0) less than 80 degrees was estimated for each 0.1 degree location of the Intra-Americas Sea. The number of Sun-glint-affected hourly observations per day [Ns(sub sg)] was also calculated based on the planned GEO-CAPE observation geometry and realistic wind speed. High-latitude and equatorial oceans showed the lowest N(sub cf) (less than 2.4) in all climatological months, and highest N(sub cf) was observed in the Gulf of Mexico (GoM) and Caribbean (greater than 4.5). Different regions showed differences in seasonality of cloud-free conditions and also showed differences in the hour of a day at which the satellite observations would have the maximal cloud-free and glint-free probability (Temperature maximum). Cloud cover from Moderate Resolution Imaging Spectroradiometer (MODIS) 1 km measurements are greater than 10 degrees higher than those from the MODIS 250 m measurements, supporting ocean color missions at subkilometer resolutions to enhance both spatial coverage and temporal frequency. These findings provide valuable information for GEO-CAPE mission planning to maximize its science value through minimizing the impacts of clouds and Sun glint.
Western US Tropospheric Ozone: An Assessment of Vertical and Seasonal Variations over California and Nevada
In the rural western US free-tropospheric O3 has risen in recent years as a result of rising Asian emissions, deep stratospheric intrusions and more frequent wildfires. This increasing O3 trend combined with the high surface elevation of much of the western US, which aids mixing between boundary layer and free-troposphere, pose challenges in attaining the more stringent O3 National Ambient Air Quality Standard (NAAQS) at many western US rural surface sites. As such, the ability to identify various sources and transport mechanisms that contribute towards surface O3 is increasingly important. This paper analyzes vertical profiles of O3 from the Alpha Jet Atmospheric eXperiment (AJAX) over California and Nevada, ozonesondes from Trinidad Head, CA and tropospheric ozone profiles from the differential absorption lidar (DIAL) at the JPL Table Mountain Facility, CA. Surface O3 from the US EPA Clean air Status and Trends Network (CASNET) are used to discuss surface trends. GEOS-Chem determines the trends in regional O3 and assess the contributions of various sources on surface O3. And Realtime Air Quality Modeling System (RAQMS) is used to forecast and interpret free-tropospheric observations. Specifically we will address the following questions: What are the effects of the lowered NAAQS? Do we observe elevated O3 during 2012 at surface sites reported in previous studies? And if so, what are the causes? How variable is free-tropospheric O3 over California and Nevada? How frequently do we observe high O3 lamina in the free troposphere and what are the surface impacts?
New Approach to Characterize CO2 and CH4 Emissions over Sacramento, California Using an Airborne Aircraft Measurement
Emission fluxes of carbon dioxide (CO2) and methane (CH4) over Sacramento, California, USA, are estimated using an aircraft equipped with a cavity ring-down greenhouse gas sensor through the Alpha Jet Atmospheric eXperiment (AJAX). To better quantify the emission fluxes over the entire city and two small point sources within the area, we designed flights in a cylindrical pattern and computed the emission fluxes from 9 flights over all seasons using the Kriging method based on Gausss divergence theorem. The concentrations at the downwind side of Sacramento show somewhat persistent patterns among the 9 flights, but the magnitudes and locations of the fluxes vary depending on the individual weather conditions and seasonality on a given flight day. The net emission fluxes tend to be smaller in summer (July) than winter (November). Both trace gas mixing ratios as well as the wind speed and direction show high spatial variability both horizontally and vertically. The local maximum emission fluxes over a landfill and a rice field measured on July 29, 2015, were 2-3 times lower than the maximum measured over the entire city. These low emission fluxes suggest that not only the local source but also the transport of greenhouse gases due to diurnal and seasonal variation in winds have a strong effect on the CO2 and CH4 flux estimation of the both local emissions and city-size emissions. Our results highlight that the aircraft-based approach is effective and useful for capturing city-size emission fluxes and estimating the greenhouse gas emissions and its sources.
Using Airborne In-Situ Profiles to Evaluate TCCON Data from Armstrong Flight Research Center
A Fourier Transform Spectrometer (FTS) was deployed to the Armstrong Flight Research Center (AFRC) in Edwards, CA as a member of the Total Carbon Column Observing Network (TCCON) and has now been in operation for over 3 years. The data record from AFRC will be presented as well as airborne validation profiles obtained during the NASA SEAC4RS, SARP, KORUS-AQ, and ATom missions utilizing various NASA aircraft. One of the reasons that the AFRC location was selected is due to its proximity to a highly reflective lakebed, which has proven to be difficult for accurate satellite retrievals. As such, the data from AFRC has been used for OCO-2 calibration. In order for accurate calibration of OCO-2, the validity of the TCCON measurements must be established. To this end, integrated airborne in-situ vertical profiles will be presented and compared with the TCCON FTS measurements, where good agreement has been found.