Ozone chemistry in western U.S. wildfire plumes.

Wildfires are a substantial but poorly quantified source of tropospheric ozone (O). Here, to investigate the highly variable O chemistry in wildfire plumes, we exploit the in situ chemical characterization of western wildfires during the FIREX-AQ flight campaign and show that O production can be predicted as a function of experimentally constrained OH exposure, volatile organic compound (VOC) reactivity, and the fate of peroxy radicals. The O chemistry exhibits rapid transition in chemical regimes.

On the sources and sinks of atmospheric VOCs: an integrated analysis of recent aircraft campaigns over North America.

We apply a high-resolution chemical transport model (GEOS-Chem CTM) with updated treatment of volatile organic compounds (VOCs) and a comprehensive suite of airborne datasets over North America to (i) characterize the VOC budget and (ii) test the ability of current models to capture the distribution and reactivity of atmospheric VOCs over this region. Biogenic emissions dominate the North American VOC budget in the model, accounting for 70 % and 95 % of annually emitted VOC carbon and reactivity, respectively. Based on current inventories anthropogenic emissions have declined to the point where biogenic emissions are the dominant summertime source of VOC reactivity even in most major North American cities.

Observing atmospheric formaldehyde (HCHO) from space: validation and intercomparison of six retrievals from four satellites (OMI, GOME2A, GOME2B, OMPS) with SEACRS aircraft observations over the Southeast US.

Formaldehyde (HCHO) column data from satellites are widely used as a proxy for emissions of volatile organic compounds (VOCs) but validation of the data has been extremely limited. Here we use highly accurate HCHO aircraft observations from the NASA SEACRS campaign over the Southeast US in August-September 2013 to validate and intercompare six retrievals of HCHO columns from four different satellite instruments (OMI, GOME2A, GOME2B and OMPS) and three different research groups. The GEOS-Chem chemical transport model is used as a common intercomparison platform.

Formaldehyde columns from the Ozone Monitoring Instrument: Urban versus background levels and evaluation using aircraft data and a global model.

[1] 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 (Ω) retrievals from the Ozone Monitoring Instrument (OMI) and assess the information they provide on HCHO across local to regional scales and urban to background regimes. OMI Ω correlates well with columns derived from aircraft measurements and GEOS-Chem ( = 0.80).

Difference frequency generation spectrometer for simultaneous multispecies detection.

A difference-frequency generation based spectrometer system for simultaneous ultra-sensitive measurements of formaldehyde (CH2O) and Methane (CH4) is presented. A new multiplexing approach using collinear quasi-phase-matching in a single grating period of periodically poled lithium niobate (PPLN) is discussed and demonstrated for two pairs of pump and signal lasers to generate mid-infrared frequencies at 2831.64 cm(-1) and 2916.

High-precision CO2 isotopologue spectrometer with a difference-frequency-generation laser source.

A precision laser spectrometer for the detection of CO(2) isotopes is reported. The spectrometer measures the fundamental absorption signatures of (13)C and (12)C isotopes in CO(2) at 4.32 microm using a tunable mid-IR laser source based on difference-frequency generation.

Development of an eye-safe solid-state tunable laser transmitter in the 1.4-1.5 microm wavelength region based on Cr4+:YAG crystal for lidar applications.

An experimental optimization of the efficiency of a gain switched tunable Cr4+:YAG laser at 10 Hz is described. The thermal lensing during pulsed operation was measured. Optimal performance occurred at a crystal temperature of 34 degrees C and resulted in an output energy of approximately 7 mJ and a pulse duration of approximately 35 ns.

First demonstration of a high performance difference frequency spectrometer on airborne platforms.

We discuss the first airborne deployment and performance tests of a mid-IR difference frequency spectrometer system for highly sensitive measurements of formaldehyde. The laser system is based upon difference-frequency generation (DFG) at ~3.5 mum by mixing a DFB diode laser at 1562 nm and a distributed feedback (DFB) fiber laser at 1083 nm in a periodically poled LiNbO(3) (PPLN) crystal.

High-power, tunable difference frequency generation source for absorption spectroscopy based on a ridge waveguide periodically poled lithium niobate crystal.

A novel waveguide for difference frequency generation in the mid-IR spectral region at 3.52 mum is characterized. High mid-IR power of 15 mW and an external conversion efficiency of up to 19 %W( -1) have been obtained.

Atomic mercury flux monitoring using an optical parametric oscillator based lidar system.

A newly developed optical parametric oscillator (OPO) based differential absorption lidar (DIAL) system has been applied to the monitoring of atomic mercury emissions at several chlor-alkali plants in Europe. The versatility of the system is illustrated by measured time series of mercury flux and movies of vertical and horizontal concentration distributions, which yield important input parameters for the environmental community. Long term measurements of the resonance absorption of mercury at 253.

Versatile mobile lidar system for environmental monitoring.

A mobile lidar (light detection and ranging) system for environmental monitoring is described. The optical and electronic systems are housed in a truck with a retractable rooftop transmission and receiving mirror, connected to a 40-cm-diameter vertically looking telescope. Two injection-seeded Nd:YAG lasers are employed in connection with an optical parametric oscillator-optical parametric amplification transmitter, allowing deep-UV to mid-IR wavelengths to be generated.

Atmospheric mercury near a chlor-alkali plant in Sweden.

Atmospheric mercury species/fractions were measured near a chlor-alkali plant in Sweden during August 28 to September 4, 2001. The concentration of total gaseous mercury in the plume from the plant was measured using TEKRAN and GARDIS instruments. Gaseous elemental mercury was measured using a light detection and ranging (LIDAR) technique.