Jean-Francois Blavier

The Total Carbon Column Observing Network

A global network of ground-based Fourier transform spectrometers has been founded to remotely measure column abundances of CO2, CO, CH4, N2O and other molecules that absorb in the near-infrared. These measurements are directly comparable with the near-infrared total column measurements from space-based instruments. With stringent requirements on the instrumentation, acquisition procedures, data processing and calibration, the Total Carbon Column Observing Network (TCCON) achieves an accuracy and precision in total column measurements that is unprecedented for remote-sensing observations (better than 0.25% for CO2). This has enabled carbon-cycle science investigations using the TCCON dataset, and allows the TCCON to provide a link between satellite measurements and the extensive ground-based in situ network.

Vertical profiles of nitrous oxide isotopomer fractionation measured in the stratosphere

We have measured the vertical profiles of several isotopomers of nitrous oxide, N2O, in the stratosphere by balloon-borne infrared remote sensing between 15 and 35 km. In particular we distinguish the individual profiles and relative enrichments of the positional isotopomers 15N14N16O and 14N15N16O for the first time. We find a distinct and reproducible relative enrichment of the isotopomers which is in general agreement with measured photolysis rates in the laboratory and theoretical predictions. The results confirm photolysis as the dominant stratospheric loss process for N2O and argue against suggestions that additional chemical sources of N2O in the stratosphere are required to explain the observed heavy isotopic enrichments there.

Balloon observations of organic and inorganic chlorine in the stratosphere: The role of HClO4 production on sulfate aerosols

Simultaneous observations of stratospheric organic and inorganic chlorine were made in September 1993 out of Fort Sumner, New Mexico, using JPL balloon-borne MkIV interferometer. Between 15 and 20 km, a significant fraction (20-60%) of the inorganic chlorine could not be accounted for by the sum of measured HCl, ClONO2, and HOCl. Laboratory measurements of the reaction of ClO radicals on sulfuric acid solutions have indicated that, along with HCl, small amounts of perchloric acid, HClO4, were formed. Very little is known about the fate of HClO4 in the stratosphere and we use a photochemical box model to determine the impact of this new species on the partitioning of inorganic chlorine in the stratosphere. Assuming that HClO4 is photochemically stable, it is shown that in the enhanced aerosol loading conditions resulting from Mt. Pinatubos eruption, HClO4 could represent a significant reservoir of chlorine in the lower stratosphere, sequestering up to 0.2 ppbv (or 50%) of the total inorganic chlorine at 16 km. The occurrence of this new species could bring to closure the inorganic chlorine budget deficiency made apparent by recent ER-2 aircraft in situ measurements of HCl.

High-resolution Fourier-transform ultraviolet–visible spectrometer for the measurement of atmospheric trace species: application to OH

A compact, high-resolution Fourier-transform spectrometer for atmospheric near-ultraviolet spectroscopy has been installed at the Jet Propulsion Laboratorys Table Mountain Facility (34.4 degrees N, 117.7 degrees W, elevation 2290 m). This instrument is designed with an unapodized resolving power near 500,000 at 300 nm to provide high-resolution spectra from 290 to 675 nm for the quantification of column abundances of trace atmospheric species. The measurement technique used is spectral analysis of molecular absorptions of solar radiation. The instrument, accompanying systems designs, and results of the atmospheric hydroxyl column observations are described.

Near IR photolysis of HO2NO2: Implications for HOx

We report observations and calculations of peroxynitric acid, HO_2NO_2, in the stratosphere and upper troposphere. The simulations show that photolysis of HO_2NO_2 via excitation of purely vibrational modes at wavelengths longward of 760 nm (the near IR) can dominate loss of this species. Consideration of this photolytic pathway reduces calculated HO_2NO_2, resolving a large discrepancy between standard model calculations and observations of HO_2NO_2 at high-latitude spring. The lower calculated abundance of HO_2NO_2 reduces the efficiency of the OH + HO_2NO_2 sink of HO_x. Consideration of this process leads to large increases in calculated HO_x (20 to 60%) for high-latitude spring and better agreement with observed stratospheric abundances of HO_x. Near IR photolysis of HO_2NO_2 alters the coupling between NO_x and HO_x in stratospheric and upper tropospheric photochemical models.

On the stratospheric chemistry of hydrogen cyanide

HCN profiles measured by solar occultation spectrometry during 10 balloon flights of the JPL MkIV instrument are presented. The HCN profiles reveal a compact correlation with stratospheric tracers. Calculations with a 2D-model using established rate coefficients for the reactions of HCN with OH and O(^1D) severely underestimate the measured HCN in the middle and upper stratosphere. The use of newly available rate coefficients for these reactions gives reasonable agreement of measured and modeled HCN. An HCN yield of ∼30% from the reaction of CH_3CN with OH is consistent with the measurements.

Infrared measurements of atmospheric CH3CN

For the first time CH_3CN has been measured in the Earths atmosphere by means of infrared remote sensing. Vertical profiles of volume mixing ratio were retrieved from 12 solar occultation measurements by the balloon-borne JPL MkIV interferometer between 1993 and 2004. Profile retrieval is possible in an altitude range between 12 and 30 km with a precision of ∼20 ppt in the Arctic and ∼30 ppt at mid-latitudes. The retrieved CH_3CN profiles show mixing ratios of 100–150 ppt a few kilometers above the tropopause that decrease to values below 40 ppt at altitudes between 22 and 30 km. The CH_3CN mixing ratios show a reasonably compact correlation with the stratospheric tracers CH_3Cl and CH_4. The CH_3CN altitude profiles and tracer correlations are well reproduced by a 2-dimensional model, suggesting that CH_3CN is long-lived in the lower stratosphere and that previously-proposed ion-molecule reactions do not play a major role as loss processes of CH_3CN.

An FPGA/SoC Approach to On-Board Data Processing Enabling New Mars Science with Smart Payloads

A proposed Mars Scout Mission known as MARVEL is vying for the 2011 launch opportunity. One of its primary instruments, MATMOS, will produce large volumes of data in short, 3-minute bursts during its on-orbit observation of sunrise and sunset. The remaining orbit time of 112 minutes is available for on-board data processing to reduce data volume prior to downlink. This data processing relies heavily on floating-point FFTs. The Xilinx Virtex-II Pro FPGA was evaluated in a previous research task, but could not meet the performance requirements, even with an integrated soft-core floating-point unit (FPU). The next-generation Virtex-4 FPGA contains an auxiliary processor unit (APU) that provides a flexible high bandwidth interface for fabric co-processor modules (FCM) to the PowerPC405 core. In this paper we show that coupling the FPU FCM with the APU provides sufficient computation power to meet MATMOSs data processing requirements when implemented in a multi-processor, dual-FPGA system.

Intercomparison of total ozone observations at Fairbanks, Alaska, during POLARIS

The pattern of seasonal ozone loss over Fairbanks, Alaska (AK), during the NASA Photochemistry of Ozone Loss in the Arctic Region In Summer (POLARIS) campaign in the spring and summer of 1997 is defined. Five independent data sets of total ozone observations at Fairbanks are presented, from the Earth Probe and ADEOS Total Ozone Mapping Spectrometer (TOMS) satellite instruments, balloon-borne electrochemical concentration cell ozonesondes, and ground-based (Brewer spectroradiometer, Dobson spectrophotometer, and the Jet Propulsion Laboratory MkIV infrared interferometer) instruments. The excellent agreement between different observational techniques lends confidence to the observed rate of summertime loss of total ozone at high latitudes. In addition, the small offsets between the data sets are well understood.

The Geostationary Fourier Transform Spectrometer

The Geostationary Fourier Transform Spectrometer (GeoFTS) is an imaging spectrometer designed for an earth science mission to measure key atmospheric trace gases and process tracers related to climate change and human activity. The GeoFTS instrument is a half meter cube size instrument designed to operate in geostationary orbit as a secondary “hosted” payload on a commercial geostationary satellite mission. The advantage of GEO is the ability to continuously stare at a region of the earth, enabling frequent sampling to capture the diurnal variability of biogenic fluxes and anthropogenic emissions from city to continental scales. The science goal is to obtain a process-based understanding of the carbon cycle from simultaneous high spatial resolution measurements of carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), and chlorophyll fluorescence (CF) many times per day in the near infrared spectral region to capture their spatial and temporal variations on diurnal, synoptic, seasonal and interannual time scales. The GeoFTS instrument is based on a Michelson interferometer design with a number of advanced features incorporated. Two of the most important advanced features are the focal plane arrays and the optical path difference mechanism. A breadboard GeoFTS instrument has demonstrated functionality for simultaneous measurements in the visible and IR in the laboratory and subsequently in the field at the California Laboratory for Atmospheric Remote Sensing (CLARS) observatory on Mt. Wilson overlooking the Los Angeles basin. A GeoFTS engineering model instrument is being developed which will make simultaneous visible and IR measurements under space flight like environmental conditions (thermal-vacuum at 180 K). This will demonstrate critical instrument capabilities such as optical alignment stability, interferometer modulation efficiency, and high throughput FPA signal processing. This will reduce flight instrument development risk and show that the GeoFTS design is mature and flight ready.