David B. Harper

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Atmospheric chloromethane (CH3Cl) plays an important role in stratospheric ozone destruction, but many uncertainties exist regarding the strengths of its sources and sinks and particularly regarding the processes generating this naturally occurring gas. Evidence is presented here that CH3Cl is produced in many terrestrial environments by a common mechanism.(More)
The NASA Langley Research Center (LaRC) airborne High Spectral Resolution Lidar (HSRL) measures vertical profiles of aerosol extinction, backscatter, and depo-larization at both 532 nm and 1064 nm. In March of 2006 the HSRL participated in the Megacity Initiative: Local and Global Research Observations (MILAGRO) campaign along with several other suites of(More)
Atmospheric chloromethane (CH 3 Cl) plays an important role in stratospheric ozone destruction, but many uncertainties still exist regarding strengths of both sources and sinks and the processes leading to formation of this naturally occurring gas. Recent work has identified a novel chemical origin for CH 3 Cl, which can explain its production in a variety(More)
We report that the most abundant C 1 units of terrestrial plants, the methoxyl groups of pectin and lignin, have a unique carbon isotope signature exceptionally depleted in 13 C. Plant-derived C 1 volatile organic compounds (VOCs) are also anomalously depleted in 13 C compared with C n+1 VOCs. The results confirm that the plant methoxyl pool is the(More)
The NASA Langley Research Center (LaRC) airborne High Spectral Resolution Lidar (HSRL) on the NASA B200 aircraft has acquired extensive datasets of aerosol extinction (532 nm), aerosol optical depth (AOD) (532 nm), backscatter (532 and 1064 nm), and depolarization (532 and 1064 nm) profiles during 18 field missions that have been conducted over North(More)
We report that the most abundant C 1 units of terrestrial plants, the methoxyl groups of pectin and lignin, have a unique carbon isotope signature exceptionally depleted in 13 C. Plant-derived C 1 volatile organic compounds (VOCs) are also anomalously depleted in 13 C compared with C n+1 VOCs. The results confirm that the plant methoxyl pool is 5 the(More)
The effect on veratryl alcohol production of supplementing cultures of the lignin-degrading fungus Phanerochaete chrysosporium with different methyl-(sup2)H(inf3)-labelled methyl precursors has been investigated. Both chloromethane (CH(inf3)Cl) and l-methionine caused earlier initiation of veratryl alcohol biosynthesis, but S-adenosyl-l-methionine (SAM)(More)
We present measurements acquired by the world's first airborne 3 backscatter (β) + 2 extinction (α) High Spectral Resolution Lidar (HSRL-2). HSRL-2 measures particle backscatter coefficients at 355, 532, and 1064 nm, and particle extinction coefficients at 355 and 532 nm. The instrument has been developed by the NASA Langley Research Center. The instrument(More)
Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASA's scientific and technical information.(More)
The NASA Langley Research Center (LaRC) airborne High Spectral Resolution Lidar (HSRL) on the NASA B200 aircraft has acquired large datasets of aerosol extinction (532nm), backscatter (532 and 1064nm), and depolarization (532 and 1064nm) profiles during 18 field missions across North America since 2006. The lidar measurements include scale-invariant aerosol(More)