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Journal of Geophysical Research. Atmospheres: JGR

C Roulston, C Paton-Walsh, T E L Smith, É-A Guérette, S Evers, C M Yule, G Rein, G R Van der Werf
Southeast Asia experiences frequent fires in fuel-rich tropical peatlands, leading to extreme episodes of regional haze with high concentrations of fine particulate matter (PM2.5 ) impacting human health. In a study published recently, the first field measurements of PM2.5 emission factors for tropical peat fires showed larger emissions than from other fuel types. Here we report even higher PM2.5 emission factors, measured at newly ignited peat fires in Malaysia, suggesting that current estimates of fine particulate emissions from peat fires may be underestimated by a factor of 3 or more...
May 27, 2018: Journal of Geophysical Research. Atmospheres: JGR
Jesús Vergara-Temprado, Mark A Holden, Thomas R Orton, Daniel O'Sullivan, Nsikanabasi S Umo, Jo Browse, Carly Reddington, María Teresa Baeza-Romero, Jenny M Jones, Amanda Lea-Langton, Alan Williams, Ken S Carslaw, Benjamin J Murray
It has been hypothesized that black carbon (BC) influences mixed-phase clouds by acting as an ice-nucleating particle (INP). However, the literature data for ice nucleation by BC immersed in supercooled water are extremely varied, with some studies reporting that BC is very effective at nucleating ice, whereas others report no ice-nucleating ability. Here we present new experimental results for immersion mode ice nucleation by BC from two contrasting fuels (n-decane and eugenol). We observe no significant heterogeneous nucleation by either sample...
April 27, 2018: Journal of Geophysical Research. Atmospheres: JGR
Thomas J Greenwald, Ralf Bennartz, Matthew Lebsock, João Teixeira
The first extended comprehensive data set of the retrieval uncertainties in passive microwave observations of cloud liquid water path (CLWP) for warm oceanic clouds has been created for practical use in climate applications. Four major sources of systematic errors were considered over the 9-year record of the Advanced Microwave Scanning Radiometer-EOS (AMSR-E): clear-sky bias, cloud-rain partition (CRP) bias, cloud-fraction-dependent bias, and cloud temperature bias. Errors were estimated using a unique merged AMSR-E/Moderate resolution Imaging Spectroradiometer Level 2 data set as well as observations from the Cloud-Aerosol Lidar with Orthogonal Polarization and the CloudSat Cloud Profiling Radar...
April 16, 2018: Journal of Geophysical Research. Atmospheres: JGR
H Moon, L Gudmundsson, S I Seneviratne
The persistence of drought events largely determines the severity of socioeconomic and ecological impacts, but the capability of current global climate models (GCMs) to simulate such events is subject to large uncertainties. In this study, the representation of drought persistence in GCMs is assessed by comparing state-of-the-art GCM model simulations to observation-based data sets. For doing so, we consider dry-to-dry transition probabilities at monthly and annual scales as estimates for drought persistence, where a dry status is defined as negative precipitation anomaly...
April 16, 2018: Journal of Geophysical Research. Atmospheres: JGR
B M Hare, O Scholten, A Bonardi, S Buitink, A Corstanje, U Ebert, H Falcke, J R Hörandel, H Leijnse, P Mitra, K Mulrey, A Nelles, J P Rachen, L Rossetto, C Rutjes, P Schellart, S Thoudam, T N G Trinh, S Ter Veen, T Winchen
Lightning mapping technology has proven instrumental in understanding lightning. In this work we present a pipeline that can use lightning observed by the LOw-Frequency ARray (LOFAR) radio telescope to construct a 3-D map of the flash. We show that LOFAR has unparalleled precision, on the order of meters, even for lightning flashes that are over 20 km outside the area enclosed by LOFAR antennas (∼3,200 km2 ), and can potentially locate over 10,000 sources per lightning flash. We also show that LOFAR is the first lightning mapping system that is sensitive to the spatial structure of the electrical current during individual lightning leader steps...
March 16, 2018: Journal of Geophysical Research. Atmospheres: JGR
Christopher J Schultz, Timothy J Lang, Eric C Bruning, Kristin M Calhoun, Sebastian Harkema, Nathan Curtis
This study examined 34 lightning flashes within four separate thundersnow events derived from lightning mapping arrays (LMAs) in northern Alabama, central Oklahoma, and Washington DC. The goals were to characterize the in-cloud component of each lightning flash, as well as the correspondence between the LMA observations and lightning data taken from national lightning networks like the National Lightning Detection Network (NLDN). Individual flashes were examined in detail to highlight several observations within the dataset...
February 27, 2018: Journal of Geophysical Research. Atmospheres: JGR
A I Gevaert, D G Miralles, R A M de Jeu, J Schellekens, A J Dolman
The land surface controls the partitioning of water and energy fluxes and therefore plays a crucial role in the climate system. The coupling between soil moisture and air temperature, in particular, has been shown to affect the severity and occurrence of temperature extremes and heat waves. Here we study soil moisture-temperature coupling in five land surface models, focusing on the terrestrial segment of the coupling in the warm season. All models are run off-line over a common period with identical atmospheric forcing data, in order to allow differences in the results to be attributed to the models' partitioning of energy and water fluxes...
February 16, 2018: Journal of Geophysical Research. Atmospheres: JGR
David C Fritts, Brian Laughman, Ling Wang, Thomas S Lund, Richard L Collins
An anelastic numerical model is employed to explore the dynamics of gravity waves (GWs) encountering a mesosphere inversion layer (MIL) having a moderate static stability enhancement and a layer of weaker static stability above. Instabilities occur within the MIL when the GW amplitude approaches that required for GW breaking due to compression of the vertical wavelength accompanying the increasing static stability. Thus, MILs can cause large-amplitude GWs to yield instabilities and turbulence below the altitude where they would otherwise arise...
January 27, 2018: Journal of Geophysical Research. Atmospheres: JGR
A M Sayer, N C Hsu, J Lee, C Bettenhausen, W V Kim, A Smirnov
The Suomi National Polar-Orbiting Partnership (S-NPP) satellite, launched in late 2011, carries the Visible Infrared Imaging Radiometer Suite (VIIRS) and several other instruments. VIIRS has similar characteristics to prior satellite sensors used for aerosol optical depth (AOD) retrieval, allowing the continuation of space-based aerosol data records. The Deep Blue algorithm has previously been applied to retrieve AOD from Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Moderate Resolution Imaging Spectro-radiometer (MODIS) measurements over land...
January 16, 2018: Journal of Geophysical Research. Atmospheres: JGR
Xuepeng Zhao, Yangang Liu, Fangquan Yu, Andrew K Heidinger
Long-term (1981-2011) satellite climate data records of clouds and aerosols are used to investigate the aerosol-cloud interaction of marine water cloud from a climatology perspective. Our focus is on identifying the regimes and regions where the aerosol indirect effects (AIEs) are evident in long-term averages over the global oceans through analyzing the correlation features between aerosol loading and the key cloud variables including cloud droplet effective radius (CDER), cloud optical depth (COD), cloud water path (CWP), cloud top height (CTH), and cloud top temperature (CTT)...
January 16, 2018: Journal of Geophysical Research. Atmospheres: JGR
Andrew Mezentsev, Nikolai Lehtinen, Nikolai Østgaard, F J Pérez-Invernón, Steven A Cummer
We compared the modeled energy spectral density of very low frequency (VLF) radio emissions from terrestrial gamma ray flashes (TGFs) with the energy spectral density of VLF radio sferics recorded by Duke VLF receiver simultaneously with those TGFs. In total, six events with world wide lightning location network (WWLLN) defined locations were analyzed to exhibit a good fit between the modeled and observed energy spectral densities. In VLF range the energy spectral density of the TGF source current moment is found to be dominated by the contribution of secondary low-energy electrons and independent of the relativistic electrons which play their role in low-frequency (LF) range...
January 16, 2018: Journal of Geophysical Research. Atmospheres: JGR
Michael Peterson, Scott Rudlosky, Wiebke Deierling
This study documents the composition, morphology, and motion of extreme optical lightning flashes observed by the Lightning Imaging Sensor (LIS). The furthest separation of LIS events (groups) in any flash is 135 km (89 km), the flash with the largest footprint had an illuminated area of 10,604 km2 , and the most dendritic flash has 234 visible branches. The longest-duration convective LIS flash lasted 28 s and is overgrouped and not physical. The longest-duration convective-to-stratiform propagating flash lasted 7...
December 27, 2017: Journal of Geophysical Research. Atmospheres: JGR
Lyatt Jaeglé, Robert Wood, Krzysztof Wargan
We examine the role of extratropical cyclones in stratosphere-to-troposphere (STT) exchange with cyclone-centric composites of O3 retrievals from the Microwave Limb Sounder (MLS) and the Tropospheric Emission Spectrometer (TES), contrasting them to composites obtained with the Modern-Era Retrospective-analysis for Research and Applications (MERRA and MERRA-2) reanalyses and the GEOS-Chem chemical transport model. We identify 15,978 extratropical cyclones in the northern hemisphere (NH) for 2005-2012. The lowermost stratosphere (261 hPa) and middle troposphere (424 hPa) composites feature a 1,000 km-wide O3 enhancement in the dry intrusion (DI) airstream to the southwest of the cyclone center, coinciding with a lowered tropopause, enhanced potential vorticity, and decreased H2 O...
December 27, 2017: Journal of Geophysical Research. Atmospheres: JGR
Pavlo Kochkin, A P J van Deursen, M Marisaldi, A Ursi, A I de Boer, M Bardet, C Allasia, J-F Boissin, F Flourens, N Østgaard
An Airbus A340 aircraft flew over Northern Australia with the In-Flight Lightning Damage Assessment System (ILDAS) installed onboard. A long-duration gamma ray emission was detected. The most intense emission was observed at 12 km altitude and lasted for 20 s. Its intensity was 20 times the background counts, and it was abruptly terminated by a distant lightning flash. In this work we reconstruct the aircraft path and event timeline. The glow-terminating flash triggered a discharge from the aircraft wing that was recorded by a video camera operating onboard...
December 16, 2017: Journal of Geophysical Research. Atmospheres: JGR
Shi Kuang, Michael J Newchurch, Anne M Thompson, Ryan M Stauffer, Bryan J Johnson, Lihua Wang
Tropospheric ozone variability occurs because of multiple forcing factors including surface emission of ozone precursors, stratosphere-to-troposphere transport (STT), and meteorological conditions. Analyses of ozonesonde observations made in Huntsville, AL, during the peak ozone season (May to September) in 2013 indicate that ozone in the planetary boundary layer was significantly lower than the climatological average, especially in July and August when the Southeastern United States (SEUS) experienced unusually cool and wet weather...
October 27, 2017: Journal of Geophysical Research. Atmospheres: JGR
A Park Williams, Benjamin I Cook, Jason E Smerdon, Daniel A Bishop, Richard Seager, Justin S Mankin
The fall 2016 drought in the southeastern United States (SE US) appeared exceptional based on its widespread impacts, but the current monitoring framework that only extends from 1979-present does not readily facilitate evaluation of soil-moisture anomalies in a centennial context. A new method to extend monthly gridded soil-moisture estimates back to 1895 is developed, indicating that since 1895, October-November 2016 soil moisture (0-200 cm) in the SE US was likely the second lowest on record, behind 1954...
October 27, 2017: Journal of Geophysical Research. Atmospheres: JGR
Daniel C Anderson, Julie M Nicely, Glenn M Wolfe, Thomas F Hanisco, Ross J Salawitch, Timothy P Canty, Russell R Dickerson, Eric C Apel, Sunil Baidar, Thomas J Bannan, Nicola J Blake, Dexian Chen, Barbara Dix, Rafael P Fernandez, Samuel R Hall, Rebecca S Hornbrook, L Gregory Huey, Beatrice Josse, Patrick Jöckel, Douglas E Kinnison, Theodore K Koenig, Michael LeBreton, Virginie Marécal, Olaf Morgenstern, Luke D Oman, Laura L Pan, Carl Percival, David Plummer, Laura E Revell, Eugene Rozanov, Alfonso Saiz-Lopez, Andrea Stenke, Kengo Sudo, Simone Tilmes, Kirk Ullmann, Rainer Volkamer, Andrew J Weinheimer, Guang Zeng
Formaldehyde (HCHO) directly affects the atmospheric oxidative capacity through its effects on HOx . In remote marine environments, such as the Tropical Western Pacific (TWP), it is particularly important to understand the processes controlling the abundance of HCHO because model output from these regions is used to correct satellite retrievals of HCHO. Here, we have used observations from the CONTRAST field campaign, conducted during January and February 2014, to evaluate our understanding of the processes controlling the distribution of HCHO in the TWP as well as its representation in chemical transport/climate models...
October 27, 2017: Journal of Geophysical Research. Atmospheres: JGR
Jaehwa Lee, N Christina Hsu, Andrew M Sayer, Corey Bettenhausen, Ping Yang
Aerosol Robotic Network (AERONET)-based nonspherical dust optical models are developed and applied to the Satellite Ocean Aerosol Retrieval (SOAR) algorithm as part of the Version 1 Visible Infrared Imaging Radiometer Suite (VIIRS) NASA 'Deep Blue' aerosol data product suite. The optical models are created using Version 2 AERONET inversion data at six distinct sites influenced frequently by dust aerosols from different source regions. The same spheroid shape distribution as used in the AERONET inversion algorithm is assumed to account for the nonspherical characteristics of mineral dust, which ensures the consistency between the bulk scattering properties of the developed optical models with the AERONET-retrieved microphysical and optical properties...
October 16, 2017: Journal of Geophysical Research. Atmospheres: JGR
Xiaomeng Jin, Arlene M Fiore, Lee T Murray, Lukas C Valin, Lok N Lamsal, Bryan Duncan, K Folkert Boersma, Isabelle De Smedt, Gonzalo Gonzalez Abad, Kelly Chance, Gail S Tonnesen
Determining effective strategies for mitigating surface ozone (O3 ) pollution requires knowledge of the relative ambient concentrations of its precursors, NO x , and VOCs. The space-based tropospheric column ratio of formaldehyde to NO2 (FNR) has been used as an indicator to identify NO x -limited versus NO x -saturated O3 formation regimes. Quantitative use of this indicator ratio is subject to three major uncertainties: (1) the split between NO x -limited and NO x -saturated conditions may shift in space and time, (2) the ratio of the vertically integrated column may not represent the near-surface environment, and (3) satellite products contain errors...
October 16, 2017: Journal of Geophysical Research. Atmospheres: JGR
Alejandro Luque
We present a full electromagnetic model of streamer propagation where the Maxwell equations are solved self-consistently together with electron transport and reactions including photoionization. We apply this model to the collision of counter-propagating streamers in gaps tens of centimeters wide and with large potential differences of hundreds of kilovolts. Our results show that streamer collisions emit electromagnetic pulses that, at atmospheric pressure, dominate the radio frequency spectrum of an extended corona in the range from about 100 MHz to a few gigahertz...
October 16, 2017: Journal of Geophysical Research. Atmospheres: JGR
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