Effects of a priori profile shape assumptions on comparisons between satellite NO2 columns and model simulations

This paper has a corresponding corrigendum published. Please read the corrigendum first before downloading the article. A critical step in satellite retrievals of trace gas columns is the calculation of the air mass factor (AMF) used to convert observed slant columns to vertical columns. This calculation requires a priori information on the shape of the vertical profile. As a result, comparisons between satellite-retrieved and model-simulated column abundances are influenced by the a priori profile shape. We examine how differences between the shape of the simulated and a priori profiles can impact the interpretation of satellite retrievals by performing an adjoint-based four-dimensional variational (4D-Var) assimilation of synthetic NO2 observations for constraining NOx emissions. We use the GEOS-Chem adjoint model to perform assimilations using a variety of AMFs to examine how a posteriori emission estimates are affected if the AMF is calculated using an a priori shape factor that is inconsistent with the simulated profile. In these tests, an inconsistent a priori shape factor increased root mean square errors in a posteriori emission estimates by up to 30&thinsp;% for realistic conditions over polluted regions. As the difference between the simulated profile shape and the a priori profile shape increases, so do the corresponding assimilated emission errors. This reveals the importance of using simulated profile information for AMF calculations when comparing that simulated output to satellite-retrieved columns. </div

Symmetric and asymmetric action integration during cooperative object manipulation in virtual environments

Cooperation between multiple users in a virtual environment (VE) can take place at one of three levels. These are defined as where users can perceive each other (Level 1), individually change the scene (Level 2), or simultaneously act on and manipulate the same object (Level 3). Despite representing the highest level of cooperation, multi-user object manipulation has rarely been studied. This paper describes a behavioral experiment in which the piano movers' problem (maneuvering a large object through a restricted space) was used to investigate object manipulation by pairs of participants in a VE. Participants' interactions with the object were integrated together either symmetrically or asymmetrically. The former only allowed the common component of participants' actions to take place, but the latter used the mean. Symmetric action integration was superior for sections of the task when both participants had to perform similar actions, but if participants had to move in different ways (e.g., one maneuvering themselves through a narrow opening while the other traveled down a wide corridor) then asymmetric integration was superior. With both forms of integration, the extent to which participants coordinated their actions was poor and this led to a substantial cooperation overhead (the reduction in performance caused by having to cooperate with another person)

El Niño, the 2006 Indonesian peat fires, and the distribution of atmospheric methane

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110818/1/grl50937.pd

Observations of Extreme Wildfire Enhancements of CH3OH, HCOOH, and PAN over the Canadian High Arctic

Wildfires are a common occurrence in many parts of the globe and can emit significant quantities of trace gases and particulate matter, negatively impacting air quality on large spatial scales. Among the various trace gases emitted by wildfires are volatile organic compounds (VOCs). Three VOCs that are of particular importance are methanol (CH3OH), formic acid (HCOOH), and peroxyacetyl nitrate (PAN). CH3OH is the one of the most abundant VOCs in the atmosphere, and it influences the budgets of many tropospheric species including the hydroxyl radical, carbon monoxide, formaldehyde, and ozone. HCOOH is the most abundant tropospheric carboxylic acid, and thus can have significant impacts on atmospheric acidity, particularly in remote regions such as the Arctic. Lastly, PAN is a key, thermally unstable reservoir species of tropospheric nitrogen radicals (NOx = NO + NO2), controlling the production of tropospheric ozone, and contributing to the ‘Arctic haze’ pollution phenomenon at high latitudes.During August 2017, two independent large-scale wildfires in British Columbia and the Northwest Territories of Canada generated vast smoke plumes that merged and were subsequently transported to the high Arctic. Simultaneous observations by a high-resolution ground-based Fourier transform infrared (FTIR) spectrometer at the Polar Environment Research Laboratory (PEARL) in Eureka, Nunavut (80.05°N, 86.42°W), and the Infrared Atmospheric Sounding Interferometer (IASI) satellite instruments display extreme enhancements in these three species relative to background concentrations during the fire-affected period in late August 2017, demonstrating the long-range transport and secondary formation of these typically short-lived species. Initial results of the analysis of this unique biomass burning event will be presented, including comparisons of observations with the GEOS-Chem global chemical transport model.info:eu-repo/semantics/nonPublishe