PAN in the eastern Pacific free troposphere: A satellite view of the sources, seasonality, interannual variability, and timeline for trend detection

Abstract

Peroxyacetyl nitrate (PAN) is an important trace gas that serves to transport nitrogen oxide radicals throughout the troposphere. We present an analysis of satellite observations of PAN from the Tropospheric Emission Spectrometer (TES) over the eastern Pacific Ocean for April and July 2006–2010 and the spring‐to‐summer seasonal transition for 2006. TES can provide quantitative estimates of free tropospheric PAN in clear‐sky or thin cloud conditions where elevated PAN (>0.2 ppbv) is present. The percentage of successful PAN detections increases from April to July and then decreases in August and September. However, there are no significant differences in the tropospheric average PAN either interannually or between these months. Plumes containing elevated PAN are present almost every day in July. Elevated PAN observed in July has multiple sources, including fires in Siberia, anthropogenic sources in eastern China, and recirculated pollution from the continental U.S. We combined the observed variability in the TES PAN retrievals over the eastern Pacific Ocean with a range of possible trends in PAN to determine the observational requirements to detect such trends. Based on the variability observed in the PAN retrievals over this region, we predict that it would be faster to detect a trend of a given magnitude in PAN using satellite observations over the eastern Pacific Ocean region rather than in situ surface observations and that a trend of a given magnitude would be more quickly detected in summer than spring.

A General Framework for Global Retrievals of Trace Gases From IASI: Application to Methanol, Formic Acid, and PAN

“…Nonetheless, these products have limitations in terms of reliability and error characterization, which are not easily addressed. Although IASI measurements of PAN have been reported in concentrated biomass burning and pollution plumes (Clarisse, Fromm, et al, 2011;Clarisse, R'Honi, et al, 2011;Coheur et al, 2009), and PAN TES data have been used to study Northern Eurasian and North American fires, long-range pollution transport, and year-to-year variations in the Tropics (Fischer et al, 2018;Jiang et al, 2016;Payne et al, 2017;Zhu et al, 2015Zhu et al, , 2017, no global daily distributions of PAN have been retrieved until now.…”

Southern Hemisphere mid- and high-latitudinal AOD, CO, NO2, and HCHO: spatiotemporal patterns revealed by satellite observations

“…Although NO 2 has a short average lifetime, on the order of 1 day (Beirle et al 2003), the distribution of high NO 2 around the source regions indicates that NO 2 can be transported away from source regions. The transport of NO 2 can occur in the form of reservoirs, such as peroxyacetyl nitrates (PANs) (Liu et al 2003;Zhu et al 2017). The higher the latitude within the study area, the lower the concentration of NO 2 , again illustrating the absence of NO 2 sources (e.g., urban and industry) near the polar region.…”

Spatial variability in tropospheric peroxyacetyl nitrate in the tropics from infrared satellite observations in 2005 and 2006

“…More recently, global measurements of tropospheric PAN from Aura-TES have been obtained and are described in Payne et al (2014). These TES PAN retrievals have so far been utilized in studies of the influence of fires in atmospheric composition in boreal spring (Zhu et al, 2015), the role of PAN in seasonal transport of East Asian pollution (Jiang et al, 2016) and the seasonality and interannual variability of PAN in the eastern Pacific (Zhu et al, 2017). Here we present new observations of TES PAN in the tropics.…”