Long-term NOx trends over large cities in the United States during the great recession: Comparison of satellite retrievals, ground observations, and emission inventories

Abstract

h i g h l i g h t sDerived multi-year urban NOx trend from satellite (OMI) and ground observations (AQS). Revealed NOx responses to the 2008 Economic Recession by OMI and AQS. The trend not well captured by emissions used for national air quality forecasting. Demonstrated how to use space and ground observations to evaluate emission updates. Emission Trend Air quality forecast Recession OMI NO2 Ozone AQS NAQFC a b s t r a c t National emission inventories (NEIs) take years to assemble, but they can become outdated quickly, especially for time-sensitive applications such as air quality forecasting. This study compares multi-year NO x trends derived from satellite and ground observations and uses these data to evaluate the updates of NO x emission data by the US National Air Quality Forecast Capability (NAQFC) for next-day ozone prediction during the 2008 Global Economic Recession. Over the eight large US cities examined here, both the Ozone Monitoring Instrument (OMI) and the Air Quality System (AQS) detect substantial downward trends from 2005 to 2012, with a seven-year total of À35% according to OMI and À38% according to AQS. The NO x emission projection adopted by NAQFC tends to be in the right direction, but at a slower reduction rate (À25% from 2005 to 2012), due likely to the unaccounted effects of the 2008 economic recession. Both OMI and AQS datasets display distinct emission reduction rates before, during, and after the 2008 global recession in some cities, but the detailed changing rates are not consistent across the OMI and AQS data. Our findings demonstrate the feasibility of using space and ground observations to evaluate major updates of emission inventories objectively. The combination of satellite, ground observations, and in-situ measurements (such as emission monitoring in power plants) is likely to provide more reliable estimates of NO x emission and its trend, which is an issue of increasing importance as many urban areas in the US are transitioning to NO x -sensitive chemical regimes by continuous emission reductions.

Impact of the 2008 Global Recession on air quality over the United States: Implications for surface ozone levels from changes in NOx emissions

“…The widespread socioeconomic slowdown caused noticeable emission reduction detected by satellite measurements [Castellanos and Boersma, 2012;Russell et al, 2012], which found that the decreases in urban NO 2 column densities in the United States accelerated during the recession, changing from À6%/yr beforehand to À8%/yr during the financial crisis and then slowing to À3%/yr thereafter [Russell et al, 2012]. A recent study using both satellite and ground observations confirmed that distinct rates of emission change were observed from both space and surface data over eight large cities [Tong et al, 2015] …”

“…These morning hours are associated with the highest NO x concentrations contributed by both typical commuter traffic peaks and the shallow planetary boundary layer, making them an ideal indicator for assessing local emission conditions [Tong et al, 2015]. Besides ground data, the OMI standard product (version 2.1, collection 3) described by Bucsela et al [2013] is used to derive the satellite-based emission trends using the data-filtering approach described in Tong et al [2015]. In the normal global operational mode, the OMI ground pixel at nadir is 13 km × 24 km, with a local equator-crossing time of 13:45 h in ascending node.…”

“…For ground measurements (AQS), morning rush hour means are calculated from quality-controlled hourly NO x values for the hours 0600, 0700, and 0800 local time, following the observed temporal patterns of NO x variations presented by Godowitch et al [2010]. These morning hours are associated with the highest NO x concentrations contributed by both typical commuter traffic peaks and the shallow planetary boundary layer, making them an ideal indicator for assessing local emission conditions [Tong et al, 2015]. Besides ground data, the OMI standard product (version 2.1, collection 3) described by Bucsela et al [2013] is used to derive the satellite-based emission trends using the data-filtering approach described in Tong et al [2015].…”

“…In the BAU case, the rate of emission change from the Cross-State Air Pollution Rule (CSAPR) is used to adjust emission inventories from the pre-recession year (2005) to postrecession year (2011) [Pan et al, 2014;Tong et al, 2015]. In the recession case, the actual NO 2 trends observed from the Air Quality System (AQS), a ground monitoring network, and the Ozone Monitoring Instrument (OMI) on the Aura satellite are used to obtain "realistic" or observed emission changes.…”

“…The effect of the emission changes on surface O 3 concentration is estimated using a CMAQ version tailored for the NOAA National Air Quality Forecast Capability (NAQFC) system [Pan et al, 2014;Tong et al, 2015]. This version of CMAQ is configured with the Carbon Bond 2005 chemical mechanism [Yarwood et al, 2005] and AERO5 aerosol module [Carlton et al, 2010].…”