A study by Jerome Brioude (of NOAA/ESRL/CSD and CIRES) and colleagues used data collected during NOAA's CalNex field campaign in California in 2010 to estimate emissions of CO, NOx and CO2. Starting with emission inventories from EPA and California Air Resources Board (CARB), the authors used a high resolution regional model WRF-Chem and aircraft measurements to derive a so-called top-down inverse estimate of emssions.
The results were able to confirm a decrease in CO and NOx emissions in LA region over the past decade. 2002 measurements from another NOAA field campaign ITCT were used to verify the change in emissions. A remarkable 43% decrease of CO emissions was reported in the past decade for LA.
Emissions outside LA County were relatively larger when constrained by observations, indicating that the study found a different spatial distribution of the emissions than the original emission inventory. NOx emissions were found to have decreased by 32% in LA. Both CO and NOx estimates carry about 10% uncertainty, but otherwise confirm previous studies showing emission decrease. Meanwhile, CO2 emissions show no statistically significant increasing or decreasing trend in the past decade, although the study revealed significant changes in spatial distribution of emissions around LA County.
This study was supported in part by CPO's Earth System Science program.
[Submitted by Monika Kopacz.]