Distribution, variability and sources of tropospheric ozone over south China in spring: Intensive ozonesonde measurements at five locations and modeling analysis

Abstract

[1] We examine the characteristics of the spatial distribution and variability of tropospheric ozone (O 3 ) by analysis of 93 ozonesonde profiles obtained at five stations over south N) during a field campaign in April-May 2004. We use a global 3-D chemical transport model (GEOS-Chem) to interpret these characteristics and to quantify the sources of tropospheric O 3 over south China during this period. The observed tropospheric O 3 mixing ratios showed strong spatiotemporal variability due to a complex interplay of various dynamical and chemical processes. A prominent feature in the upper and middle troposphere (UT/MT) was the frequent occurrence of high O 3 mixing ratios shown as tongues extending down from the lower stratosphere or as isolated layers at all stations. The model largely captured the observed pattern of day-to-day variability in tropospheric O 3 mixing ratios at all stations, but often underestimated those tongues or isolated layers of O 3 enhancements observed in the UT/MT, especially at low-latitude stations. We found that tropospheric O 3 along the southeast China coast was mainly produced within Asia. Lightning NO x emissions (over South Asia and equatorial Africa) and/or stratospheric influences were responsible for major events of high O 3 observed in the UT/MT at all stations. Underestimated contributions of these sources likely led to the model's underestimate in the low-latitude UT/MT O 3 . This study emphasizes the need for improved understanding of lightning NO x emissions and stratospheric influences over the Eurasian and African continents and for better representation of these processes in current global models.

Sensitivity of tropical tropospheric composition to lightning NOx production as determined by replay simulations with GEOS‐5

“…For all four locations, TES SHADOZ is Comparisons with observed O 3 appear to yield somewhat different results depending on observation type and location. The inconsistencies in the agreement from model to observations and between observations lead to somewhat inconclusive results that underline our need to (a) better resolve regional variations in flash rate and NO production per flash (see also Zhang et al [2012]), and to (b) understand and correct for biases in the observational data sets. Further analysis over longer time periods with more observational data should help resolve the current discrepancies.…”

Tropospheric Ozone Assessment Report: Assessment of global-scale model performance for global and regional ozone distributions, variability, and trends

“…Availability of such datasets over Asia and particularly the U.S. and Europe has facilitated modeling studies of extreme ozone pollution over these regions, while sparse observational records limit extreme episode analysis in other regions of the world. The focus here is on the U.S. and Europe as these are the regions with high-quality, long-term observations used in most evaluations of model skill, although there are growing examples of studies from Asia (e.g., Liu et al, 2010;Zhang et al, 2012;Huang et al, 2015).…”

Origin of springtime ozone enhancements in the lower troposphere over Beijing: in situ measurements and model analysis

“…We use two sets of in situ O 3 vertical profiles over Beijing obtained during April-May 2005: one from the Transport of Air Pollutants and Tropospheric Ozone over China (TAPTO-China) (Chan et al, 2007;Zhang et al, 2012) ozonesonde campaign and the other from the MOZAIC program . The concurrent availability of these two data sets allows cross validation of such measurements.…”

“…TAPTO-China was an intensive ozonesonde sounding campaign over China, conducted at five locations across southern China in the spring of 2004 (Zhang et al, 2012) and four locations across northern China in the spring of 2005. The main objective of TAPTO-China was to investigate the mechanisms controlling the spatiotemporal distribution, variability, and sources of springtime tropospheric O 3 over China and its surrounding regions.…”