Jacob, Daniel J.

X. Lu, L. Zhang, T. Wu, M. S. Long, J. Wang, D.J. Jacob, F. Zhang, J. Zhang, S. D. Eastham, L. Hu, L. Zhu, X. Liu, and M. Wei. 2020. “Development of the global atmospheric general circulation-chemistry model BCC-GEOS-Chem v1.0: model description and evaluation.” Geoscientific Model Development, 13, 9, Pp. 3817–3838. Publisher's VersionAbstract
Chemistry plays an indispensable role in investigations of the atmosphere; however, many climate models either ignore or greatly simplify atmospheric chemistry, limiting both their accuracy and their scope. We present the development and evaluation of the online global atmospheric chemical model BCC-GEOS-Chem v1.0, coupling the GEOS-Chem chemical transport model (CTM) as an atmospheric chemistry component in the Beijing Climate Center atmospheric general circulation model (BCC-AGCM). The GEOS-Chem atmospheric chemistry component includes detailed troposphericHOx–NOx–volatile organic compounds–ozone–bromine–aerosol chemistry and online dry and wet deposition schemes. We then demonstrate the new capabilities of BCC-GEOS-Chem v1.0 relative to the base BCC-AGCM model through a 3-year (2012–2014) simulation with anthropogenic emissions from the Community Emissions Data System (CEDS) used in the Coupled Model Intercomparison Project Phase 6 (CMIP6). The model captures well the spatial distributions and seasonal variations in tropospheric ozone, with seasonal mean biases of 0.4–2.2 ppbv at 700–400 hPa compared to satellite observations and within 10 ppbv at the surface to 500 hPa compared to global ozonesonde observations. The model has larger high-ozone biases over the tropics which we attribute to an overestimate of ozone chemical production. It underestimates ozone in the upper troposphere which is likely due either to the use of a simplified stratospheric ozone scheme or to biases in estimated stratosphere–troposphere exchange dynamics. The model diagnoses the global tropospheric ozone burden, OH concentration, and methane chemical lifetime to be 336 Tg, 1.16×106 molecule cm−3, and 8.3 years, respectively, which is consistent with recent multimodel assessments. The spatiotemporal distributions of NO2, CO, SO2, CH2O, and aerosol optical depth are generally in agreement with satellite observations. The development of BCC-GEOS-Chem v1.0 represents an important step for the development of fully coupled earth system models (ESMs) in China.
S.J. Song, M. Gao, W.Q. Xu, Y.L. Sun, D.R. Worsnop, J.T. Jayne, Y.Z. Zhang, L. Zhu, M. Li, Z. Zhou, C.L. Cheng, Y.B. Lv, Y. Wang, W. Peng, X.B. Xu, N. Lin, Y.X. Wang, S.X. Wang, J. W. Munger, D. Jacob, and M.B. McElroy. 2019. “Possible heterogeneous hydroxymethanesulfonate (HMS) chemistry in northern China winter haze and implications for rapid sulfate formation.” Atmospheric Chemistry and Physics, 19, Pp. 1357-1371. Publisher's VersionAbstract
The chemical mechanisms responsible for rapid sulfate production, an important driver of winter haze formation in northern China, remain unclear. Here, we propose a potentially important heterogeneous hydroxymethanesulfonate (HMS) chemical mechanism. Through analyzing field measurements with aerosol mass spectrometry, we show evidence for a possible significant existence in haze aerosols of organosulfur primarily as HMS, misidentified as sulfate in previous observations. We estimate that HMS can account for up to about one-third of the sulfate concentrations unexplained by current air quality models. Heterogeneous production of HMS by SO2 and formaldehyde is favored under northern China winter haze conditions due to high aerosol water content, moderately acidic pH values, high gaseous precursor levels, and low temperature. These analyses identify an unappreciated importance of formaldehyde in secondary aerosol formation and call for more research on sources and on the chemistry of formaldehyde in northern China winter.
ACP paper
Jonathan M. Moch, Eleni Dovrou, Loretta J. Mickley, Frank N. Keutsch, Yuan Cheng, Daniel J. Jacob, Jingkun Jiang, Meng Li, J. William Munger, Xiaohui Qiao, and Qiang Zhang. 2018. “Contribution of hydroxymethane sulfonate to ambient particulate matter: A potential explanation for high particulate sulfur during severe winter haze in Beijing.” Geophysical Research Letters, 45, Pp. 11969-11979. Publisher's VersionAbstract

PM 2.5 during severe winter haze in Beijing, China, has reached levels as high as 880μg/m3, with sulfur compounds contributing significantly to PM 2.5 composition. This sulfur has been traditionally assumed to be sulfate, although atmospheric chemistry models are unable to account for such large sulfate enhancements under dim winter conditions. Using a 1-D model, we show that well-characterized but previously overlooked chemistry of aqueous-phase HCHO and S(IV) in cloud droplets to form a S(IV)-HCHO adduct, hydroxymethane sulfonate, may explain high particulate sulfur in wintertime Beijing. We also demonstrate in the laboratory that methods of ion chromatography typically used to measure ambient particulates easily misinterpret hydroxymethane sulfonate as sulfate. Our findings suggest that HCHO and not SO2 has been the limiting factor in many haze events in Beijing and that to reduce severe winter pollution in this region, policymakers may need to address HCHO sources such as transportation.


GRL paper.pdf
Y.X. Wang, M.B. McElroy, D.J. Jacob, and R.M. Yantosca. 2004. “A nested grid formulation for chemical transport over Asia: Applications to CO.” Journal of Geophysical Research, 109, D22307. Publisher's VersionAbstract
A global three-dimensional chemical transport model (GEOS-CHEM) was modified to permit treatment of a limited spatial regime with resolution higher than that adopted for the global background. Identified as a one-way nested grid formulation, the model was applied to a simulation of CO over Asia during spring 2001. Differences between results obtained using the nested grid (resolution 1° × 1°), the coarse global model (resolution 4° × 5°), and the intermediate global model (resolution 2° × 2.5°) are discussed. The higher-resolution model allows for more efficient, advection-related, ventilation of the lower atmosphere, reflecting the significance of localized regions of intense upward motion not resolved in a coarser-resolution simulation. Budget analysis suggests that upward transfer to higher altitudes through large-scale advection provides the major sink for CO below 4 km. Horizontal advection, mainly through the north boundary, contributes a net source of CO to the window domain despite the polluted nature of the study region. The nested-grid model is shown to provide good agreement with measurements made during the Transport and Chemical Evolution over the Pacific (TRACE-P) campaign in spring 2001, notably better than the low-resolution model in simulating frontal lifting process and differences across the boundary separating the regions of cyclonic and anticyclonic flow. The high-resolution window approach also allows us to differentiate transport mechanisms for individual subregions of China on a much finer scale than was possible previously. Suggestions are made as to how to allow for subgrid vertical advective motions in the low-resolution model through a carefully designed and broadly tested eddy diffusion treatment.