Juno Hsu

University of California, Irvine | UCI · Department of Earth System Science

Some key photochemical uncertainties that cannot be readily eliminated by current observations translate into a range of stratospheric O3 abundances in the tens of percent. The uncertainty in O3 production due to that in the cross sections for O2 in the Hertzberg continuum is studied here with the NCAR Community Atmosphere Model, which allows for i...

1] Changes in the stratosphere-troposphere exchange (STE) of ozone over the last few decades have altered the tropospheric ozone abundance and are likely to continue doing so in the coming century as climate changes. Combining an updated linearized stratospheric ozone chemistry (Linoz v2) with parameterized polar stratospheric clouds (PSCs) chemist...

Nitrous oxide (N2O) and methane (CH4) are chemically reactive greenhouse gases with well-documented atmospheric concentration increases that are attributable to anthropogenic activities. We quantified the link between N2O and CH4 emissions through the coupled chemistries of the stratosphere and troposphere. Specifically, we simulated the coupled pe...

Stratosphere-troposphere exchange (STE) of ozone (O3) is key in the budget of tropospheric O3, in turn affecting climate forcing and global air quality. We compare three commonly used diagnostics meant to quantify cross-tropopause O3 fluxes with a Chemistry-Transport Model driven by two distinct European Centre forecast fields. Our reference case c...

Stratospheric ozone affects climate directly as the predominant heat source in the stratosphere and indirectly through chemical reactions controlling other greenhouse gases. The U.S. Department of Energy's Energy Exascale Earth System Model version 1 (E3SMv1) implemented a new ozone chemistry module that improves the simulation of the sharp tropopa...

Abstract In calculating solar radiation, climate models make many simplifications, in part to reduce computational cost and enable climate modeling, and in part from lack of understanding of critical atmospheric information. Whether known errors or unknown errors, the community's concern is how these could impact the modeled climate. The simplifica...

Stratospheric ozone affects climate directly as the predominant heat source in the stratosphere and indirectly through chemical feedbacks controlling other greenhouse gases. The U.S. Department of Energy's Energy Exascale Earth System Model version 1 (E3SMv1) implemented a new ozone chemistry module that improves the simulation of the sharp tropopa...

Significance Early climate and weather models, constrained by computing resources, made numerical approximations on modeling the real world. One process, the radiative transfer of sunlight through the atmosphere, has always been a costly component. As computational ability expanded, these models added resolution, processes, and numerical methods to...

Solar-J is a comprehensive radiative transfer model for the solar spectrum that addresses the needs of both solar heating and photochemistry in Earth system models. Solar-J is a spectral extension of Cloud-J, a standard in many chemical models that calculates photolysis rates in the 0.18–0.8 µm region. The Cloud-J core consists of an eight-stream s...

Solar-J is a comprehensive model for radiative transfer over the solar spectrum that addresses the needs of both photochemistry and solar heating in Earth system models. Solar-J includes an 8-stream scattering, plane-parallel radiative transfer solver with corrections for sphericity. It uses the scattering phase function of aerosols and clouds expa...

The lifetime of nitrous oxide, the third-most-important human-emitted greenhouse gas, is based to date primarily on model studies or scaling to other gases. This work calculates a semiempirical lifetime based on Microwave Limb Sounder satellite measurements of stratospheric profiles of nitrous oxide, ozone, and temperature; laboratory cross-section...

We present here the global chemical transport model Oslo CTM3, an update of the Oslo CTM2. The update comprises a faster transport scheme, an improved wet scavenging scheme for large scale rain, updated photolysis rates and a new lightning parameterization. Oslo CTM3 is better parallelized and allows for stable, large time steps for advection, enab...

We present here the global chemical transport model Oslo CTM3, an update of the Oslo CTM2. The update comprises a faster transport scheme, an improved wet scavenging scheme for large scale rain, updated photolysis rates and a new lightning parameterization. Oslo CTM3 is better parallelized and allows for stable, large time steps for advection, enab...

Knowledge of the atmospheric chemistry of reactive greenhouse gases is needed to accurately quantify the relationship between human activities and climate, and to incorporate uncertainty in our projections of greenhouse gas abundances. We present a method for estimating the fraction of greenhouse gases attributable to human activities, both current...

The Asian summer Monsoon circulation is driven by differential thermal heating, primarily associated with the localized latent heat release from enhanced precipitation over the India sub-continent. Although this heating is of limited zonal extent, it drives a time-averaged, upper level anticylone which is of global extent, extending from the wester...

Delineating the boundary between troposphere and stratosphere in a chemistry transport model requires a state variable for each air mass that maps out the ever shifting, overlapping three-dimensional (3-D) boundary at each time step. Using an artificial tracer, e90, with surface sources and 90 day decay time, the model e90 tropopause matches the 1-...

We study the mechanisms driving stratosphere-troposphere exchange of ozone fluxes within a chemistry-transport model. For years 2004–2006, year-round, most of the stratosphere-to-troposphere flux of O3 is associated with shear and folding around the subtropical jet, and this jet-related flux peaks for the northern hemisphere in May. Over the northe...

Abstract Available from http://www.agu.org

The two longest-lived, major chemical response patterns (eigenmodes) of the atmosphere, coupling N2O and CH4, are identified with the UCI chemistry-transport model using a linearized (N2O, NOy, O3, CH4, H2O)-system for stratospheric chemistry and specified tropospheric losses. As in previous 1D and 2D studies, these century-long 3D simulations show...

The tropopause, however defined, is meant to describe the boundary between the well mixed troposphere and the stably stratified stratosphere. Ozone abundances in the vicinity of the tropopause exhibit large variations with latitude and season, being controlled by a combination of large-scale transport like the Brewer-Dobson circulation, small-scale...

Nitrogen trifluoride (NF3) can be called the missing greenhouse gas: It is a synthetic chemical produced in industrial quantities; it is not included in the Kyoto basket of greenhouse gases or in national reporting under the United Nations Framework Convention on Climate Change (UNFCCC); and there are no observations documenting its atmospheric abu...

1] Events involving stratosphere-troposphere exchange (STE) of ozone, such as tropopause folds and westerly ducts, are readily identified in observations and models, but a quantitative flux specifying where and when stratospheric ozone is mixed into the troposphere is not readily discerned from either. This work presents a new diagnostic based on d...

1] Observations of CO and O 3 from the Transport and Chemical Evolution over the Pacific (TRACE-P) campaign are compared with modeled distributions from the FRSGC/ UCI CTM driven by the Oslo T63L40 ECMWF forecast meteorology. The model-measurement comparison is made within the context of how well the TRACE-P observations represent the springtime ch...

TOMS swath data of total column ozone, TRACE-P observations, and high resolution CTM 4-D data are used to identify signatures of stratospheric intrusions into the troposphere over Pacific areas during March 2001. The events with significant total ozone anomalies are singled out for detailed analysis and compared with chemical transport simulations....

Observations of CO abundance made along TRACE-P flights in the western Pacific off the coast of Asia (3 Mar - 3 Apr 2001) provide a valuable test for chemistry-transport models (CTMs). We compare these observations with the simulated CO from the UCI chemistry-transport model driven by high-resolution T63L40 meteorological fields from the Oslo/EC mo...

We identify recurrent regimes of atmospheric states in observed and model-simulated data with and without anomalous greenhouse gas and aerosol forcing by testing against the null hypothesis that the atmospheric states are produced by a Gaussian autoregressive process of the order of 1 in a reduced phase space. In one approach the phase space is des...

The authors investigate the change of atmospheric angular momentum (AAM) in long, transient, coupled atmosphere-ocean model simulations with increasing atmospheric greenhouse gas concentration and sulfate aerosol loading. A significant increase of global AAM, on the order of 4 × 1025 kg m2 s1 for 3 × CO2-1 × CO2, was simulated by the Canadian Centr...

The authors investigate the nonlinear dynamics of almost inviscid, thermally forced, divergent circulations in situations that are not axisymmetric. In shallow-water numerical calculations, asymmetry is imposed on a locally forced anticyclone by imposition of a mean wind, or a planetary vorticity gradient. Behavior is similar in the two cases. With...