SPEAKERS: Gabriele Pfister, Scientist III, National Center for Atmospheric Research (NCAR) Brad Pierce, Physical Scientist, NOAA Salient Questions: 1.What are the present constraints on using satellite data to quantify trans-boundary anthropogenic ozone (TAO) surface impacts? 2.To what extent and in what context can our current satellite capabilities be used to assist in 179B demonstrations and, more generally, in SIP modeling? 3.What are some promising strategies for using in situ measurements and surface- based remote sensing to complement satellite data? What types of research investments will be necessary? 4.What is the near-term potential for enhanced satellite capacity to estimate TAO surface impacts based on future satellite launches (e.g. GEO-CAPE)? Session 5: Current and prospective capacity to measure trans-boundary ozone fluxes via satellite retrievals, in situ measurements and surface-based remote sensing.

Question 1: What are the present constraints on using satellite data to quantify trans- boundary anthropogenic ozone (TAO) surface impacts? Satellite measurements of ozone and carbon monoxide provide the best current estimates of intercontinental pollution transport. However, while the satellite measurements are able to provide significant information regarding the horizontal extent of the pollution plumes they cannot provide much information on the vertical extent of the plumes. Identification of TAO requires satellite measurements of both ozone and anthropogenic pollution. It is hard to distinguish from biomass burning signatures, which are a dominate source of intercontinental pollution transport, without fire specific tracer hydrogen cyanide (HCN). HCN has been retrieved from ground based and satellite (ACE-FTS) FTIR solar occultation measurements, and satellite limb measurements (MIPAS). Experimental products are available from some nadir viewing space based instruments (TES, IASI). Tracer Correlations (AOD, O3, CO, fire counts) can also help making some distinctions on a case by case basis. Most current satellite ozone retrievals use hyper-spectral UV-VIS and IR wavelengths, which are most sensitive to stratospheric (UV-VIS) or upper tropospheric (IR) ozone, so surface ozone cannot currently be measured from space. However, satellites can observe ozone aloft prior to descent into the western US.

Question 2: To what extent and in what context can our current satellite capabilities be used to assist in 179B demonstrations and, more generally, in SIP modeling? The best way to utilize satellite measurements of ozone and it’s percursors (ozone, carbon monoxide, nitrogen dioxide) is through chemical data assimilation. This allows the information content from the satellite retrievals to be properly accounted for through the use of averaging kernels in the observation operator (to properly constrain the chemical analysis) and provides a means of propagating the information content forward in time (through the analysis/forecast cycle) and also to improve emission estimates. Chemical Data Assimilation is an active field of research and vastly progressing. Use of global chemical analyses to constrain lateral boundary conditions for continental scale air quality model simulations provides the most effective means of using satellite data to assist in SIP modeling. Global chemical analysis from total column ozone assimilation put constraints on photolysis rate calculations in an air quality model if used as upper boundary conditions (stratosphere). Use of hyperspectral IR ozone and carbon monoxide retrievals at upwind locations, combined with back-trajectory analysis from the receptor regions, could be used to provide weight of evidence for 179B TAO demonstrations. Satellite data are an additional highly valuable source to evaluate models - global models that provide boundary conditions and SIP models.

Question 3: What are some promising strategies for using in situ measurements and surface-based remote sensing to complement satellite data? What types of research investments will be necessary? Transport quality insitu measurements of carbon monoxide (ppbv precision) and hydrogen cyanide (pptv precision?), along with Tunable Infrared Laser Differential Absorption Spectroscopy (TILDAS) measurements of NO2, could be combined with ground-based remote FTIR instruments, ozone and aerosol LIDAR. Targeted field campaigns are important to improve process-level understanding and as a result modeling capabilities. Question 4: What is the near-term potential for enhanced satellite capacity to estimate TAO surface impacts based on future satellite launches (e.g. GEO-CAPE)? Multi-spectral O3 retrieval studies using synthetic radiances show Degrees of Freedom of Signal (DOFS) for daytime UV-VIS (TEMPO) and DOFS for daytime UV- VIS-IR between 0-2km. Retrieval products from current satellites are continued to being revised and enhanced (e.g. IASI/GOME for UV-VIS-O3 retrieval, Cuesta et al., ACP 2013)

Diurnally resolved Multi-Spectral O 3 Retrieval Results (S. Kulawik/V. Natraj) Diurnally resolved Degrees of Freedom of Signal (DOFS) for different pressure ranges and spectral combinations for all GEOCAPE Regional OSSE sites (no VIS, UV, or UV/VIS retrievals between 02-09Z) Note UV/VIS has the same spectral range and noise as TEMPO. (nighttime) Total Troposphere 0-2 km 0-1 km VIS UV-VIS UV UV-VIS-TIR UV-TIR TIR VIS UV-VIS UV UV-VIS-TIR UV-TIR TIR VIS UV-VIS UV UV-VIS-TIR UV-TIR TIR VIS UV-VIS UV UV-VIS-TIR UV-TIR TIR