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10. Optimizing UV index determination from broadband irradiances.

Author

Tereszchuk, Keith A., Rochon, Yves J., McLinden, Chris A., and Vaillancourt, Paul A.

Subjects
*ULTRAVIOLET radiation, *OZONE layer, *CLIMATE change
Abstract

Amidst mounting concerns about the depletion of stratospheric ozone (O3), and for subsequent increases in the surface irradiances of ultraviolet (UV) light and its effects on human health, a daily UV forecast program was launched by Environment Canada in 1993. The program serves to monitor harmful surface UV radiation and provide this information to the Canadian public through the UV index, a scale which reports the relative intensity of the Sun's UV radiation at the Earth's surface, and the corresponding protection actions to be taken. The UV index was accepted as a standard method of reporting surface UV irradiances by the World Meteorological Organization (WMO) and World Health Organization (WHO) in 1994. A study was undertaken to improve upon the prognosticative capability of Environment and Climate Change Canada's (ECCC) UV index forecast model. An aspect of that work, and the topic of this communication, was to investigate the use of the four UV broadband surface irradiance fields generated by ECCC's Global Environmental Multi-scale (GEM) numerical prediction model to determine the UV index. The basis of the investigation involves the creation of a suite of routines which employ high spectral resolution radiative transfer code developed to calculate UV index fields from GEM forecasts. These routines employ a modified version of the Cloud-J v7.4 radiative transfer model, which integrates GEM output to produce high spectral resolution surface irradiance fields. The output generated using the high-resolution radiative transfer code served to verify and calibrate GEM broadband surface irradiances under clear-sky conditions and their use in providing the UV index. A subsequent comparison of irradiances and UV index under cloudy conditions was also performed. Linear correlation agreement of surface irradiances from the two models for each of the two higher UV bands covering 310-330 nm and 330-400 nm is typically greater than 95 % for clear-sky conditions with associated root mean square relative errors of 5.5 % and 3.8 %. On the other hand, underestimations of clear-sky GEM irradiances were found on the order of ~30-50 % for the 294-310 nm band and by a factor of ~30 for the 280-294 nm band. This underestimation can be significant for UV index determination but would not impact weather forecasting. Corresponding empirical adjustments were applied to the broadband irradiances now giving a correlation coefficient of unity. From these, a least-squares fitting was derived for the calculation of the UV index. The resultant differences in UV indices from the high spectral resolution irradiances and the resultant GEM broadband irradiances are typically within 0.2 with a root mean square relative error in the scatter of ~5.5 % for clear-sky conditions. Similar results are reproduced under cloudy conditions with light to moderate clouds, having a relative error comparable to the clear-sky counterpart; under strong attenuation due to clouds, a substantial increase in the root mean square relative error of up to 30 % is observed due to differing cloud radiative transfer models. [ABSTRACT FROM AUTHOR]

Published
2017
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12. ACE-FTS observations of pyrogenic trace species in boreal biomass burning plumes during BORTAS

Author

Tereszchuk, Keith, Gonzalez Abad, Gonzalo, Clerbaux, C., Hadji-Lazaro, Juliette, Hurtmans, Daniel, Coheur, Pierre, Bernath, Peter, Tereszchuk, Keith, Gonzalez Abad, Gonzalo, Clerbaux, C., Hadji-Lazaro, Juliette, Hurtmans, Daniel, Coheur, Pierre, and Bernath, Peter

Abstract

To further our understanding of the effects of biomass burning emissions on atmospheric composition, the BORTAS campaign (BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites) was conducted on 12 July to 3 August 2011 during the boreal forest fire season in Canada. The simultaneous aerial, ground and satellite measurement campaign sought to record instances of boreal biomass burning to measure the tropo-spheric volume mixing ratios (VMRs) of short- and long-lived trace molecular species from biomass burning emissions. The goal was to investigate the connection between the composition and the distribution of these pyrogenic outflows and their resulting perturbation to atmospheric chemistry, with particular focus on oxidant species to determine the overall impact on the oxidizing capacity of the free troposphere. Measurements of pyrogenic trace species in boreal biomass burning plumes were made by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) onboard the Canadian Space Agency (CSA) SCISAT-1 satellite during the BORTAS campaign. Even though biomass burning emissions are typically confined to the boundary layer, outflows are often injected into the upper troposphere by isolated convection and fire-related convective processes, thus allowing space-borne instruments to measure these pyrogenic outflows. An extensive set of 14 molecules - CH 3OH, C2H2, C2H6, C 3H6O, CO, HCN, HCOOH, HNO3, H2CO, NO, NO2, OCS, O3, and PAN -have been analysed. Included in this analysis is the calculation of age-dependent sets of enhancement ratios for each of the species originating from fires in North America (Canada, Alaska) and Siberia for a period of up to 7 days. Ratio values for the shorter lived primary pyrogenic species decrease over time primarily due to oxidation by the OH radical as the plume ages and values for longer lived species such as HCN and C2H6 remain relatively unchanged. Increasing negative values are, SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2013

13. Investigation of CO, C2H6 and aerosols in a boreal fire plume over eastern Canada during BORTAS 2011 using ground-and satellite-based observations and model simulations

Author

Griffin, Debora, Walker, Kaley, Franklin, Jonathan, Parrington, Mark, Whaley, Cynthia, Hopper, J., Drummond, James, Palmer, Paul, Strong, Kimberly, Duck, Thomas, Abboud, Ihab, Bernath, Peter, Clerbaux, Cathy, Coheur, Pierre, Curry, K.R., Dan, L., Hyer, Edward, Kliever, J., Lesins, Glen, Maurice, M, Saha, A., Tereszchuk, Keith, Weaver, David R., Griffin, Debora, Walker, Kaley, Franklin, Jonathan, Parrington, Mark, Whaley, Cynthia, Hopper, J., Drummond, James, Palmer, Paul, Strong, Kimberly, Duck, Thomas, Abboud, Ihab, Bernath, Peter, Clerbaux, Cathy, Coheur, Pierre, Curry, K.R., Dan, L., Hyer, Edward, Kliever, J., Lesins, Glen, Maurice, M, Saha, A., Tereszchuk, Keith, and Weaver, David R.

Abstract

We present the results of total column measurements of CO, C2H6 and fine-mode aerosol optical depth (AOD) during the "Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites" (BORTAS-B) campaign over eastern Canada. Ground-based observations, using Fourier transform spectrometers (FTSs) and sun photometers, were carried out in July and August 2011. These measurements were taken in Halifax, Nova Scotia, which is an ideal location to monitor the outflow of boreal fires from North America, and also in Toronto, Ontario. Measurements of fine-mode AOD enhancements were highly correlated with enhancements in coincident trace gas (CO and C2H6) observations between 19 and 21 July 2011, which is typical for a smoke plume event. In this paper, we focus on the identification of the origin and the transport of this smoke plume. We use back trajectories calculated by the Canadian Meteorological Centre as well as FLEXPART forward trajectories to demonstrate that the enhanced CO, C2H6 and fine-mode AOD seen near Halifax and Toronto originated from forest fires in northwestern Ontario that occurred between 17 and 19 July 2011. In addition, total column measurements of CO from the satellite-borne Infrared Atmospheric Sounding Interferometer (IASI) have been used to trace the smoke plume and to confirm the origin of the CO enhancement. Furthermore, the enhancement ratio-that is, in this case equivalent to the emission ratio (ERC2H6/CO)-was estimated from these ground-based observations. These C2H6 emission results from boreal fires in northwestern Ontario agree well with C2H6 emission measurements from other boreal regions, and are relatively high compared to fires from other geographical regions. The ground-based CO and C2H6 observations were compared with outputs from the 3-D global chemical transport model GEOS-Chem, using the Fire Locating And Modeling of Burning Emissions (FLAMBE) inventory. Agreement within the state, SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2013

17. Infrared emission spectra of BeH2 and BeD2

Author

Shayesteh, Alireza, Tereszchuk, Keith, Bernath, Peter, Colin, Réginald, Shayesteh, Alireza, Tereszchuk, Keith, Bernath, Peter, and Colin, Réginald

Abstract

SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2003

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