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NASA NTRS1999

Shipboard and Satellite Views of Elevated Tropospheric Ozone over the Tropical Atlantic in January-February 1999

During the Aerosols99 trans-Atlantic cruise from Norfolk, VA, to Cape Town, South Africa, daily ozonesondes were launched from the NOAA R/V Ronald H Brown between 17 January and 6 February l999. A composite of tropospheric ozone profiles along the latitudinal transect shows 4 zones, which are interpreted using correlative shipboard ozone, CO, water vapor, and overhead aerosol optical thickness measurements. Elevated ozone associated with biomass burning north of the ITCZ (Intertropical Convergence Zone) is prominent at 3-5 km from 10-0N, but even higher ozone (100 ppbv, 7-10 km) occurred south of the ITCZ, where it was not burning. Column-integrated tropospheric ozone was 44 Dobson Units (DU) in one sounding, 10 DU lower than the maximum in a January-February 1993 Atlantic cruise with ozonesondes [Weller et al., 1996]. TOMS tropospheric ozone shows elevated ozone extending throughout the tropical Atlantic in January 1999. Several explanations are considered. Back trajectories, satellite aerosol observations and shipboard tracers suggest a combination of convection and interhemispheric transport of ozone and/or ozone precursors, probably amplified by a lightning NO source over Africa.

Thompson, Anne M.↗
NASA NTRS2000

Critical Evaluation of 0-30 km Profile Information in Ground-Based Zenith-Sky and Satellite-Measured Backscattered UV Radiation

We now have several decades of experience in deriving vertical ozone profiles from the measurements of diffuse ultraviolet radiation by both ground and satellite-based instruments using Umkehr and BUV techniques. Continuing technological advances are pushing the state-of-the-art of these measurements to high spectral resolution and broader wavelength coverage. These modern instruments include the ground-based Brewer and satellite-based Global Ozone Monitoring Experiment (GOME) instruments, as well as advanced instruments being developed by ESA(SCIAMACHY), Netherlands(OMI) and Japan(ODUS). However, one of the issues that remains unresolved is the 0-30 km ozone profile information retrievable from these measurements. Though it is commonly believed that both the Umkehr and the satellite-based BUV techniques have very limited profile information below 30 km, there are those who argue that the data from these instruments should continue to be reported in this altitude range for they compare well with ozonesondes and hence there is useful scientific information. Others claim that the limitations of the Umkehr and BUV techniques are largely due to their low spectral resolution, and that the profile information below 30 km can be greatly improved by going to high spectral resolution instruments, such as Brewer and GOME. The purpose of this paper is to provide a critical evaluation of the 0-30 km ozone profile information in the various UV remote sensing techniques. We use a database of individual ozone profiles created using ozonesondes and SAGE and 4D ozone fields generated by data assimilation techniques to simulate radiances measured by the various techniques. We then apply a common inversion approach to all the methods to systematically examine how much profile information is available simply from the knowledge of total ozone, how much additional profile information is added by the traditional Dobson Umkehr and satellite buv techniques, and how much better one can do by adding additional wavelengths and by going to higher spectral resolution. An open and honest discussion of these issues is critical to provide the ozone science community a realistic assessment of the quality of data in the lower stratosphere and troposphere expected from both past and future instruments.

Bhartia, Pawan↗
NASA NTRS2001

Vertical Distribution and Variability of Ozone During July 1999 Over Andenes, Norway

Ozonesonde measurements of the polar atmosphere obtained at Andenes, Norway during July 1999 showed unusual characteristics when compared with mid- or low-latitude ozone profiles. A minimum of two ozonesondes each day were released, one in late afternoon and one in early evening. A very well-defined ledge in the ozone profile corresponding to the tropopause appears to form as a result of transport. The ozone amount increases four to five times, from about 30 nb at the tropopause to 120 nb at a pressure about 10-20 hPa lower. The typical peak ozone value, although at a higher altitude than the ledge, appears at a much lower pressure (approx. 140 hPa) than found in midor low-latitudes (approx. 18-25 hPa), Total column ozone amounts are consistently higher than 300 DU. Analysis of the variation with regard to wind conditions will be discussed.

Schmidlin, F. J.↗
NASA NTRS2002

Assessment of SAGE Version 6.1 Ozone Data Quality

The SAGE-II V6.1 ozone retrievals are shown to be of better precision at all levels and to be much more accurate than previous retrievals in the lower stratosphere below 20 km altitude. A filtering procedure for removing anomalous ozone profiles associated with volcanic aerosol/cloud effects and other identified artifacts in V6.1 ozone is described. The agreement between SAGE and ozonesondes in the mean is shown to be approximately 10% down to the tropopause. Relative to the sondes SAGE tends to slightly overestimate ozone (less than 5%) between 15 and 20 km altitude, and systematically underestimates ozone in the troposphere by approximately 30% in the regions between 8 km altitude and 2 km below the tropopause. The precisions (random errors) of SAGE ozone retrievals above 25 km altitude are estimated to be 4% or better; they are a factor of ten worse below 16 km altitude. Linear trends in the differences between coincident SAGE and ozonesondes measurement are generally less than 0.3 %/year and not significantly different from zero in 95% confidence intervals. Compared to V5.96 retrievals, ozone trend differences between 20 and 50 km altitude are approximately 0. 1 %/year, below 20 km altitude the SAGE II trends are more positive by approximately 0.2 %/year. For the 1984-1999 period the SAGE-II shows a localized ozone loss of -0.4(+/- 0.25) %/year (2gigma) in the tropics at 20 km altitude. In the lower stratosphere between 16 and 22 km altitudes, the SAGE shows significant ozone losses in the mid-latitudes in both Hemispheres during the 1979-1999 periods. The ozone trends range from -0.24(+/- 0.18) to -0.77(+/- 0.46) (2sigma)%/year. However in the 1984-1999 period, the downward trends are smaller (-0.07 to - 0.25 %/year) in this altitude range, and the trends in the integrated column from 12 to 17 km altitude in mid-latitudes (35 deg - 60 deg) are not significantly different from zero (0.1 +?- 0.6 (2sigma)%/year). Averaged over the tropics (20 deg S to 20 deg N) the ozone column above 15 km altitude exhibit a trend of -0.12 +/- 0.08 (2sigma)%/year.

Wang, Hsiang J.↗
NASA NTRS2003

Investigation of the Short-Time Variability of Tropical Tropospheric Ozone

Since 1998, a ground based tropospheric ozone lidar has been running at Reunion Island and has been involved with a daily measurement campaign that was performed in the latter part of the biomass burning season, during November-December 1999. The averaged ozone profile obtained during November-December 1 999 agrees well with averaged ozone profile obtained from ozonesondes launch at Reunion during November-December (1992- 2001). Comparing weekly sonde launches (part of the Southern Hemisphere Additional Ozonesondes: SHADOZ program) with the daily ground-based lidar observations shows that some striking features of the day to day variability profiles are not observed in the sonde measurements. Ozone profiles respond to the nature of disturbances which vary from the one day to the next. The vertical ozone distribution at Reunion is examined as a function of prevailing atmospheric circulation. Backtrajectories show that most of the enhanced ozone crossed over biomass burning and convectively active regions in Madagascar and the southern African continent. The analyses of the meteorological data show that ozone stratification profiles are in agreement with the movement of the synoptical situations in November-December 1999. Three different sequences of transport are explained using wind fields. The first sequence from 23 to 25 November is characterized by Northerly transport, the second sequence from 26 to 30 November, the air masses are influenced by meridional transport. The third sequence from 2 to 6 December is characterized by westerly transport associated with the subtropical jet stream. The large standard deviations of lidar profiles in the middle and upper troposphere are in agreement with the upper wind variabilities which evidence passing ridge and trough disturbances. During the transition period between the dry season and the wet season, multiple ozone sources including stratosphere-troposphere exchanges, convection and biomass burning contribute to tropospheric ozone at Reunion Island through sporadic events characterized by a large spatial and temporal variability.

Randriambelo, Tantely↗
NASA NTRS2003

Ozone Pollution, Transport and Variability: Examples from Satellite and In-Situ Observations

Regional and intercontinental transport of ozone has been observed from satellite, aircraft and sounding data. Over the past several years, we have developed new tropospheric ozone retrieval techniques from the TOMS (Total Ozone Mapping Spectrometer) satellite instrument that are of sufficient resolution to follow pollution episodes. The modified-residual technique uses Level 2 total ozone and was used to follow the 1997 fires in the wake of the El-Nino-related fires in southeast Asia and the Indonesian maritime continent. The TOMS-direct method ('TDOT' = TOMS Direct Ozone in the Troposphere) is a newer algorithm that uses TOMS radiances directly to extract tropospheric ozone. Ozonesonde data that have been taken in campaigns (e.g. TRACE-P) and more consistently in the SHADOZ (Southern Hemisphere Additional Ozonesondes) project, reveal layers of pollution traceable with trajectories. Examples will be shown of long-range transport and recirculation over Africa during SAFARI-2000.

Thompson, Anne↗
NASA NTRS2004

A Review of the Match Technique as Applied to AASE-2/EASOE and SOLVE/THESEO 2000

We apply the GSFC trajectory model with a series of ozonesondes to derive ozone loss rates in the lower stratosphere for the AASE-2/EASOE mission (January - March 1992) and for the SOLVE/THESEO 2000 mission (January - March 2000) in an approach similar to Match. Ozone loss rates are computed by comparing the ozone concentrations provided by ozonesondes launched at the beginning and end of the trajectories connecting the launches. We investigate the sensitivity of the Match results on the various parameters used to reject potential matches in the original Match technique and conclude that only a filter based on potential vorticity changes along the calculated back trajectory seems necessary. Our study also demonstrates that calculated ozone loss rates can vary by up to a factor of two depending upon the precise trajectory paths calculated for each trajectory. As a result an additional systematic error might need to be added to the statistical uncertainties published with previous Match results. The sensitivity to the trajectory path is particularly pronounced in the month of January, the month during which the largest ozone loss rate discrepancies between photochemical models and Match are found. For most of the two study periods, our ozone loss rates agree with those previously published. Notable exceptions are found for January 1992 at 475 K and late February/early March 2000 at 450 K, both periods during which we find less loss than the previous studies. Integrated ozone loss rates in both years compare well with those found in numerous other studies and in a potential vorticity/potential temperature approach shown previously and in this paper. Finally, we suggest an alternate approach to Match using trajectory mapping that appears to more accurately reflect the true uncertainties associated with Match and reduces the dependence upon filters that may bias the results of Match through the rejection of greater than or equal to 80% of the matched sonde pairs and >99% of matched observations.

Morris, Gary A.↗
NASA NTRS2004

Discoveries about Tropospheric Ozone Pollution from Satellite and Sounding

We have been producing near-real time tropospheric ozone satellite maps from the TOMS (Total Ozone Mapping Spectrometer) sensor since 1997. This is most readily done for the tropics, where the stratospheric and tropospheric ozone column amounts can be discriminated readily. Maps for 1996-2000 for the operational Earth-Probe instrument reside at: chttp://www.atmos.umd.edu/-trope>. Pollution in the tropics is influenced by biomass burning and by transport patterns that favor recirculation and in other cases reflect climate variability like the El-Nino-Southern Oscillation [Thompson et al., 2001]. Time permitting, examples of mid-latitude, intercontinental transport of ozone pollution sensed by TOMS will be shown. The satellite view of chemical-dynamical interactions in tropospheric ozone is not adequate to capture vertical variability. Thus, in 1998, NASA's Goddard Space Flight Center and a team of international sponsors established the SHADOZ (Southern Hemisphere ADditional OZonesondes) project to address the gap in tropical ozone soundings. SHADOZ augments launches and provides a public archive of ozonesonde data from twelve tropical stations at http://croc.gsfc.nasa.gov/shadoz. Further insights into the role of chemical and dynamical influences have emerged from the first 4-5 years of SHADOZ data (less than 2000 ozone profiles): (a) highly variable tropospheric ozone; (b) a zonal wave-one pattern in tropospheric column ozone; (c) convective variability affects tropospheric ozone over the Indian and Pacific Ocean; (d) a "tropical Atlantic Paradox" appears in December-January-February.

Thompson, Anne M.↗
NASA NTRS2004

Discoveries about Tropospheric Ozone Pollution from Satellite and Soundings

We have been producing near-red time tropospheric ozone satellite maps from the TOMS (Total Ozone Mapping Spectrometer) sensor since 1997. Maps for 1996-2000 for the operational Earth-Probe instrument are at: . Pollution in the tropics is influenced by biomass burning and by transport patterns that favor recirculation and in other cases reflect climate variability like the El-Nino-Southern Oscillation [Thompson et al., 2001]. The satellite view of chemical-dynamical interactions in tropospheric ozone is not adequate to capture vertical gradients in pollution. Thus, in 1998, NASA's Goddard Space Flight Center and a team of international sponsors established the SHADOZ (Southern Hemisphere ADditional OZonesondes) project to address the gap in tropical ozone soundings. SHADOZ augments launches and provides a public archive of ozonesonde data from twelve tropical stations at http://croc.gsfc.nasa.gov/shadoz. Further insights into the role of chemical and dynamical influences have emerged from the first 4-5 years of SHADOZ data (more than 2000 ozone profiles). Highly variable tropospheric ozone and a zonal wave-one pattern in tropospheric ozone suggest that dynamics is as important as pollution in determining tropical ozone distributions.

Thompson, Anne M.↗
NASA NTRS2004

Optimal Aerosol Parameterization for Remote Sensing Retrievals

We have developed a new algorithm for the retrieval of aerosol and gases from SAGE It1 solar transmission measurements. This algorithm improves upon the NASA operational algorithm in several key aspects, including solving the problem non-linearly and incorporating a new methodology for separating the contribution of aerosols and gases. In order to extract aerosol information we have built a huge database of aerosol models for both stratospheric and tropospheric aerosols, and polar stratospheric cloud particles. This set of models allows us to calculate a vast range of possible extinction spectra for aerosols. and from these, derive a set of eigenvectors which then provide the basis set used in our inversion algorithm. Our aerosol algorithm and retrievals are described in several articles (listed in References Section) published under this grant. In particular they allow us to analyze the spectral properties of aerosols and PSCs and ultimately derive their microphysical properties. We have found some considerable differences between our spectra and the ones derived from the SAGE III operational algorithm. These are interesting as they provide an independent check on the validity of published aerosol data and, in particular, on their associated uncertainties. In order to understand these differences, we are assembling independent aerosol data from other sources with which to make comparisons. We have carried out extensive comparisons of our ozone retrievals with both SAGE III and independent lidar, ozonesonde, and satellite measurements (Polyakov et al., 2004). These show very good agreement throughout the stratosphere and help to quantify differences which can be attributed to natural variation in ozone versus that produced by algorithmic differences. In the mid - upper stratosphere, agreement with independent data was generally within 5 - 20%. but in the lower stratosphere the differences were considerably larger. We believe that a large proportion of this discrepancy in the lower stratosphere is attributable to natural variation, and is also seen in comparisons between lidar and ozonesonde measurements. NO2 profiles obtained with our algorithm were compared to those obtained through the SAGE III operational algorithm and exhibited differences of 20 - 40%. Our retrieved profiles agree with the HALOE NO2 measurements significantly better than those of the operational retrieval. In other work (described below), we are extending our aerosol retrievals into the infrared regime and plan to perform retrievals from combined uv-visible-infrared spectra. This work will allow us to use the spectra to derive the size and composition of aerosols, and we plan to employ our algorithms in the analysis of PSC spectra. We are presently also developing a limb-scattering algorithm to retrieve aerosol data from limb measurements of solar scattered radiation.

Newchurch, Michael J.↗
NASA NTRS2008

The Quasi-biennial Oscillation and Annual Variations in Tropical Ozone from SHADOZ and HALOE

We examine the tropical ozone mixing ratio perturbation fields generated from a monthly ozone climatology using 1998 to 2006 ozonesonde data from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network and the 13-year satellite record from 1993 to 2005 obtained from the Halogen Occultation Experiment (HALOE). The long time series and high vertical resolution of the ozone and temperature profiles from the SHADOZ sondes coupled with good tropical coverage north and south of the equator gives a detailed picture of the ozone structure in the lowermost stratosphere down through the tropopause where the picture obtained from HALOE measurements is blurred by coarse vertical resolution. Ozone perturbations respond to annual variations in the Brewer-Dobson Circulation (BDC) in the region just above the cold-point tropopause to around 20 km. Annual cycles in ozone and temperature are well correlated. Above 20 km, ozone and temperature perturbations are dominated by the Quasi-biennial Oscillation (QBO). Both satellite and sonde records show good agreement between positive and negative ozone mixing ratio anomalies and alternating QBO westerly and easterly wind shears from the Singapore rawinsondes with a mean periodicity of 26 months for SHADOZ and 25 months for HALOE. There is a temporal offset of one to three months with the QBO wind shear ahead of the ozone anomaly field. The meridional length scales for the annual cycle and the QBO, obtained using the temperature anomalies and wind shears in the thermal wind equation, compare well with theoretical calculations.

Witte, J. C.↗
NASA NTRS2010

A Balloon Sounding Technique for Measuring SO2 Plumes

This paper reports on the development of a new technique for inexpensive measurements of SO2 profiles using a modified dual-ozonesonde instrument payload. The presence of SO2 interferes with the standard electrochemical cell (ECC) ozonesonde measurement, resulting in -1 molecule of O3 reported for each molecule of SO2 present (provided [O3] > [SO2]). In laboratory tests, an SO2 filter made with Cr03 placed on the inlet side of the sonde removes nearly 100% of the SO2 present for concentrations up to 60 ppbv and remained effective after exposure to 2.8 X 10(exp 16) molecules of SO2 [equivalent to a column approximately 150 DU (1 DU = 2.69 X 10(exp 20) molecules m(exp -2))]. Flying two ECC instruments on the same payload with one filtered and the other unfiltered yields SO2 profiles, inferred by subtraction. Laboratory tests and field experience suggest an SO2 detection limit of approximately 3 pbb with profiles valid from the surface to the ozonopause [i.e., approximately (8-10 km)]. Two example profiles demonstrate the success of this technique for both volcanic and industrial plumes.

Morris, Gary A.↗
NASA NTRS2009

Demonstration of Aerosol Property Profiling by Multiwavelength Lidar Under Varying Relative Humidity Conditions

During the months of July-August 2007 NASA conducted a research campaign called the Tropical Composition, Clouds and Climate Coupling (TC4) experiment. Vertical profiles of ozone were measured daily using an instrument known as an ozonesonde, which is attached to a weather balloon and launch to altitudes in excess of 30 km. These ozone profiles were measured over coastal Las Tablas, Panama (7.8N, 80W) and several times per week at Alajuela, Costa Rica (ION, 84W). Meteorological systems in the form of waves, detected most prominently in 100-300 in thick ozone layer in the tropical tropopause layer, occurred in 50% (Las Tablas) and 40% (Alajuela) of the soundings. These layers, associated with vertical displacements and classified as gravity waves ("GW," possibly Kelvin waves), occur with similar stricture and frequency over the Paramaribo (5.8N, 55W) and San Cristobal (0.925, 90W) sites of the Southern Hemisphere Additional Ozonesondes (SHADOZ) network. The gravity wave labeled layers in individual soundings correspond to cloud outflow as indicated by the tracers measured from the NASA DC-8 and other aircraft data, confirming convective initiation of equatorial waves. Layers representing quasi-horizontal displacements, referred to as Rossby waves, are robust features in soundings from 23 July to 5 August. The features associated with Rossby waves correspond to extra-tropical influence, possibly stratospheric, and sometimes to pollution transport. Comparison of Las Tablas and Alajuela ozone budgets with 1999-2007 Paramaribo and San Cristobal soundings shows that TC4 is typical of climatology for the equatorial Americas. Overall during TC4, convection and associated meteorological waves appear to dominate ozone transport in the tropical tropopause layer.

Veselovskii, I.↗
NASA NTRS2009

Convective and Wave Signatures in Ozone Profiles Over the Equatorial Americas: Views from TC4 (2007) and SHADOZ

During the months of July-August 2007 NASA conducted a research campaign called the Tropical Composition, Clouds and Climate Coupling (TC4) experiment. Vertical profiles of ozone were measured daily using an instrument known as an ozonesonde, which is attached to a weather balloon and launch to altitudes in excess of 30 km. These ozone profiles were measured over coastal Las Tablas, Panama (7.8N, 80W) and several times per week at Alajuela, Costa Rica (ION, 84W). Meteorological systems in the form of waves, detected most prominently in 100- 300 in thick ozone layer in the tropical tropopause layer, occurred in 50% (Las Tablas) and 40% (Alajuela) of the soundings. These layers, associated with vertical displacements and classified as gravity waves ("GW," possibly Kelvin waves), occur with similar stricture and frequency over the Paramaribo (5.8N, 55W) and San Cristobal (0.925, 90W) sites of the Southern Hemisphere Additional Ozonesondes (SHADOZ) network. The gravity wave labeled layers in individual soundings correspond to cloud outflow as indicated by the tracers measured from the NASA DC-8 and other aircraft data, confirming convective initiation of equatorial waves. Layers representing quasi-horizontal displacements, referred to as Rossby waves, are robust features in soundings from 23 July to 5 August. The features associated with Rossby waves correspond to extra-tropical influence, possibly stratospheric, and sometimes to pollution transport. Comparison of Las Tablas and Alajuela ozone budgets with 1999-2007 Paramaribo and San Cristobal soundings shows that TC4 is typical of climatology for the equatorial Americas. Overall during TC4, convection and associated meteorological waves appear to dominate ozone transport in the tropical tropopause layer.

Thompson, Anne M.↗
NASA NTRS2015

The Global Structure of UTLS Ozone in GEOS-5: A Multi-Year Assimilation of EOS Aura Data

Eight years of ozone measurements retrieved from the Ozone Monitoring Instrument (OMI) and the Microwave Limb Sounder, both on the EOS Aura satellite, have been assimilated into the Goddard Earth Observing System version 5 (GEOS-5) data assimilation system. This study thoroughly evaluates this assimilated product, highlighting its potential for science. The impact of observations on the GEOS-5 system is explored by examining the spatial distribution of the observation-minus-forecast statistics. Independent data are used for product validation. The correlation coefficient of the lower-stratospheric ozone column with ozonesondes is 0.99 and the bias is 0.5%, indicating the success of the assimilation in reproducing the ozone variability in that layer. The upper-tropospheric assimilated ozone column is about 10% lower than the ozonesonde column but the correlation is still high (0.87). The assimilation is shown to realistically capture the sharp cross-tropopause gradient in ozone mixing ratio. Occurrence of transport-driven low ozone laminae in the assimilation system is similar to that obtained from the High Resolution Dynamics Limb Sounder (HIRDLS) above the 400 K potential temperature surface but the assimilation produces fewer laminae than seen by HIRDLS below that surface. Although the assimilation produces 5 - 8 fewer occurrences per day (up to approximately 20%) during the three years of HIRDLS data, the interannual variability is captured correctly. This data-driven assimilated product is complementary to ozone fields generated from chemistry and transport models. Applications include study of the radiative forcing by ozone and tracer transport near the tropopause.

GEOS-5↗
NASA NTRS2013

An Elevated Reservoir of Air Pollutants over the Mid-Atlantic States During the 2011 DISCOVER-AQ Campaign: Airborne Measurements and Numerical Simulations

During a classic heat wave with record high temperatures and poor air quality from July 18 to 23, 2011, an elevated reservoir of air pollutants was observed over and downwind of Baltimore, MD, with relatively clean conditions near the surface. Aircraft and ozonesonde measurements detected approximately 120 parts per billion by volume ozone at 800 meters altitude, but approximately 80 parts per billion by volume ozone near the surface. High concentrations of other pollutants were also observed around the ozone peak: approximately 300 parts per billion by volume CO at 1200 meters, approximately 2 parts per billion by volume NO2 at 800 meters, approximately 5 parts per billion by volume SO2 at 600 meters, and strong aerosol optical scattering (2 x 10 (sup 4) per meter) at 600 meters. These results suggest that the elevated reservoir is a mixture of automobile exhaust (high concentrations of O3, CO, and NO2) and power plant emissions (high SO2 and aerosols). Back trajectory calculations show a local stagnation event before the formation of this elevated reservoir. Forward trajectories suggest an influence on downwind air quality, supported by surface ozone observations on the next day over the downwind PA, NJ and NY area. Meteorological observations from aircraft and ozonesondes show a dramatic veering of wind direction from south to north within the lowest 5000 meters, implying that the development of the elevated reservoir was caused in part by the Chesapeake Bay breeze. Based on in situ observations, Community Air Quality Multi-scale Model (CMAQ) forecast simulations with 12 kilometers resolution overestimated surface ozone concentrations and failed to predict this elevated reservoir; however, CMAQ research simulations with 4 kilometers and 1.33 kilometers resolution more successfully reproduced this event. These results show that high resolution is essential for resolving coastal effects and predicting air quality for cities near major bodies of water such as Baltimore on the Chesapeake Bay and downwind areas in the Northeast.

ozone↗
NASA NTRS2017

Evaluation of the Ozone Fields in NASA's MERRA-2 Reanalysis

The assimilated ozone product from the Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2), produced at NASAs Global Modeling and Assimilation Office (GMAO) is summarized. The reanalysis begins in 1980 with the use of retrieved partial-column ozone concentrations from a series of Solar Backscatter Ultraviolet Radiometer (SBUV) instruments on NASA and NOAA spacecraft. Beginning in October 2004, retrieved ozone profiles from the Microwave Limb Sounder (MLS) and total column ozone from the Ozone Monitoring Instrument (OMI) on NASAs EOS Aura satellite are assimilated. While this change in data streams does lead to a discontinuity in the assimilated ozone fields in MERRA-2, making it not useful for studies in decadal (secular) trends in ozone, this choice was made to prioritize demonstrating the value NASAs high-quality research data in the reanalysis context. The MERRA-2 ozone is compared with independent satellite and ozonesonde data, focusing on the representation of the spatial and temporal variability of stratospheric and upper-tropospheric ozone. The comparisons show agreement within 10 (standard deviation of the difference) between MERRA-2 profiles and independent satellite data in most of the stratosphere. The agreement improves after 2004, when EOS Aura data are assimilated. The standard deviation of the differences between the lower-stratospheric and upper-tropospheric MERRA-2 ozone and ozonesondes is 11.2 and 24.5, respectively, with correlations of 0.8 and above. This is indicative of a realistic representation of the UTLS ozone variability in MERRA-2. After 2004, the upper tropospheric ozone in MERRA-2 shows a low bias compared to the sondes, but the covariance with independent observations is improved compared to earlier years. Case studies demonstrate the integrity of MERRA-2 analyses in representing important features such as tropopause folds.

Ozone↗
NASA NTRS2018

Analysis of the Planetary Boundary Layer Height During DISCOVER-AQ Baltimore–Washington, D.C., with Lidar and High-Resolution WRF Modeling

The daytime planetary boundary layer (PBL) was examined for the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) Baltimore (Maryland)–Washington, D.C., campaign of July 2011 using PBL height (PBLH) retrievals from aerosol backscatter measurements from ground-based micropulse lidar (MPL), the NASA Langley Research Center airborne High Spectral Resolution Lidar-1 (HSRL-1), and the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) on the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite. High-resolution Weather Research and Forecasting (WRF) Model simulations with horizontal grid spacing of 1 km and different combinations of PBL schemes, urban parameterization, and sea surface temperature inputs were evaluated against PBLHs derived from lidars, ozonesondes, and radiosondes. MPL and WRF PBLHs depicted a growing PBL in the morning that reached a peak height by midafternoon. WRF PBLHs calculated from gridded output profiles generally showed more rapid growth and higher peak heights than did the MPLs, and all WRF–lidar differences were dependent on model configuration, PBLH calculation method, and synoptic conditions. At inland locations, WRF simulated an earlier descent of the PBL top in the afternoon relative to the MPL retrievals and radiosonde PBLHs. At Edgewood, Maryland, the influence of the Chesapeake Bay breeze on the PBLH was captured by both the ozonesonde and WRF data but generally not by the MPL PBLH retrievals because of generally weaker gradients in the aerosol backscatter profile and limited normalized relative backscatter data near the top height of the marine layer.

Hegarty, Jennifer D.↗