The Applicability of Remote Sensing in the Field of Air Pollution

This report prepared by KNMI and JRC is the final result of a study on the applicability of remote sensing in the field of air pollution requested by the DG Environment. The objectives of this study were to: Have an assessment of presently available scientific information on the feasibility of utilising remote sensing techniques in the implementation of existing legislation, and describe opportunities for realistic streamlining of monitoring in air quality and emissions, based on greater use of remote sensing. Have recommendations for the next policy cycle on the use of remote sensing through development of appropriate provisions and new concepts, including, if appropriate, new environmental objectives, more suited to the use of remote sensing. Have guidance on how to effectively engage with GMES and other initiatives in the air policy field projects Satellite remote sensing of the troposphere is a rapidly developing field. Today several satellite sensors are in orbit that measure trace gases and aerosol properties relevant to air quality. Satellite remote sensing data have the following unique properties: Near-simultaneous view over a large area; Global coverage; Good spatial resolution. The properties of satellite data are highly complementary to ground-based in-situ networks, which provide detailed measurements at specific locations with a high temporal resolution. Although satellite data have distinct benefits, the interpretation is often less straightforward as compared to traditional in-situ measurements. Maps of air pollution measured from space are widespread in the scientific community as well as in the media, and have had a strong impact on the general public and the policy makers. The next step is to make use of satellite data in a quantitative way. Applications based solely on satellite data are foreseen, however an integrated approach using satellite data, ground-based data and models combined with data assimilation, will make the best use of the satellite remote-sensing potential, as well as of the synergy with ground-based observations.JRC.H.4-Transport and air qualit

The Ozone Monitoring Instrument: Overview of 14 years in space

This overview paper highlights the successes of the Ozone Monitoring Instrument (OMI) on board the Aura satellite spanning a period of nearly 14 years. Data from OMI has been used in a wide range of applications and research resulting in many new findings. Due to its unprecedented spatial resolution, in combination with daily global coverage, OMI plays a unique role in measuring trace gases important for the ozone layer, air quality, and climate change. With the operational very fast delivery (VFD; direct readout) and near real-time (NRT) availability of the data, OMI also plays an important role in the development of operational services in the atmospheric chemistry domain

From photon paths to pollution plumes: better radiative transfer calculations to monitor NOx emissions with OMI and TROPOMI

Nitrogen oxides (NOx = NO + NO2) play an important role in atmospheric chemistry, therefore affecting air quality and Earth's radiative forcing, which impact public health, ecosystems and climate. Remote sensing from satellites in the ultraviolet and visible (UV-Vis) spectral range results in measurements of tropospheric NO2 column densities with high spatial and temporal resolution that allow, among many applications, to monitor NO2 concentrations and to estimate NOx emissions. NO2 satellite retrievals have improved extensively in the last decade, together with the increased need of having traceable characterization of the uncertainties associated with the NO2 satellite measurements. The spatial resolution of the satellite instruments is improving such that the observed NO2 pollution can now be traced back to emissions from individual cities, power plants, and transportation sectors. However, the uncertainty of satellite NO2 retrievals is still considerable and mainly related to the adequacy of the assumptions made on the state of the atmosphere. In this thesis we have improved the critical assumptions and our understanding in the radiative transfer modelling for NO2 satellite measurements, and we use the new TROPOMI NO2 measurements to quantify daily NOx emissions from a single urban hot spot. The work presented in this thesis contributes to the satellite remote sensing community (1) because of the improvement of the satellite retrieval and the knowledge of its main uncertainty sources (Chapter 2, 3 and 4), and (2) because of the application of TROPOMI NO2 measurements for the first time to infer daily NOx emissions at urban scales (Chapter 5). </p

Satellite observations of ozone and nitrogen dioxide : from retrievals to emission estimates

In the last decades, measurements of atmospheric composition from satellites have become very important for scientific research as well as applications for monitoring and forecasting the state of the atmosphere. Instruments such as GOME-2, and OMI look at backscattered sunlight in nadir view, measuring the ultraviolet and visible spectrum in high resolution. Launched in a sun-synchronous orbit at ??800 km altitude, they scan the Earth’s surface daily in 14–15 orbits, providing a homogeneous dataset with (almost) daily global coverage. Combining the spectral measurements with radiative transport models, concentrations can be inferred for important trace gases such as ozone (O3) and nitrogen dioxide (NO2). Chemical transport models can be used to calculate the strength and location of the underlying emissions. Long time series of satellite retrievals give insight on how human activity contributes to changes of atmospheric composition, affecting health and climate. Information in the vertical distribution of ozone can be retrieved from the sharp decrease in the ozone absorption cross-section in the ultraviolet spectrum. Chapter 2 deals with the question how the performance of the ozone profile retrieval algorithm (OPERA) can be improved. To produce consistent global datasets, the algorithm needs to have good global performance, while short computation time facilitates the use of the algorithm in near real time applications. Because the retrieval is ill-posed (in the sense that many profiles give similar simulated spectra within the measurement errors), the solution depends on a priori (climatological) ozone profiles. The non-linearity of the problem asks for an iteration scheme to find the best fitting solution numerically. We use the convergence behaviour of the iteration as a diagnostic tool for the ozone profile retrievals from the GOME instrument for February and October 1998. In this way, we reveal several retrieval problems of different origin, and we improve issues related to the Southern Atlantic Anomaly, low cloud fractions e.g. above deserts, and ozone cross sections. The a priori ozone climatology and its associated variability is also an important source for retrieval problems. By using a priori ozone profiles that are selected on the expected total ozone column, retrieval problems due to anomalous ozone distributions (such as in the ozone hole) can be avoided. Applying the algorithm adaptations improve the convergence statistics considerably, not only increasing the number of successful retrievals, but also reducing the average computation time, due to less iteration steps per retrieval. For February 1998, non-convergence was brought down from 10.7% to 2.1%, while the mean number of iteration steps (which dominates the computational time) dropped 26% from 5.11 to 3.79. Total nitrogen dioxide columns can be retrieved from space in the 405–465 nm window, but the NO2 spectrum does not contain any significant height information. Instead, data assimilation techniques can be used to distinguish the tropospheric part from the stratospheric part, which gives valuable information of NO2 in the lowest part of the atmosphere. Here it acts as an air pollutant, often from man-made origin. The case study in Chapter 3 evaluates how NO2 air pollution can be controlled with air quality measures. Due to strong economic growth in the last decades, air pollution in large Chinese megacities has become a serious issue. In reparation for the Olympic Games in Beijing in 2008, extensive air quality measures were taken to improve air quality during the event, affecting traffic, industry and power production. We evaluate the effect of the air quality measures on reducing air pollution, by analysing the tropospheric NO2 retrievals over the greater Beijing area before, during and after the Olympic Games. To compensate for the strong variability due to meteorology, we compare the observations with model simulations from the regional chemistry transport model CHIMERE based on a pre-Olympic emission inventory. The relative change between observation and simulation shows that the measures caused a reduction of tropospheric NO2 column concentrations of approximately 60% above Beijing during the Olympic period. The air quality measures were especially effective in the Beijing area, but also noticeable in surrounding cities of Tianjin (30% reduction) and Shijiazhuang (20% reduction). In the months after the Olympic events, NOx emissions in Beijing show a slow recovery towards pre-Olympic levels. In a next step, we use the difference between NO2 observations and simulations to adjust the emission inventory used by the model. Emission inventories of air pollutants are crucial information for policy makers and form important input data for air quality models. Chapter 4 presents a new algorithm specifically designed to use daily satellite observations of column concentrations for fast updates of emission estimates of short-lived atmospheric constituents on a mesoscopic scale (??25??25 km2). The algorithm needs only one forward model run from a chemical transport model to calculate the sensitivity of concentration to emission, using trajectory analysis to account for transport away from the source. By using a Kalman filter in the inverse step, optimal use of the a priori knowledge and the newly observed data is made. We apply the algorithm for NOx emission estimates of East China, using the CHIMERE model on a 0.25 degree resolution together with tropospheric NO2 column retrievals of the OMI and GOME-2 satellite instruments. Closed loop tests show that the algorithm is capable of reproducing new emission scenarios. Applied with real satellite data, the algorithm is able to detect emerging sources (e.g. new power plants), and improves emission information for areas where proxy data are not or badly known (e.g. shipping emissions). It is shown that chemical transport model runs with the daily updated emission estimates provide better spatial and temporal agreement between observed and simulated NO2 concentrations, which facilitates an improved air quality forecast for East China. Monthly emission estimates give valuable insight in changing biogenic and anthropogenic activity. In Chapter 5, the emission estimation algorithm is used to construct a monthly NOx emission time series for 2007–2010 from tropospheric NO2 observations of GOME-2 over East Asia. Most Chinese provinces show a strong positive trend during this period, related to the country’s economic development. Negative emission trends are found in Japan and South Korea, which can be attributed to a combined effect of local environmental policy and global economic crises. The algorithm is also used to quantify the direct effect of regional NOx emissions on tropospheric NO2 concentrations elsewhere. Due to transport of air pollution, high NOx emissions not only affect local air quality, but also contribute significantly to tropospheric NO2 in remote downwind areas

CEOS Intercalibration of Ground-Based Spectrometers and Lidars: First Progress Report

This document reports on activities and achievements obtained during the first part of the ESA CEOS Intercalibration project. The period covered extends from March 2009 until December 2009.This document is the first progress report of the CEOS Intercalibration of Ground-Based Spectrometers and Lidars project. It summarizes activities performed and results achieved within each team

Izaña Atmospheric Research Center. Activity Report 2019-2020

Editors: Emilio Cuevas, Celia Milford and Oksana Tarasova.[EN]The Izaña Atmospheric Research Center (IARC), which is part of the State Meteorological Agency of Spain (AEMET), is a site of excellence in atmospheric science. It manages four observatories in Tenerife including the high altitude Izaña Atmospheric Observatory. The Izaña Atmospheric Observatory was inaugurated in 1916 and since that date has carried out uninterrupted meteorological and climatological observations, contributing towards a unique 100-year record in 2016. This reports are a summary of the many activities at the Izaña Atmospheric Research Center to the broader community. The combination of operational activities, research and development in state-of-the-art measurement techniques, calibration and validation and international cooperation encompass the vision of WMO to provide world leadership in expertise and international cooperation in weather, climate, hydrology and related environmental issues.[ES]El Centro de Investigación Atmosférica de Izaña (CIAI), que forma parte de la Agencia Estatal de Meteorología de España (AEMET), representa un centro de excelencia en ciencias atmosféricas. Gestiona cuatro observatorios en Tenerife, incluido el Observatorio de Izaña de gran altitud, inaugurado en 1916 y que desde entonces ha realizado observaciones meteorológicas y climatológicas ininterrumpidas y se ha convertido en una estación centenaria de la OMM. Estos informes resumen las múltiples actividades llevadas a cabo por el Centro de Investigación Atmosférica de Izaña. El liderazgo del Centro en materia de investigación y desarrollo con respecto a las técnicas de medición, calibración y validación de última generación, así como la cooperación internacional, le han otorgado una reputación sobresaliente en lo que se refiere al tiempo, el clima, la hidrología y otros temas ambientales afines

Improvement of algorithms for the assessment of air quality and atmospheric composition from observations of spectral radiances

O principal objetivo deste trabalho consiste na aplicação e aperfeiçoamento de algoritmos numéricos para a inversão de medidas espectrais feitas com um instrumento de deteção remota instalado no Observatório do Centro de Geofísica de Évora (38.6ºN, 7.9ºW, 300 a.s.l.). Os algoritmos explorados são os seguintes: i) metodologia DOAS para a determinação da concentração média de compostos atmosféricos ao longo do caminho ótico, ii) duas diferentes abordagens ao algoritmo de inversão de Chahine que consiste num método iterativo para a obtenção dos perfis dos constituintes atmosféricos minoritários usando o output da técnica espetral. Os resultados obtidos permitiram a avaliação dos ciclos diurnos e sazonais e de variações anuais das colunas totais de ozono, dióxido de azoto e de óxido de bromo, dos perfis verticais de dióxido de azoto e informação acerca de massas de ar poluídas no período compreendido entre 2007-2011. As quantidades obtidas são comparadas/validadas com os respectivos resultados obtidos com instrumentos instalados em satélites; Abstract: The central part of this work is the application and improvement of numerical algorithms for the inversion of spectral measurements carried out with a remote sensing instrument, installed at the Geophysics Centre of Évora´s Observatory (38.6ºN, 7.9ºW, 300 a.s.l.).The exploited algorithms are: i) the Differential Optical Absorption Spectroscopy method, for the determination of the mean concentration of an atmospheric compound along an optical path; ii) two different approaches to the Chahine inversion algorithm that is an iterative method for profile retrieval of atmospheric tracers using the output of the spectroscopic technique. The obtained results allow for the assessment of diurnal cycles, seasonal and inter-annual variations for the total columns of ozone, nitrogen dioxide and bromine oxide, the atmospheric profiles of nitrogen dioxide and information about nitrogenous air masses transported over Évora for the period 2007-2011. In addition, the retrieved quantities are compared/ validated with analogous results obtained with satellite borne instruments

Atmospheric Instrument Systems and Technology in the Goddard Earth Sciences Division

Studies of the Earths atmosphere require a comprehensive set of observations that rely on instruments flown on spacecraft, aircraft, and balloons as well as those deployed on the surface. Within NASAs Goddard Space Flight Center (GSFC) Earth Sciences Division-Atmospheres, laboratories and offices maintain an active program of instrument system development and observational studies that provide: 1) information leading to a basic understanding of atmospheric processes and their relationships with the Earths climate system, 2) prototypes for future flight instruments, 3) instruments to serve as calibration references for satellite missions, and 4) instruments for future field validation campaigns that support ongoing space missions. Our scientists participate in all aspects of instrument activity, including component and system design, calibration techniques, retrieval algorithm development, and data processing systems. The Atmospheres Program has well-equipped labs and test equipment to support the development and testing of instrument systems, such as a radiometric calibration and development facility to support the calibration of ultraviolet and visible (UV/VIS), space-borne solar backscatter instruments. This document summarizes the features and characteristics of 46 instrument systems that currently exist or are under development. The report is organized according to active, passive, or in situ remote sensing across the electromagnetic spectrum. Most of the systems are considered operational in that they have demonstrated performance in the field and are capable of being deployed on relatively short notice. Other systems are under study or of low technical readiness level (TRL). The systems described herein are designed mainly for surface or airborne platforms. However, two Cubesat systems also have been developed through collaborative efforts. The Solar Disk Sextant (SDS) is the single balloon-borne instrument. The lidar systems described herein are designed to retrieve clouds, aerosols, methane, water vapor pressure, temperature, and winds. Most of the lasers operate at some wavelength combination of 355, 532, and 1064 nm. The various systems provide high sensitivity measurements based on returns from backscatter or Raman scattering including intensity and polarization. Measurements of the frequency (Doppler) shift of light scattered from various atmospheric constitutes can also be made. Microwave sensors consist of both active (radar) and passive (radiometer) systems. These systems are important for studying processes involving water in various forms. The dielectric properties of water affect microwave brightness temperatures, which are used to retrieve atmospheric parameters such as rainfall rate and other key elements of the hydrological cycle. Atmosphere radar systems operate in the range from 9.6 GHz to 94 GHz and have measurement accuracies from -5 to 1 dBZ; radiometers operate in the 50 GHz to 874 GHz range with accuracies from 0.5 to 1 degree K; conical and cross-track scan modes are used. Our passive optical sensors, consisting of radiometers and spectrometers, collectively operate from the UV into the infrared. These systems measure energy fluxes and atmospheric parameters such as trace gases, aerosols, cloud properties, or altitude profiles of various species. Imager spatial resolution varies from 37 m to 400 m depending on altitude; spectral resolution is as small as 0.5 nm. Many of the airborne systems have been developed to fly on multiple aircraft

U.S. Participation in the GOME and SCIAMACHY Projects

This report summarizes research done under NASA Grant NAGW-2541 from April 1, 1996 through March 31, 1997. The research performed during this reporting period includes development and maintenance of scientific software for the GOME retrieval algorithms, consultation on operational software development for GOME, consultation and development for SCIAMACHY near-real-time (NRT) and off-line (OL) data products, and development of infrared line-by-line atmospheric modeling and retrieval capability for SCIAMACHY. SAO also continues to participate in GOME validation studies, to the limit that can be accomplished at the present level of funding. The Global Ozone Monitoring Experiment was successfully launched on the ERS-2 satellite on April 20, 1995, and remains working in normal fashion. SCIAMACHY is currently in instrument characterization. The first two European ozone monitoring instruments (OMI), to fly on the Metop series of operational meteorological satellites being planned by Eumetsat, have been selected to be GOME-type instruments (the first, in fact, will be the refurbished GOME flight spare). K. Chance is the U.S. member of the OMI Users Advisory Group