News

2017-04-13: Surface reflectivity climatologies from UV to NIR determined from observations by GOME-2 and SCIA

The primary goal of this paper is to introduce two new surface reflectivity climatologies. The two databases contain the Lambertian-equivalent reflectivity (LER) of the Earth’s surface, and they are meant to support satellite retrieval of trace gases and of cloud and aerosol information. The surface LER databases are derived from the Global Ozone Monitoring Experiment (GOME)-2 and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instruments and can be considered as improved and extended descendants of earlier surface LER climatologies based on the Total Ozone Mapping Spectrometer (TOMS), GOME-1, and Ozone Monitoring Instrument (OMI) instruments.

Read more...

2017-04-12: A geostationary product for near-real-time identification of high ice water content environments

We developed a satellite data product for identification of atmospheric environments with a high chance of the presence of high ice water content (IWC > > 1 g/m3). This High IWC mask is based on measurements of cloud properties using the cloud physical properties (CPP) algorithm applied to the geostationary Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI).

Read more...

2017-03-13: Space-based NOx emission estimates over remote regions improved in DECSO

We improve the emission estimate algorithm DECSO (Daily Emission estimates Constrained by Satellite Observations) to better detect NOx emissions over remote areas. The new version is referred to as DECSO v5. The error covariance of the sensitivity of NO2 column observations to gridded NOx emissions has been better characterized. This reduces the background noise of emission estimates by a factor of 10. An emission update constraint has been added to avoid unrealistic day-to-day fluctuations of emissions. We estimate total NOx emissions, which include biogenic emissions that often drive the seasonal cycle of the NOx emissions. We demonstrate the improvements implemented in DECSO v5 for the domain of East Asia in the year 2012 and 2013. The emissions derived by DECSO v5 are in good agreement with other inventories like MIX. In addition, the improved algorithm is able to better capture the seasonality of NOx emissions and for the first time it reveals ship tracks near the Chinese coasts that are otherwise hidden by the outflow of NO2 from the Chinese mainland. The precision of monthly emissions derived by DECSO v5 for each grid cell is about 20%.

Read more...

2016-12-22: Improvements to the OMI O2–O2 operational cloud algorithm

The OMI (Ozone Monitoring Instrument on board of NASA’s EOS Aura satellite) OMCLDO2 cloud product supports trace gas retrievals of for example ozone and nitrogen dioxide. A new version of the OMI OMCLDO2 cloud product is presented that contains several improvements, of which the introduction of a temperature correction on the O2?O2 slant columns and the updated look-up-tables have the largest impact. The cloud pressure retrievals of the improved algorithm are compared with ground-based Radar-Lidar observations for three sites in the mid-latitudes, including the CESAR Cabauw site in The Netherlands.

Read more...

2016-11-03: Spaceborne Vegetation Fluorescence Time Series Evaluated with Flux Tower Measurements

A global, monthly averaged time series of Sun-induced Fluorescence (SiF), spanning January 2007 to June 2015, was derived from Metop-A Global Ozone Monitoring Experiment 2 (GOME-2) spectral measurements. Far-red SiF was retrieved using the filling-in of deep solar Fraunhofer lines and atmospheric absorption bands based on the general methodology described by Joiner et al, AMT, 2013. A Principal Component (PC) analysis of spectra over non-vegetated areas was performed to describe the effects of atmospheric absorption. Our implementation (SiF KNMI) is an independent algorithm and differs from the latest implementation of Joiner et al, AMT, 2013 (SiF NASA, v26), because we used desert reference areas for determining PCs (as opposed to cloudy ocean and some desert) and a wider fit window that covers water vapour and oxygen absorption bands (as opposed to only Fraunhofer lines). As a consequence, more PCs were needed (35 as opposed to 12). The two time series (SiF KNMI and SiF NASA, v26) correlate well (overall R of 0.78) except for tropical rain forests. Sensitivity experiments suggest the strong impact of the water vapour absorption band on retrieved SiF values. Furthermore, we evaluated the SiF time series with Gross Primary Productivity (GPP) derived from twelve flux towers in Australia. Correlations for individual towers range from 0.37 to 0.84. They are particularly high for managed biome types. In the de-seasonalized Australian SiF time series, the break of the Millennium Drought during local summer of 2010/2011 is clearly observed.

Read more...

2016-10-25: Reduction in NOx emissions over China: synthesis of satellite observations and emission inventories

Tropospheric nitrogen dioxide (NO2) column densities detected from space are widely used to infer trends in terrestrial nitrogen oxide (NOx) emissions. We study changes in NO2 column densities using the Ozone Monitoring Instrument (OMI) over China from 2005 to 2015 and compare them with the bottom-up inventory to examine NOx emission trends and their driving forces. From OMI measurements we detect the peak of NO2 column densities at a national level in the year 2011, with average NO2 column densities deceasing by 32% from 2011 to 2015 and corresponding to a simultaneous decline of 21% in bottom-up emission estimates.

Read more...

2016-08-05: New paper published in AMT: How big is an OMI pixel?

Last week our department published a new paper in Atmospheric Measurement Techniques on the Field of View (FoV) of the Ozone Monitoring Instrument (OMI): "How big is an OMI pixel?", by M. de Graaf, H. Sihler, L.G Tilstra, and P. Stammes. First author Martin de Graaf works both at the R&D Satellite Observations department and Geosciences and Remote Sensing (GRS) of TU Delft. The paper describes the OMI FoV as determined in-flight, by finding the optimal correlation between OMI reflectances and collocated measurements from MODerate resolution Imaging Spectrometer (MODIS), which have a much higher spatial resolution than OMI, and overlap with the visible channel of OMI.

Read more...

2015-09-23: Rapid increases in tropospheric ozone production and export from China

Rapid population growth and industrialization have driven substantial increases in Asian ozone precursor emissions over the last decade, with highly uncertain impacts on regional and global tropospheric ozone (O3). Ozonesonde measurements from two Asian sites show that tropospheric O3 has increased by 1 to 3% per year since 2000, which is thought to contribute to positive O3 trends observed at North America’s West Coast.

Read more...

2015-08-25: NOx emission estimates during the 2014 Youth Olympic Games in Nanjing

We derived the NOx emissions from the OMI satellite observations. We find a NOx emission reduction of at least 25% during the Youth Olympic Games in Nanjing in 2014. The emission estimate algorithm is able to detect an emission reduction of 10% during the Chinese Spring Festival. This paper also show that the observed concentrations and the derived emissions from space show different patterns that provide complimentary information.

Read more...

2015-08-03: Extended and refined multi sensor reanalysis of total ozone for the period 1970–2012

The ozone multi-sensor reanalysis (MSR) is a multi-decadal ozone column data record constructed using all available ozone column satellite data sets, surface Brewer and Dobson observations and a data assimilation technique with detailed error modelling. The result is a high-resolution time series of 6-hourly global ozone column fields and forecast error fields that may be used for ozone trend analyses as well as detailed case studies.

Read more...

2015-05-11: Using self-organising maps to explore ozone profile validation results - SCIAMACHY limb vs lidar

In this study we use self-organising maps to study possible origins of differences between two datasets that describe the same phenomenon.

Read more...

2015-04-20: Analysis of actinic flux profiles measured from an ozonesonde balloon

A green light sensor has been developed at KNMI to measure actinic flux profiles using an ozone sonde balloon.

Read more...

2015-04-16: Improved spectral fitting of nitrogen dioxide from OMI in the 405 - 465 nm window

An improved nitrogen dioxide (NO2) slant column density retrieval for the Ozone Monitoring Instrument (OMI) in the 405-465 nm spectral region is presented.

Read more...

2015-02-06: MAX-DOAS tropospheric nitrogen dioxide column measurements compared with the Lotos-Euros model

A 14-month data set of MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy) tropospheric NO2 column observations in De Bilt, the Netherlands, has been compared with the regional air quality model Lotos-Euros.

Read more...

2015-01-12: A depolarisation lidar-based method for the determination of liquid-cloud microphysical properties

The fact that polarisation lidars measure a depolarisation signal in liquid clouds due to the occurrence of multiple scattering is well known. The degree of measured depolarisation depends on the lidar characteristics (e.g. wavelength and receiver field of view) as well as the cloud macrophysical (e.g. cloud-base altitude) and microphysical (e.g. effective radius, liquid water content) properties.

Read more...

2015-01-08: Tracing the second stage of ozone recovery in the Antarctic ozone-hole

This study presents a sensitivity analysis of multivariate regressions of recent springtime Antarctic vortex ozone trends using a "big data" ensemble approach. Our results indicate that the poleward heat flux (Eliassen–Palm flux) and the effective chlorine loading respectively explain most of the short-term and long-term variability in different Antarctic springtime total ozone records. The inclusion in the regression of stratospheric volcanic aerosols, solar variability and the quasi-biennial oscillation is shown to increase rather than decrease the overall uncertainty in the attribution of Antarctic springtime ozone because of large uncertainties in their respective records.

Read more...

2014-11-20: Validation of nine-years of MOPITT V5 NIR using MOZAIC/IAGOS measurements.

Validation results from a comparison between Measurement Of Pollution In The Troposphere (MOPITT) V5 Near InfraRed (NIR) Carbon Monoxide (CO) total column measurements and Measurement of Ozone and Water Vapour on Airbus in-service Aircraft (MOZAIC)/In-Service Aircraft for a. Global Observing System (IAGOS) aircraft measurements are presented. A good agreement is found between MOPITT and MOZAIC/IAGOS measurements, consistent with results from earlier studies using different validation data and despite large variability in MOPITT CO total columns along the spatial footprint of the MOZAIC/IAGOS measurements.

Read more...

2014-08-25: Spatial regression analysis on 32 years of total column ozone data

Multiple-regression analyses have been performed on 32 years of total ozone column data that was spatially gridded with a 1×1.5 resolution. The total ozone data consist of the MSR (Multi Sensor Reanalysis; 1979-2008) and 2 years of assimilated SCIAMACHY ozone data (2009-2010).

Read more...

2014-07-15: OMI 10 years in orbit

On 15 July 2014 we celebrated at KNMI the 10-th anniversary of OMI, the Ozone Monitoring Instrument.

Read more...

2014-07-10: Contiguous polarisation spectra of the Earth from 300 to 850 nm measured by GOME-2 onboard MetOp-A

In this paper we present the first contiguous high-resolution spectra of the Earth's polarisation observed by a satellite instrument. The measurements of the Stokes fraction Q/I are performed by the spectrometer GOME-2 onboard the MetOp-A satellite.

Read more...

2014-05-20: Evaluation of SCIAMACHY Oxygen A band cloud heights using Cloudnet measurements

Two SCIAMACHY O2 A band cloud height products (FRESCO v6 and ESA Level 2 v5.02) are evaluated using ground-based radar/lidar measurements between January 2003 and December 2011. The radar/lidar profiles are obtained at the Cloudnet sites of Cabauw and Lindenberg, and are averaged for 1 h centered at the SCIAMACHY overpass time. In total we have 217 cases of single-layer clouds and 204 cases of multilayer clouds. We find that the ESA L2 cloud top height has a better agreement with the Cloudnet cloud top height than the Cloudnet cloud middle height.

Read more...

2014-05-13: Evaluation of broadband surface solar irradiance derived from the Ozone Monitoring Instrument

Surface solar irradiance (SSI) data are important for planning and estimating the production of solar power plants. Long-term high quality surface solar radiation data are needed for monitoring climate change. This paper presents a new surface solar irradiance data set, the broadband (0.2–4 ?m) surface solar irradiance product derived from the Ozone Monitoring Instrument (OMI).

Read more...

2014-03-31: Ozone ProfilE Retrieval Algorithm (OPERA) for nadir-looking satellite instruments in the UV-VIS

For the retrieval of the vertical distribution of ozone in the atmosphere the Ozone ProfilE Retrieval Algorithm (OPERA) has been further developed. The new version (1.26) of OPERA is capable of retrieving ozone profiles from UV–VIS observations of most nadir-looking satellite instruments like GOME, SCIAMACHY, OMI and GOME-2.

Read more...

2014-02-25: Retrieving Hurricane Wind Speeds using Cross Polarization C-band measurements

Hurricane-force wind speeds can have a large societal impact and in the following paper microwave C-band cross-polarized (VH) signals are investigated to assess if they can be used to derive extreme wind speed conditions.

Read more...

2013-12-13: Regional nitrogen oxides emission trends in East Asia observed from space

Due to changing economic activity, emissions of air pollutants in East Asia are changing rapidly in space and time. Monthly emission estimates of nitrogen oxides (NOx) derived from satellite observations provide valuable insight into the evolution of human activity on a regional scale.

Read more...

2013-11-04: OMI - News: Antarctic Ozone Hole in 2013

According NASA's Ozone Hole Watch team and based upon a combination of ozone column data from OMI and from the Ozone Monitoring and Profiler Suite (OMPS) on the NASA-NOAA Suomi NPP satellite, the ozone hole over Antarctica was slightly smaller in 2013 than the average for recent decades. The combined set of satellite data showed an the average size of the hole in September-October 2013 of 21.0 million square kilometers. The average size since the mid 1990s is 22.5 million square kilometers.

Read more...

2013-10-29: Retrieval of aerosols using the oxygen A band in the presence of vegetation fluorescence

Within ESA's Sentinel-5 Precursor / TROPOMI project researchers at KNMI are currently developing a new operational aerosol product that is specifically dedicated to retrieval of the height of tropospheric aerosols. Aerosol height information will contribute to ash-forecasting systems for aviation safety and it will improve our understanding of aerosol interactions in climate research. The aerosol layer height product is based on the oxygen A band in the near-infrared wavelength range. In the same wavelength region vegetation exhibits fluorescence emissions as a byproduct of photosynthesis. Studies shows that aerosol retrieval may be inaccurate if fluorescene emissions are not taken into account. In a recently published article we have investigated how vegetation fluorescence should be treated in an O2 A band aerosol retrieval algorithm.

Read more...

2013-09-30: Inter-calibration of polar imager solar channels using SEVIRI

Accurate calibration of satellite imagers is a prerequisite for using their measurements in climate applications. We have developed a method for the inter-calibration of geostationary and polar-orbiting imager solar channels based on regressions of collocated near-nadir reflectances.

Read more...

2013-08-26: Satellites improve air quality monitoring in South Africa

Economic development often means an increase of harmful gases into the atmosphere. ESA’s GlobEmission project uses satellite data to monitor atmospheric pollution from emissions. ESA reported on the GlobEmission project, led by KNMI.

Read more...

2013-07-15: Tandem mode for two GOME-2's

Since 15 July 2013, the GOME-2 instruments on EUMETSAT's Metop-A and Metop-B satellites have a new measurement mode, called the tandem mode. In the tandem mode, the youngest instrument, GOME-2 on Metop-B, measures with a wide swath of 1920 km and pixels of 40×80 km2, while the oldest instrument, GOME-2 on Metop-A, measures with a reduced swath of 960 km and pixels of 40×40 km2.


Read more...

2013-06-28: Smoke from Colorado wildfires reaches Europe

On 25 June 2013, smoke from the large wildfires in Colorado (USA) reached Europe. This was seen in the GOME-2 and OMI aerosol images, processed at KNMI.


Read more...

2013-06-20: Eruptions from Popocatépetl observed from space

Located about 70 km southeast of Mexico City, Popocatépetl (pronounced poh-poh-kah-TEH-peh-til) is one of Mexico’s most active volcanoes. It reaches an altitude of 5,426 meters above sea level and is permanently covered with ice and snow. Historical records, including Aztec codices, record frequent eruptions from Popocatépetl. The volcano has become quite active during the last 20 years, with frequent venting from fumaroles punctuated by minor steam, gas, and ash emissions, and more or less permanent smoke plume hanging around the volcano.

Read more...

2013-05-27: TES tropospheric O3 validated with sonde data: spatial patterns and temporal stability in the bias

Satellite measurements provide a relatively new perspective on global tropospheric ozone (O3) distributions and their changes in time. The Tropospheric Emission Spectrometer, TES, is operational since mid 2004 and is a suitable sensor to investigate multi-annual changes in tropospheric O3 from space.

Read more...

2012-12-11: A new pole hole

In winter 2011, an ozone hole appeared over the Arctic for the first time.

Read more...

2012-10-05: Monitoring volcanic ash aerosol height from GOME-2 Oxygen A band measurements

Large volcanic ash plumes can have a serious impact on aviation. The height of the ash layer is an relevant parameter in the derivation of aerosol mass concentration which can be harmful for aircraft engines in case of high concentration. Recently Wang et al. (2012) demonstrate that it is possible to derive aerosol height from Oxygen A band measurement for absorbing aerosols such as volcanic ash plumes, biomass burning aerosols and desert dust aerosols.

Read more...

2012-09-05: Using daily satellite observations to estimate emissions of short-lived air pollutants

Emission inventories of air pollutants are crucial information for policy makers and form important input data for air quality models. Using satellite observations for emission estimates has important advantages over bottom-up emission inventories: they are spatially consistent, have high temporal resolution, and enable updates shortly after the satellite data become available. We present 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 (about 25 x 25 km2) .

Read more...

2012-05-04: Retrieval of the aerosol direct radiative effect over clouds from space-borne spectrometry.

Aerosols play an important role in the Earth's radiation balance, by scattering and absorbing solar radiation. More importantly, aerosols can change cloud dynamics as cloud condensation nuclei and by absorbing solar radiation, thereby heating the atmosphere. This will influence the atmospheric column stability and cloud forming processes. In this paper the absorption of solar radiation by aerosols is quantified using satellite spectrometry, for aerosol layers that are present over clouds.

Read more...

2012-02-28: The Cabauw Intercomparison campaign for Nitrogen Dioxide Measuring Instruments (CINDI)

From June to July 2009 more than thirty different in-situ and remote sensing instruments from all over the world participated in the Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI). The campaign took place at KNMI's Cabauw Experimental Site for Atmospheric Research (CESAR) in the Netherlands. Its main objectives were to determine the accuracy of state-of-the-art ground-based measurement techniques for the detection of atmospheric nitrogen dioxide (both in-situ and remote sensing), and to investigate their usability in satellite data validation.

Read more...

2012-02-20: Smoke cloud reveals process of nuclear winter

Soot in clouds of smoke can absorb much sunlight due to their ‘darkness’ and generate so much heat that smoke clouds can rise up to 20 km within a few days. Scientists from the Royal Netherlands Meteorological Institute have revealed the existence of this process by analyzing measurements of the large smoke cloud that emerged after the severe bush fires in Australia on 7 February 2009. This self-lifting effect of smoke clouds is comparable to the process in dust and smoke clouds that emerge after nuclear attacks and on which nuclear winter scenario’s are based.


Read more...

2012-02-01: In-flight degradation correction of SCIAMACHY UV reflectances and Absorbing Aerosol Index

L.G. Tilstra, M. de Graaf, I. Aben, and P. Stammes

In this paper we study the close relationship between the radiometric calibration of a satellite instrument and the Absorbing Aerosol Index (AAI) derived from the observed Earth reflectance.

Read more...

2011-12-15: Phd defense of Tim Vlemmix

On Thursday, December 15, Tim Vlemmix succesfully defended his PhD-thesis 'Tropospheric Nitrogen Dioxide Inversions based on Spectral Measurements of Scattered Sunlight' at the technical university of Eindhoven.

Read more...

2011-12-02: OMI instrument used in pollution reduction study

Scientists using the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite observed major reductions in sulfur dioxide (SO2) between 2005 and 2010 in Alabama, Georgia, Indiana, Kentucky, North Carolina, Ohio, Pennsylvania, and West Virginia. Led by Vitali Fioletov of Environment Canada, the research team found that sulfur dioxide levels near the region’s coal-fired power plants fell by nearly half since 2005.

Original Article on NASA's Earth Observatory

2011-09-20: Validation of Operational Ozone Profiles from the Ozone Monitoring Instrument

It is with pleasure that I announce the publication on September 20th, 2011 of our paper “Validation of operational ozone profiles from the Ozone Monitoring Instrument” in the Journal of Geophysical Research - Atmospheres. This paper describes the operational OMI ozone profile retrieval algorithm in ample detail, and presents the results of validation against a multitude of reference data sources, including cross-platform validation with EOS Aura instruments.

Read more...

2011-09-12: Climate science: Explaining Antarctic ozone hole anomalies

The strongly reduced Antarctic stratospheric ozone hole destruction in 2010 and several other recent years, results from the occurrence of dramatic meteorological events in the polar winter known as sudden stratospheric warmings (SSWs).
These findings are reported in a paper published in Scientific Reports, a new online and open access publication of the Nature Publishing Group.

Read more...

2011-08-31: Evaluation of model predicted top-of-atmosphere radiation and cloud parameters over Africa

In a paper recently published in the Journal of Climate, Wouter Greuell, Erik van Meijgaard, Jan Fokke Meirink present an evaluation of KNMI's regional climate model RACMO for Africa and the surrounding oceans. They compared model output for July 2006 with satellite data by simultaneously looking at cloud properties retrieved from SEVIRI data and at top-of-atmosphere fluxes measured by GERB.

Read more...

2011-08-17: Mapping pollutants from space

CNN made an item together with Paul Monks of the University of Leicester (UK) on mapping atmophseric pollutants and carbon from space. In this item OMI NO2 data are used as an example of what can be measured from space.

Read more...

2011-07-04: Last ozone data of GOME-1

After more than 16 years of service, the ERS-2 satellite was decommissioned (switched off) by ESA on 4 July 2011. This day marked the end of the very succesfull GOME instrument.

Read more...

2011-05-16: Surface solar irradiance from SCIAMACHY measurements

Wang, Stammes and Mueller have, for the first time, derived broadband surface solar irradiances (SSI) from SCIAMACHY satellite measurements. The SCIAMACHY SSI product is validated against globally distributed BSRN measurements and compared with ISCCP surface shortwave downwelling fluxes.

Read more...

2011-04-16: Radiative closure achieved for cloudy skies over Cabauw

A long standing problem in atmospheric research is the radiative closure of clouds. Radiative closure means that radiative transfer modelling of clouds agrees with the observations within the measurement uncertainty. This has now been achieved for shortwave radiation at Cabauw by Wang, Knap and Stammes.

Read more...

2011-04-11: EGU presentations

For a complete list of the Climate Observation departments presentations and posters at this years EGU conference, click on the link below.


Read more...

2011-03-01: The development of a nitrogen dioxide sonde

KNMI has developed a working NO2 sonde. The NO2 sonde can be applied in an operational network and also be used for satellite and AQ-model validation. The sonde is attached to a small meteorological balloon and measures a tropospheric NO2 profile. The NO2 sonde has a vertical resolution of 5m and a measurement range between 1 and 100 ppbv.

Read more...

2011-02-18: Satellite measurements provide information on the chemical composition of aerosols

A KNMI study uses satellite data from the Dutch Finnish OMI and the U.S. MODIS instruments to provide global information on the composition of anthropogenic (“man-made”) aerosols. Aerosols are important for climate forcing, but the magnitude of these effects is poorly quantified.

Read more...

2011-02-03: Evaluation of rainfall retrievals from SEVIRI reflectances over West Africa using TRMM-PR and CMORPH

Precipitation is a crucial factor in the hydrological cycle and needs to be measured at a high temporal and spatial resolution. Over several regions, such as the tropical areas and over the oceans, the amount of observations from rain gauges and rain radar is insufficient. Geostationary satellite instruments, like SEVIRI onboard the Meteosat Second Generation (MSG) satellites, are suitable to observe precipitation characteristics at various spatio-temporal scales.

Read more...

2011-02-02: OMI mentioned in NASA's Earth Observatory newsletter

This time there are two subjects in NASA's Earth Observatory newsletter in which OMI is involved:

Read more...

2010-12-03: Thirty year ozone record: the Multi Sensor Reanalysis (MSR)

A single coherent total ozone dataset, called the Multi Sensor Reanalysis (MSR), has been created from all available ozone column data measured by polar orbiting satellites in the near-ultraviolet Huggins band in the last thirty years.

Read more...

2010-12-02: Optimized fractional cloudiness determination from five ground-based remote sensing techniques

A 1 year record of fractional cloudiness at 10 min intervals was generated for the Cabauw Experimental Site for Atmospheric Research (CESAR) (51°58'N, 4°55'E) using an integrated assessment of five different observational methods. The five methods are based on active as well as passive systems and use either a hemispheric or column remote sensing technique.

Read more...

2010-12-01: Lifting potential of solar-heated aerosol layers

Absorption of shortwave solar radiation can potentially heat aerosol layers and create buoyancy that can result in the ascent of the aerosol layer over several kilometres altitude within 24–48 hours. Such heating is seasonally dependent with the summer pole region producing the largest lifting in solstice because aerosol layers are exposed to sunshine for close to 24 hours a day.

Read more...

2010-08-13: Ozone hole shift exposed South America to increased ultraviolet light

The ozone layer, which protects humans, plants, and animals from potentially damaging ultraviolet (UV) light from the Sun, develops a hole above Antarctica in September that typically lasts until early December. However, in November 2009, that hole shifted its position, leaving the southern tip of South America exposed to UV light at levels much greater than normal.

Read more...

2010-05-29: The impact of broken and inhomogeneous clouds on the retrieval of effective radius and cloud phase

In the retrieval of cloud properties from space, a generally applied assumption is that each pixel labeled as cloud-filled contains overcast clouds that are horizontally homogeneous. However, in nature a considerable amount of the clouds are broken and inhomogeneous. Wolters et al. (2010) investigated the effect of broken clouds and inhomogeneous overcast clouds on the cloud particle effective radius (re) and cloud-phase retrieval.

Read more...

2010-01-14: An aerosol boomerang observed from space.

In December 2006 southeastern Australia suffered from severe forest fires. Using the OMI instrument we observed how a smoke plume released by these fires on 14 December rapidly crossed the Pacific and reached southern America only five days later. After passing south America the plume continued its journey over the Atlantic and the Indian Ocean to return to home base on 25 December, making it the first-time observation of rapid around-the-world transport in the extra-tropical southern hemisphere.

Read more...

2009-07-06: Reductions of air pollution detected from space during the 2008 Beijing Olympic Games.

During the 2008 Olympic and Paralympic Games in Beijing (from 8 August to 17 September), local authorities enforced strong measures to reduce air pollution during the events. Inside and outside Beijing traffic was restricted, polluting industry was shut down temporarily and construction activities were put on hold.

Read more...

2009-05-14: Ozone hole tomography with GOME-2

The evolution and three dimensional structure of the Antarctic ozone hole can now be studied on a day-to-day basis using the latest data from the GOME-2 satellite instrument, as shown in a new study that just has been accepted for publication in Geophysical Research Letters.

Read more...

2009-04-20: Towards a standard procedure for validation of satellite-derived cloud properties.

Validation of satellite-derived cloud properties with ground-based data is necessary to ensure meaningful use of satellite cloud observations. Validation is difficult because differences between satellite and ground values are not only due to errors in the data, but also due to validation issues.

Read more...

2009-03-23: Collection 3: improved level-1b data for OMI retrievals.

OMI retrievals of trace gases, clouds and aerosols depend critically on the quality of the observed radiance and irradiance data. The Ozone Monitoring Instrument is equipped with a CCD-camera that allows simultaneous Earth-viewing under 60 individual angles. In the first years of operation, this novel technique appeared susceptible to calibration offsets that changed with viewing angle. In a recent paper, Dobber et al. [2008] have significantly improved the calibration of the OMI level-1b data.

Read more...

2008-12-18: FRESCO+: an improved O2-A band cloud retrieval algorithm for trace gas retrievals

More than 85% of the ground pixels of GOME(-2) and SCIAMACHY are influenced by clouds. Therefore, detection of clouds is essential in obtaining precise tropospheric pollution information from these satellite sensors.

Read more...

2008-11-14: Earth surface reflectance climatology from 3 years of OMI data

The reflectance of the Earth surface is a critical parameter for satellite retrievals of the atmospheric trace gases, clouds and aerosols. Also, it is often a critial parameter to describe the radiation balance in climate models. Kleipool et al. [2008] used three years of data from the Ozone Monitoring Instrument (OMI) to derive the surface reflectance of the globe on a 0.5 by 0.5 degree grid for every month of the year. The reflectance is given for 23 wavelengths between 328 and 500 nm. The data compares well with existing albedo climatologies derived from other satellite instruments (TOMS, GOME, MODIS), and significantly improves on these data sets by better spectral and/or spatial resolution.

Read more...

2008-10-01: Evaluation of satellite cloud phase retrieval methods from SEVIRI data

The thermodynamic phase of clouds plays an important role in the Earth's energy balance, as water clouds reflect incoming shortwave radiation back to space and ice clouds absorb and emit terrestrial radiation back to the surface. Geostationary satellite instruments, such as SEVIRI onboard METEOSAT-8 and -9, are capable of providing cloud phase information at both high temporal and spatial resolution. Wolters et al. [2008] evaluated three methods for cloud phase determination from SEVIRI data against collocated and synchronized cloud phase observations from lidar and cloud radar at Cabauw, The Netherlands.

Read more...

2008-09-03: DANDELIONS 2005 and 2006 Campaigns at Cabauw: Intercomparisons of NO2 measurements

The 2005 and 2006 DANDELIONS campaigns were unique because they brought together an unprecedented variety of measurement techniques to measure NO2, aerosols and ozone at Cabauw, The Netherlands. Also unique was that in 2006, the vertical dimension was used by placing instrumentation at ground level as well as in the 220 m. tower.

Read more...

2008-07-27: Daily Air Quality Forecast for China

The AMFIC project addresses atmospheric environmental monitoring over China. The aim is to develop an integrated information system for monitoring and forecasting tropospheric pollutants over China. The web site of the forecast service has been launched recently. Every day it publishes a 3-day forecast calculated by the chemical transport model Chimere, which has been implemented for a domain covering the densely populated eastern part of China.

Read more...

2008-07-01: Assuring quality for long-term ozone trend studies

The record of total ozone derived from the TOMS instrument series since November 1978 and continued by the Ozone Monitoring Instrument (OMI) since July 2004, is the longest to date and essential to study the recovery of the ozone layer. To verify the quality of the OMI-TOMS ozone data and its potential for trend analysis, Kroon et al. [2008] compare two ozone retrieval methods applied for the OMI instrument.

Read more...

2008-06-02: The eye of the beholder

The Ozone Monitoring Instrument (OMI) uses reflected sunlight to retrieve concentrations of trace gases in the atmosphere, like O3 and NO2. These retrieved trace gas amounts must be corrected for the presence of clouds in the atmosphere. Cloud heights are derived from OMI observations of scattered light in the UV-visible range. However, satellite imagers like MODIS use thermal infra-red radiation, emitted by the clouds themselves. The two observation methods give a different view of clouds: OMI sees the middle of the cloud, whereas MODIS sees the top of the cloud.

Read more...

2008-05-01: A ten year trend in NOx emissions measured from space

For the period 1996-2006 tropospheric nitrogen dioxide (NO2) measurements from GOME and SCIAMACHY have been analyzed to derive trends and seasonal variability for this period on a global scale. We see significant reductions (up to 7% per year) in NO2 in Europe and parts of the eastern United States, and a strong increase in Asia, most particularly in China (up to 29% per year) but also in Iran and Russia.

Read more...