Song Liu

Song Liu
German Aerospace Center (DLR) | DLR · Department: Atmospheric Processors

Doctor of Engineering

About

26
Publications
2,971
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137
Citations
Additional affiliations
March 2020 - present
German Aerospace Center (DLR)
Position
  • Research Associate

Publications

Publications (26)
Article
Full-text available
Nitrogen dioxide (NO2) at the ground level poses a serious threat to environmental quality and public health. This study developed a novel, artificial intelligence approach by integrating spatiotemporally weighted information into the missing extra-trees and deep forest models to first fill the satellite data gaps and increase data availability by...
Article
Full-text available
The Geostationary Environmental Monitoring Spectrometer (GEMS) is the world's first air quality instrument in the geostationary (GEO) orbit to monitor trace gases and aerosols at an unprecedented spatial and temporal resolution over East Asia, shedding light on the gradually alarming ozone pollution contrary to declining precursor emissions in this...
Article
Full-text available
. Lightning, one of the major sources of nitro�gen oxides (NOx ) in the atmosphere, contributes to the tropospheric concentration of ozone and to the oxidiz�ing capacity of the atmosphere. Lightning produces be�tween 2 and 8 Tg N yr−1 globally and on average about 250 ± 150 mol NOx per flash. In this work, we estimate the moles of NOx produced per...
Article
Full-text available
Launched in October 2017, the TROPOspheric Monitoring Instrument (TROPOMI) aboard Sentinel-5 Precursor provides the potential to monitor air quality over point sources across the globe with a spatial resolution as high as 5.5 km × 3.5 km (7 km × 3.5 km before 6 August 2019). The DLR nitrogen dioxide (NO2) retrieval algorithm for the TROPOMI instrum...
Preprint
Full-text available
Lightning is one of the major sources of nitrogen oxides (NOx) in the atmosphere, contributing to the tropospheric concentration of ozone and to the oxidising capacity of the atmosphere. Lightning produces between 2–8 Tg N per year globally and on average about 250 ± 150 mol NOx per flash. In this work, we estimate the moles of NOx produced per fla...
Article
Full-text available
Since its first confirmed case in December 2019, coronavirus disease 2019 (COVID-19) has become a worldwide pandemic with more than 90 million confirmed cases by January 2021. Countries around the world have enforced lockdown measures to prevent the spread of the virus, introducing a temporal change of air pollutants such as nitrogen dioxide (NO2)...
Preprint
Nitrogen dioxide (NO2) at the ground level poses a serious threat to environmental quality and public health. This study developed a novel, artificial intelligence approach by integrating spatiotemporally weighted information into the missing extra-trees and deep forest models to first fill the satellite data gaps and increase data availability by...
Article
Full-text available
Coronavirus disease 2019 (COVID-19) pandemic has led to a rare reduction in human activities. In such a background, data from ground-based environmental stations, satellites, and reanalysis materials are utilized to conduct a comprehensive analysis of the global air quality changes during the COVID-19 outbreak. The results showed that under the imp...
Article
Full-text available
In this paper, we present the estimation of surface NO2 concentrations over Germany using a machine learning approach. TROPOMI satellite observations of tropospheric NO2 vertical column densities (VCDs) and several meteorological parameters are used to train the neural network model for the prediction of surface NO2 concentrations. The neural netwo...
Preprint
Full-text available
Launched in October 2017, the TROPOspheric Monitoring Instrument (TROPOMI) aboard Sentinel-5 Precursor provides the potential to monitor air quality over point sources across the globe with a spatial resolution as high as 5.5 km × 3.5 km (7 km × 3.5 km before 6 August 2019). The nitrogen dioxide (NO2) retrieval algorithm for the TROPOMI instrument...
Article
Full-text available
An improved tropospheric nitrogen dioxide (NO2) retrieval algorithm from the Global Ozone Monitoring Experiment-2 (GOME-2) instrument based on air mass factor (AMF) calculations performed with more realistic model parameters is presented. The viewing angle dependency of surface albedo is taken into account by improving the GOME-2 Lambertian-equival...
Article
Full-text available
Onboard the Chinese GaoFen-5 (GF5) satellite, the Environmental trace gases Monitoring Instrument (EMI) is a nadir-viewing wide-field spectrometer that was launched on May 9, 2018. EMI measures the back-scattered earthshine solar radiance in the ultraviolet and visible spectral range. By using the differential optical absorption spectrometry (DOAS)...
Article
Full-text available
Inversion models for retrieving the total and tropospheric nitrogen dioxide ( NO 2 ) columns from spaceborne remote sensing data are presented. For total column retrieval, we propose the so-called differential radiance models with internal and external closure and solve the underlying nonlinear equations by using the method of Tikhonov regularizati...
Conference Paper
This contribution focuses on the operational GOME-2 trace gas column products developed in the framework of EUMETSAT's Satellite Application Facility on Atmospheric Composition Monitoring (AC-SAF). We present an overview of the retrieval algorithms for ozone, the minor trace gases NO2, SO2 and formaldehyde, as well as water vapour. We show examples...
Article
Full-text available
An improved tropospheric nitrogen dioxide (NO2) retrieval algorithm from the Global Ozone Monitoring Experiment-2 (GOME-2) instrument based on air mass factor (AMF) calculations performed with more realistic model parameters is presented. The viewing angle-dependency of surface albedo is taken into account by improving the GOME-2 Lambertian-equival...
Article
Full-text available
An improved algorithm for the retrieval of total and tropospheric nitrogen dioxide (NO2) columns from the Global Ozone Monitoring Experiment-2 (GOME-2) is presented. The refined retrieval will be implemented in a future version of the GOME Data Processor (GDP) as used by the EUMETSAT Satellite Application Facility on Atmospheric Composition and UV...
Conference Paper
This presentation focuses on tropospheric NO2 and ozone products from TROPOMI/Sentinel-5P as developed at the Remote Sensing Technology institute of the German Aerospace Center (DLR). We present an overview of the retrieval algorithms and show examples of air quality applications. The retrieval of tropospheric NO2 columns from TROPOMI uses an Diffe...
Article
Full-text available
An improved algorithm for the retrieval of total and tropospheric nitrogen dioxide (NO2) columns from the Global Ozone Monitoring Experiment-2 (GOME-2) is presented. The refined retrieval will be implemented in a future version of the GOME Data Processor (GDP) as used by the EUMETSAT Satellite Application Facility on Atmospheric Composition and UV...
Article
Full-text available
NO2 is an important trace gas in both the stratosphere and troposphere. Since January 2007, the nadir-looking GOME-2 satellite instrument has been providing NO2 data on a global scale which is of great interest for climate research and atmospheric chemistry studies. In this contribution, we report on an improved algorithm for the retrieval of total...
Conference Paper
This work is framed in the Dragon 3 cooperation program between the European Space Agency and NASCC (National Remote Sensing Center of P.R.of China) with the aim of examining and improving the accuracy of GOME-2 retrieval algorithm of NO2 tropospheric columns over highly polluted regions by means of ground-based measurements. GOME-2 instrument is c...
Article
Full-text available
The STRatospheric Estimation Algorithm from Mainz (STREAM) determines stratospheric columns of NO2 which are needed for the retrieval of tropospheric columns from satellite observations. It is based on the total column measurements over clean, remote regions as well as over clouded scenes where the tropospheric column is effectively shielded. The c...
Conference Paper
This paper focuses on an improved algorithm for the retrieval of total and tropospheric NO2 columns from the Global Ozone Monitoring Experiment–2 (GOME-2). A larger 425-497 nm wavelength fitting window with correction for GOME-2 slit function variations is used to determine the NO2 slant column density. The STRatospheric Estimation Algorithm from M...
Conference Paper
This contribution focuses on the improvement of the operational total and tropospheric NO2 column products from GOME-2 as developed in the framework of EUMETSAT’s Satellite Application Facility on Atmospheric Composition and UV Radiation (O3M-SAF). Total NO2 columns from GOME-2 are retrieved with the Differential Optical Absorption Spectroscopy (DO...
Conference Paper
This contribution focuses on the development and refinement of novel scientific algorithms for the retrieval of total and tropospheric nitrogen dioxide (NO2) columns for the GOME-2 satellite instrument. NO2 plays significant roles in atmospheric chemistry. It strongly related to ozone destruction in the stratosphere, and is regarded as an important...

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