scholarly journals Multi-satellite sensor study on precipitation-induced emission pulses of NO<sub><i>x</i></sub> from soils in semi-arid ecosystems

2016 ◽  
Vol 16 (14) ◽  
pp. 9457-9487 ◽  
Author(s):  
Jan Zörner ◽  
Marloes Penning de Vries ◽  
Steffen Beirle ◽  
Holger Sihler ◽  
Patrick R. Veres ◽  
...  
Keyword(s):  
Time Series ◽  
Arid Ecosystems ◽  
Nox Emissions ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
Dry Spell ◽  
Before And After ◽  
Soil Emissions ◽  
Sahel Region ◽  
Semi Arid

Abstract. We present a top-down approach to infer and quantify rain-induced emission pulses of NOx ( ≡  NO + NO2), stemming from biotic emissions of NO from soils, from satellite-borne measurements of NO2. This is achieved by synchronizing time series at single grid pixels according to the first day of rain after a dry spell of prescribed duration. The full track of the temporal evolution several weeks before and after a rain pulse is retained with daily resolution. These are needed for a sophisticated background correction, which accounts for seasonal variations in the time series and allows for improved quantification of rain-induced soil emissions. The method is applied globally and provides constraints on pulsed soil emissions of NOx in regions where the NOx budget is seasonally dominated by soil emissions. We find strong peaks of enhanced NO2 vertical column densities (VCDs) induced by the first intense precipitation after prolonged droughts in many semi-arid regions of the world, in particular in the Sahel. Detailed investigations show that the rain-induced NO2 pulse detected by the OMI (Ozone Monitoring Instrument), GOME-2 and SCIAMACHY satellite instruments could not be explained by other sources, such as biomass burning or lightning, or by retrieval artefacts (e.g. due to clouds). For the Sahel region, absolute enhancements of the NO2 VCDs on the first day of rain based on OMI measurements 2007–2010 are on average 4 × 1014  molec cm−2 and exceed 1 × 1015  molec cm−2 for individual grid cells. Assuming a NOx lifetime of 4 h, this corresponds to soil NOx emissions in the range of 6 up to 65 ng N m−2 s−1, which is in good agreement with literature values. Apart from the clear first-day peak, NO2 VCDs are moderately enhanced (2 × 1014  molec cm−2) compared to the background over the following 2 weeks, suggesting potential further emissions during that period of about 3.3 ng N m−2 s−1. The pulsed emissions contribute about 21–44 % to total soil NOx emissions over the Sahel.

scholarly journals Multi-satellite sensor study on precipitation-induced emission pulses of NO<sub><i>x</i></sub> from soils in semi-arid ecosystems

2016 ◽  
Author(s):  
J. Zörner ◽  
M. J. M. Penning de Vries ◽  
S. Beirle ◽  
H. Sihler ◽  
P. R. Veres ◽  
...  
Keyword(s):  
Time Series ◽  
Arid Ecosystems ◽  
Vertical Column ◽  
Dry Spell ◽  
Before And After ◽  
Soil Emissions ◽  
Sahel Region ◽  
Individual Grid ◽  
Semi Arid ◽  
Good Agreement

Abstract. We present a top-down approach to infer and quantify rain-induced emission pulses of NOx (≡ NO + NO2), stemming from biotic emissions of NO from soils, globally with a spatial resolution of 0.25° from satellite-borne measurements of NO2. This is achieved by synchronizing time series at single grid pixels according to the first day of rain after a dry spell of prescribed duration. The full track of the temporal evolution several weeks before and after a rain pulse is retained with daily resolution. These are needed for a sophisticated background correction, which accounts for seasonal variations in the time series and allows for improved quantification of rain-induced soil emissions. We find strong peaks of enhanced NO2 Vertical Column Densities (VCDs) on the first day of rainfall after prolonged droughts in many semi-arid regions of the world, in particular in the Sahel. Detailed investigations show that the rain-induced NO2 pulse detected by the OMI, GOME-2 and SCIAMACHY satellite instruments could not be explained by other sources, such as biomass burning or lightning, or by retrieval artefacts (e.g. due to clouds). For the Sahel region, absolute enhancements of the NO2 VCDs on the first day of rain based on OMI measurements 2007–2010 are on average 4 × 1014 molec cm−2 and exceed 1 × 1015 molec cm−2 for individual grid cells. Assuming a NOx lifetime of 4 h, this corresponds to soil NOx emissions in the range of 6 ng N m−2 s−1 up to 65 ng N m−2 s−1, in good agreement with literature values. Apart from the clear first-day peak, NO2 VCDs show moderately enhanced NO2 VCDs of 2 × 1014 molec cm−2 compared to background over the following two weeks suggesting potential further emissions during that period of about 3.3 ng N m−2 s−1.

Semi-automated mapping of burned areas in semi-arid ecosystems using MODIS time-series imagery

2015 ◽  
Vol 38 ◽  
pp. 25-35 ◽  
Author(s):  
Leonardo A. Hardtke ◽  
Paula D. Blanco ◽  
Héctor F.del Valle ◽  
Graciela I. Metternicht ◽  
Walter F. Sione
Keyword(s):  
Time Series ◽  
Arid Ecosystems ◽  
Automated Mapping ◽  
Burned Areas ◽  
Semi Arid

scholarly journals Satellite constraint for emissions of nitrogen oxides from anthropogenic, lightning and soil sources over East China on a high-resolution grid

2011 ◽  
Vol 11 (11) ◽  
pp. 29807-29843 ◽  
Author(s):  
J.-T. Lin
Keyword(s):  
High Resolution ◽  
Nitrogen Oxides ◽  
A Priori ◽  
East China ◽  
Anthropogenic Emissions ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
The North ◽  
Sensitivity Tests ◽  
Soil Emissions

Abstract. Vertical column densities (VCDs) of tropospheric nitrogen dioxide (NO2) retrieved from space provide valuable information to estimate emissions of nitrogen oxides (NOx) inversely. Accurate emission attribution to individual sources, important both for understanding the global biogeochemical cycling of nitrogen and for emission control, remains difficult. This study presents a regression-based multi-step inversion approach to estimate emissions of NOx from anthropogenic, lightning and soil sources individually for 2006 over East China on a 0.25° long × 0.25° lat grid, employing the DOMINO product version 2 retrieved from the Ozone Monitoring Instrument. The nested GEOS-Chem model for East Asia is used to simulate the seasonal variations of different emission sources and impacts on VCDs of NO2 for the inversion purpose. Sensitivity tests are conducted to evaluate key assumptions embedded in the inversion process. The inverse estimate suggests annual budgets of about 7.1 TgN (±38%), 0.22 TgN (±46%), and 0.40 TgN (±48%) for the a posteriori anthropogenic, lightning and soil emissions, respectively, each about 24% higher than the respective a priori values. The enhancements in anthropogenic emissions are largest in cities and areas with extensive use of coal, particularly in the north in winter, as evident on the high-resolution grid. Derived soil emissions are consistent with recent bottom-up estimates. They are each less than 6% of anthropogenic emissions annually, increasing to about 13% for July. Overall, anthropogenic emissions are found to be the dominant source of NOx over East China with important implications for nitrogen control.

scholarly journals Observations of SO<sub>2</sub> and NO<sub>2</sub> by mobile DOAS in the Guangzhou eastern area during the Asian Games 2010

2013 ◽  
Vol 6 (9) ◽  
pp. 2277-2292 ◽  
Author(s):  
F. C. Wu ◽  
P. H. Xie ◽  
A. Li ◽  
K. L. Chan ◽  
A. Hartl ◽  
...  
Keyword(s):  
Optical Absorption Spectroscopy ◽  
Nox Emissions ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
So2 Emission ◽  
Usual Condition ◽  
Eastern Area ◽  
Spatial And Temporal Distributions ◽  
Ozone Monitoring ◽  
University Town

Abstract. Mobile passive differential optical absorption spectroscopy measurements of SO2 and NO2 were performed in the Guangzhou eastern area (GEA) during the Guangzhou Asian Games 2010 from November 2010 to December 2010. The observations were carried out between 10:00 to 13:00 (local time, i.e., during daylight). Spatial and temporal distributions of SO2 and NO2 in this area were obtained and emission sources were determined using wind field data. The NO2 vertical column densities were found to agree with Ozone Monitoring Instrument values. The correlation coefficient (referred to as R2) was 0.88 after cloud filtering within a specific ground pixel. During the Guangzhou Asian Games and Asian Paralympics (Para) Games, the SO2 and NOx emissions in the area were quantified using averaged wind speed and wind direction. For times outside the games the average SO2 emission was estimated to be 9.50 ± 0.90 tons per hour and the average NOx emission was estimated to be 5.87 ± 3.46 tons per hour. During the phases of the Asian and Asian Para Games, the SO2 and NOx emissions were reduced by 53.50% and 43.50%, respectively, compared to the usual condition. We also investigated the influence of GEA on Guangzhou University Town, the main venue located northwest of the GEA, and found that SO2 concentrations here were about tripled by emissions from the GEA.

scholarly journals Comprehensive evaluations of diurnal NO<sub>2</sub> measurements during DISCOVER-AQ 2011: effects of resolution-dependent representation of NO<sub><i>x</i></sub> emissions

2021 ◽  
Vol 21 (14) ◽  
pp. 11133-11160
Author(s):  
Jianfeng Li ◽  
Yuhang Wang ◽  
Ruixiong Zhang ◽  
Charles Smeltzer ◽  
Andrew Weinheimer ◽  
...  
Keyword(s):  
Transport Model ◽  
Global Radiation ◽  
Vertical Mixing ◽  
Spatial Variations ◽  
Radiation Budget ◽  
Nox Emissions ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
Model Simulations ◽  
Ozone Monitoring

Abstract. Nitrogen oxides (NOx = NO + NO2) play a crucial role in the formation of ozone and secondary inorganic and organic aerosols, thus affecting human health, global radiation budget, and climate. The diurnal and spatial variations in NO2 are functions of emissions, advection, deposition, vertical mixing, and chemistry. Their observations, therefore, provide useful constraints in our understanding of these factors. We employ a Regional chEmical and trAnsport model (REAM) to analyze the observed temporal (diurnal cycles) and spatial distributions of NO2 concentrations and tropospheric vertical column densities (TVCDs) using aircraft in situ measurements and surface EPA Air Quality System (AQS) observations as well as the measurements of TVCDs by satellite instruments (OMI: the Ozone Monitoring Instrument; GOME-2A: Global Ozone Monitoring Experiment – 2A), ground-based Pandora, and the Airborne Compact Atmospheric Mapper (ACAM) instrument in July 2011 during the DISCOVER-AQ campaign over the Baltimore–Washington region. The model simulations at 36 and 4 km resolutions are in reasonably good agreement with the regional mean temporospatial NO2 observations in the daytime. However, we find significant overestimations (underestimations) of model-simulated NO2 (O3) surface concentrations during nighttime, which can be mitigated by enhancing nocturnal vertical mixing in the model. Another discrepancy is that Pandora-measured NO2 TVCDs show much less variation in the late afternoon than simulated in the model. The higher-resolution 4 km simulations tend to show larger biases compared to the observations due largely to the larger spatial variations in NOx emissions in the model when the model spatial resolution is increased from 36 to 4 km. OMI, GOME-2A, and the high-resolution aircraft ACAM observations show a more dispersed distribution of NO2 vertical column densities (VCDs) and lower VCDs in urban regions than corresponding 36 and 4 km model simulations, likely reflecting the spatial distribution bias of NOx emissions in the National Emissions Inventory (NEI) 2011.

scholarly journals Satellite constraint for emissions of nitrogen oxides from anthropogenic, lightning and soil sources over East China on a high-resolution grid

2012 ◽  
Vol 12 (6) ◽  
pp. 2881-2898 ◽  
Author(s):  
J.-T. Lin
Keyword(s):  
High Resolution ◽  
Nitrogen Oxides ◽  
A Priori ◽  
East China ◽  
Anthropogenic Emissions ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
The North ◽  
Sensitivity Tests ◽  
Soil Emissions

Abstract. Vertical column densities (VCDs) of tropospheric nitrogen dioxide (NO2) retrieved from space provide valuable information to estimate emissions of nitrogen oxides (NOx) inversely. Accurate emission attribution to individual sources, important both for understanding the global biogeochemical cycling of nitrogen and for emission control, remains difficult. This study presents a regression-based multi-step inversion approach to estimate emissions of NOx from anthropogenic, lightning and soil sources individually for 2006 over East China on a 0.25° long × 0.25° lat grid, employing the DOMINO product version 2 retrieved from the Ozone Monitoring Instrument. The inversion is done gridbox by gridbox to derive the respective emissions, taking advantage of differences in seasonality between anthropogenic and natural sources. Lightning and soil emissions are combined together for any given gridbox due to their similar seasonality; and their different spatial distributions are used implicitly for source separation to some extent. The nested GEOS-Chem model for East Asia is used to simulate the seasonal variations of different emission sources and impacts on VCDs of NO2 for the inversion purpose. Sensitivity tests are conducted to evaluate key assumptions embedded in the inversion process. The inverse estimate suggests annual budgets of about 7.1 TgN (±39%), 0.21 TgN (±61%), and 0.38 TgN (±65%) for the a posteriori anthropogenic, lightning and soil emissions, respectively, about 18–23% higher than the respective a priori values. The enhancements in anthropogenic emissions are largest in cities and areas with extensive use of coal, particularly in the north in winter, as evident on the high-resolution grid. Derived soil emissions are consistent with recent bottom-up estimates. They are less than 6% of anthropogenic emissions annually, increasing to about 13% for July. Derived lightning emissions are about 3% of anthropogenic emissions annually and about 10% in July. Overall, anthropogenic emissions are found to be the dominant source of NOx over East China with important implications for nitrogen control.

scholarly journals Automated mapping of burned areas in semi-arid ecosystems using modis time-series imagery

2015 ◽  
Vol XL-7/W3 ◽  
pp. 811-814 ◽  
Author(s):  
L. A. Hardtke ◽  
P. D. Blanco ◽  
H. F. del Valle ◽  
G. I. Metternicht ◽  
W. F. Sione
Keyword(s):  
Time Series ◽  
Reference Data ◽  
Regional Scale ◽  
Arid Ecosystems ◽  
Burned Area ◽  
Second Phase ◽  
Commission Error ◽  
Spatial And Temporal Patterns ◽  
Burned Areas ◽  
Semi Arid

Understanding spatial and temporal patterns of burned areas at regional scales, provides a long-term perspective of fire processes and its effects on ecosystems and vegetation recovery patterns, and it is a key factor to design prevention and post-fire restoration plans and strategies. Standard satellite burned area and active fire products derived from the 500-m MODIS and SPOT are avail - able to this end. However, prior research caution on the use of these global-scale products for regional and sub-regional applica - tions. Consequently, we propose a novel algorithm for automated identification and mapping of burned areas at regional scale in semi-arid shrublands. The algorithm uses a set of the Normalized Burned Ratio Index products derived from MODIS time series; using a two-phased cycle, it firstly detects potentially burned pixels while keeping a low commission error (false detection of burned areas), and subsequently labels them as seed patches. Region growing image segmentation algorithms are applied to the seed patches in the second-phase, to define the perimeter of fire affected areas while decreasing omission errors (missing real burned areas). Independently-derived Landsat ETM+ burned-area reference data was used for validation purposes. The correlation between the size of burnt areas detected by the global fire products and independently-derived Landsat reference data ranged from R<sup>2</sup> = 0.01 - 0.28, while our algorithm performed showed a stronger correlation coefficient (R<sup>2</sup> = 0.96). Our findings confirm prior research calling for caution when using the global fire products locally or regionally.

scholarly journals Dust Storm Satellite Images

2021 ◽  
pp. 1-46
Author(s):  
Meshari Al-Obed ◽  
Sief Uddin ◽  
Ashraf Ramadhan
Keyword(s):  
Time Series ◽  
Rate Of Change ◽  
List Type ◽  
Dust Deposition ◽  
Ozone Monitoring Instrument ◽  
Laboratory Equipment ◽  
Suspended Particulate ◽  
Before And After ◽  
Ozone Monitoring ◽  
Dust Events

Abstract DATA of Aerosol Robotic Network (Aeronet) stations and Ozone Monitoring Instrument (OMI) were obtained to get valuable and reliable information about the occurrence of dust events. In addition to Total Ozone Mapping Spectrometer (TOMS) provide informative and long dust events record. To analyze the dust time series, monthly, annual and seasonal linear trends are applied to the dust time series. This is achieved by summing the total number of dusty hours for each month and then the total number of dusty days for the month is calculated. Dust trend analysis includes; annual, winter, spring, summer and autumn with the rate of change. Dust frequency of seasons in days/season before and after sorting in a descending manner from 1984 to 2013. Satelliteimagesuse for PM2.5 Estimation and concentrations Remote sensing-based measurements Calibration of Field and Laboratory Equipment. Particle concentrations in different size ranges and the total suspended particulate matter in the air in Kuwait. Dust deposition rates were monitored and analyzed in Kuwait at the northern ArabianGulf to estimate quantities of fallen dust within major eight dust trajectories in the ArabianGulf. Kuwait is surrounded by five major sources of dust rather than intermediate dust source areas that are listed. Satelliteimages from 2000 to 2010 were used to identify major dust trajectories within seven major deserts in the world.

scholarly journals Influence of satellite-derived photolysis rates and NO<sub>x</sub> emissions on Texas ozone modeling

2015 ◽  
Vol 15 (4) ◽  
pp. 1601-1619 ◽  
Author(s):  
W. Tang ◽  
D. S. Cohan ◽  
A. Pour-Biazar ◽  
L. N. Lamsal ◽  
A. T. White ◽  
...  
Keyword(s):  
Direct Method ◽  
Model Performance ◽  
State Level ◽  
Nox Emissions ◽  
Air Quality Model ◽  
Ozone Monitoring Instrument ◽  
Quality Model ◽  
Vertical Column ◽  
Joint Application ◽  
Photolysis Rates

Abstract. Uncertain photolysis rates and emission inventory impair the accuracy of state-level ozone (O3) regulatory modeling. Past studies have separately used satellite-observed clouds to correct the model-predicted photolysis rates, or satellite-constrained top-down NOx emissions to identify and reduce uncertainties in bottom-up NOx emissions. However, the joint application of multiple satellite-derived model inputs to improve O3 state implementation plan (SIP) modeling has rarely been explored. In this study, Geostationary Operational Environmental Satellite (GOES) observations of clouds are applied to derive the photolysis rates, replacing those used in Texas SIP modeling. This changes modeled O3 concentrations by up to 80 ppb and improves O3 simulations by reducing modeled normalized mean bias (NMB) and normalized mean error (NME) by up to 0.1. A sector-based discrete Kalman filter (DKF) inversion approach is incorporated with the Comprehensive Air Quality Model with extensions (CAMx)–decoupled direct method (DDM) model to adjust Texas NOx emissions using a high-resolution Ozone Monitoring Instrument (OMI) NO2 product. The discrepancy between OMI and CAMx NO2 vertical column densities (VCDs) is further reduced by increasing modeled NOx lifetime and adding an artificial amount of NO2 in the upper troposphere. The region-based DKF inversion suggests increasing NOx emissions by 10–50% in most regions, deteriorating the model performance in predicting ground NO2 and O3, while the sector-based DKF inversion tends to scale down area and nonroad NOx emissions by 50%, leading to a 2–5 ppb decrease in ground 8 h O3 predictions. Model performance in simulating ground NO2 and O3 are improved using sector-based inversion-constrained NOx emissions, with 0.25 and 0.04 reductions in NMBs and 0.13 and 0.04 reductions in NMEs, respectively. Using both GOES-derived photolysis rates and OMI-constrained NOx emissions together reduces modeled NMB and NME by 0.05, increases the model correlation with ground measurement in O3 simulations, and makes O3 more sensitive to NOx emissions in the O3 non-attainment areas.

Global-scale characterization of turning points in arid and semi-arid ecosystems functioning

2020 ◽  
Author(s):  
Paulo Bernardino ◽  
Wanda De Keersmaecker ◽  
Rasmus Fensholt ◽  
Jan Verbesselt ◽  
Ben Somers ◽  
...  
Keyword(s):  
Time Series ◽  
Ecosystem Functioning ◽  
Turning Point ◽  
Turning Points ◽  
Human Action ◽  
Global Scale ◽  
Arid Ecosystems ◽  
Ancillary Data ◽  
Before And After ◽  
Scale Characterization

&lt;p&gt;Ecosystems in drylands are highly susceptible to changes in their way of functioning due to extreme and prolonged droughts or anthropogenic perturbation. Long-standing pressure, from climate or human action, may result in severe alterations in their dynamics. Moreover, changes in dryland ecosystems functioning can take place abruptly (Horion et al., 2016). Such abrupt changes may have severe ecological and economic consequences, disturbing the livelihood of drylands inhabitants and causing increased poverty and food insecurity. Considering that drylands cover 40% of Earth&amp;#8217;s land surface and are home to around one-third of the human population, detecting and characterizing hotspots of abrupt changes in ecosystem functioning (here called turning points) becomes even more crucial.&lt;/p&gt;&lt;p&gt;BFAST, a time series segmentation technique, was used to detect breakpoints in time series (1982-2015) of rain-use efficiency. An abrupt change in rain-use efficiency time series points towards a significant change in the way an ecosystem responds to precipitation, allowing the study of turning points in ecosystem functioning in both natural and anthropogenic landscapes. Moreover, we here proposed a new typology to characterize turning points in ecosystem functioning, which takes into account the trend in ecosystem functioning before and after the turning point, as well as differences in the rate of change. Case studies were used to evaluate the performance of the new typology. Finally, ancillary data on population density and drought were used to have some first insights about the potential determinants of hotspots of turning point occurrence.&lt;/p&gt;&lt;p&gt;Our results showed that 13.6% of global drylands presented a turning point in ecosystem functioning between 1982 and 2015. Hotspots of turning point occurrence were observed in North America (where 62.6% of the turning points were characterized by a decreasing trend in ecosystem functioning), the Sahel, Central Asia, and Australia. The last three hotspot regions were mainly characterized by a positive trend in ecosystem functioning after the turning point. The ancillary data pointed to an influence of both droughts and human action on turning point occurrence in North America, while in Asia and Australia turning point occurrence was higher in areas with higher anthropogenic pressure. In the grasslands of the Sahel, turning points were potentially related to drought.&amp;#160;&lt;/p&gt;&lt;p&gt;By detecting where and when hotspots of turning points occurred in recent decades, and by characterizing the trends in ecosystem functioning before and after the turning points, we advanced towards better supporting decision making related to ecosystems conservation and management in drylands. Moreover, we provided first insights about the drivers of ecosystem functioning change in hotspots of turning point occurrence in global drylands (Bernardino et al., 2019).&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Bernardino PN, De Keersmaecker W, Fensholt R, Verbesselt J, Somers B, Horion S (2019) Global-scale characterization of turning points in arid and semi-arid ecosystems functioning. Manuscript submitted for publication.&lt;/p&gt;&lt;p&gt;Horion S, Prishchepov A V., Verbesselt J, de Beurs K, Tagesson T, Fensholt R (2016) Revealing turning points in ecosystem functioning over the Northern Eurasian agricultural frontier. Global change biology, &lt;strong&gt;22&lt;/strong&gt;, 2801&amp;#8211;2817.&lt;/p&gt;

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