Responses of the Optical Properties and Distribution of Aerosols to the Summer Monsoon in the Main Climate Zones of China

The influence of aerosols on climate varies greatly within different spatial zones. China has a very prominent summer monsoon climate and summer monsoon activity basically determines the climate distribution pattern. Consequently, we need to understand the aerosol optical properties and spatial distribution under the background of summer monsoon activity in China, which is the basis for further research on the impact of aerosols on the climate system. Based on Moderate Resolution Imaging Spectroradiometer (MODIS) and Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) data, the spatial response of the high aerosol optical depth (AOD) region in China to the advance and retreat of summer monsoon was analyzed. The main types of aerosol and the contribution of each type of aerosol particles to the total AOD were discussed. The results showed that before the landing of summer monsoon, the high value areas of AOD were distributed in the eastern Sichuan Basin, Changsha, Wuhan and Pearl River Delta regions. With the northward advance of the monsoon, the high value areas moved to the transition region affected by the summer monsoon and the AOD in this region was highly sensitive to the summer monsoon. The main aerosol types were dust and sulfate in this region and the contribution to total AOD was 27% and 57%, respectively; before the monsoon onset, the contribution of dust to total AOD was 16%, and that of sulfate was 18%; after the monsoon onset, the contribution of dust decreased by half to 8%, while the contribution of sulfate aerosol increased to 20%.

Download Full-text

Derivation of Shortwave Radiometric Adjustments for SNPP and NOAA-20 VIIRS for the NASA MODIS-VIIRS Continuity Cloud Products

Remote Sensing ◽

10.3390/rs12244096 ◽

2020 ◽

Vol 12 (24) ◽

pp. 4096 ◽

Cited By ~ 2

Author(s):

Kerry Meyer ◽

Steven Platnick ◽

Robert Holz ◽

Steve Dutcher ◽

Greg Quinn ◽

...

Keyword(s):

Optical Properties ◽

Infrared Imaging ◽

Trend Detection ◽

Adjustment Factors ◽

Moderate Resolution ◽

Resolution Imaging ◽

Water Cloud ◽

Moderate Resolution Imaging Spectroradiometer ◽

New Generation ◽

Cloud Mask

Climate studies, including trend detection and other time series analyses, necessarily require stable, well-characterized and long-term data records. For satellite-based geophysical retrieval datasets, such data records often involve merging the observational records of multiple similar, though not identical, instruments. The National Aeronautics and Space Administration (NASA) cloud mask (CLDMSK) and cloud-top and optical properties (CLDPROP) products are designed to bridge the observational records of the Moderate-resolution Imaging Spectroradiometer (MODIS) onboard NASA’s Aqua satellite and the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the joint NASA/National Oceanic and Atmospheric Administration (NOAA) Suomi National Polar-orbiting Partnership (SNPP) satellite and NOAA’s new generation of operational polar-orbiting weather platforms (NOAA-20+). Early implementations of the CLDPROP algorithms on Aqua MODIS and SNPP VIIRS suffered from large intersensor biases in cloud optical properties that were traced back to relative radiometric inconsistency in analogous shortwave channels on both imagers, with VIIRS generally observing brighter top-of-atmosphere spectral reflectance than MODIS (e.g., up to 5% brighter in the 0.67 µm channel). Radiometric adjustment factors for the SNPP and NOAA-20 VIIRS shortwave channels used in the cloud optical property retrievals are derived from an extensive analysis of the overlapping observational records with Aqua MODIS, specifically for homogenous maritime liquid water cloud scenes for which the viewing/solar geometry of MODIS and VIIRS match. Application of these adjustment factors to the VIIRS L1B prior to ingestion into the CLDMSK and CLDPROP algorithms yields improved intersensor agreement, particularly for cloud optical properties.

Download Full-text

Signature of tropical fires in the diurnal cycle of tropospheric CO as seen from Metop-A/IASI

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-26003-2014 ◽

2014 ◽

Vol 14 (19) ◽

pp. 26003-26039 ◽

Cited By ~ 1

Author(s):

T. Thonat ◽

C. Crevoisier ◽

N. A. Scott ◽

A. Chédin ◽

R. Armante ◽

...

Keyword(s):

Burned Area ◽

Tropical Region ◽

Fire Emissions ◽

Diurnal Difference ◽

Moderate Resolution ◽

Resolution Imaging ◽

Emissions Inventories ◽

Moderate Resolution Imaging Spectroradiometer ◽

The Impact ◽

Local Emissions

Abstract. Five years (July 2007–June 2012) of CO tropospheric columns derived from the IASI hyperspectral infrared sounder onboard Metop-A are used to study the impact of fires on the concentrations of CO in the mid-troposphere. Following Chédin et al. (2005, 2008), who showed the existence of a daily tropospheric excess of CO2 quantitatively related to fire emissions, we show that tropospheric CO also displays a diurnal signal with a seasonality that is in very good agreement with the seasonal evolution of fires given by GFED3.1 (Global Fire Emission Database) emissions and MODIS (Moderate Resolution Imaging Spectroradiometer) burned area. Unlike daytime or nighttime CO fields, which mix local emissions with nearby emissions transported to the region of study, the day-night difference of CO allows to highlight the CO signal due to local fire emissions. A linear relationship is found in the whole tropical region between CO fire emissions from the GFED3.1 inventory and the diurnal difference of IASI CO (R2 ~ 0.6). Based on the specificity of the two main phases of the combustion (flaming vs. smoldering) and on the vertical sensitivity of the sounder to CO, the following mechanism is proposed to explain such a CO diurnal signal: at night, after the passing of IASI at 9.30 p.m. LT, a large amount of CO emissions from the smoldering phase is trapped in the boundary layer before being uplifted the next morning by natural and pyro-convection up to the free troposphere, where it is seen by IASI at 9.30 a.m. LT. The results presented here highlight the need for developing complementary approaches to bottom-up emissions inventories and for taking into account the specificity of both the flaming and smoldering phases of fire emissions in order to fully take advantage of CO observations.

Download Full-text

Influence of observed diurnal cycles of aerosol optical depth on aerosol direct radiative effect

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-7895-2013 ◽

2013 ◽

Vol 13 (15) ◽

pp. 7895-7901 ◽

Cited By ~ 22

Author(s):

A. Arola ◽

T. F. Eck ◽

J. Huttunen ◽

K. E. J. Lehtinen ◽

A. V. Lindfors ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Radiative Forcing ◽

Radiative Effect ◽

Diurnal Variability ◽

Diurnal Cycles ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

The Impact

Abstract. The diurnal variability of aerosol optical depth (AOD) can be significant, depending on location and dominant aerosol type. However, these diurnal cycles have rarely been taken into account in measurement-based estimates of aerosol direct radiative forcing (ADRF) or aerosol direct radiative effect (ADRE). The objective of our study was to estimate the influence of diurnal aerosol variability at the top of the atmosphere ADRE estimates. By including all the possible AERONET sites, we wanted to assess the influence on global ADRE estimates. While focusing also in more detail on some selected sites of strongest impact, our goal was to also see the possible impact regionally. We calculated ADRE with different assumptions about the daily AOD variability: taking the observed daily AOD cycle into account and assuming diurnally constant AOD. Moreover, we estimated the corresponding differences in ADREs, if the single AOD value for the daily mean was taken from the the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra or Aqua overpass times, instead of accounting for the true observed daily variability. The mean impact of diurnal AOD variability on 24 h ADRE estimates, averaged over all AERONET sites, was rather small and it was relatively small even for the cases when AOD was chosen to correspond to the Terra or Aqua overpass time. This was true on average over all AERONET sites, while clearly there can be much stronger impact in individual sites. Examples of some selected sites demonstrated that the strongest observed AOD variability (the strongest morning afternoon contrast) does not typically result in a significant impact on 24 h ADRE. In those cases, the morning and afternoon AOD patterns are opposite and thus the impact on 24 h ADRE, when integrated over all solar zenith angles, is reduced. The most significant effect on daily ADRE was induced by AOD cycles with either maximum or minimum AOD close to local noon. In these cases, the impact on 24 h ADRE was typically around 0.1–0.2 W m−2 (both positive and negative) in absolute values, 5–10% in relative ones.

Download Full-text

Satellite analysis to identify changes and drivers of CyanoHABs dynamics in Lake Taihu

Water Science & Technology Water Supply ◽

10.2166/ws.2016.074 ◽

2016 ◽

Vol 16 (5) ◽

pp. 1451-1466 ◽

Cited By ~ 7

Author(s):

Yuchao Zhang ◽

Ronghua Ma ◽

Hongtao Duan ◽

Steven Loiselle ◽

Jinduo Xu

Keyword(s):

Lake Taihu ◽

Detrended Correspondence Analysis ◽

Environmental Drivers ◽

Before And After ◽

Main Driver ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

Satellite Analysis ◽

The Impact

A long-term satellite-based analysis was performed to assess the impact of environmental factors on cyanobacterial harmful blooms (CyanoHABs) dynamics in a typical shallow lake, Lake Taihu. A sub-pixel approach (algae pixel-growing algorithm) was used with 13 years of MOderate-resolution Imaging Spectroradiometer (MODIS) data to evaluate changes in bloom extension, initiation date, duration, and occurrence frequency before and after a massive bloom event (2007). Results indicated that the conditions after this event changed, with a general delay in bloom initiation and a reduction in bloom duration. The environmental drivers of daily, monthly and inter-annual CyanoHABs dynamics were analyzed by detrended correspondence analysis, principal components analysis and redundancy analysis. This demonstrated that wind speed was the main driver for daily CyanoHABs dynamics, and CODmn, total phosphorus and water temperature were closely related to monthly CyanoHABs dynamics. For the year scale, Tmean and nutrients were the main drivers of CyanoHABs initiation date and duration, and meteorological factors influenced CyanoHABs frequency for the whole lake. Regular monitoring of CyanoHABs by remote sensing has become a key element in the continued assessment of bloom conditions in Lake Taihu, and nutrient reduction policies contribute to decrease CyanoHABs occurrence.

Download Full-text

A Global MODIS Water Vapor Database for the Operational Atmospheric Correction of Historic and Recent Landsat Imagery

Remote Sensing ◽

10.3390/rs11030257 ◽

2019 ◽

Vol 11 (3) ◽

pp. 257 ◽

Cited By ~ 4

Author(s):

David Frantz ◽

Marion Stellmes ◽

Patrick Hostert

Keyword(s):

Water Vapor ◽

Landsat Imagery ◽

Atmospheric Correction ◽

Atmospheric Conditions ◽

Wet Season ◽

Moderate Resolution ◽

Resolution Imaging ◽

Daily Water ◽

Moderate Resolution Imaging Spectroradiometer ◽

The Impact

Analysis Ready Data (ARD) have undergone the most relevant pre-processing steps to satisfy most user demands. The freely available software FORCE (Framework for Operational Radiometric Correction for Environmental monitoring) is capable of generating Landsat ARD. An essential step of generating ARD is atmospheric correction, which requires water vapor data. FORCE relies on a water vapor database obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS). However, two major drawbacks arise from this strategy: (1) The database has to be compiled for each study area prior to generating ARD; and (2) MODIS and Landsat commissioning dates are not well aligned. We have therefore compiled an application-ready global water vapor database to significantly increase the operational readiness of ARD production. The free dataset comprises daily water vapor data for February 2000 to July 2018 as well as a monthly climatology that is used if no daily value is available. We systematically assessed the impact of using this climatology on surface reflectance outputs. A global random sample of Landsat 5/7/8 imagery was processed twice (i) using daily water vapor (reference) and (ii) using the climatology (estimate), followed by computing accuracy, precision, and uncertainty (APU) metrics. All APU measures were well below specification, thus the fallback usage of the climatology is generally a sound strategy. Still, the tests revealed that some considerations need to be taken into account to help quantify which sensor, band, climate, and season are most or least affected by using a fallback climatology. The highest uncertainty and bias is found for Landsat 5, with progressive improvements towards newer sensors. The bias increases from dry to humid climates, whereas uncertainty increases from dry and tropic to temperate climates. Uncertainty is smallest during seasons with low variability, and is highest when atmospheric conditions progress from a dry to a wet season (and vice versa).

Download Full-text

Spatial distribution of dust's optical properties over the Sahara and Asia inferred from Moderate Resolution Imaging Spectroradiometer

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-10827-2013 ◽

2013 ◽

Vol 13 (21) ◽

pp. 10827-10845 ◽

Cited By ~ 6

Author(s):

M. Yoshida ◽

J. M. Haywood ◽

T. Yokohata ◽

H. Murakami ◽

T. Nakajima

Keyword(s):

Optical Properties ◽

Spatial Distribution ◽

Single Scattering ◽

Surface Reflectance ◽

Carbonaceous Aerosols ◽

Dust Aerosols ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

Earth’S Climate

Abstract. There is great uncertainty regarding the role of mineral dust aerosols in Earth's climate system. One reason for this uncertainty is that the optical properties of mineral dust, such as its single scattering albedo (the ratio of scattering to total extinction), are poorly constrained because ground observations are limited to a few locations and satellite standard products are not available due to the excessively bright surface of the desert in the visible wavelength, which makes robust retrievals difficult. Here, we develop a method to estimate the spatial distributions of the aerosol single scattering albedo (ω0) and optical depth (τa), with daily 1°×1° spatial resolution using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) as well as model simulations of radiative transfer. This approach is based on the "critical surface reflectance" method developed in the literature, which estimates ω0 from the top of the atmospheric radiance. We estimate the uncertainties in ω0 over the Sahara (Asia) to be approximately 0.020 and 0.010 (0.023 and 0.017) for bands 9 and 1, respectively, while the uncertainty in τa is approximately 0.235 and 0.228 (0.464 and 0.370) for bands 9 and 1, respectively. The 5–95% range of the spatial distribution of ω0 over the Sahara (Asia) is approximately 0.90–0.94 and 0.96–0.99 (0.87–0.94 and 0.89–0.97) for bands 9 and 1, respectively, and that of τa over the Sahara (Asia) is approximately 0.8–1.4 and 0.8–1.7 (0.7–2.0 and 0.7–1.9) for bands 9 and 1, respectively. The results for the Sahara indicate a good correlation between ω0 and the surface reflectance, and between ω0 and τa. However, the relationships between ω0, τa, and surface reflectance are less clear in Asia than in the Sahara, and the ω0 values are smaller than those in the Sahara. The regions with small ω0 values are consistent with the regions where coal-burning smoke and carbonaceous aerosols are reported to be transported in previous studies. Because the coal-burning and carbonaceous aerosols are known to be more absorptive and have smaller ω0 values than dust aerosols, our results indicate that the dust aerosols in Asia are contaminated by these anthropogenic aerosols. The spatial distribution of dust optical properties obtained in our work could be useful in understanding the role of dust aerosols in Earth's climate system, most likely through future collaboration with regional and global modelling studies.

Download Full-text

Implications of satellite swath width on global aerosol optical thickness statistics

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-5-2795-2012 ◽

2012 ◽

Vol 5 (2) ◽

pp. 2795-2820 ◽

Cited By ~ 3

Author(s):

P. R. Colarco ◽

L. A. Remer ◽

R. A. Kahn ◽

R. C. Levy ◽

E. J. Welton

Keyword(s):

Optical Thickness ◽

Aerosol Optical Thickness ◽

Temporal Scales ◽

Spatial And Temporal Scales ◽

Moderate Resolution ◽

Direct Forcing ◽

Resolution Imaging ◽

Sun Photometer ◽

Moderate Resolution Imaging Spectroradiometer ◽

The Impact

Abstract. We assess the impact of swath width on the statistics of aerosol optical thickness (AOT) retrieved by satellite, as inferred from observations made by the Moderate Resolution Imaging Spectroradiometer (MODIS). Using collocated AERONET sun photometer observations we develop a correction to the MODIS data to account for calibration and algorithmic view angle dependency in the retrieved AOT. We sub-sample and correct the AOT data from the MODIS Aqua instrument along several candidate swaths of various widths for the years 2003–2011. We find that over ocean the global, annual mean AOT is within ± 0.01 of the full swath AOT for all of our sub-samples. Over land, however, most of our sub-samples are outside of this criterion range in the global, annual mean. Moreover, at smaller spatial and temporal scales we find wide deviation in the sub-sample AOT relative to the full swath over both land and ocean. In all, the sub-sample AOT is within ± 0.01 of the full swath value less than 25% of the time over land, and less than 50% of the time over ocean (less than 35% for all but the widest of our sub-sample swaths). These results suggest that future aerosol satellite missions having only narrow swath views may not sample the true AOT distribution sufficiently to reduce significantly the uncertainty in aerosol direct forcing of climate.

Download Full-text

Aerosol optical properties and direct radiative effect over Gobabeb, Namibia

Clean Air Journal ◽

10.17159/caj/2019/29/2.7518 ◽

2019 ◽

Vol 29 (2) ◽

Cited By ~ 1

Author(s):

Joseph A. Adesina ◽

Stuart J. Piketh ◽

Paola Formenti ◽

Gillian Maggs-Kölling ◽

Brent N. Holben ◽

...

Keyword(s):

Optical Properties ◽

Atmospheric Aerosols ◽

Radiative Forcing ◽

Fine Particles ◽

Single Scattering ◽

Columnar Water Vapor ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

Visible Wavelengths

Atmospheric aerosols contribute significantly to the uncertainty in radiative forcing effects that influence the climate and pose a significant health risk to humans. The climatic implications of aerosols are dependent on many variables, including aerosol size, shape, chemical composition, and position in the atmospheric column. The radiative impact of aerosols transported over the west coast of southern Africa has been found, in particular, to be complicated by the aforementioned aerosol properties. This study investigated the columnar optical properties of aerosols over Gobabeb, Namibia (23.56oS, 15.04oE, 400 m asl) using sunphotometer data between December 2014 and November 2015. Aerosol mean optical depth AOD500 had its maximum and minimum values in 2015 August (0.37±0.30) and June (0.06±0.02), respectively. The Angström parameter was mostly above unity during the study period and indicated the prevalence of fine particles for the most part of the year with maximum and minimum values observed in August 2015 (1.44±0.19) and December 2014 (0.57±0.19), respectively. The columnar water vapor was highest in January (2.62±0.79) and lowest in June (0.76±0.27). The volume size distribution showed the fine particles having a mean radius of about 0.16 μm and the coarse mode had variation in sizes with a radius ranging between 3 μm and 7 μm. The single scattering albedo at visible wavelengths ranged between 0.87 and 0.88. The phase function was high at small angles but minimum at about 140o in all seasons. The radiative forcing showed a heating effect in all seasons with maximum and minimum in winter (9.41 Wm-2) and autumn (3.64 Wm-2), respectively. Intercomparison of the sunphotometer data with the Moderate Resolution Imaging Spectroradiometer (MODIS) showed that the satellite sensor overestimates the aerosol loading compared to the ground-based sunphotometer measurements. Both sets of observations were better correlated during the spring and winter seasons than for summer and autumn.

Download Full-text

Spatial distribution of dust's optical properties over the Sahara and Asia inferred from Moderate Resolution Imaging Spectroradiometer

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-31107-2012 ◽

2012 ◽

Vol 12 (12) ◽

pp. 31107-31151

Author(s):

M. Yoshida ◽

J. M. Haywood ◽

B. T. Johnson ◽

H. Murakami ◽

T. Nakajima

Keyword(s):

Optical Properties ◽

Single Scattering ◽

Spatial Distributions ◽

Surface Reflectance ◽

Carbonaceous Aerosols ◽

Dust Aerosols ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

Earth’S Climate

Abstract. There is a great deal of uncertainty surrounding the role of mineral dust aerosols in the earth's climate system. One reason for this uncertainty is that the optical properties of mineral dust, such as its single scattering albedo (the ratio of scattering to total extinction), are poorly understood because ground observations are limited to several locations and the satellite standard products are not available due to the excessively bright surface of the desert in the visible wavelength. We develop a method in this paper to estimate the spatial distributions of the aerosol single scattering albedo (ω0) and optical depth (τa), with daily 1 degree latitude and 1 degree longitude resolution, using data from Moderate Resolution Imaging Spectroradiometer (MODIS), as well as model simulations of radiative transfer. This approach is based on the "critical surface reflectance" method developed in the literature, which estimates ω0 from the top of the atmospheric radiance. We confirm that the uncertainties in our estimation of ω0 and τa are suitably minor and that the characteristic spatial distributions estimated over the Sahara and Asia are significant. The results for the Sahara indicate good correlation between ω0 and the surface reflectance and between ω0 and τa. Therefore, ω0 is determined mainly by the mineral composition of surface dust and/or the optical depth of airborne dust in the Sahara. On the other hand, the relationships between ω0, τa, and the surface reflectance are less clear in Asia than in the Sahara, and the values of ω0 are smaller than those in the Sahara. The regions with small ω0 values are consistent with the regions where coal-burning smoke and carbonaceous aerosols are thought to be transported, as reported in previous studies. Because the coal-burning and carbonaceous aerosols are known to be more absorptive and have smaller ω0 values than dust aerosols, our results indicate that the dust aerosols in Asia are contaminated by these anthropogenic aerosols. The spatial distribution of dust optical properties obtained in our work could be useful in understanding the roles of dust aerosols in the earth's climate system, most likely through future collaboration with regional and global modelling studies.

Download Full-text

Response of net primary productivity to grassland phenological changes in Xinjiang, China

PeerJ ◽

10.7717/peerj.10650 ◽

2021 ◽

Vol 9 ◽

pp. e10650

Author(s):

Renping Zhang ◽

Jing Guo ◽

Gang Yin

Keyword(s):

Primary Productivity ◽

Net Primary Productivity ◽

Growing Season ◽

Casa Model ◽

Phenological Changes ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

Phenological Metrics ◽

The Impact

Determining the relationship between net primary productivity (NPP) and grassland phenology is important for an in-depth understanding of the impact of climate change on ecosystems. In this study, the NPP of grassland in Xinjiang, China, was simulated using the Carnegie-Ames-Stanford approach (CASA) model with Moderate Resolution Imaging Spectroradiometer (MODIS) grassland phenological (MCD12Q2) data to study trends in phenological metrics, grassland NPP, and the relations between these factors from 2001–2014. The results revealed advancement of the start of the growing season (SOS) for grassland in most regions (55.2%) in Xinjiang. The percentage of grassland area in which the end of the growing season (EOS) was delayed (50.9%) was generally the same as that in which the EOS was advanced (49.1%). The percentage of grassland area with an increase in the length of the growing season (LOS) for the grassland area (54.6%) was greater than that with a decrease in the LOS (45.4%). The percentage of grassland area with an increase in NPP (61.6%) was greater than that with a decrease in NPP (38.4%). Warmer regions featured an earlier SOS and a later EOS and thus a longer LOS. Regions with higher precipitation exhibited a later SOS and an earlier EOS and thus a shorter LOS. In most regions, the SOS was earlier, and spring NPP was higher. A linear statistical analysis showed that at various humidity (K) levels, grassland NPP in all regions initially increased but then decreased with increasing LOS. At higher levels of K, when NPP gradually increased, the LOS gradually decreased.

Download Full-text