Scientific impact of MODIS C5 calibration degradation and C6+ improvements

Lyapustin, A.; Wang, Yujie; Xiong, X.; Meister, Gerhard; Platnick, S.; Levy, Robert C.; Franz, Bryan A.; Korkin, Sergey; Hilker, Thomas; Tucker, J.; Hall, Forrest G.; Sellers, P. J.; Wu, Aisheng; Angal, Amit

doi:10.5194/amt-7-4353-2014

Cited by 207 publications

(210 citation statements)

References 38 publications

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“…These so-called pseudo-invariant targets such as deserts, deep convective clouds and high-elevation ice sheet investigations led to a new vicarious approach for calibration, which relies on collection of pseudo-invariant Earth site data continually to provide a reference over time. The approach permits calibration at multiple angles of incidence (AOIs) on the challenging-to-characterize scan mirror, rather than two angles of incidence available through the onboard solar diffuser and moon observations through the space view port (Sun et al, 2012;Lyapustin et al, 2014). The resulting calibration is of lower precision than a well-characterized mirror calibrated on a lunar standard but provides significant improvement to the C5 data (Lyapustin et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…Because the optics of the sensor (including reflecting mirrors and electronics) were expected to degrade over time, the MODIS sensor design included methods for post-launch onboard calibration. However, the onboard calibration did not sufficiently account for degradation of the calibrators due to the large degradation of the solar diffuser (detailed in Lyapustin et al, 2014). This led to a long-term drift in calibration, most pronounced on the Terra sensor, with the largest in the blue band (B3), and decreasing with increasing wavelength (Xiong and Barnes, 2006).…”

Section: Introductionmentioning

confidence: 99%

“…A challenge in using long-term satellite records to detect change is maintaining consistent instrument performance. Recent literature has discussed MODIS Terra sensor calibration degradation and its impacts on apparent data trends (e.g., Franz et al, 2008;Wang et al, 2012;Lyapustin et al, 2014;Polashenski et al, 2015;Sayer et al, 2015). Specifically related to GrIS trends, a recent work by Polashenski et al (2015) indicated that uncorrected sensor degradation in MODIS Collection 5 (C5) data, particularly on the Terra platform, was contributing significantly to an apparent albedo declining trend over the GrIS and that the albedo trend in large areas of the ice sheet which do not experience melt (the dry snow area) may disappear once Collection 6 (C6) calibrations are applied.…”

Section: Introductionmentioning

confidence: 99%

“…The approach permits calibration at multiple angles of incidence (AOIs) on the challenging-to-characterize scan mirror, rather than two angles of incidence available through the onboard solar diffuser and moon observations through the space view port (Sun et al, 2012;Lyapustin et al, 2014). The resulting calibration is of lower precision than a well-characterized mirror calibrated on a lunar standard but provides significant improvement to the C5 data (Lyapustin et al, 2014). Long-term degradation of the solar diffuser stability monitor and detectors will continue to be evaluated and addressed as the MODIS record proceeds (Toller et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Impact of MODIS sensor calibration updates on Greenland Ice Sheet surface reflectance and albedo trends

2017

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Abstract. We evaluate Greenland Ice Sheet (GrIS) surface reflectance and albedo trends using the newly released Collection 6 (C6) MODIS (Moderate Resolution Imaging Spectroradiometer) products over the period [2001][2002][2003][2004][2005][2006][2007][2008][2009][2010][2011][2012][2013][2014][2015][2016]. We find that the correction of MODIS sensor degradation provided in the new C6 data products reduces the magnitude of the surface reflectance and albedo decline trends obtained from previous MODIS data (i.e., Collection 5, C5). Collection 5 and 6 data product analysis over GrIS is characterized by surface (i.e., wet vs. dry) and elevation (i.e., 500-2000 m, 2000 m and greater) conditions over the summer season from 1 June to 31 August. Notably, the visible-wavelength declining reflectance trends identified in several bands of MODIS C5 data from previous studies are only slightly detected at reduced magnitude in the C6 versions over the dry snow area. Declining albedo in the wet snow and ice area remains over the MODIS record in the C6 product, albeit at a lower magnitude than obtained using C5 data. Further analyses of C6 spectral reflectance trends show both reflectance increases and decreases in select bands and regions, suggesting that several competing processes are contributing to Greenland Ice Sheet albedo change. Investigators using MODIS data for other ocean, atmosphere and/or land analyses are urged to consider similar re-examinations of trends previously established using C5 data.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impact of MODIS sensor calibration updates on Greenland Ice Sheet surface reflectance and albedo trends

2017

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“…Positive trends over seasonally snow-covered areas are most likely due to a decrease in snow coverage (e.g., Qu and Hall, 2007;Vaughan et al, 2013), and the trend in LCrRE that we find over northern Asia is consistent with studies showing recent declines in snow cover over this region (e.g., Dery and Brown, 2007;Brown and Robinson, 2011;Derksen et al, 2014). Possible reasons for the positive trends seen over Greenland include (1) increased snow metamorphism and black carbon deposition (e.g., Box et al, 2012;Keegan et al, 2014); (2) transport and deposition of dust and other light-absorbing impurities over the ice sheets due to increased dust source areas associated with increased snowfree area (Dumont et al, 2014); (3) higher melt extent across the Greenland ice sheet expose more fresh water at the surface (Tedesco et al, 2014); and (4) MODIS sensor degradation on the Terra satellite during recent years (Sun et al, 2014;Lyapustin et al, 2014), which would indicate a spurious decline in albedo. We also observe slightly negative LCrRE trends over Antarctica, which may be due to increases in snowfall that have decreased the duration that surface snow has to "age", thereby increasing surface albedo (Picard et al, 2012).…”

Section: Interannual Trendsmentioning

confidence: 99%

The global land shortwave cryosphere radiative effect during the MODIS era

Singh¹,

Flanner²,

Perket³

2015

The Cryosphere

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Abstract. The shortwave cryosphere radiative effect (CrRE) is the instantaneous influence of snow and ice cover on Earth's top-of-atmosphere (TOA) solar energy budget. Here, we apply measurements from the MODerate resolution Imaging Spectroradiometer (MODIS), combined with microwave retrievals of snow presence and radiative kernels produced from four different models, to derive CrRE over global land during 2001-2013. We estimate global annualmean land CrRE during this period of −2.6 W m −2 , with variations from −2.2 to −3.0 W m −2 resulting from use of different kernels and variations of −2.4 to −2.6 W m −2 resulting from different algorithmic determinations of snow presence and surface albedo. Slightly more than half of the global land CrRE originates from perennial snow on Antarctica, whereas the majority of the northern hemispheric effect originates from seasonal snow. Consequently, the northern hemispheric land CrRE peaks at −6.0 W m −2 in April, whereas the southern hemispheric effect more closely follows the austral insolation cycle, peaking at −9.0 W m −2 in December. Mountain glaciers resolved in 0.05 • MODIS data contribute about −0.037 W m −2 (1.4 %) of the global effect, with the majority (94 %) of this contribution originating from the Himalayas. Interannual trends in the global annual-mean land CrRE are not statistically significant during the MODIS era, but trends are positive (less negative) over large areas of northern Asia, especially during spring, and slightly negative over Antarctica, possibly due to increased snowfall. During a common overlap period of 2001-2008, our MODIS estimates of the northern hemispheric land CrRE are about 18 % smaller (less negative) than previous estimates derived from coarse-resolution AVHRR data, though interannual variations are well correlated (r = 0.78), indicating that these data are useful in determining longer-term trends in land CrRE.

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Comparison and evaluation of the MODIS Collection 6 aerosol data in China

et al. 2015

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Several important improvements have been made in recent Moderate Resolution ImagingSpectroradiometer (MODIS) Collection 6 aerosol retrievals, but few regional validations are conducted. We compared Deep Blue (DB) and Dark Target (DT) retrievals over China and evaluated their performance with ground observations. Sampling frequency of DB was much higher than that of DT, which was mainly caused by unavailable retrieval of DT in bright surface and heavy pollution conditions. It is found that merged aerosol optical depth (AOD) will miss some cases if it was determined only by vegetation density. Collocated comparison shows that DT AOD was substantially higher than DB with seasonal difference exceeding 0.3-0.4 over eastern China. However, when all available retrievals were considered, DT AOD was obviously lower than DB in all the seasons except spring due to their large difference in spatial coverage in high-AOD conditions. DB can well reveal spatial extent of the widespread haze pollution while there were few values in DT. More than one half of the situations with AOD > 1.0 was missed by DT, which largely underestimated the common regional haze pollution in eastern China. Ground validations show that DT tended to overestimate the aerosol loading by underestimation of the surface contribution and single scattering albedo of aerosols. DB performed generally well with higher accuracy in northern China but exhibited obvious underestimation in northwestern and southern China. Despite of slight decrease in accuracy, DB retrievals with all quality enable a large increase in spatial coverage, especially when dense haze clouds existed.

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Scientific impact of MODIS C5 calibration degradation and C6+ improvements

Cited by 207 publications

References 38 publications

Impact of MODIS sensor calibration updates on Greenland Ice Sheet surface reflectance and albedo trends

Impact of MODIS sensor calibration updates on Greenland Ice Sheet surface reflectance and albedo trends

The global land shortwave cryosphere radiative effect during the MODIS era

Comparison and evaluation of the MODIS Collection 6 aerosol data in China

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