scholarly journals Comparative Analysis of Four Models to Estimate Chlorophyll-a Concentration in Case-2 Waters Using MODerate Resolution Imaging Spectroradiometer (MODIS) Imagery

2012 ◽  
Vol 4 (8) ◽  
pp. 2373-2400 ◽  
Author(s):  
Anas El-Alem ◽  
Karem Chokmani ◽  
Isabelle Laurion ◽  
Sallah E. El-Adlouni
Keyword(s):  
Comparative Analysis ◽  
Chlorophyll A ◽  
Chlorophyll A Concentration ◽  
Modis Imagery ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer

Annual mapping of large forest disturbances across Canada’s forests using 250 m MODIS imagery from 2000 to 2011

2014 ◽  
Vol 44 (12) ◽  
pp. 1545-1554 ◽  
Author(s):  
L. Guindon ◽  
P.Y. Bernier ◽  
A. Beaudoin ◽  
D. Pouliot ◽  
P. Villemaire ◽  
...  
Keyword(s):  
Validation Dataset ◽  
Commission Error ◽  
Forest Disturbances ◽  
Forest Change ◽  
Modis Imagery ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Supplementary Material ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Data Layers

Disturbances such as fire and harvesting shape forest dynamics and must be accounted for when modelling forest properties. However, acquiring timely disturbance information for all of Canada’s large forest area has always been challenging. Therefore, we developed an approach to detect annual forest change resulting from fire, harvesting, or flooding using Moderate Resolution Imaging Spectroradiometer (MODIS) imagery at 250 m spatial resolution across Canada and to estimate the within-pixel fractional change (FC). When this approach was applied to the period from 2000 to 2011, the accuracy of detection of burnt, harvested, or flooded areas against our validation dataset was 82%, 80%, and 85%, respectively. With FC, 77% of the area burnt and 82% of the area harvested within the validation dataset were correctly identified. The methodology was optimized to reduce the commission error but tended to omit smaller disturbances as a result. For example, the omitted area for harvest blocks greater than 80 ha was less than 14% but increased to between 38% and 50% for harvest blocks of 20 to 30 ha. Detection of burnt and harvested areas in some regions was hindered by persistent haze or cloud cover or by insect outbreaks. All resulting data layers are available as supplementary material.

scholarly journals Ice extent in sub-arctic fjords and coastal areas from 2001 to 2019 analyzed from MODIS imagery

2020 ◽  
Vol 61 (82) ◽  
pp. 210-226
Author(s):  
Megan O'Sadnick ◽  
Chris Petrich ◽  
Camilla Brekke ◽  
Jofrid Skarðhamar
Keyword(s):  
Coastal Areas ◽  
Degree Days ◽  
Weather Variables ◽  
Modis Imagery ◽  
Moderate Resolution ◽  
Long Term Trends ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Arctic Fjords

AbstractResults examining variations in the ice extent along the Norwegian coastline based on the analysis of Moderate Resolution Imaging Spectroradiometer (MODIS) images from 2001 to 2019, February through May, are presented. A total of 386 fjords and coastal areas were outlined and grouped into ten regions to assess seasonal and long-term trends in ice extent. In addition, three fjords were examined to investigate how ice extent may vary over short distances (<100 km). Of the 386 outlined, 47 fjords/coastal areas held >5 km2 of ice at least once between 2001 and 2019. Over this span of time, no statistically significant trend in ice extent is found for all ten regions; however, variations between regions and years are evident. Ice extent is assessed through comparison to three weather variables – freezing degree days (FDD), daily new snowfall and daily freshwater supply from rainfall plus snowmelt. Six out of ten regions are significantly positively correlated (p < 0.05) to FDD. In addition, ice in two regions is significantly positively correlated to daily new snowfall, and in one region negatively correlated to rainfall plus snowmelt. The importance of fjord geometry and bathymetry as well as other weather variables including wind is discussed.

scholarly journals Northern Hemisphere Contrail Properties Derived from Terra and Aqua MODIS Data for 2006 and 2012

2018 ◽  
Author(s):  
David P. Duda ◽  
Sarah T. Bedka ◽  
Patrick Minnis ◽  
Douglas Spangenberg ◽  
Konstantin Khlopenkov ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Radiative Forcing ◽  
Detection Algorithm ◽  
Air Traffic ◽  
Effective Diameter ◽  
Spreading Factor ◽  
Modis Imagery ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract. Linear contrail coverage, optical property, and radiative forcing data over the Northern Hemisphere (NH) are derived from a year (2012) of Terra and Aqua Moderate-resolution Imaging Spectroradiometer (MODIS) imagery, and are compared with previously published 2006 results (Duda et al., 2013; Bedka et al., 2013; Spangenberg et al., 2013) using a consistent retrieval methodology. Differences in the observed Terra-minus-Aqua screened contrail coverage and patterns in the 2012 annual-mean air traffic estimated with respect to satellite overpass time suggest that most contrails detected by the contrail detection algorithm (CDA) form approximately 2 h before overpass time. The 2012 screened NH contrail coverage (Mask B) shows a relative 3 % increase (from 0.136 % to 0.140 %) compared to 2006 data for Terra and increased by almost 7 % (0.134 % to 0.143 %) for Aqua. A new post-processing algorithm added to the contrail mask processing estimated that the total contrail cirrus coverage visible in the MODIS imagery may be three to four times larger than the linear contrail coverage detected by the CDA. This estimate is similar in magnitude to the spreading factor estimated by Minnis et al. (2013). Contrail property retrievals of the 2012 data indicate that both contrail optical depth and contrail effective diameter decreased approximately 10 % between 2006 and 2012. The decreases may be attributed to better background cloudiness characterization, changes in the waypoint screening, or changes in contrail temperature. The total mean contrail radiative forcing (TCRF) for all 2012 Terra observations were −6.3, 14.3, and 8.0 mW m−2 for the shortwave (SWCRF), longwave (LWCRF), and net forcings, respectively. These values are approximately 20 % less than the corresponding 2006 Terra estimates. The decline in TCRF results from the decrease in normalized CRF, partially offset by the 3 % increase in overall contrail coverage in 2012. The TCRFs for 2012 Aqua are similar, −6.4, 15.5, and 9.0 mW m−2 for shortwave, longwave, and net radiative forcing. The strong correlation between the relative changes in both total SWCRF and LWCRF between 2006 and 2012 and the corresponding relative changes in screened contrail coverage over each air traffic region suggests that regional changes in TCRF from year to year are dominated by interannual changes in contrail coverage over each area.

scholarly journals MISR calibration issues in high-contrast scenes, and empirical corrections

2015 ◽  
Vol 8 (3) ◽  
pp. 2521-2554 ◽  
Author(s):  
J. A. Limbacher ◽  
R. A. Kahn
Keyword(s):  
Near Infrared ◽  
High Contrast ◽  
Green Band ◽  
Validation Data ◽  
Modis Imagery ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Terra Satellite ◽  
Cloud Screening

Abstract. We diagnose the potential causes for the Multi-angle Imaging SpectroRadiometer's (MISR) persistent high aerosol optical depth (AOD) bias at low AOD with the aid of coincident MODerate-resolution Imaging Spectroradiometer (MODIS) imagery from NASA's Terra satellite. Internal reflections within the MISR instrument are responsible for a large portion of the high AOD bias in high-contrast scenes, which are especially common as broken-cloud situations over ocean. Discrepancies between MODIS and MISR nadir-viewing near-infrared (NIR) images are used to optimize nine parameters, along with a background reflectance modulation term (that was modeled separately), to represent the observed features. Independent, surface-based AOD measurements from the AErosol RObotic NETwork (AERONET) and the Marine Aerosol Network (MAN) are compared with MISR Research Algorithm (RA) AOD retrievals for 1118 coincidences to validate the corrections when applied to the nadir and off-nadir cameras. Additionally, the calibration coefficients for the red and NIR channels used for MISR over-water aerosol retrievals were reassessed with the RA to be consistent on a camera-by-camera basis. With these corrections, plus the baseline RA corrections applied (except enhanced cloud screening), the median AOD bias in the mid-visible (green) band decreases from 0.010 to 0.002, the RMSE decreases by ~ 10%, and the slope and correlation of the MISR vs. sun photometer Ångström Exponent improves. For AOD558 nm < 0.10 and with additional cloud screening, the median bias for the RA-retrieved AOD in the green band decreases from 0.011 to 0.003, compared to ~ 0.023 for the Standard Algorithm (SA). RMSE decreases by ~ 20% compared to the baseline (uncorrected) RA and by 17–53% compared to the SA. After all corrections and cloud screening are implemented, for AOD558 nm < 0.10, which includes about half the validation data, 68% absolute AOD errors for the RA have dropped to < 0.02 (~ 0.018).

Southeast Pacific Stratocumulus: High-Frequency Variability and Mesoscale Structures over San Félix Island

2010 ◽  
Vol 49 (3) ◽  
pp. 463-477 ◽  
Author(s):  
David Painemal ◽  
René Garreaud ◽  
José Rutllant ◽  
Paquita Zuidema
Keyword(s):  
High Frequency ◽  
Large Scale ◽  
Atmospheric Stability ◽  
Mesoscale Structures ◽  
High Frequency Variability ◽  
Southeast Pacific ◽  
Modis Imagery ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract Stratocumulus cloud cover patterns and their relationship to drizzle were characterized at San Felix Island (SFI; 26.5°S, 80°W) in the southeast Pacific Ocean. Small closed, large closed, and open cells were identified in about 65% of the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite images during 2003. The MODIS imagery was combined with ceilometer and surface meteorological measurements, human observations of cloud types and drizzle, and large-scale meteorological analyses for January through June. The authors identified two drizzle regimes: a synoptically quiescent summer (January–March) regime characterized by a strong anticyclone, large closed cells, and frequent drizzle, and an autumn (April–June) regime characterized by a weaker anticyclone, small closed cells and open cells, and precipitation that was mainly associated with synoptic activity. The large closed cells had higher mean cloud bases and tops than the small closed cells and accounted for 45% of the cumulus-under-stratocumulus reports and 29% of the total drizzle and rain reports. Large closed cells occupied more intermittently coupled boundary layers than did the small closed cells. Open cells also occurred in more decoupled conditions but only accounted for 18% of the total reports of drizzle and rain. The atmospheric stability of large and small closed cells was similar, but large closed cells were more commonly associated with a strong anticyclone, and small closed cells with wave activity superimposed upon a weakened anticyclone. The increased drizzle and occurrence of cumulus-under-stratocumulus in the summer rather than autumn is consistent with higher nighttime liquid water paths. A contribution of this study is the documentation of the ways in which synoptic activity can affect stratocumulus decks.

scholarly journals Comparative analysis of MODIS, MISR, and AERONET climatology over the Middle East and North Africa

2019 ◽  
Vol 37 (1) ◽  
pp. 49-64 ◽  
Author(s):  
Ashraf Farahat
Keyword(s):  
Comparative Analysis ◽  
Middle East ◽  
North Africa ◽  
Geographic Location ◽  
Positive Trend ◽  
Data Sampling ◽  
Modis Aod ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract. Comparative analysis of Multi-angle Imaging SpectroRadiometer (MISR), Moderate Resolution Imaging Spectroradiometer (MODIS), and Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) products is performed over seven AERONET stations located in the Middle East and North Africa for the period of 2000–2015. Sites are categorized into dust, biomass burning, and mixed aerosol conditions. MISR and MODIS AOD agree during high-dust seasons but MODIS tends to underestimate AOD during low-dust seasons. Over dust-dominated sites, MODIS/Terra AODs indicate a negative trend over time, while MODIS/Aqua, MISR, and AERONET depict a positive trend. A deviation between MODIS/Aqua and MODIS/Terra was observed regardless of the geographic location and data sampling. The performance of MODIS is similar over the entire region with ∼64 % of AOD within the Δτ=±0.05±0.15τAERO confidence range. MISR AOD retrievals fall within 84 % of the same confidence range for all sites examined here. Both MISR and MODIS capture aerosol climatology; however few cases were observed where one of the two sensors better captures the climatology over a certain location or AOD range than the other sensor. AERONET Level 2.0 version 3, MODIS Collection 6.1, and MISR V23 data have been used in analyzing the results presented in this study.

scholarly journals Pre-melt-season sediment plume variability at Jökulsárlón, Iceland, a preliminary evaluation using in-situ spectroradiometry and satellite imagery

2016 ◽  
Vol 57 (73) ◽  
pp. 39-46 ◽  
Author(s):  
Richard Hodgkins ◽  
Robert Bryant ◽  
Eleanor Darlington ◽  
Mark Brandon
Keyword(s):  
Short Interval ◽  
Preliminary Evaluation ◽  
Linear Calibration ◽  
Tidewater Glaciers ◽  
Modis Imagery ◽  
Study Interval ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer

ABSTRACTHigh-latitude atmospheric warming is impacting freshwater cycling, requiring techniques for monitoring the hydrology of sparsely-gauged regions. The submarine runoff of tidewater glaciers presents a particular challenge. We evaluate the utility of Moderate Resolution Imaging Spectroradiometer (MODIS) imagery for monitoring turbid meltwater plume variability in the glacier lagoon Jökulsárlón, Iceland, for a short interval before the onset of the main melt season. Total Suspended Solids concentrations (TSS) of surface waters are related to remotely-sensed reflectance via empirical calibration between in-situ-sampled TSS and reflectance in a MODIS band 1-equivalent wavelength window. This study differs from previous ones in its application to an overturning tidewater glacier plume, rather than one derived from river runoff. The linear calibration improves on previous studies by facilitating a wider range of plume metrics than areal extent, notably pixel-by-pixel TSS values. Increasing values of minimum plume TSS over the study interval credibly represent rising overall turbidity in the lagoon as melting accumulates. Plume extent responds principally to consistently-strong offshore winds. Further work is required to determine the temporal persistence of the calibration, but remote plume observation holds promise for monitoring hydrological outputs from ungauged or ungaugeable systems.

Morning-to-Afternoon Evolution of Marine Stratus Polluted by Underlying Ships: Implications for the Relative Lifetimes of Polluted and Unpolluted Clouds

2009 ◽  
Vol 66 (7) ◽  
pp. 2097-2106 ◽  
Author(s):  
Matthew W. Christensen ◽  
James A. Coakley ◽  
William R. Tahnk
Keyword(s):  
Liquid Water ◽  
The United States ◽  
Marine Stratus ◽  
The Pacific ◽  
Modis Imagery ◽  
Moderate Resolution ◽  
The Pacific Ocean ◽  
Resolution Imaging ◽  
Ship Tracks ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract Ship tracks appearing in both the morning and afternoon Moderate Resolution Imaging Spectroradiometer (MODIS) imagery for the Pacific Ocean off the west coast of the United States were used to study the morning-to-afternoon evolution of marine stratus polluted by underlying ships and nearby uncontaminated stratus. Analyzed 925-hPa winds were used to predict the afternoon positions of ship tracks found in the morning imagery. Droplet effective radii, visible optical depths, and liquid water amounts were analyzed for morning and afternoon clouds that, based on the low-level winds, were taken to be the same clouds. As found in a previous study by Segrin et al., both morning and afternoon polluted clouds had smaller droplet radii, larger optical depths, and smaller liquid water amounts than the nearby unpolluted clouds. In contrast to the Segrin et al. study, however, the droplet effective radii decreased significantly from morning to afternoon in both the polluted and unpolluted clouds, with the rate of decrease being twice as large for the unpolluted clouds. The larger decrease in the unpolluted clouds is thought to be caused by drizzle, which is probably absent in the polluted clouds. The observations suggest that, with their slower rate of liquid loss, polluted clouds could have longer lifetimes than their unpolluted counterparts. Of interest is that clouds with similar droplet radii but smaller optical depths, and thus smaller droplet number concentrations and liquid water amounts, exhibited higher sensitivities to the effects of elevated particle concentrations and a greater likelihood of appearing in both the morning and afternoon satellite overpasses.

scholarly journals Differentiating between Clouds and Heavy Aerosols in Sun-Glint Regions

2010 ◽  
Vol 27 (6) ◽  
pp. 1085-1094 ◽  
Author(s):  
Keith D. Hutchison ◽  
Bruce Hauss ◽  
Barbara D. Iisager ◽  
Hiroshi Agravante ◽  
Robert Mahoney ◽  
...  
Keyword(s):  
Satellite System ◽  
Sensor Data ◽  
Infrared Imager ◽  
Modis Imagery ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Cloud Mask ◽  
Data Dropouts ◽  
New Procedures

Abstract An approach is presented to distinguish between clouds and heavy aerosols in sun-glint regions with automated cloud classification algorithms developed for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) program. The approach extends the applicability of an algorithm that has already been applied successfully in areas outside the geometric and wind-induced sun-glint areas of the earth over both land and water surfaces. The successful application of this approach to include sun-glint regions requires an accurate cloud phase analysis, which can be degraded, especially in regions of sun glint, because of poorly calibrated radiances of the National Aeronautics and Space Administration (NASA) Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Consequently, procedures have been developed to replace bad MODIS level 1B (L1B) data, which may result from saturation, dead/noisy detectors, or data dropouts, with radiometrically reliable values to create the Visible Infrared Imager Radiometer Suite (VIIRS) proxy sensor data records (SDRs). Cloud phase analyses produced by the NPOESS VIIRS cloud mask (VCM) algorithm using these modified VIIRS proxy SDRs show excellent agreement with features observed in color composites of MODIS imagery. In addition, the improved logic in the VCM algorithm provides a new capability to differentiate between clouds and heavy aerosols within the sun-glint cone. This ability to differentiate between clouds and heavy aerosols in strong sun-glint regions is demonstrated using MODIS data collected during the recent fires that burned extensive areas in southern Australia. Comparisons between heavy aerosols identified by the VCM algorithm with imagery and heritage data products show the effectiveness of the new procedures using the modified VIIRS proxy SDRs. It is concluded that it is feasible to accurately detect clouds, identify cloud phase, and distinguish between clouds and heavy aerosol using a single cloud mask algorithm, even in extensive sun-glint regions.

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