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).

scholarly journals MISR empirical stray light corrections in high-contrast scenes

2015 ◽  
Vol 8 (7) ◽  
pp. 2927-2943 ◽  
Author(s):  
J. A. Limbacher ◽  
R. A. Kahn
Keyword(s):  
Near Infrared ◽  
Stray Light ◽  
Retrieval Algorithm ◽  
High Contrast ◽  
Validation Data ◽  
Modis Imagery ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Terra Satellite

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. Stray light in the MISR instrument is responsible for a large portion of the high AOD bias in high-contrast scenes, such as broken-cloud scenes that are quite common over ocean. Discrepancies among MODIS and MISR nadir-viewing blue, green, red, and near-infrared images are used to optimize seven parameters individually for each wavelength, along with a background reflectance modulation term that is 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 aerosol retrieval algorithm (RA) AOD retrievals for 1118 coincidences to validate the corrections when applied to the nadir and off-nadir cameras. With these corrections, plus the baseline RA corrections and enhanced cloud screening applied, the median AOD bias for all data in the mid-visible (green, 558 nm) band decreases from 0.006 (0.020 for the MISR standard algorithm (SA)) to 0.000, and the RMSE decreases by 5 % (27 % compared to the SA). For AOD558 nm < 0.10, which includes about half the validation data, 68th percentile absolute AOD558 nm errors for the RA have dropped from 0.022 (0.034 for the SA) to < 0.02 (~ 0.018).

scholarly journals Critical evaluation of cloud contamination in the MISR aerosol products using MODIS cloud masking products

2013 ◽  
Vol 6 (6) ◽  
pp. 10057-10079 ◽  
Author(s):  
Y. Shi ◽  
J. Zhang ◽  
J. S. Reid ◽  
B. Liu ◽  
E. J. Hyer
Keyword(s):  
High Latitude ◽  
Near Infrared ◽  
Critical Evaluation ◽  
Mean Value ◽  
Screening Methods ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
One Year ◽  
Cloud Screening

Abstract. For the first time, using the Terra Moderate Resolution Imaging Spectroradiometer (MODIS)-based cloud screening methods, we have evaluated the impacts of cloud contamination on the Terra Multi-angle Imaging Spectroradiometer (MISR) aerosol optical depth (AOD) product. Our study, based on one year of collocated MISR and MODIS data, suggests that cloud contamination exists in both over-water and over-land MISR AOD data with heavier cloud contamination occurring over the high latitude Southern hemispheric oceans. On average globally, our study shows that thin cirrus cloud contamination introduces a possible ~0.01 high bias for the over-water MISR AOD retrievals. Over the mid to high latitude oceans and Southeast Asia, this number increases to 0.015–0.02. However, biases much larger than this mean value are found in individual retrievals. This study suggests that cloud-clearing methods using observations from MISR alone, which has only visible and near infrared channels, may not be sufficient. Measurements from MODIS can be applied to assist cloud-clearing of the MISR aerosol retrievals. Cloud screening algorithms based on multi-sensor approaches are feasible and should be considered for current and future satellite aerosol studies.

scholarly journals Dynamics of Muddy Rain of 15 June 2018 in Nepal

Atmosphere ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 529
Author(s):  
Ashok Kumar Pokharel ◽  
Tianli Xu ◽  
Xiaobo Liu ◽  
Binod Dawadi
Keyword(s):  
Dust Emission ◽  
Dust Storms ◽  
Strong Wind ◽  
Hysplit Model ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Upper Level ◽  
Terra Satellite ◽  
Negative Buoyancy

It has been revealed from the Modern-Era Retrospective analysis for Research and Applications MERRA analyses, Moderate Resolution Imaging Spectroradiometer MODIS/Terra satellite imageries, Naval Aerosol Analysis and Prediction System NAAPS model outputs, Cloud –Aerosol Lidar and Infrared Pathfinder Satellite Observations CALIPSO imageries, Hybrid Single Particle Lagrangian Integrated Trajectory HYSPLIT model trajectories, atmospheric soundings, and observational records of dust emission that there were multiple dust storms in the far western parts of India from 12 to 15 June 2018 due to thunderstorms. This led to the lifting of the dust from the surface. The entry of dust into the upper air was caused by the generation of a significant amount of turbulent kinetic energy as a function of strong wind shear generated by the negative buoyancy of the cooled air aloft and the convective buoyancy in the lower planetary boundary layer. Elevated dust reached a significant vertical height and was advected towards the northern/northwestern/northeastern parts of India. In the meantime, this dust was carried by northwesterly winds associated with the jets in the upper level, which advected dust towards the skies over Nepal where rainfall was occurring at that time. Consequently, this led to the muddy rain in Nepal.

scholarly journals The decreasing albedo of Zhadang glacier on western Nyainqentanglha and the role of light-absorbing impurities

2014 ◽  
Vol 14 (9) ◽  
pp. 13109-13131 ◽  
Author(s):  
B. Qu ◽  
J. Ming ◽  
S.-C. Kang ◽  
G.-S. Zhang ◽  
Y.-W. Li ◽  
...  
Keyword(s):  
Mass Balance ◽  
Atmospheric Aerosols ◽  
Radiative Forcing ◽  
Large Change ◽  
In Situ Data ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Glacier Ablation ◽  
Terra Satellite

Abstract. The large change in albedo has a great effect on glacier ablation. Atmospheric aerosols (e.g. black carbon (BC) and dust) can reduce the albedo of glaciers and thus contribute to their melting. In this study, we investigated the measured albedo as well as the relationship between albedo and mass balance in Zhadang glacier on Mt. Nyanqentanglha associated with MODIS (10A1) data. The impacts of BC and dust in albedo reduction in different melting conditions were identified with SNow ICe Aerosol Radiative (SNICAR) model and in-situ data. It was founded that the mass balance of the glacier has a significant correlation with its surface albedo derived from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Terra satellite. The average albedo of Zhadang glacier from MODIS increased with the altitude and fluctuated but overall had a decreasing trend during 2001–2010, with the highest (0.722) in 2003 and the lowest (0.597) in 2009 and 2010, respectively. The sensitivity analysis via SNICAR showed that BC was a major factor in albedo reduction when the glacier was covered by newly fallen snow. Nevertheless, the contribution of dust to albedo reduction can be as high as 58% when the glacier experienced strong surficial melting that the surface was almost bare ice. And the average radiative forcing (RF) caused by dust could increase from 1.1 to 8.6 W m−2 exceeding the forcings caused by BC after snow was deposited and surface melting occurred in Zhadang glacier. This suggest that it may be dust rather than BC, dominating the melting of some glaciers in the TP during melting seasons.

Test of a Modified Infrared-Only ABI Cloud Mask Algorithm for AHI Radiance Observations

2016 ◽  
Vol 55 (11) ◽  
pp. 2529-2546 ◽  
Author(s):  
X. Zhuge ◽  
X. Zou
Keyword(s):  
Near Infrared ◽  
Extended System ◽  
Clear Sky ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Cloud Mask ◽  
Very High ◽  
Lower False Alarm Rate ◽  
Infrared Channel

AbstractAssimilation of infrared channel radiances from geostationary imagers requires an algorithm that can separate cloudy radiances from clear-sky ones. An infrared-only cloud mask (CM) algorithm has been developed using the Advanced Himawari Imager (AHI) radiance observations. It consists of a new CM test for optically thin clouds, two modified Advanced Baseline Imager (ABI) CM tests, and seven other ABI CM tests. These 10 CM tests are used to generate composite CMs for AHI data, which are validated by using the Moderate Resolution Imaging Spectroradiometer (MODIS) CMs. It is shown that the probability of correct typing (PCT) of the new CM algorithm over ocean and over land is 89.73% and 90.30%, respectively and that the corresponding leakage rates (LR) are 6.11% and 4.21%, respectively. The new infrared-only CM algorithm achieves a higher PCT and a lower false-alarm rate (FAR) over ocean than does the Clouds from the Advanced Very High Resolution Radiometer (AVHRR) Extended System (CLAVR-x), which uses not only the infrared channels but also visible and near-infrared channels. A slightly higher FAR of 7.92% and LR of 6.18% occurred over land during daytime. This result requires further investigation.

scholarly journals Identifying drought events in sugarcane using drought indices derived from Modis sensor

2017 ◽  
Vol 52 (11) ◽  
pp. 1063-1071 ◽  
Author(s):  
Michelle Cristina Araujo Picoli ◽  
Daniel Garbellini Duft ◽  
Pedro Gerber Machado
Keyword(s):  
Near Infrared ◽  
Sensor Data ◽  
Drought Indices ◽  
Spectral Indices ◽  
Seasonal Fluctuations ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Aqua Satellite ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Shortwave Infrared

Abstract: The objective of this work was to evaluate the potential of several spectral indices, used on moderate resolution imaging spectroradiometer (Modis) images, in identifying drought events in sugarcane. Images of Terra and Aqua satellites were used to calculate the spectral indices, using visible (red), near infrared, and shortwave infrared bands, and eight indices were selected: NDVI, EVI2, GVMI, NDI6, NDI7, NDWI, SRWI, and MSI. The indices were calculated using images between October and April of the crop years 2007/08, 2008/09, 2009/10, and 2013/14. These indices were then correlated with the standardized precipitation-evapotranspiration index (SPEI), calculated for 1, 3, and 6 months. Four of them had significant correlations with SPEI: GVMI, MSI, NDI7, and NDWI. Spectral indices from Modis sensor on board the Aqua satellite (MYD) were more suited for drought detection, and March provided the most relevant indices for that purpose. Drought indices calculated from Modis sensor data are effective for detecting sugarcane drought events, besides being able to indicate seasonal fluctuations.

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 Critical evaluation of cloud contamination in the MISR aerosol products using MODIS cloud mask products

2014 ◽  
Vol 7 (6) ◽  
pp. 1791-1801 ◽  
Author(s):  
Y. Shi ◽  
J. Zhang ◽  
J. S. Reid ◽  
B. Liu ◽  
E. J. Hyer
Keyword(s):  
High Latitude ◽  
Near Infrared ◽  
Critical Evaluation ◽  
Mean Value ◽  
Screening Methods ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
One Year ◽  
Cloud Mask ◽  
Cloud Screening

Abstract. Using Terra Moderate Resolution Imaging Spectroradiometer (MODIS)-based cloud screening methods, the impacts of cloud contamination on the Terra Multi-angle Imaging Spectroradiometer (MISR) aerosol optical depth (AOD) product are evaluated. Based on one year of collocated MISR and MODIS data, this study suggests that cloud contamination exists in both over-water and over-land MISR AOD data, with heavier cloud contamination occurring over the high latitude southern hemispheric oceans. On average globally, this study shows that thin cirrus cloud contamination introduces a possible ~ 0.01 high bias for the over-water MISR AOD retrievals. Over the mid- to high-latitude oceans and Southeast Asia, this number increases to 0.015–0.02. However, biases much larger than this mean value are found in individual retrievals, especially in retrievals that are near cloud edges. This study suggests that cloud-clearing methods using observations from MISR alone, which has only visible and near-infrared channels, may not be sufficient for all scenarios. Measurements from MODIS can be applied to assist cloud-clearing of the MISR aerosol retrievals. Cloud screening algorithms based on multi-sensor approaches are feasible and should be considered for current and future satellite aerosol studies.

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.

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