Identification of the cloud base height over the central Himalayan region: Intercomparison of Ceilometer and Doppler Lidar

Abstract. We present the measurement of cloud base height (CBH) derived from the Doppler Lidar (DL), Ceilometer (CM) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite over a high altitude station in the central Himalayan region for the first time. We analyzed six cases of cloud overpass during the daytime convection period by using the cloud images captured by total sky imager. The occurrence of thick clouds (> 50 %) over the site is more frequent than thin clouds (< 40 %). In every case, the CBH indicates less than 1.2 km, above ground level (AGL) observed by both DL and CM instruments. The presence of low level clouds in the height-time variation of signal to noise ratio of DL and backscatter of CM shows a similar diurnal pattern on all days. Cloud fraction is found to be maximum during the convective period. The CBH estimated by the DL and CM showed reasonably good correlation (R2 = 0.76). The DL observed updraft fraction and cloud base vertical velocity also shows good correlation (R2 = 0.66). The inter-comparison between DL and CM will have implications in filling the gap of CBH measurements by the DL, in absence of CM. More deployments of such instruments will be invaluable for the validations of meteorological models over the observationally sparse Indian regions.

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Investigating the frequency and interannual variability in global above-cloud aerosol characteristics with CALIOP and OMI

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-47-2016 ◽

2016 ◽

Vol 16 (1) ◽

pp. 47-69 ◽

Cited By ~ 13

Author(s):

R. Alfaro-Contreras ◽

J. Zhang ◽

J. R. Campbell ◽

J. S. Reid

Keyword(s):

Interannual Variability ◽

Orthogonal Polarization ◽

Cloud Detection ◽

Ozone Monitoring Instrument ◽

Data Set ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

First Time ◽

Aerosol Index

Abstract. Seven and a half years (June 2006 to November 2013) of Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol and cloud layer products are compared with collocated Ozone Monitoring Instrument (OMI) aerosol index (AI) data and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) cloud products in order to investigate variability in estimates of biannual and monthly above-cloud aerosol (ACA) events globally. The active- (CALIOP) and passive-based (OMI-MODIS) techniques have their advantages and caveats for ACA detection, and thus both are used to derive a thorough and robust comparison of daytime cloudy-sky ACA distribution and climatology. For the first time, baseline above-cloud aerosol optical depth (ACAOD) and AI thresholds are derived and examined (AI  =  1.0, ACAOD  =  0.015) for each sensor. Both OMI-MODIS and CALIOP-based daytime spatial distributions of ACA events show similar patterns during both study periods (December–May) and (June–November). Divergence exists in some regions, however, such as Southeast Asia during June through November, where daytime cloudy-sky ACA frequencies of up to 10 % are found from CALIOP yet are non-existent from the OMI-based method. Conversely, annual cloudy-sky ACA frequencies of 20–30 % are reported over northern Africa from the OMI-based method yet are largely undetected by the CALIOP-based method. Using a collocated OMI-MODIS-CALIOP data set, our study suggests that the cloudy-sky ACA frequency differences between the OMI-MODIS- and CALIOP-based methods are mostly due to differences in cloud detection capability between MODIS and CALIOP as well as QA flags used. An increasing interannual variability of ∼  0.3–0.4 % per year (since 2009) in global monthly cloudy-sky ACA daytime frequency of occurrence is found using the OMI-MODIS-based method. Yet, CALIOP-based global daytime ACA frequencies exhibit a near-zero interannual variability. Further analysis suggests that the OMI-derived interannual variability in cloudy-sky ACA frequency may be affected by OMI row anomalies in later years. A few regions are found to have increasing slopes in interannual variability in cloudy-sky ACA frequency, including the Middle East and India. Regions with slightly negative slopes of the interannual variability in cloudy-sky ACA frequencies are found over South America and China, while remaining regions in the study show nearly zero change in ACA frequencies over time. The interannual variability in ACA frequency is not, however, statistically significant on both global and regional scales, given the relatively limited sample sizes. A longer data record of ACA events is needed in order to establish significant trends of ACA frequency regionally and globally.

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Estimates of aerosol absorption over India using multi-satellite retrieval

Annales Geophysicae ◽

10.5194/angeo-31-1773-2013 ◽

2013 ◽

Vol 31 (10) ◽

pp. 1773-1778 ◽

Cited By ~ 5

Author(s):

D. Narasimhan ◽

S. K. Satheesh

Keyword(s):

Regional Distribution ◽

Single Scattering ◽

Ozone Monitoring Instrument ◽

Satellite Retrieval ◽

Aerosol Absorption ◽

Moderate Resolution ◽

Indian Landmass ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

First Time

Abstract. Aerosol absorption is poorly quantified because of the lack of adequate measurements. It has been shown that the Ozone Monitoring Instrument (OMI) aboard EOS-Aura and the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard EOS-Aqua, which fly in formation as part of the A-train, provide an excellent opportunity to improve the accuracy of aerosol retrievals. Here, we follow a multi-satellite approach to estimate the regional distribution of aerosol absorption over continental India for the first time. Annually and regionally averaged aerosol single-scattering albedo over the Indian landmass is estimated as 0.94 ± 0.03. Our study demonstrates the potential of multi-satellite data analysis to improve the accuracy of retrieval of aerosol absorption over land.

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Investigating the frequency and trends in global above-cloud aerosol characteristics with CALIOP and OMI

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-4173-2015 ◽

2015 ◽

Vol 15 (4) ◽

pp. 4173-4217 ◽

Cited By ~ 1

Author(s):

R. Alfaro-Contreras ◽

J. Zhang ◽

J. R. Campbell ◽

J. S. Reid

Keyword(s):

Orthogonal Polarization ◽

Ozone Monitoring Instrument ◽

Regional Trends ◽

Data Record ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

Increasing Trends ◽

First Time ◽

Aerosol Index

Abstract. Seven and a half years (June 2006–November 2013) of Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol and cloud layer products are compared with collocated Ozone Monitoring Instrument (OMI) Aerosol Index (AI) data and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) cloud products, to investigate variability in estimates of bi-annual and monthly above-cloud aerosol (ACA) events globally. The active- (CALIOP) and passive-based (OMI-MODIS) techniques have their advantages and caveats for ACA detection, and thus both are used to get a thorough and robust comparison of daytime cloudy-sky ACA distribution and climatology. For the first time, baseline above-cloud aerosol optical depth (ACAOD) and AI thresholds are derived and examined (AI = 1.0, ACAOD = 0.015) for each sensor. Both OMI-MODIS and CALIOP-based daytime spatial distributions of ACA events show similar patterns during both study periods (December–May) and (June–November). Divergence exists in some regions, however, such as Southeast Asia during June through November, where daytime cloudy-sky ACA frequencies of up to 10% are found from CALIOP yet are non-existent from the OMI-based method. Conversely, annual cloudy-sky ACA frequencies of 20–30% are reported over Northern Africa from the OMI-based method, yet are largely undetected by the CALIOP-based method. This is possibly due to a misclassification of thick dust plumes as clouds by the OMI-MODIS based method. An increasing trend of ~0.5% per year (since 2009) in global monthly cloudy-sky ACA daytime frequency of occurrence is found using the OMI-MODIS based method. Yet, CALIOP-based global daytime ACA frequencies exhibit a near-zero trend. Further analysis suggests that the OMI derived cloudy-sky ACA frequency trend may be affected by OMI row anomalies in later years. A few regions are found to have increasing trends of cloudy-sky ACA frequency, including the Middle-East and India. Regions with slightly negative cloudy-sky ACA frequency trends are found over South America and the Southern Oceans, while remaining regions in the study show a near-zero trend. Global and regional trends are not statistically significant, though, given relatively lacking sample sizes. A longer data record of ACA events is needed in order to establish a more significant trend of ACA frequency regionally and globally.

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Construction of Nighttime Cloud Layer Height and Classification of Cloud Types

Remote Sensing ◽

10.3390/rs12040668 ◽

2020 ◽

Vol 12 (4) ◽

pp. 668 ◽

Cited By ~ 1

Author(s):

Sijie Chen ◽

Chonghui Cheng ◽

Xingying Zhang ◽

Lin Su ◽

Bowen Tong ◽

...

Keyword(s):

Dead Zone ◽

Cloud Layer ◽

Spectral Radiance ◽

Cloud Base ◽

Track Reconstruction ◽

Cloud Structure ◽

Ground Track ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer

A cloud structure construction algorithm adapted for the nighttime condition is proposed and evaluated. The algorithm expands the vertical information inferred from spaceborne radar and lidar via matching of infrared (IR) radiances and other properties at off-nadir locations with their counterparts that are collocated with active footprints. This nighttime spectral radiance matching (NSRM) method is tested using measurements from CloudSat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Moderate Resolution Imaging Spectroradiometer (MODIS). Cloud layer heights are estimated up to 400 km on both sides of the ground track and reconstructed with the dead zone setting for an approximate evaluation of the reliability. By mimicking off-nadir pixels with a dead zone around pixels along the ground track, reconstruction of nadir profiles shows that, at 200 km from the ground track, the cloud top height (CTH) and the cloud base height (CBH) reconstructed by the NSRM method are within 1.49 km and 1.81 km of the original measurements, respectively. The constructed cloud structure is utilized for cloud classification in the nighttime. The same method is applied to the daytime measurements for comparison with collocated MODIS classification based on the International Satellite Cloud Climatology Project (ISCCP) standard. The comparison of eight cloud types over the expanded distance shows good agreement in general.

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INTER-COMPARISON BETWEEN MODIS SATELLITE-BASED AND AERONET GROUND-BASED AEROSOL OPTICAL DEPTH PRODUCTS IN VIETNAM

Vietnam Journal of Science and Technology ◽

10.15625/2525-2518/58/3a/14340 ◽

2020 ◽

Vol 58 (3A) ◽

pp. 124

Author(s):

DUC LUONG NGUYEN ◽

Thi Hieu Bui ◽

Hoang Hiep Nguyen ◽

Quang Trung Bui ◽

Hoang Duong Do

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Subtropical Climate ◽

Deep Blue ◽

Modis Aod ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

First Time ◽

Climatic Characteristics

Although a number of studies have extensively inter-compared the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite-based aerosol optical depth (AOD) with the Aerosol Robotic Network (AERONET) ground-based AOD on both global and regional scales, almost no similar studies have been conducted for Vietnam - a humid subtropical climate region. For the first time, inter-comparison between the MODIS Terra and Aqua Collection 6.1 (C6.1) Dark Target (DT) 10 km, Deep Blue (DB) 10 km, and merged DT-DB 10 km with the AERONET AODs has been performed in different areas with different surface types and different climatic characteristics in Vietnam. Three investigated AERONET stations are Nghia Do (urban), Son La (mountainous rural), and Bac Lieu (coastal urban) with the studying periods of 2010 - 2016, 2012 - 2017, and 2010 - 2017, respectively. Our findings showed the better performances of DB algorithm than those of DT and DT-DB products in the urban area. Additionally, all MODIS AOD algorithm performed worse over the coastal area compared to those in the non-coastal areas. Generally, the ability of all the MODIS AODs to catch up the monthly-mean AERONET AODs has been expressed in this study.

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Comparison of Aerosol Optical Depth (AOD) Derived from Ground-Based LIDAR and MODIS

The Open Atmospheric Science Journal ◽

10.2174/1874282300903010131 ◽

2009 ◽

Vol 3 (1) ◽

pp. 131-137 ◽

Cited By ~ 8

Author(s):

P.W. Chan

Keyword(s):

Hong Kong ◽

Extinction Coefficient ◽

Doppler Lidar ◽

Moderate Resolution ◽

Resolution Imaging ◽

Sun Photometer ◽

Moderate Resolution Imaging Spectroradiometer ◽

Ground Based Lidar ◽

Hong Kong International Airport

The performance and application of AOD products from the Moderate Resolution Imaging Spectroradiometer (MODIS) are studied by comparing with the AOD derived from the ground-based Doppler LIDAR inside the Hong Kong International Airport (HKIA). The backscattered power data of the LIDAR are used to determine the extinction coefficient profile, from which the AOD is calculated. The AOD determined from the LIDAR is found to have good quality by comparing with the AOD measurements from a hand-held sun photometer at HKIA over a period of three months, and as such it is used to study the quality of AOD estimated from MODIS. The 1-km resolution AOD product from MODIS is found to have better correlation with the LIDAR AOD in comparison to the 10-km resolution product. Moreover, since AOD is a column-integrated quantity, its application to the monitoring of the surface visibility changes should be made with caution during the presence of elevated layers of higher aerosol concentrations. Examples of the effects of such elevated aerosol layers are studied.

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Using RST approach and EOS-MODIS radiances for monitoring seismically active regions: a study on the 6 April 2009 Abruzzo earthquake

Natural Hazards and Earth System Science ◽

10.5194/nhess-10-239-2010 ◽

2010 ◽

Vol 10 (2) ◽

pp. 239-249 ◽

Cited By ~ 31

Author(s):

N. Pergola ◽

C. Aliano ◽

I. Coviello ◽

C. Filizzola ◽

N. Genzano ◽

...

Keyword(s):

Active Regions ◽

Environmental Risks ◽

Infrared Observations ◽

Thermal Anomalies ◽

Earth Observing System ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

Eos Modis ◽

First Time

Abstract. In the last few years, Robust Satellite data analysis Techniques (RST) have been proposed and successfully applied for monitoring major natural and environmental risks. Among the various fields of application, RST analysis has been used as a suitable tool for satellite TIR surveys in seismically active regions, devoted to detect and monitor thermal anomalies possibly related to earthquake occurrence. In this work, RST has been applied, for the first time, to thermal infrared observations collected by MODIS (Moderate Resolution Imaging Spectroradiometer) – the sensor onboard EOS (Earth Observing System) satellites – in the case of Abruzzo (Italy) earthquake occurred on 6 April 2009 (ML~5.8). First achievements, shown in this work, seem to confirm the sensitivity of the proposed approach in detecting perturbations of the Earth�s emission thermal field few days before the event. The reliability of such results, based on the analysis of 10 years of MODIS observations, seems to be supported by the results achieved analyzing the same area in similar observation conditions but in seismically unperturbed periods (no earthquakes with ML≥5) that will be also presented.

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Comparison of the cloud top heights retrieved from MODIS and AHI satellite data with ground-based Ka-band radar

Atmospheric Measurement Techniques ◽

10.5194/amt-13-1-2020 ◽

2020 ◽

Vol 13 (1) ◽

pp. 1-11 ◽

Cited By ~ 2

Author(s):

Juan Huo ◽

Daren Lu ◽

Shu Duan ◽

Yongheng Bi ◽

Bo Liu

Keyword(s):

Satellite Data ◽

Cloud Base ◽

Ka Band ◽

Retrieval Accuracy ◽

Moderate Resolution ◽

Resolution Imaging ◽

Radar Measurements ◽

The Mean ◽

Moderate Resolution Imaging Spectroradiometer ◽

The Difference

Abstract. To better understand the accuracy of cloud top heights (CTHs) derived from passive satellite data, ground-based Ka-band radar measurements from 2016 and 2017 in Beijing are compared with CTH data inferred from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Himawari Imager (AHI). Relative to the radar CTHs, the MODIS CTHs are found to be underestimated by−1.10 ± 2.53 km on average and 49 % of CTH differences are within 1.0 km. The AHI CTHs are underestimated by −1.10 ± 2.27 km and 42 % are within 1.0 km. Both the MODIS and AHI CTH retrieval accuracy depends strongly on the cloud depth (CD). Large differences are mainly due to the retrieval of thin clouds of CD <1 km, especially when the cloud base height is higher than 4 km. For clouds with CD >1 km, the mean CTH difference decreases to -0.48±1.70 km for MODIS and to -0.76±1.63 km for AHI. It is found that MODIS CTHs with higher values (i.e. >6 km) show smaller discrepancy with radar CTH than those MODIS CTHs with lower values (i.e. <4 km). Statistical analysis illustrate that the CTH difference between the two satellite instruments is lower than the difference between the satellite instrument and the ground-based Ka-band radar. The monthly accuracy of both CTH retrieval algorithms is investigated and it is found that summer has the smallest retrieval difference.

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Evaluation of cloud base height measurements from ceilometer CL31 and MODIS satellite over Ahmedabad, India

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-8-11729-2015 ◽

2015 ◽

Vol 8 (11) ◽

pp. 11729-11752 ◽

Cited By ~ 1

Author(s):

S. Sharma ◽

R. Vaishnav ◽

M. V. Shukla ◽

P. Kumar ◽

...

Keyword(s):

Cloud Base ◽

Monsoon Period ◽

Post Monsoon ◽

Cloud Dynamics ◽

Cloud Characteristics ◽

Moderate Resolution ◽

Moderate Resolution Imaging Spectroradiometer ◽

High Level ◽

Terra Satellite ◽

Cloud Base Height

Abstract. Clouds play a tangible role in the Earth's atmosphere and in particular, the cloud base height (CBH) which is linked to cloud type is one of the important characteristic to describe the influence of clouds on the environment. In present study, CBH observations from ceilometer CL31 have been extensively studied during May 2013 to January 2015 over Ahmedabad (23.03° N, 72.54° E), India. A detail comparison has been performed with the use of ground-based CBH measurements from ceilometer CL31 and CBH retrieved from MODIS (Moderate Resolution Imaging Spectroradiometer) onboard Aqua and Terra satellite. Some interesting features of cloud dynamics viz. strong downdraft and updraft have been observed over Ahmedabad which revealed different cloud characteristics during monsoon and post-monsoon periods. CBH shows seasonal variation during Indian summer monsoon and post-monsoon period. Results indicate that ceilometer is one of the excellent instruments to precisely detect low and mid-level clouds and MODIS satellite provides accurate retrieval of high-level clouds over this region. The CBH algorithm used for MODIS satellite is also able to capture the low-level clouds.

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Impact of data quality and surface-to-column representativeness on the PM<sub>2.5</sub> / satellite AOD relationship for the contiguous United States

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-6049-2014 ◽

2014 ◽

Vol 14 (12) ◽

pp. 6049-6062 ◽

Cited By ~ 39

Author(s):

T. D. Toth ◽

J. Zhang ◽

J. R. Campbell ◽

E. J. Hyer ◽

J. S. Reid ◽

...

Keyword(s):

United States ◽

Data Quality ◽

Ground Level ◽

Dry Mass ◽

Orthogonal Polarization ◽

Data Sets ◽

Moderate Resolution ◽

Resolution Imaging ◽

Moderate Resolution Imaging Spectroradiometer ◽

Total Column

Abstract. Satellite-derived aerosol optical depth (AOD) observations have been used to estimate particulate matter smaller than 2.5 μm (PM2.5). However, such a relationship could be affected by the representativeness of satellite-derived AOD to surface aerosol particle mass concentration and satellite AOD data quality. Using purely measurement-based methods, we have explored the impacts of data quality and representativeness on the AOD-inferred PM2.5 / AOD relationship for the contiguous United States (CONUS). This is done through temporally and spatially collocated data sets of PM2.5 and AOD retrievals from Aqua/Terra Moderate Resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging Spectroradiometer (MISR), and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). These analyses show that improving data quality of satellite AOD, such as done with data assimilation-grade retrievals, increases their correlation with PM2.5. However, overall correlation is relatively low across the CONUS. Also, integrated extinction observed within 500 m above ground level (a.g.l.), as measured by CALIOP, is not well representative of the total column AOD. Surface aerosol in the eastern CONUS is better correlated with total column AOD than in the western CONUS. The best correlation values are found for estimated dry mass CALIOP extinction at 200–300 m a.g.l. and PM2.5, but additional work is needed to address the ability of using actively sensed AOD as a proxy for PM2.5 concentrations.

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