CALIPSO Lidar Description and Performance Assessment

Hunt, William H.; Winker, David M.; Vaughan, Mark; Powell, Kathleen A.; Lucker, Patricia L.; Weimer, Carl

doi:10.1175/2009jtecha1223.1

Cited by 497 publications

(374 citation statements)

References 17 publications

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“…In photomultipliers and avalanche photodiodes used in detectors, there is always some background signal even in the absence of incident photons, caused by random generation of electrons in the system, which is called 'dark noise' and is handled in a statistical framework. The CALIOP detectors show a significant increase of dark noise in the region of SAA (Hunt et al, 2009). This interference is caused by the particle flux increase in the region, so it can be used as a substitute.…”

Section: Caliop -Dark Noise Datamentioning

confidence: 97%

The South Atlantic Anomaly throughout the solar cycle

Domingos

Jault

Pais

et al. 2017

Earth and Planetary Science Letters

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The Sun-Earth's interaction is characterized by a highly dynamic electromagnetic environment, in which the magnetic field produced in the Earth's core plays an important role. One of the striking characteristics of the present geomagnetic field is denoted the South Atlantic Anomaly (SAA) where the total field intensity is unusually low and the flux of charged particles, trapped in the inner Van Allen radiation belts, is maximum. Here, we use, on one hand, a recent geomagnetic field model, CHAOS-6, and on the other hand, data provided by different platforms (satellites orbiting the Earth -POES NOAA for 1998 and CALIPSO for 2006. Evolution of the SAA particle flux can be seen as the result of two main effects, the secular variation of the Earth's core magnetic field and the modulation of the density of the inner radiation belts during the solar cycle, as a function of the L value that characterises the drift shell, where charged particles are trapped. To study the evolution of the particle flux anomaly, we rely on a Principal Component Analysis (PCA) of either POES particle flux or CALIOP dark noise. Analysed data are distributed on a geographical grid at satellite altitude, based on a L-shell reference frame constructed from the moving eccentric dipole. Changes in the main magnetic field are responsible for the observed westward drift. Three PCA modes account for the time evolution related to solar effects. Both the first and second modes have a good correlation with the thermospheric density, which varies in response to the solar cycle. The first mode represents the total intensity variation of the particle flux in the SAA, and the second the movement of the anomaly between different L-shells. The proposed analysis allows us to well recover the westward drift rate, as well as the latitudinal and longitudinal solar cycle oscillations, although the analysed data do not cover a complete (Hale) magnetic solar cycle (around 22 yr). Moreover, the developments made here would enable us to forecast the impact of the South Atlantic Anomaly on space weather. A model of the evolution of the eccentric dipole field (magnitude, offset and tilt) would suffice, together with a model for the solar cycle evolution.

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Section: Caliop -Dark Noise Datamentioning

confidence: 97%

The South Atlantic Anomaly throughout the solar cycle

Domingos

Jault

Pais

et al. 2017

Earth and Planetary Science Letters

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“…It was launched in April 2006 into a sunsynchronous orbit as part of the A-Train satellite constellation. A brief description is given here; details of the CALIOP instrument can be found in Hunt et al (2009). CALIOP is a 2-wavelength (532 nm and 1064 nm) polarization sensitive lidar.…”

Section: Caliop Spaceborne Lidarmentioning

confidence: 99%

A decadal cirrus clouds climatology from ground-based and spaceborne lidars above the south of France (43.9° N–5.7° E)

et al. 2013

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This study provides an analysis of cirrus cloud properties at midlatitude in the southern part of France from ground-based and spaceborne lidars. A climatology of cirrus cloud properties and their evolution over more than 12 yr is presented and compared to other mid-latitude climatological studies. Cirrus clouds occur ~37% of the total observation time and remain quasi-constant across seasons with a variation within ~5% around the mean occurrence. Similar results are obtained from CALIOP and the ground-based lidar, with a mean difference in occurrence of ~5% between both instruments. From the ground-based lidar data, a slight decrease in occurrence of ~3% per decade is observed but found statistically insignificant. Based on a clustering analysis of cirrus cloud parameters, three distinct classes have been identified and investigations concerning their origin are discussed. Properties of these different classes are analysed, showing that thin cirrus in the upper troposphere represent ~50% of cloud cover detected in summer and fall, decreasing by 15–20% for other seasons

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“…Given that the lidar is duly capable of nighttime measurements, additional validation is necessary to fully evaluate CALIOP aerosol retrieval performance. Furthermore, given that particle layer identification and the accuracy of the CALIOP-derived 0.532 µm extinction coefficient and, thus, its column-integrated sum AOD, are each a function of the amount of ambient solar background light measured in any given scattering profile (i.e., noise; Hunt et al, 2009;Liu et al, 2009;Vaughan et al, 2009;Young and Vaughan, 2009), nighttime AOD retrievals should exhibit relative accuracies and skill that differ from, and nominally exceed, those from daytime.…”

Section: Introductionmentioning

confidence: 99%

Evaluating nighttime CALIOP 0.532 μm aerosol optical depth and extinction coefficient retrievals

Campbell¹,

Tackett

Reid³

et al. 2012

Atmos. Meas. Tech.

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Abstract. NASA Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) Version 3.01 5-km nighttime 0.532 µm aerosol optical depth (AOD) datasets from 2007 are screened, averaged and evaluated at 1 • × 1 • resolution versus corresponding/co-incident 0.550 µm AOD derived using the US Navy Aerosol Analysis and Prediction System (NAAPS), featuring two-dimensional variational assimilation of quality-assured NASA Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging Spectroradiometer (MISR) AOD. In the absence of sunlight, since passive radiometric AOD retrievals rely overwhelmingly on scattered radiances, the model represents one of the few practical global estimates available from which to attempt such a validation. Daytime comparisons, though, provide useful context. Regional-mean CALIOP vertical profiles of night/day 0.532 µm extinction coefficient are compared with 0.523/0.532 µm ground-based lidar measurements to investigate representativeness and diurnal variability. In this analysis, mean nighttime CALIOP AOD are mostly lower than daytime (0.121 vs. 0.126 for all aggregated data points, and 0.099 vs. 0.102 when averaged globally per normalised 1 • × 1 • bin), though the relationship is reversed over land and coastal regions when the data are averaged per normalised bin (0.134/0.108 vs. 0140/0.112, respectively). Offsets assessed within single bins alone approach ±20 %. CALIOP AOD, both day and night, are higher than NAAPS over land (0.137 vs. 0.124) and equal over water (0.082 vs. 0.083) when averaged globally per normalised bin. However, for all data points inclusive, NAAPS exceeds CALIOP over land, coast and ocean, both day and night. Again, differences assessed within single bins approach 50 % in extreme cases. Correlation between CALIOP and NAAPS AOD is comparable during both day and night. Higher correlation is found nearest the equator, both as a function of sample size and relative signal magnitudes inherent at these latitudes. Root mean square deviation between CALIOP and NAAPS varies between 0.1 and 0.3 globally during both day/night. Averaging of CALIOP along-track AOD data points within a single NAAPS grid bin improves correlation and RMSD, though day/night and land/ocean biases persist and are believed systematic. Vertical profiles of extinction coefficient derived in the Caribbean compare well with ground-based lidar observations, though potentially anomalous selection of a priori lidar ratios for CALIOP retrievals is likely inducing some discrepancies. Mean effective aerosol layer top heights are stable between day and night, indicating consistent layeridentification diurnally, which is noteworthy considering the potential limiting effects of ambient solar noise during day.

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CALIPSO Lidar Description and Performance Assessment

Cited by 497 publications

References 17 publications

The South Atlantic Anomaly throughout the solar cycle

The South Atlantic Anomaly throughout the solar cycle

A decadal cirrus clouds climatology from ground-based and spaceborne lidars above the south of France (43.9° N–5.7° E)

Evaluating nighttime CALIOP 0.532 μm aerosol optical depth and extinction coefficient retrievals

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