First results of cirrus clouds properties by means of a pollyxt raman lidar at two measurement sites

Geometrical and optical characteristics of cirrus clouds using Raman lidar PollyXT measurements at different locations are presented. The PollyXT has been participated in two long-term experimental campaigns, one close to New Delhi in India and one at Elandsfontein in South Africa, providing continuous measurements and covering a wide range of cloud types. First results of cirrus cloud properties at different latitudes, as well as their temporal distributions are presented in this study. An automatic cirrus clouds detection algorithm is applied based on the wavelet covariance transform. The measurements at New Delhi performed from March 2008 to February 2009, while at Elandsfontein measurements were performed from December 2009 to January 2011.

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Variability in cirrus cloud properties using a Polly<sup>XT</sup> Raman lidar over high and tropical latitudes

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-4427-2020 ◽

2020 ◽

Vol 20 (7) ◽

pp. 4427-4444 ◽

Cited By ~ 2

Author(s):

Kalliopi Artemis Voudouri ◽

Elina Giannakaki ◽

Mika Komppula ◽

Dimitris Balis

Keyword(s):

Optical Properties ◽

Cirrus Clouds ◽

Cirrus Cloud ◽

Raman Lidar ◽

Mean Values ◽

Cloud Optical Depth ◽

Geometrical Properties ◽

Depolarisation Ratio ◽

Cloud Properties ◽

Lidar Ratio

Abstract. Measurements of geometrical and optical properties of cirrus clouds, performed with a multi-wavelength PollyXT Raman lidar during the period 2008 to 2016, are analysed. The measurements were performed with the same instrument, during sequential periods, in three places at different latitudes, Gwal Pahari (28.43∘ N, 77.15∘ E; 243 m a.s.l.) in India, Elandsfontein (26.25∘ S, 29.43∘ E; 1745 m a.s.l.) in South Africa and Kuopio (62.74∘ N, 27.54∘ E; 190 m a.s.l.) in Finland. The lidar dataset was processed by an automatic cirrus cloud masking algorithm, developed in the frame of this work. In the following, we present a statistical analysis of the lidar-retrieved geometrical characteristics (cloud boundaries, geometrical thickness) and optical properties of cirrus clouds (cloud optical depth, lidar ratio, ice crystal depolarisation ratio) measured over the three areas that correspond to subtropical and subarctic regions as well as their seasonal variability. The effect of multiple scattering from ice particles to the derived optical products is also considered and corrected in this study. Our results show that cirrus layers, which have a noticeable monthly variability, were observed between 6.5 and 13 km, with temperatures ranging from −72 to −27 ∘C. The observed differences on cirrus clouds' geometrical and optical properties over the three regions are discussed in terms of latitudinal and temperature dependence. The latitudinal dependence of the geometrical properties is consistent with satellite observations, following the pattern observed with CloudSat, with decreasing values towards the poles. The geometrical boundaries have their highest values in the subtropical regions, and overall, our results seem to demonstrate that subarctic cirrus clouds are colder, lower and optically thinner than subtropical cirrus clouds. The dependence of cirrus cloud geometrical thickness and optical properties on mid-cirrus temperatures shows a quite similar tendency for the three sites but less variability for the subarctic dataset. Cirrus clouds are geometrically and optically thicker at temperatures between −45 and −35 ∘C, and a second peak is observed at lower temperatures ∼-70 ∘C for the subarctic site. Lidar ratio values also exhibit a pattern, showing higher values moving toward the poles, with higher mean values observed over the subarctic site. The dependency of the mid-cirrus temperatures on the lidar ratio values and the particle depolarisation values is further examined. Our study shows that the highest values of the cirrus lidar ratio correspond to higher values of cirrus depolarisation and warmer cirrus. The kind of information presented here can be rather useful in the cirrus parameterisations required as input to radiative transfer models and can be a complementary tool for satellite products that cannot provide cloud vertical structure. In addition, ground-based statistics of the cirrus properties could be useful in the validation and improvement of the corresponding derived products from satellite retrievals.

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Variability of cirrus cloud properties using a Polly<sup>XT</sup> Raman Lidar over high and tropical latitudes

10.5194/acp-2019-565 ◽

2019 ◽

Author(s):

Kalliopi Artemis Voudouri ◽

Elina Giannakaki ◽

Mika Komppula ◽

Dimitris Balis

Keyword(s):

Optical Properties ◽

Optical Depth ◽

Middle Latitude ◽

Detection Algorithm ◽

Cirrus Clouds ◽

Cirrus Cloud ◽

Raman Lidar ◽

Cloud Detection ◽

Cloud Optical Depth ◽

Lidar Ratio

Abstract. Measurements of cirrus clouds geometrical and optical properties, performed with a multi-wavelength PollyXT Raman Lidar, during the period 2008 to 2016 are analysed. The measurements were performed with the same instrument, during sequential periods, in three places at different latitudes, Gual Pahari (28.43° N, 77.15° E, 243 m a.s.l) in India, Elandsfontein (26.25° S, 29.43° E, 1745 m a.s.l) in South Africa and Kuopio (62.74° N, 27.54° E, 190 m a.s.l) in Finland. The lidar dataset has been processed by an automatic cirrus cloud detection algorithm. In the following, we present a statistical analysis of the lidar derived geometrical characteristics (cloud boundaries, geometrical thickness) and optical properties of cirrus clouds (cloud optical depth, lidar ratio, ice crystal depolarization ratio) measured in different latitudes that correspond to subtropical and subarctic regions as well as their seasonal variability. The effect of multiple-scattering from ice particles to the derived optical products is also considered and corrected in this study. Our results show that, over the subtropical stations, cirrus layers, which have a noticeable monthly variability, were observed between 7 to 13 km, with mid-cloud temperatures ranging from −60 °C to −21 °C and a mean thickness of 1295 ± 489 m and 1383 ± 735 m for Gual Pahari and Elandsfontein respectively. The corresponding overall mean cirrus optical depth at 355 nm is calculated to be 0.59 ± 0.39 and 0.40 ± 0.33, with lidar ratio values at 355 nm of 26 ± 12 sr and 25 ± 6 sr, respectively. A more extended dataset was acquired for the subarctic area of Kuopio Finland, between 2012 and 2016. The estimated average geometrical thickness of the cirrus clouds over Kuopio is 1200 ± 585 m and the temperature values vary from −71 °C to −21 °C, while the mean cirrus optical depth at 355 nm is 0.25 ± 0.2, with an estimated mean lidar ratio of 33 ± 7 sr, similar to the idar ratio values observed over middle latitude stations. The kind of information presented here can be rather useful in the cirrus parameterizations required as input to radiative transfer models, and can be a complementary tool to satellite products that cannot provide cloud vertical structure. In addition, a ground-based statistics of the cirrus properties could be useful in the validation and improvement of the corresponding derived products from satellite retrievals.

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Balloon-borne and Raman lidar observations of Asian dust and cirrus cloud properties over Tsukuba, Japan

Journal of Geophysical Research Atmospheres ◽

10.1002/2013jd020987 ◽

2014 ◽

Vol 119 (6) ◽

pp. 3295-3308 ◽

Cited By ~ 6

Author(s):

Tetsu Sakai ◽

Narihiro Orikasa ◽

Tomohiro Nagai ◽

Masataka Murakami ◽

Takuya Tajiri ◽

...

Keyword(s):

Asian Dust ◽

Cirrus Cloud ◽

Raman Lidar ◽

Cloud Properties ◽

Lidar Observations

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One year of Raman lidar observations of free-tropospheric aerosol layers over South Africa

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-5429-2015 ◽

2015 ◽

Vol 15 (10) ◽

pp. 5429-5442 ◽

Cited By ~ 16

Author(s):

E. Giannakaki ◽

A. Pfüller ◽

K. Korhonen ◽

T. Mielonen ◽

L. Laakso ◽

...

Keyword(s):

South Africa ◽

Optical Properties ◽

Biomass Burning ◽

Mean Value ◽

Aerosol Layer ◽

Raman Lidar ◽

Tropospheric Aerosol ◽

Wide Range ◽

Significant Difference ◽

532 Nm

Abstract. Raman lidar data obtained over a 1 year period has been analysed in relation to aerosol layers in the free troposphere over the Highveld in South Africa. In total, 375 layers were observed above the boundary layer during the period 30 January 2010 to 31 January 2011. The seasonal behaviour of aerosol layer geometrical characteristics, as well as intensive and extensive optical properties were studied. The highest centre heights of free-tropospheric layers were observed during the South African spring (2520 ± 970 m a.g.l., also elsewhere). The geometrical layer depth was found to be maximum during spring, while it did not show any significant difference for the rest of the seasons. The variability of the analysed intensive and extensive optical properties was high during all seasons. Layers were observed at a mean centre height of 2100 ± 1000 m with an average lidar ratio of 67 ± 25 sr (mean value with 1 standard deviation) at 355 nm and a mean extinction-related Ångström exponent of 1.9 ± 0.8 between 355 and 532 nm during the period under study. Except for the intensive biomass burning period from August to October, the lidar ratios and Ångström exponents are within the range of previous observations for urban/industrial aerosols. During Southern Hemispheric spring, the biomass burning activity is clearly reflected in the optical properties of the observed free-tropospheric layers. Specifically, lidar ratios at 355 nm were 89 ± 21, 57 ± 20, 59 ± 22 and 65 ± 23 sr during spring (September–November), summer (December–February), autumn (March–May) and winter (June–August), respectively. The extinction-related Ångström exponents between 355 and 532 nm measured during spring, summer, autumn and winter were 1.8 ± 0.6, 2.4 ± 0.9, 1.8 ± 0.9 and 1.8 ± 0.6, respectively. The mean columnar aerosol optical depth (AOD) obtained from lidar measurements was found to be 0.46 ± 0.35 at 355 nm and 0.25 ± 0.2 at 532 nm. The contribution of free-tropospheric aerosols on the AOD had a wide range of values with a mean contribution of 46%.

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The roles of dynamical variability and aerosols in cirrus cloud formation

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-3-1415-2003 ◽

2003 ◽

Vol 3 (2) ◽

pp. 1415-1451 ◽

Cited By ~ 4

Author(s):

B. Kärcher ◽

J. Ström

Keyword(s):

Probability Distributions ◽

Cirrus Clouds ◽

Cloud Formation ◽

Cirrus Cloud ◽

Ice Crystal ◽

Mesoscale Variability ◽

Aerosol Composition ◽

Airborne Measurements ◽

Cloud Properties

Abstract. The probability of occurrence of ice crystal number densities in young cirrus clouds is examined based on airborne measurements. The observations have been carried out at midlatitudes in both hemispheres at equivalent latitudes (~52–55° N/S) during the same season (local autumn in 2000). The in situ measurements considered in the present study include temperatures, vertical velocities, and ice crystal concentrations, the latter determined with high precision and accuracy using a counterflow virtual impactor. Most young cirrus clouds typically contain high number densities (1–10 cm−3) of small (diameter <20 μm) ice crystals. This mode dominates the probability distributions in both hemispheres and is shown to be caused by rapid cooling rates associated with updraft speeds in the range 10–100 cm s-1. A second mode containing larger crystals extends from ~1 cm−3 to low concentrations close to the detection threshold (~3×104cm−3) and is associated with lower updraft speeds. Results of a statistical analysis provide compelling evidence that the dynamical variability of vertical air motions on the mesoscale is the key factor determining the observed probability distributions of pristine ice crystal concentrations in cirrus. Other factors considered are variations of temperature as well as size, number, and ice nucleation thresholds of the freezing aerosol particles. The variability in vertical velocities is likely caused by atmospheric waves. Inasmuch as gravity waves are widespread, mesoscale variability in vertical velocities can be viewed as a universa feature of young cirrus clouds. Large-scale models that do not account for this subgrid-scale variability yield erroneous predictions of the variability of basic cirrus cloud properties. Climate change may bring about changes in the global distribution of updraft speeds, mean air temperatures, and aerosol properties. As shown in this work, these changes could significantly modify the probability distribution of cirrus ice crystal concentrations. This study emphasizes the key role of vertical velocities and mesoscale variability in vertical velocities in controlling cirrus properties. The results suggest that, in any effort to ascribe cause to trends of cirrus cloud properties, a careful evaluation of dynamical changes in cloud formation should be done before conclusions regarding the role of other anthropogenic factors, such as changes in aerosol composition, are made.

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Dynamic Processes in Cirrus Clouds: Concepts and Models

Cirrus ◽

10.1093/oso/9780195130720.003.0022 ◽

2002 ◽

Author(s):

David O’C. Starr ◽

Markus Quante

Keyword(s):

Cirrus Clouds ◽

Radiative Properties ◽

Cirrus Cloud ◽

Early Model ◽

Minimum Requirement ◽

Microphysical Properties ◽

Cloud Properties ◽

Cloud Models ◽

New Concepts

Advancement in the understanding of cirrus clouds and their life cycle comes through symbiotic use of models, observations, and related concepts (fig. 18.1). Models of cirrus clouds represent an integration of our knowledge of cirrus cloud properties and processes. They provide a capacity to extend knowledge and enhance understanding in ways that complement existing observational capabilities. Models can be used to develop new theories, such as parameterizations, and focus science issues and observational requirements and developments. For example, early model results of Starr and Cox (1985a) and Starr (1987b) predicted that fine cellular structure (~lkm or less) would be found in the upper part of extended stratiform cirrus clouds. This prediction was confirmed when high-frequency sensors were deployed both for active remote sensing (Sassen et al. 1990a, 1995) and later for in-situ measurements (Quante and Brown 1992; Gultepe et al. 1995; Quante et al. 1996). Sampling rates of 10Hz, or better, are now accepted as a minimum requirement for resolving cirrus cloud internal structure and circulation where 1-Hz or coarser measurements were previously used. Similarly, discrepancies between observed cloud radiative properties and calculations (theory) based on corresponding in-situ observations of cloud microphysical properties (Sassen et al. 1990b) led to the development of improved observing capabilities for small ice crystals (Arnott et al. 1994; Miloshevich and Heymsfield 1997; Lawson et al. 1998). Such sensors are now regarded as part of the standard complement when doing in-situ microphysical measurements in cirrus. At the same time, observations are absolutely essential in developing and evaluating cloud models. No cloud modeler wants to apply a model or theory too far beyond the limits of what can be observationally confirmed, at least in gross terms. The third aspect of this triad is concepts. Although models and observations can lead to predictions or diagnosis of unexpected relationships, they are each limited by the concepts that were used in their design and/or implementation. In the end, new concepts arising from analogy to other phenomena and/or from synergistic integration of existing knowledge can lead to new understanding, new models, new instruments, and new sampling strategies (fig. 18.1). Chapter 17 focuses on observations of internal cloud circulation and structure.

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UV Raman lidar measurements of relative humidity for the characterization of cirrus cloud microphysical properties

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-8799-2009 ◽

2009 ◽

Vol 9 (22) ◽

pp. 8799-8811 ◽

Cited By ~ 34

Author(s):

P. Di Girolamo ◽

D. Summa ◽

R.-F. Lin ◽

T. Maestri ◽

R. Rizzi ◽

...

Keyword(s):

Relative Humidity ◽

Cloud Model ◽

Cirrus Clouds ◽

Cloud Layer ◽

Cirrus Cloud ◽

Raman Lidar ◽

Heating Rates ◽

Night Time ◽

Microphysical Properties ◽

Lidar Measurements

Abstract. Raman lidar measurements performed in Potenza by the Raman lidar system BASIL in the presence of cirrus clouds are discussed. Measurements were performed on 6 September 2004 in the frame of the Italian phase of the EAQUATE Experiment. The major feature of BASIL is represented by its capability to perform high-resolution and accurate measurements of atmospheric temperature and water vapour, and consequently relative humidity, both in daytime and night-time, based on the application of the rotational and vibrational Raman lidar techniques in the UV. BASIL is also capable to provide measurements of the particle backscatter and extinction coefficient, and consequently lidar ratio (at the time of these measurements, only at one wavelength), which are fundamental to infer geometrical and microphysical properties of clouds. A case study is discussed in order to assess the capability of Raman lidars to measure humidity in presence of cirrus clouds, both below and inside the cloud. While air inside the cloud layers is observed to be always under-saturated with respect to water, both ice super-saturation and under-saturation conditions are found inside these clouds. Upper tropospheric moistening is observed below the lower cloud layer. The synergic use of the data derived from the ground based Raman Lidar and of spectral radiances measured by the NAST-I Airborne Spectrometer allows the determination of the temporal evolution of the atmospheric cooling/heating rates due to the presence of the cirrus cloud. Lidar measurements beneath the cirrus cloud layer have been interpreted using a 1-D cirrus cloud model with explicit microphysics. The 1-D simulations indicate that sedimentation-moistening has contributed significantly to the moist anomaly, but other mechanisms are also contributing. This result supports the hypothesis that the observed mid-tropospheric humidification is a real feature which is strongly influenced by the sublimation of precipitating ice crystals. Results illustrated in this study demonstrate that Raman lidars, like the one used in this study, can resolve the spatial and temporal scales required for the study of cirrus cloud microphysical processes and appear sensitive enough to reveal and quantify upper tropospheric humidification associated with cirrus cloud sublimation.

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A permanent raman lidar station in the Amazon: description, characterization and first results

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-7-769-2014 ◽

2014 ◽

Vol 7 (1) ◽

pp. 769-817

Author(s):

H. M. J. Barbosa ◽

B. Barja ◽

T. Pauliquevis ◽

D. A. Gouveia ◽

P. Artaxo ◽

...

Keyword(s):

Mean Square ◽

Experimental Characterization ◽

Raman Lidar ◽

First Results ◽

Uv Raman ◽

Lidar Ratio ◽

Sun Photometer ◽

And Performance ◽

Automated Data Acquisition

Abstract. A permanent UV Raman Lidar station, designed to perform continuous measurements of aerosols and water vapor and aiming to study and monitor the atmosphere on the weather to climatic time scales, became operational in central Amazon in July 2011. The automated data acquisition and internet monitoring enabled extended hours of daily measurements when compared to a manually operated instrument. This paper gives a technical description of the system, presents its experimental characterization and the algorithms used for obtaining the aerosol optical properties and identifying the cloud layers. Data from one week of measurements during the dry season of 2011 were analyzed as a mean to assess the overall system capability and performance. A comparison of the aerosol optical depth from the Lidar and a co-located AERONET sun photometer showed a root mean square error of about 0.06, small compared to the range of observed AOD values (0.1 to 0.75) and to the typical AERONET AOD uncertainty (0.02). By combining nighttime measurements of the aerosol lidar ratio (50–65 sr), backtrajectories calculations and fire spots observed from satellites we showed that observed particles originated from biomass burning. Cirrus clouds were observed in 60% of our measurements. Most of the time they were distributed into three layers between 11.5 and 13.4 km a.g.l. The systematic and long-term measurements being made by this new scientific facility have the potential to significantly improve our understanding of the climatic implications of the anthropogenic changes in aerosol concentrations over the pristine Amazônia.

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-6951-2013 ◽

2013 ◽

Vol 13 (14) ◽

pp. 6951-6963 ◽

Cited By ~ 19

Author(s):

C. Hoareau ◽

P. Keckhut ◽

V. Noel ◽

H. Chepfer ◽

J.-L. Baray

Keyword(s):

Observation Time ◽

Cirrus Clouds ◽

Cirrus Cloud ◽

Upper Troposphere ◽

Cloud Parameters ◽

Cloud Properties ◽

Total Observation Time ◽

The Mean ◽

Ground Based Lidar ◽

Total Observation

Abstract. 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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A Raman lidar at La Reunion (20.8° S, 55.5° E) for monitoring water vapor and cirrus distributions in the subtropical upper troposphere: preliminary analyses and description of a future system

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-4-6449-2011 ◽

2011 ◽

Vol 4 (5) ◽

pp. 6449-6496

Author(s):

C. Hoareau ◽

P. Keckhut ◽

J.-L. Baray ◽

L. Robert ◽

Y. Courcoux ◽

...

Keyword(s):

Water Vapor ◽

Cirrus Cloud ◽

La Réunion ◽

Raman Lidar ◽

Data Set ◽

Upper Troposphere ◽

Future System ◽

Rayleigh Lidar ◽

Term Monitoring

Abstract. A ground based Rayleigh lidar has provided continuous observations of tropospheric water vapor profiles and cirrus cloud using a preliminary Raman channels setup on an existing Rayleigh lidar above La Reunion over the period 2002–2005. With this instrument, we performed a first measurement campaign of 350 independent water vapor profiles. A statistical study of the distribution of water vapor profiles is presented and some investigations concerning the calibration are discussed. The data set having several long acquisition measurements during nighttime, an analysis of the diurnal cycle of water vapor has also been investigated. Analysis regarding the cirrus clouds is presented and a classification has been performed showing 3 distinct classes. Based on these results, the characteristics and the design of a future lidar system to be implemented at the new Reunion Island altitude observatory (2200 m) for long-term monitoring is presented and numerical simulations of system performance have been realized to compare both instruments.

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