Cloud Area Distributions of Shallow Cumuli: A New Method for Ground-Based Images

We develop a new approach that resolves cloud area distributions of single-layer shallow cumuli from ground-based observations. Our simple and computationally inexpensive approach uses images obtained from a Total Sky Imager (TSI) and complementary information on cloud base height provided by lidar measurements to estimate cloud equivalent diameter (CED) over a wide range of cloud sizes (about 0.01–3.5 km) with high temporal resolution (30 s). We illustrate the feasibility of our approach by comparing the estimated CEDs with those derived from collocated and coincident high-resolution (0.03 km) Landsat cloud masks with different spatial and temporal patterns of cloud cover collected over the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site. We demonstrate that (1) good (~7%) agreement between TSI and Landsat characteristic cloud size can be obtained for clouds that fall within the region of the sky observable by the TSI and (2) large clouds that extend beyond this region are responsible for noticeable (~16%) underestimation of the TSI characteristic cloud size. Our approach provides a previously unavailable dataset for process studies in the convective boundary layer and evaluation of shallow cumuli in cloud-resolving models.

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Prediction for cloud spacing confirmed using stereo cameras

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-21-0026.1 ◽

2021 ◽

Author(s):

Ruşen Öktem ◽

David M. Romps

Keyword(s):

Great Plains ◽

Cloud Base ◽

Effective Diameter ◽

Horizontal Scale ◽

Convective Boundary ◽

Southern Great Plains ◽

Stereo Cameras ◽

Atmospheric Radiation Measurement ◽

The Mean ◽

Lifting Condensation Level

AbstractUsing three years of the Clouds Optically Gridded by Stereo (COGS) product, the mean cloud base, cloud top, cloud width, and cloud spacing are described with respect to their seasonal and/or diurnal evolution at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site. In addition to confirming and extending prior results, the data show that the effective diameter of shallow cumuli are approximately equal to the height above ground of the lifting condensation level (LCL). Furthermore, the cloud spacing is found to closely match a prediction by Thuburn and Efstathiou for the horizontal scale of the largest unstable eddies in an unsheared convective boundary layer.

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Ten Years of Aerosol Effects on Single-Layer Overcast Clouds over the US Southern Great Plains and the China Loess Plateau

Advances in Meteorology ◽

10.1155/2020/6719160 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15 ◽

Cited By ~ 4

Author(s):

Hongru Yan ◽

Tianhe Wang

Keyword(s):

Great Plains ◽

Indirect Effect ◽

Negative Relationship ◽

Single Layer ◽

Cloud Base ◽

Atmospheric Conditions ◽

Southern Great Plains ◽

Aerosol Loading ◽

The Us ◽

The Impact

Using almost 10 years of observations of clouds and aerosols from the US Southern Great Plains (SGP) atmospheric observatory and the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) in China, the impact of aerosols on single-layer overcast clouds over continental land for different regimes were investigated. Atmospheric conditions at the two sites were first compared in an attempt to isolate the influence of aerosols on cloud properties from dynamic and thermodynamic influences. Cloud types and amounts are similar at the two sites. The dominant aerosol types at the SGP and SACOL sites are sulphate and dust, respectively, with greater aerosol optical depths (AODs) and absorption at the SACOL site. Aerosol first indirect effect (FIE) ranges from 0.021 to 0.152 and from −0.078 to 0.047 at the SGP and SACOL sites, respectively, when using the AOD below cloud base as CCN proxy. Although differences exist, the influence of meteorological conditions on the FIE at the two sites is consistent. FIEs are easily detected under descending motion and dry condition. The FIE at the SGP site is larger than that at the SACOL site, which suggests that the cloud albedo effect is more sensitive under relatively cleaner atmospheric conditions and the dominating aerosol at the SACOL site has less hygroscopicity. The radiative forcing of the FIE over the SGP site is −3.2 W m−2 for each 0.05 increment in FIE. Cloud durations generally prolong as aerosol loading increases, which is consistent with the hypothesis of the aerosol second indirect effect. The negative relationship between cloud duration time and aerosol loading when aerosol loading reaches a large value further might suggest a semidirect effect.

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Retrieval of aerosol optical depth in vicinity of broken clouds from reflectance ratios: case study

Atmospheric Measurement Techniques ◽

10.5194/amt-3-1333-2010 ◽

2010 ◽

Vol 3 (5) ◽

pp. 1333-1349 ◽

Cited By ~ 9

Author(s):

E. Kassianov ◽

M. Ovchinnikov ◽

L. K. Berg ◽

S. A. McFarlane ◽

C. Flynn ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Great Plains ◽

Land Surface ◽

Single Layer ◽

Department Of Energy ◽

High Spectral Resolution ◽

Data Sets ◽

Atmospheric Radiation Measurement

Abstract. A recently developed reflectance ratio (RR) method for the retrieval of aerosol optical depth (AOD) is evaluated using extensive airborne and ground-based data sets collected during the Cloud and Land Surface Interaction Campaign (CLASIC) and the Cumulus Humilis Aerosol Processing Study (CHAPS), which took place in June 2007 over the US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains site. A detailed case study is performed for a field of single-layer shallow cumuli observed on 12 June 2007. The RR method is applied to retrieve the spectral values of AOD from the reflectance ratios measured by the MODIS Airborne Simulator (MAS) for two pairs of wavelengths (660 and 470 nm, 870 and 470 nm) collected at a spatial resolution of 0.05 km. The retrieval is compared with an independent AOD estimate from three ground-based Multi-filter Rotating Shadowband Radiometers (MFRSRs). The interpolation algorithm that is used to project MFRSR point measurements onto the aircraft flight tracks is tested using AOD derived from NASA Langley High Spectral Resolution Lidar (HSRL). The RR AOD estimates are in a good agreement (within 5%) with the MFRSR-derived AOD values for the 660-nm wavelength. The AODs obtained from MAS reflectance ratios overestimate those derived from MFRSR measurements by 15–30% for the 470-nm wavelength and underestimate the 870-nm AOD by the same amount.

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Retrieval of aerosol optical depth in vicinity of broken clouds from reflectance ratios: case study

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-3-1889-2010 ◽

2010 ◽

Vol 3 (2) ◽

pp. 1889-1932

Author(s):

E. Kassianov ◽

M. Ovchinnikov ◽

L. K. Berg ◽

S. A. McFarlane ◽

C. Flynn ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Great Plains ◽

Land Surface ◽

Single Layer ◽

Department Of Energy ◽

High Spectral Resolution ◽

Data Sets ◽

Atmospheric Radiation Measurement

Abstract. A recently developed reflectance ratio (RR) method for the retrieval of aerosol optical depth (AOD) is evaluated using extensive airborne and ground-based data sets collected during the Cloud and Land Surface Interaction Campaign (CLASIC) and the Cumulus Humilis Aerosol Processing Study (CHAPS), which took place in June 2007 over the US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains site. A detailed case study is performed for a field of single-layer shallow cumuli observed on 12 June 2007. The RR method is applied to retrieve the spectral values of AOD from the reflectance ratios measured by the MODIS Airborne Simulator (MAS) for two pairs of wavelengths (660 and 470 nm and 870 and 470 nm) collected at a spatial resolution of 0.05 km. The retrieval is compared with an independent AOD estimate from three ground-based Multi-filter Rotating Shadowband Radiometers (MFRSRs). The interpolation algorithm that is used to project MFRSR point measurements onto the aircraft flight tracks is tested using AOD derived from NASA Langley High Spectral Resolution Lidar (HSRL). The RR AOD estimates are in a good agreement (within 5%) with the MFRSR-derived AOD values for the 660-nm wavelength. The AODs obtained from MAS reflectance ratios overestimate those derived from MFRSR measurements by 15–30% for the 470-nm wavelength and underestimate the 870-nm AOD by the same amount.

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Investigations to Hygroscopic Aerosol Growth Within the Convective Boundary Layer

EPJ Web of Conferences ◽

10.1051/epjconf/202023702016 ◽

2020 ◽

Vol 237 ◽

pp. 02016

Author(s):

Dietrich Althausen ◽

Andrew Reigert ◽

Ulla Wandinger ◽

Jens Reichardt

Keyword(s):

Microwave Radiometer ◽

High Temporal Resolution ◽

Mixing Ratio ◽

Hygroscopic Growth ◽

Backscatter Coefficient ◽

Convective Boundary ◽

Air Mass ◽

Lidar Measurements ◽

Water Vapor Mixing Ratio ◽

Mass Case

We present a new method to determine the hygroscopic growth of atmospheric particles. This method combines lidar measurements with high temporal resolution of the particle backscatter coefficient and water vapor mixing ratio with temperature measurements from radiosondes and a microwave radiometer. The hygroscopic growth is described by an equation that represents the two observed branches of the growth curve with different dependencies on the relative humidity. An example is presented to illustrate a first result from a continental air mass case.

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Climatological sensitivities of shallow-cumulus bulk entrainment in continental and oceanic locations

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-20-0377.1 ◽

2021 ◽

Author(s):

Daniel J. Kirshbaum ◽

Katia Lamer

Keyword(s):

Great Plains ◽

Cumulus Parameterization ◽

Cloud Base ◽

Shallow Cumulus ◽

Mass Fluxes ◽

Complex Process ◽

The Us ◽

Atmospheric Radiation Measurement ◽

Cumulus Parameterization Schemes ◽

Eastern North Atlantic

AbstractCumulus entrainment is a complex process that has long challenged conceptual understanding and atmospheric prediction. To investigate this process observationally, two retrievals are used to generate multi-year climatologies of shallow-cumulus bulk entrainment (ϵ) at two Atmospheric Radiation Measurement cloud observatories, one in the US southern Great Plains (SGP) and the other in the Azores archipelago in the eastern North Atlantic (ENA). The statistical distributions of ϵ thus obtained, as well as certain environmental and cloud-related sensitivities of ϵ, are consistent with previous findings from large-eddy simulations. The retrieved ϵ robustly increases with cloudlayer relative humidity and decreases in wider clouds and cloud ensembles with larger cloud-base mass fluxes. While ϵ also correlates negatively with measures of cloud-layer vigor (e.g., maximum in-cloud vertical velocity and cloud depth), the extent to which these metrics actually regulate ϵ (or vice-versa) is unclear. Novel sensitivities of ϵ include a robust decrease of ϵ with increasing subcloud wind speed in oceanic flows, as well as a decrease of ϵ with increasing cloud-base mass flux in individual cumuli. A strong land–ocean contrast in ϵ is also found, with median values of 0.5-0.6 km−1 at the continental SGP site and and 1.0-1.1 km−1 at the oceanic ENA site. This trend is associated with drier and deeper cloud layers, along with larger cloud-base mass fluxes, at SGP, all of which favor reduced ϵ. The flow-dependence of retrieved ϵ implies that its various sensitivities should be accounted for in cumulus parameterization schemes.

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First Observations of Tracking Clouds Using Scanning ARM Cloud Radars

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-13-0182.1 ◽

2014 ◽

Vol 53 (12) ◽

pp. 2732-2746 ◽

Cited By ~ 13

Author(s):

Paloma Borque ◽

Pavlos Kollias ◽

Scott Giangrande

Keyword(s):

Great Plains ◽

Temporal Evolution ◽

Department Of Energy ◽

High Temporal Resolution ◽

Advantages And Disadvantages ◽

Weather Radars ◽

Maximum Reflectivity ◽

Cloud Properties ◽

Atmospheric Radiation Measurement ◽

Size Threshold

AbstractTracking clouds using scanning cloud radars can help to document the temporal evolution of cloud properties well before large-drop formation (weather radar “first echo”). These measurements also complement cloud and precipitation tracking using geostationary satellites and weather radars. Here, two-dimensional (2D) along-wind range–height indicator observations of a population of shallow cumuli (with and without precipitation) from the 35-GHz scanning Atmospheric Radiation Measurement Program (ARM) cloud radar (SACR) at the U.S. Department of Energy (DOE)–ARM Southern Great Plains (SGP) site are presented. Observations from the ARM SGP network of scanning precipitation radars are used to provide the larger-scale context of the cloud field and to highlight the advantages of the SACR to detect the numerous small nonprecipitating cloud elements. A new cloud identification and tracking algorithm (CITA) is developed to track cloud elements. In CITA, a cloud element is identified as a region having a contiguous set of pixels exceeding a preset reflectivity and size threshold. The high temporal resolution of the SACR 2D observations (30 s) allows for an area superposition criteria algorithm to match cloud elements at consecutive times. Following CITA, the temporal evolution of cloud-element properties (number, size, and maximum reflectivity) is presented. The vast majority of the designated elements during this cumulus event were short-lived nonprecipitating clouds having an apparent life cycle shorter than 15 min. The advantages and disadvantages of cloud tracking using an SACR are discussed.

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Evaluation of a land-atmosphere coupling metric computed from a ground-based infrared interferometer

Journal of Hydrometeorology ◽

10.1175/jhm-d-20-0303.1 ◽

2021 ◽

Author(s):

Ryann A. Wakefield ◽

David D. Turner ◽

Jeffrey B. Basara

Keyword(s):

Great Plains ◽

Land Surface ◽

Surface Flux ◽

Observation Time ◽

High Temporal Resolution ◽

Vertical Profiles ◽

Sensing Platforms ◽

Humidity Index ◽

Atmospheric Radiation Measurement ◽

Meteorological Observations

AbstractLand-atmosphere feedbacks are a critical component of the hydrologic cycle. Vertical profiles of boundary layer temperature and moisture, together with information about the land surface, are used to compute land-atmosphere coupling metrics. Ground based remote sensing platforms, such as the Atmospheric Emitted Radiance Interferometer (AERI), can provide high temporal resolution vertical profiles of temperature and moisture. When co-located with soil moisture, surface flux, and surface meteorological observations, such as at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site, it is possible to observe both the terrestrial and atmospheric legs of land-atmosphere feedbacks. In this study, we compare a commonly used coupling metric computed from radiosonde-based data to that obtained from the AERI to characterize the accuracy and uncertainty in the metric derived from the two distinct platforms. This approach demonstrates the AERI’s utility where radiosonde observations are absent in time and/or space. Radiosonde and AERI based observations of the Convective Triggering Potential and Low-Level Humidity Index (CTP-HIlow) were computed during the 1200 UTC observation time and displayed good agreement during both 2017 and 2019 warm seasons. Radiosonde and AERI derived metrics diagnosed the same atmospheric preconditioning based upon the CTP-HIlow framework a majority of the time. When retrieval uncertainty was considered, even greater agreement was found between radiosonde and AERI derived classification. The AERI’s ability to represent this coupling metric well enabled novel exploration of temporal variability within the overnight period in CTP and HIlow. Observations of CTP-HIlow computed within a few hours of 1200 UTC were essentially equivalent, however with greater differences in time arose greater differences in CTP and HIlow.

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Erroneous Attribution of Deep Convective Invigoration to Aerosol Concentration

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-17-0217.1 ◽

2018 ◽

Vol 75 (4) ◽

pp. 1351-1368 ◽

Cited By ~ 13

Author(s):

Adam Varble

Keyword(s):

Great Plains ◽

Convective Available Potential Energy ◽

Meteorological Factor ◽

Department Of Energy ◽

Cloud Base ◽

Neutral Buoyancy ◽

Aerosol Effect ◽

Surface Condensation ◽

Atmospheric Radiation Measurement ◽

Upper Level

Abstract Contiguous time–height cloud objects at the Department of Energy Atmospheric Radiation Measurement Southern Great Plains (SGP) site are matched with surface condensation nuclei (CN) concentrations and retrieved thermodynamic and kinematic vertical profiles for warm-cloud-base, cold-cloud-top systems in convectively unstable environments. Statistical analyses show that previously published conclusions that increasing CN concentrations cause a decrease in minimum cloud-top temperature (CTT) at the SGP site through the aerosol convective invigoration effect are unfounded. The CN–CTT relationship is statistically insignificant, while correlations between convective available potential energy (CAPE), level of neutral buoyancy (LNB), and CN concentration account for most of the change in the CN–CTT positive correlation. Removal of clouds with minimum CTTs > −36°C from the analysis eliminates the CN–CTT correlation. Composited dirty conditions at the SGP have ~1°C-warmer low levels and ~1°C-cooler upper levels than clean conditions. This correlation between aerosol concentrations and thermodynamic profiles may be caused by an increase in regional rainfall preceding deep convective conditions as CN concentration decreases. Increased rainfall can be expected to increase wet deposition of aerosols, cool low-level temperatures, and warm upper-level temperatures. The masking of a potential aerosol effect by such small thermodynamic changes implies that the strategy of analyzing subsets of aerosol data by binned meteorological factor values is not a valid method for discerning an aerosol effect in some situations. These findings highlight the need for more careful, detailed, and strategic observations to confidently isolate and quantify an aerosol deep convective invigoration effect.

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Clouds, Aerosols, and Precipitation in the Marine Boundary Layer: An Arm Mobile Facility Deployment

Bulletin of the American Meteorological Society ◽

10.1175/bams-d-13-00180.1 ◽

2015 ◽

Vol 96 (3) ◽

pp. 419-440 ◽

Cited By ~ 69

Author(s):

Robert Wood ◽

Matthew Wyant ◽

Christopher S. Bretherton ◽

Jasmine Rémillard ◽

Pavlos Kollias ◽

...

Keyword(s):

Boundary Layer ◽

Marine Boundary Layer ◽

Weather Forecast ◽

Radiative Properties ◽

Cloud Base ◽

Back Trajectory ◽

Back Trajectory Analysis ◽

Wide Range ◽

Forecast Models ◽

Atmospheric Radiation Measurement

Abstract The Clouds, Aerosol, and Precipitation in the Marine Boundary Layer (CAP-MBL) deployment at Graciosa Island in the Azores generated a 21-month (April 2009–December 2010) comprehensive dataset documenting clouds, aerosols, and precipitation using the Atmospheric Radiation Measurement Program (ARM) Mobile Facility (AMF). The scientific aim of the deployment is to gain improved understanding of the interactions of clouds, aerosols, and precipitation in the marine boundary layer. Graciosa Island straddles the boundary between the subtropics and midlatitudes in the northeast Atlantic Ocean and consequently experiences a great diversity of meteorological and cloudiness conditions. Low clouds are the dominant cloud type, with stratocumulus and cumulus occurring regularly. Approximately half of all clouds contained precipitation detectable as radar echoes below the cloud base. Radar and satellite observations show that clouds with tops from 1 to 11 km contribute more or less equally to surface-measured precipitation at Graciosa. A wide range of aerosol conditions was sampled during the deployment consistent with the diversity of sources as indicated by back-trajectory analysis. Preliminary findings suggest important two-way interactions between aerosols and clouds at Graciosa, with aerosols affecting light precipitation and cloud radiative properties while being controlled in part by precipitation scavenging. The data from Graciosa are being compared with short-range forecasts made with a variety of models. A pilot analysis with two climate and two weather forecast models shows that they reproduce the observed time-varying vertical structure of lower-tropospheric cloud fairly well but the cloud-nucleating aerosol concentrations less well. The Graciosa site has been chosen to be a permanent fixed ARM site that became operational in October 2013.

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