Cirrus Cloud Properties from a Cloud-Resolving Model Simulation Compared to Cloud Radar Observations

2003 ◽  
Vol 60 (3) ◽  
pp. 510-525 ◽  
Author(s):  
Yali Luo ◽  
Steven K. Krueger ◽  
Gerald G. Mace ◽  
Kuan-Man Xu
Keyword(s):  
Model Simulation ◽  
Cirrus Cloud ◽  
Radar Observations ◽  
Cloud Radar ◽  
Cloud Properties ◽  
Cloud Resolving Model

Association of Tropical Cirrus in the 10–15-km Layer with Deep Convective Sources: An Observational Study Combining Millimeter Radar Data and Satellite-Derived Trajectories

2006 ◽  
Vol 63 (2) ◽  
pp. 480-503 ◽  
Author(s):  
Gerald G. Mace ◽  
Min Deng ◽  
Brian Soden ◽  
Ed Zipser
Keyword(s):  
Deep Convection ◽  
Source Region ◽  
Winter Monsoon ◽  
Boreal Summer ◽  
Doppler Velocity ◽  
Boreal Winter ◽  
Radar Observations ◽  
Back Trajectories ◽  
Cloud Radar ◽  
Cloud Properties

Abstract In this paper, millimeter cloud radar (MMCR) and Geosynchronous Meteorological Satellite (GMS) data are combined to study the properties of tropical cirrus that are common in the 10–15-km layer of the tropical troposphere in the western Pacific. Millimeter cloud radar observations collected by the Atmospheric Radiation Measurement program on the islands of Manus and Nauru in the western and central equatorial Pacific during a 12-month period spanning 1999 and 2000 show differences in cirrus properties: over Manus, where clouds above 7 km are observed 48% of the time, the cirrus are thicker and warmer on average and the radar reflectivity and Doppler velocity are larger; over Nauru clouds above 7 km are observed 23% of time. To explain the differences in cloud properties, the relationship between tropical cirrus and deep convection is examined by combining the radar observations with GMS satellite-derived back trajectories. Using a data record of 1 yr, it is found that 47% of the cirrus observed over Manus can be traced to a deep convective source within the past 12 h while just 16% of the cirrus observed over Nauru appear to have a convective source within the previous 12 h. Of the cirrus that can be traced to deep convection, the evolution of the radar-observed cloud properties is examined as a function of apparent cloud age. The radar Doppler moments and ice water path of the observed cirrus at both sites generally decrease as the cirrus age increase. At Manus, it is found that cirrus during boreal winter typically advect over the site from the southeast from convection associated with the winter monsoon, while during boreal summer, the trajectories are mainly from the northeast. The properties of these two populations of cirrus are found to be different, with the winter cirrus having higher concentrations of smaller particles. Examining statistics of the regional convection using Tropical Rainfall Measuring Mission (TRMM), it is found that the properties of the winter monsoon convection in the cirrus source region are consistent with more intense convection compared to the convection in the summer source region.

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

2014 ◽  
Vol 119 (6) ◽  
pp. 3295-3308 ◽  
Author(s):  
Tetsu Sakai ◽  
Narihiro Orikasa ◽  
Tomohiro Nagai ◽  
Masataka Murakami ◽  
Takuya Tajiri ◽  
...  
Keyword(s):  
Asian Dust ◽  
Cirrus Cloud ◽  
Raman Lidar ◽  
Cloud Properties ◽  
Lidar Observations

scholarly journals How frequent is natural cloud seeding from ice cloud layers ( < −35 °C) over Switzerland?

2021 ◽  
Vol 21 (6) ◽  
pp. 5195-5216
Author(s):  
Ulrike Proske ◽  
Verena Bessenbacher ◽  
Zane Dedekind ◽  
Ulrike Lohmann ◽  
David Neubauer
Keyword(s):  
Prediction Models ◽  
Water Cycle ◽  
Weather Prediction ◽  
Ice Crystals ◽  
Occurrence Frequency ◽  
Climate Projections ◽  
Cirrus Cloud ◽  
Cloud Seeding ◽  
Cloud Properties ◽  
Layer Cloud

Abstract. Clouds and cloud feedbacks represent one of the largest uncertainties in climate projections. As the ice phase influences many key cloud properties and their lifetime, its formation needs to be better understood in order to improve climate and weather prediction models. Ice crystals sedimenting out of a cloud do not sublimate immediately but can survive certain distances and eventually fall into a cloud below. This natural cloud seeding can trigger glaciation and has been shown to enhance precipitation formation. However, to date, an estimate of its occurrence frequency is lacking. In this study, we estimate the occurrence frequency of natural cloud seeding over Switzerland from satellite data and sublimation calculations. We use the DARDAR (radar lidar) satellite product between April 2006 and October 2017 to estimate the occurrence frequency of multi-layer cloud situations, where a cirrus cloud at T < −35 ∘C can provide seeds to a lower-lying feeder cloud. These situations are found to occur in 31 % of the observations. Of these, 42 % have a cirrus cloud above another cloud, separated, while in 58 % the cirrus is part of a thicker cloud, with a potential for in-cloud seeding. Vertical distances between the cirrus and the lower-lying cloud are distributed uniformly between 100 m and 10 km. They are found to not vary with topography. Seasonally, winter nights have the most multi-layer cloud occurrences, in 38 % of the measurements. Additionally, in situ and liquid origin cirrus cloud size modes can be identified according to the ice crystal mean effective radius in the DARDAR data. Using sublimation calculations, we show that in a significant number of cases the seeding ice crystals do not sublimate before reaching the lower-lying feeder cloud. Depending on whether bullet rosette, plate-like or spherical crystals were assumed, 10 %, 11 % or 20 % of the crystals, respectively, could provide seeds after sedimenting 2 km. The high occurrence frequency of seeding situations and the survival of the ice crystals indicate that the seeder–feeder process and natural cloud seeding are widespread phenomena over Switzerland. This hints at a large potential for natural cloud seeding to influence cloud properties and thereby the Earth's radiative budget and water cycle, which should be studied globally. Further investigations of the magnitude of the seeding ice crystals' effect on lower-lying clouds are necessary to estimate the contribution of natural cloud seeding to precipitation.

scholarly journals The roles of dynamical variability and aerosols in cirrus cloud formation

2003 ◽  
Vol 3 (2) ◽  
pp. 1415-1451 ◽  
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.

scholarly journals Lidar observation and model simulation of a volcanic-ash-induced cirrus cloud during the Eyjafjallajökull eruption

2012 ◽  
Vol 12 (6) ◽  
pp. 15675-15707 ◽  
Author(s):  
C. Rolf ◽  
M. Krämer ◽  
C. Schiller ◽  
M. Hildebrandt ◽  
M. Riese
Keyword(s):  
Volcanic Ash ◽  
Model Simulation ◽  
Cirrus Cloud ◽  
Backward Trajectories ◽  
Microphysical Properties ◽  
Ice Nuclei ◽  
A Value ◽  
Lidar Measurements ◽  
Before And After ◽  
Western Germany

Abstract. Heterogeneous ice formation induced by volcanic ash from the Eyjafjallajökull volcano eruption in April 2010 is investigated based on the combination of a cirrus cloud observed with a backscatter lidar over Jülich (Western Germany) and model simulations along backward trajectories. The microphysical properties of the cirrus cloud could only be represented by the microphysical model under the assumption of an enhanced number of efficient ice nuclei originating from the volcanic eruption. The ice nuclei (IN) concentration determined by lidar measurements directly before and after cirrus cloud occurrence implies a value of around 0.1 cm−3 (in comparison clean IN conditions: 0.01 cm−3). This leads to a cirrus cloud with rather small ice crystals having a mean radius of 12 μm and a modification of the ice particle number (0.08 cm−3 instead of 3 × 10−4 cm−3 under clean IN conditions). The effectiveness of ice nuclei was estimated by the use of the microphysical model and the backward trajectories based on ECMWF data, establishing a freezing threshold of around 105% relative humidity with respect to ice in a temperature range from −45 to −55 °C. Only with these highly efficient ice nuclei was it possible for the cirrus cloud to be formed in a slightly supersaturated environment.

Climatology of Melting Layer Heights Estimated from Cloud Radar Observations at Various Locations

2021 ◽  
Author(s):  
Jae In Song ◽  
Seong Soo Yum ◽  
Sung‐Hwa Park ◽  
Ki‐Hoon Kim ◽  
Ki‐Jun Park ◽  
...  
Keyword(s):  
Radar Observations ◽  
Melting Layer ◽  
Cloud Radar

Dynamic Processes in Cirrus Clouds: Concepts and Models

Cirrus ◽  
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.

scholarly journals tobac 1.2: towards a flexible framework for tracking and analysis of clouds in diverse datasets

2019 ◽  
Vol 12 (11) ◽  
pp. 4551-4570 ◽  
Author(s):  
Max Heikenfeld ◽  
Peter J. Marinescu ◽  
Matthew Christensen ◽  
Duncan Watson-Parris ◽  
Fabian Senf ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Longwave Radiation ◽  
Geostationary Satellite ◽  
Model Assessment ◽  
Model Simulations ◽  
Cloud Properties ◽  
Level Data ◽  
Different Types ◽  
Cloud Resolving Model ◽  
High Level

Abstract. We introduce tobac (Tracking and Object-Based Analysis of Clouds), a newly developed framework for tracking and analysing individual clouds in different types of datasets, such as cloud-resolving model simulations and geostationary satellite retrievals. The software has been designed to be used flexibly with any two- or three-dimensional time-varying input. The application of high-level data formats, such as Iris cubes or xarray arrays, for input and output allows for convenient use of metadata in the tracking analysis and visualisation. Comprehensive analysis routines are provided to derive properties like cloud lifetimes or statistics of cloud properties along with tools to visualise the results in a convenient way. The application of tobac is presented in two examples. We first track and analyse scattered deep convective cells based on maximum vertical velocity and the three-dimensional condensate mixing ratio field in cloud-resolving model simulations. We also investigate the performance of the tracking algorithm for different choices of time resolution of the model output. In the second application, we show how the framework can be used to effectively combine information from two different types of datasets by simultaneously tracking convective clouds in model simulations and in geostationary satellite images based on outgoing longwave radiation. The tobac framework provides a flexible new way to include the evolution of the characteristics of individual clouds in a range of important analyses like model intercomparison studies or model assessment based on observational data.

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