Search results for "Cloud computing"

2017

Abstract. In situ observations of cloud properties in complex alpine terrain where research aircraft cannot sample are commonly conducted at mountain-top research stations and limited to single-point measurements. The HoloGondel platform overcomes this limitation by using a cable car to obtain vertical profiles of the microphysical and meteorological cloud parameters. The main component of the HoloGondel platform is the HOLographic Imager for Microscopic Objects (HOLIMO 3G), which uses digital in-line holography to image cloud particles. Based on two-dimensional images the microphysical cloud parameters for the size range from small cloud particles to large precipitation particles are obtai…

The Role of Wind Speed and Wind Shear for Banner Cloud Formation

2019

Abstract Banner clouds are clouds that appear to be attached to the leeward face of a steep mountain. This paper investigates the role of wind speed and wind shear for the formation of banner clouds. Large-eddy simulations are performed to simulate the flow of dry air past an idealized pyramid-shaped mountain. The potential for cloud formation is diagnosed through the Lagrangian vertical parcel displacement, which in the case of a banner cloud shows a plume of large values in the lee of the mountain. In addition, vortical structures are visualized through streamlines and their curvature. A series of sensitivity experiments indicates that both the flow and the banner cloud occurrence are lar…

Effective cloud optical depth and enhancement effects for broken liquid water clouds in Valencia (Spain)

2017

Partly cloudy skies with liquid water clouds have been analysed, founding that it is essential to distinguish data if the Sun is obstructed or not by clouds. Both cases can be separated considering simultaneously the Cloud Modification Factor (CMF) and the clearness index (kt). For partly cloudy skies and the Sun obstructed the effective cloud optical depth (τ) has been obtained by the minimization method for overcast skies. This method was previously developed by the authors but, in this case, taking into account partial cloud cover. This study has been conducted for the years 2011–2015 with the multiple scattering model SBDART and irradiance measurements for the UV Erythemal Radiation (UV…

Mixed-Phase Clouds: Progress and Challenges

2017

Mixed-phase clouds represent a three-phase colloidal system consisting of water vapor, ice particles, and coexisting supercooled liquid droplets. Mixed-phase clouds are ubiquitous in the troposphere, occurring at all latitudes from the polar regions to the tropics. Because of their widespread nature, mixed-phase processes play critical roles in the life cycle of clouds, precipitation formation, cloud electrification, and the radiative energy balance on both regional and global scales. Yet, in spite of many decades of observations and theoretical studies, our knowledge and understanding of mixed-phase cloud processes remains incomplete. Mixed-phase clouds are notoriously difficult to represe…

The challenge of simulating the sensitivity of the Amazonian clouds microstructure to cloud condensation nuclei number concentrations

2019

The realistic representation of cloud-aerosol interactions is of primary importance for accurate climate model projections. The investigation of these interactions in strongly contrasting clean and polluted atmospheric conditions in the Amazon area has been one of the motivations for several field observations, including the airborne Aerosol, Cloud, Precipitation, and Radiation Interactions and DynamIcs of CONvective cloud systems – Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement) (ACRIDICON-CHUVA) campaign based in Manaus, Brazil in September 2014. In this work we combine in situ …

The Arctic Cloud Puzzle: Using ACLOUD/PASCAL Multiplatform Observations to Unravel the Role of Clouds and Aerosol Particles in Arctic Amplification

2019

A consortium of polar scientists combined observational forces in a field campaign of unprecedented complexity to uncover the secrets of clouds and their role in Arctic amplification. Two research aircraft, an icebreaker research vessel, an ice-floe camp including an instrumented tethered balloon, and a permanent ground-based measurement station were employed in this endeavour. Clouds play an important role in Arctic amplification. This term represents the recently observed enhanced warming of the Arctic relative to the global increase of near-surface air temperature. However, there are still important knowledge gaps regarding the interplay between Arctic clouds and aerosol particles, surfa…

Reply to a comment by R. Brown on ‘a numerical model of the cloud‐topped planetary boundary‐layer: Radiation, turbulence and spectral microphysics in…

1997

A Theoretical Study of the Wet Removal of Atmospheric Pollutants. Part V: The Uptake, Redistribution, and Deposition of (NM4)4SO4by a Convective Clou…

1995

Abstract The effects of an ice phase on the wet deposition of aerosol particles was studied by means of the authors’ 2D cloud dynamics model with spectral microphysics applied to the Cooperative Convective Precipitation Experiment in Miles City, Montana, on 19 July 1981. The cloud macrostructure as well as the cloud microstructure simulated by the model was found to agree well with observations. Although no on-site observations were available with respect to the chemical composition of the cloud and rain water, the values predicted by the model compared well with typical nearby measurements. The following conclusions can be derived from the model computations: (1) In confirmation of the aut…

Comparison of ERA40 cloud top phase with POLDER-1 observations

2008

[1] A detailed grid-point-based comparison of the cloud top phase derived from the 40-year reanalyses (ERA40) of the European Centre for Medium-Range Weather Forecasts (ECMWF) with satellite measurements is presented. For this purpose an algorithm is implemented to extract a two-dimensional “satellite-like” field of the cloud top phase from ERA40 data. This field is compared with cloud top phase data from the Polarization and Directionality of the Earth Reflectances (POLDER-1) instrument which was in orbit from November 1996 to June 1997. The thermodynamic cloud phase in ERA40 data is parameterized as a function of temperature with pure liquid clouds above 0°C, pure ice clouds below −23°C a…

A numerical model of the cloud-topped planetary boundary-layer: Radiation, turbulence and spectral microphysics in marine stratus

1996

A numerical model of the cloud-topped planetary boundary-layer is presented. The model is one-dimensional with special emphasis on a detailed description of cloud microphysical processes. Aerosols and cloud droplets are treated in a two-dimensional particle-distribution whereby the activation of aerosols is calculated explicitly by solving the droplet-growth equation at all relative humidities. Atmospheric radiation is determined with a δ-two-stream radiation scheme. Turbulent fluxes are parametrized as a function of the turbulent kinetic energy. Numerical results are presented which are obtained by utilizing measurements made over the North Sea. The interaction between radiation, turbulenc…