Global Cloud-system Research Articles

Precipitation Diurnal Cycle over Tropical Coastal Regions Represented in Climate Experiments with a Global Cloud-System Resolving Model

Precipitation Diurnal Cycle over Tropical Coastal Regions Represented in Climate Experiments with a Global Cloud-System Resolving Model

Analysis of United States Cyberpower Domination through the Cloud Act on Data Security in Europe

This study aims to analyze the dominance of US cyberpower through the Cloud Act on data security in Europe. Currently, the business of storing and processing data via a network, commonly known as the cloud, is dominated by US technology giants. Meanwhile in Europe, business people and governments failed to reach an agreement to form a cloud service to match that dominance. One of the causes of European concern is the law in the US called the Cloud Act. This agreement provides for complying with their obligations to store, back up, or disclose electronic data in their possession regardless of where that information is located. That way, the United States can have special access to be able to access state data without the need for a warrant. The research method used is descriptive qualitative with data collection techniques through interviews, documentation, and literature study from books and e-journals. Determination of informants using purposive sampling method. the validity and reliability of the data were tested using data triangulation techniques. The results of the analysis in this study show the dominance of US cyberpower in the global cloud system business. The conclusion of this study is that it is very important to build readiness in facing the onslaught of American cyber power dominance starting from setting regulations that can be agreed upon by the international community by prioritizing technological modernization so that every country has the same opportunity to build and secure its own cloud system

PECULIARITIES OF MARTIAN HYDROLOGY

Mars is characterized by a rather complex hydrological cycle. The images of the planet show the northern and southern polar caps. A global cloud system often appears near aphelion. There are several million cubic kilometers of ice in the polar caps. In te

Projection of High Clouds and the Link to Ice Hydrometeors: An Approach Using Long-Term Global Cloud System–Resolving Simulations

AbstractThis study examines projections of high clouds related to sea surface temperature (SST) change using 14-km simulation output from NICAM, a global cloud system–resolving model. This study focuses on the vertical and horizontal structure of high cloud response to the SST pattern and how these cloud responses are linked to ice hydrometeors, such as cloud ice, snow, and graupel, which are not resolved by conventional general circulation models (GCMs). Under the present climate, the vertical and horizontal structure of the simulated increase in tropical high cloud amount for positive tropical mean HadISST SST anomalies has similar behavior to that of the GCM-OrientedCALIPSOCloud Product (GOCCP) cloud fraction for HadISST SST. We further show that cloud ice is the main contributor to the simulated high cloud amount. Under a warming climate, the composite vertical and horizontal structure of the tropical high cloud response to the SST shows similar behavior to that under the present climate, but the amplitude of the variation is greater by a factor of 1.5 and the variation is more widespread. This amplification contributes to the high cloud increase under the warming climate, which is directly linked to the wider spatial extent of cloud ice in the eastern Pacific region. This study specifically reveals the similarity of the patterns of the responses of the high cloud fraction and cloud ice to global warming, indicating that an appropriate treatment of the complete spectrum of ice hydrometeors in global climate models is key to simulating high clouds and their response to global warming.

Assessments of Doppler Velocity Errors of EarthCARE Cloud Profiling Radar Using Global Cloud System Resolving Simulations: Effects of Doppler Broadening and Folding

The Earth Clouds, Aerosol, and Radiation Explorer (EarthCARE) is a satellite mission jointly developed by the Japan Aerospace Exploration Agency (JAXA) and the European Space Agency (ESA). One challenging feature of this mission is the observation of Doppler velocity by the Cloud Profiling Radar (EC-CPR). The Doppler measurement accuracy is affected by random errors induced by Doppler broadening due to the finite beamwidth and Doppler folding caused by the finite pulse repetition frequency. We investigated the impact of horizontal (along-track) integration and unfolding methods on the reduction of Doppler errors, in order to improve Doppler data processing in the JAXA standard algorithm. We simulated EC-CPR-observed Doppler velocities from pulse-pair covariances with the latest EC-CPR specifications using the radar reflectivity factor and Doppler velocity fields simulated by a satellite data simulator and a global cloud system resolving simulation. Two representative cases of a cirrus cloud and precipitation were examined. In the cirrus cloud case, the standard deviation of random error was decreased to 0.5 m/s for −10 dB <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Z} _{\mathbf {e}}$ </tex-math></inline-formula> after 10-km horizontal integration. In the precipitation case, large falling speeds of precipitation caused Doppler folding errors due to larger Doppler velocities than that in the cirrus cloud case. When <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Z} _{\mathbf {e}}$ </tex-math></inline-formula> is larger than −15 dB <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Z} _{\mathbf {e}}$ </tex-math></inline-formula> , the standard deviations of random error were less than 1.0 m/s after 10-km horizontal integration and unfolding.

Aerosol effects on cloud water amounts were successfully simulated by a global cloud-system resolving model

Aerosols affect climate by modifying cloud properties through their role as cloud condensation nuclei or ice nuclei, called aerosol–cloud interactions. In most global climate models (GCMs), the aerosol–cloud interactions are represented by empirical parameterisations, in which the mass of cloud liquid water (LWP) is assumed to increase monotonically with increasing aerosol loading. Recent satellite observations, however, have yielded contradictory results: LWP can decrease with increasing aerosol loading. This difference implies that GCMs overestimate the aerosol effect, but the reasons for the difference are not obvious. Here, we reproduce satellite-observed LWP responses using a global simulation with explicit representations of cloud microphysics, instead of the parameterisations. Our analyses reveal that the decrease in LWP originates from the response of evaporation and condensation processes to aerosol perturbations, which are not represented in GCMs. The explicit representation of cloud microphysics in global scale modelling reduces the uncertainty of climate prediction.

A Madden‐Julian Oscillation event remotely accelerates ocean upwelling to abruptly terminate the 1997/1998 super El Niño

AbstractThe termination of the superintense 1997/1998 El Niño was extraordinarily abrupt. The May 1998 Madden‐Julian Oscillation (MJO), a massive complex of stormy tropical clouds, is among possible contributors to the abrupt termination. Despite having been sensationally proposed 18 years ago, the role of the MJO remained controversial and speculative because of the difficulty of sufficiently simulating the El Niño and MJO simultaneously. An ensemble simulation series using a newly developed, fully ocean‐coupled version of a global cloud system resolving numerical model replicated the specific atmosphere and ocean conditions of May 1998 in unprecedented detail, extending the prediction skill of the MJO to 46 days. Simulation ensemble members with stronger MJO activities over the Maritime Continent experienced quicker sea surface temperature drop in the eastern Pacific, confirming that the easterly winds associated with the remote MJO accelerated ocean upwelling to abruptly terminate the El Niño.

Multi-tier cloud infrastructure support for reliable global health awareness system

The exceptional outbreaks of a number of epidemic diseases such as Ebola, SARS, Zika and H1N1 and their wide distribution over multiple regions calls for a reliable global health awareness system. This system is needed to achieve early detection of such emergencies. Furthermore, such health awareness system should be capable of predicting the outbreaks patterns to facilitate future countermeasure planning. This health awareness system should cover large scale regions that can be extended to multiple countries, continents and ultimately the globe. Many advanced and industrial countries are still struggling in building such system effectively even with the availability of resources and domain experts. The realization of a reliable health awareness system is accompanied with multiple challenges such as the availability of resources and experts, the global agreements about the system from the legislative and control point of view and the availability of the infrastructure that will support the system functionality with a reasonable cost. This paper presents a novel global health awareness system that overcomes the aforementioned challenges. The system is exploiting the emerging cloud computing services availability over the globe. To handle the large scale requirements, we introduce a multi-tier based cloud system that spans over four tiers starting from the monitored subjects to a centralized global cloud system. Also, we present a mixed integer optimization formulation to tackle the issues related to the latency of detecting outbreaks. Our results show that processing the data in multi-tier health awareness system will reduce the overall delay significantly and enable efficient health data sharing.

Resolution Dependence of the Diurnal Cycle of Precipitation Simulated by a Global Cloud-System Resolving Model

Resolution Dependence of the Diurnal Cycle of Precipitation Simulated by a Global Cloud-System Resolving Model

Tropical synoptic-scale wave disturbances over the western Pacific simulated by a global cloud-system resolving model

Lower-tropospheric tropical synoptic-scale disturbances (TSDs) are associated with severe weather systems in the Asian Monsoon region. Therefore, exact prediction of the development and behavior of TSDs using atmospheric general circulation models is expected to improve weather forecasting for this region. Recent state-of-the art global cloud-system resolving modeling approaches using a Nonhydrostatic Icosahedral Atmospheric Model (NICAM) may improve representation of TSDs. This study evaluates TSDs over the western Pacific in output from an Atmospheric Model Intercomparison Project (AMIP)-like control experiment using NICAM. Data analysis compared the simulated and observed fields. NICAM successfully simulates the average activity, three-dimensional structures, and characteristics of the TSDs during the Northern summer. The variance statistics and spectral analysis showed that the average activity of the simulated TSDs over the western Pacific during Northern summer broadly captures that of observations. The composite analysis revealed that the structures of the simulated TSDs resemble the observed TSDs to a large degree. The simulated TSDs exhibited a typical southeast- to northwest-oriented wave-train pattern that propagates northwestward from near the equator around 150 ∘ E toward the southern coast of China. However, the location of the simulated wave train and wave activity center was displaced northward by approximately a few degrees of latitude from that in the observation. This displacement can be attributed to the structure and strength of the background basic flow in the simulated fields. Better representation of the background basic states is required for more successful simulation of TSDs.

Electrostatic stratification of the global cloud system by the self-consistent field of the metastable electronion subsystem of the atmosphere

Analysis of frequency distribution of the heights of clouds formation has been conducted by the data of airplane sounding for compatibility to the structure of surface and highaltitude electrostatic field. Coincidence of maximal sites of frequency distribution of cloud heights with zero values of distribution of threedimensional charges of atmosphere has been found. Correspondence does not depend on the type of cloudiness, though cloud distributions by themselves differ essentially for the different types. It has been shown that frequency distribution of the heights of clouds formation is related to gravity polarization of the active atmospheric medium — metastable undercooled coulomb plasma of thermalizing atmospheric electrons. Effective dielectric permeability of such a medium varies within the limits of 104—106 CGSE. Approximate solution of self consistent Poisson equation for medium field of atmospheric electrons corresponding to Landau equation for the firstorder phase transitions has been given. Exact solution has been found for the equation depending on boundary conditions. Parameters of solution, module of elliptic function and effective length of screening have been chosen in accordance with the experiment and reproduce altitude run of potential correctly. Module dependence has a critical character of firstorder phase transitions. The nature of dependence is related to heavy mode of lengmure vibrations of ionicelectronic atmosphere subsystem.

Possible Impact of a Tropical Cyclone on the Northward Migration of the Baiu Frontal Zone

The impact of a tropical cyclone on the northward migration of the Baiu frontal zone (BFZ) is investigated in the case of the tropical cyclone MAWAR (2012) using a global cloud-system resolving model, called NICAM. From 4 to 6 June in 2012, the BFZ rapidly shifts northward with MAWAR. A simulation with the initial data of 29 May reproduces the northward migration of the BFZ and the tropical cyclone. Strong southerlies on the eastern side of the tropical cyclone transport moist and high-temperature air into the BFZ. This horizontal advection affects the northward migration of the BFZ. In contrast, the BFZ stagnates to the south of Japan in another simulation with the initial data of 30 May because the tropical cyclone track is diverted eastward. Thus, realistic reproducibility of a tropical cyclone is needed for better simulations and prediction of the BFZ migration.

Sensitivity of Hadley Circulation to Physical Parameters and Resolution through Changing Upper-Tropospheric Ice Clouds Using a Global Cloud-System Resolving Model

AbstractThe relationship between upper-tropospheric ice cloud properties and the Hadley circulation intensity is examined through parameter sensitivity studies of global cloud-system-resolving simulations with explicit cloud convection. Experiments under a perpetual July condition were performed by changing parameters in the boundary layer and cloud microphysics schemes, with a mesh size of approximately 14 km. One additional experiment with a mesh size of approximately 7 km was also conducted. These experiments produced a variety of upper-cloud coverage and outgoing longwave radiation (OLR) distributions. The authors found that, as the upper-cloud coverage increased, the total precipitation decreased and the intensity of the Hadley circulation weakened because of energy balance constraints that radiative cooling are balanced by adiabatic warming. Interestingly, the ice water path was not correlated with the upper ice-loud coverage or OLR, indicating that the spatial coverage of upper ice clouds, rather than the ice water content, was the key factor in the radiation budget.

Hardware/software co-design of global cloud system resolving models

[1] We present an analysis of the performance aspects of an atmospheric general circulation model at the ultra-high resolution required to resolve individual cloud systems and describe alternative technological paths to realize the integration of such a model in the relatively near future. Due to a superlinear scaling of the computational burden dictated by the Courant stability criterion, the solution of the equations of motion dominate the calculation at these ultra-high resolutions. From this extrapolation, it is estimated that a credible kilometer scale atmospheric model would require a sustained computational rate of at least 28 Petaflop/s to provide scientifically useful climate simulations. Our design study portends an alternate strategy for practical power-efficient implementations of next-generation ultra-scale systems. We demonstrate that hardware/software co-design of low-power embedded processor technology could be exploited to design a custom machine tailored to ultra-high resolution climate model specifications at relatively affordable cost and power considerations. A strawman machine design is presented consisting of in excess of 20 million processing elements that effectively exploits forthcoming many-core chips. The system pushes the limits of domain decomposition to increase explicit parallelism, and suggests that functional partitioning of sub-components of the climate code (much like the coarse-grained partitioning of computation between the atmospheric, ocean, land, and ice components of current coupled models) may be necessary for future performance scaling.

Properties of Precipitation and In-Cloud Vertical Motion in a Global Nonhydrostatic Aquaplanet Experiment

To gain insight into properties of in-cloud vertical motion and precipitation production in the tropics, three-dimensional outputs from an aquaplanet experiment using a 3.5-km mesh global cloud-system resolving model (GCRM) were analyzed.Probability distributions of precipitation and latent heating in the 10°N–10°S domain are evaluated in comparison with Tropical Rainfall Measurement Mission (TRMM) observations. Despite biases of generally higher precipitation top height (PTH) and deficiencies near the melting level, the model reproduced the general morphology of the precipitation and total latent heating profiles. Relationship between PTH and cloud top height (CTH) in the simulated clouds reproduced clear contrast between deep and shallow convection in active and suppressed environments, respectively. The simulated in-cloud vertical velocities were on the order of O(0.1 m s-1) in anvil clouds and O(1 m s-1) in updraft cores, as in the range of those in previous observations. Focusing on relatively strong upward motion, the maximum in-cloud vertical motion (w_max) was defined in each column. Probabilities of w_max had double peaks (z = 1–4 and 7–12 km) with minima in the middle troposphere. Vigorous upward motions most frequently occurred in the upper troposphere as the active portion of well-organized convective systems. They were often surrounded by updrafts with w_max height in the lower to middle troposphere, forming a group of updraft regions (w_max > 1 m s-1) with horizontal scale of O(10 km). In the regions of compensating subsidence, updrafts tended to be capped below the middle troposphere and small in horizontal size. In both regions the updrafts were accompanied by cold pools of their characteristic horizontal scale.Finally, time evolutions of in-cloud updrafts were analyzed to explore the roles of in-cloud updrafts at different altitude. It was found that the updrafts with w_max height in the middle troposphere produced the heaviest surface precipitation, preceded by moisture transport in the lower to middle troposphere. This suggests that middle tropospheric updrafts most efficiently produced surface precipitation through tight linkage between dynamics and cloud processes, although their occurrence was rare.

Statistical Relation between Maximum Vertical Velocity and Surface Precipitation of Tropical Convective Clouds in a Global Nonhydrostatic Aquaplanet Experiment

This study investigated the properties of heavy precipitation and its associated vertical motion in an aquaplanet experiment with a 3.5-km mesh global cloud-system resolving model (GCRM). The statistics of precipitation and vertical velocity were examined in terms of the precipitation top height (PTH) and the maximum in-cloud vertical velocity in each column (w_max) for the grid points with the top 1% and 1–10% of the surface precipitation rate (pr_sfc) in the 10°N–10°S domain. To support the findings, realistic simulation cases were also analyzed. In the columns with the top 1% (1–10%) of pr_sfc, peak frequencies of w_max height were found at z = 4–6 (1–4) km with the PTH several kilometers above that. Thermodynamic conditions were more humid and warmer in these columns than in the columns with average precipitation. These results were common to all simulation cases. Composite time evolution of convection with heavy surface precipitation was also examined for the aquaplanet experiment. The results suggest that the vigorous upward motion in the middle (lower) troposphere for columns with the top 1% (1–10%) of pr_sfc enabled efficient moisture transport from the boundary layer to the middle troposphere.

Evaluations of cloud properties of global and local cloud system resolving models using CALIPSO and CloudSat simulators

This study proposes a method of using a local‐area cloud system resolving model (LCRM) to evaluate and improve cloud properties simulated by a global cloud system resolving model (GCRM). We study the sensitivity to cloud microphysics schemes by comparing the simulated data of LCRM with CloudSat and Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) using satellite simulators. In particular, the impacts of the improved cloud microphysics scheme, which is more comprehensive than the scheme used for the GCRM experiment, with six water categories are studied. We focus on the active convective phase over the maritime continent. During the 4 day integration period of LCRM, 11 tracks of A‐Train satellite observations are available. Cloud properties along the cross sections of these tracks are first examined to find the bias of the simulated data compared to the CloudSat and CALIPSO observations. The improved cloud microphysics scheme used in the LCRM reproduces the overall characteristics of the observed contoured frequency by altitude diagrams (CFADs) well, although biases are still present in the upper layers. We find that the simulated domain‐averaged cloud properties can be evaluated using the observed track data. The comparison of the CFADs between LCRM and GCRM clarifies the bias in GCRM, and the new cloud microphysics scheme improves this bias. Using LCRM, sensitivities to cloud microphysics parameters are examined, and the CFADs are further improved if the ice sedimentation speed is increased. These results indicate that introduction of the graupel category or faster sedimentation of ice clouds reduces the total amount of hydrometeors and leads to more efficiency of precipitation.

Comparison of high‐level clouds represented in a global cloud system–resolving model with CALIPSO/CloudSat and geostationary satellite observations

Vertical and horizontal distributions of high‐level clouds (ice and snow) simulated in high‐resolution global cloud system–resolving simulations by the Nonhydrostatic Icosahedral Atmospheric Model (NICAM) are compared with satellite observations. Ice and snow data in a 1 week experiment by the NICAM 3.5 km grid mesh global simulation initiated at 0000 UTC 25 December 2006 are used in this study. The vertical structure of ice and snow represented by NICAM was compared with Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat observations. High‐level clouds (cumulonimbus and cirrus type clouds) classified by the split window (11 and 12 μm) data on board geostationary meteorological satellites (GMSs) were used for comparison of the horizontal distributions of ice and snow in NICAM. The vertical distributions of ice and snow simulated by NICAM qualitatively agree well with those of cloud signals observed by CALIPSO and CloudSat. We computed corresponding cloud lidar backscatter coefficients and cloud radar reflectivity signals from ice and snow data of NICAM using Cloud Feedback Model Intercomparison Project (CFMIP) observational simulator packages. The contoured frequency by altitude diagram for the cloud lidar backscatter coefficients shows lower frequency at higher altitude of 8–14 km by NICAM than CALIOP observations. This suggests that the amount of ice is not well represented in NICAM. The simulated cloud radar reflectivity signals by NICAM indicated higher frequency at 8–10 km altitude than CloudSat observations, although there were some differences between over oceans and continents. This implies that the amount of snow is larger in NICAM simulations. The horizontal pattern of ice clouds (column‐integrated ice and snow of greater than 0.01 kg/m2) in NICAM shows good agreement with that of high‐level clouds identified by the split window analysis. During this 1 week simulation, 48–59% of ice clouds in NICAM matches with observed high‐level clouds. The cross correlation between the spatial distributions of simulated ice clouds and satellite‐observed high‐level clouds is 0.40–0.51, and the equitable threat score is 0.31–0.45. Furthermore, temporal variations of column‐integrated ice clouds in NICAM are compared with high‐level clouds classified by the split window at the decaying stage of deep convection over the tropics. The results indicate that the mean decaying speed of ice clouds of NICAM and high‐level clouds by satellite observations agrees well for this analysis area and period, although the variances are larger in NICAM. This implies that the fall speed of snow in this NICAM experiment is appropriate to depict the decay of anvil clouds by compensating for the excess of snow in NICAM simulations, when we assume that the decay of anvil clouds is largely controlled by the evaporation of ice and snow.

Tests of Monte Carlo Independent Column Approximation in the ECHAM5 Atmospheric GCM

Abstract The Monte Carlo Independent Column Approximation (McICA) method for computing domain-average radiative fluxes allows a flexible treatment of unresolved cloud structure, and it is unbiased with respect to the full ICA, but its flux estimates contain conditional random noise. Here, tests of McICA in the ECHAM5 atmospheric GCM are reported. ECHAM5 provides an interesting test bed for McICA because it carries prognostic variables for the subgrid-scale probability distribution of total water content, which allows us to determine subgrid-scale cloud variability directly from the resolved-scale model variables. Three experiments with differing levels of radiative noise, each consisting of ten 6-yr runs, are performed to estimate the impact of McICA noise on simulated climate. In an experiment that attempted to deliberately maximize McICA noise, a systematic reduction in low cloud fraction occurred. For a more reasonable implementation of McICA, the impact of noise is very small, although statistically discernible. In terms of the impacts of noise, McICA appears to be a viable approach for use in ECHAM5. However, to improve the simulation of cloud radiative effects, realistic representation of both unresolved and resolved cloud structures is needed, which remains a challenging problem. Comparison of ECHAM5 data with a global cloud system–resolving model dataset and with International Satellite Cloud Climatology Project data suggested two problems related to unresolved cloud structures. First, ECHAM5 appears to underestimate subgrid-scale cloud variability. This problem seems partly related to the use of the beta distribution scheme for total water content in ECHAM5: in its current form, the scheme is unable to generate highly inhomogeneous clouds (relative standard deviation of condensate amount &amp;gt;1). Second, it appears that in ECHAM5, overcast cloud layers occur too frequently and partially cloudy layers too rarely. This problem is not unique to the beta distribution scheme; in fact, it is more pronounced when using an alternative, relative humidity–based cloud fraction scheme.

Small-Scale Processes and Entrainment in a Stratocumulus Marine Boundary Layer

Numerical studies of boundary layer meteorology are increasingly reliant on large eddy simulation (LES) models, but few detailed validation studies of these types of models have been done. In this paper the authors investigate the behavior of an LES model for simulation of a marine boundary layer. Specifically, the authors focus on the mechanisms that control numerical predictions of entrainment into the tops of marine stratus in a moist generalization of the 1995 Global Energy and Water Cycle Experiment Cloud System Studies model intercomparison. For the computational study the authors present a sequence of simulations of varying resolution, from a typical resolution (50 m horizontal and 25 m vertical mesh size) to a fine resolution (8 m horizontal and 4 m vertical mesh size). The authors also explore variations in the model such as different subgrid models and modifications of the advection scheme. It was found that the thickness of the inversion, the depth of entraining eddies, and the shape of vertical velocity spectra were determined mainly by the mesh spacing used. However, the entrainment rate was found to have a distinct dependence on the amount of combined numerical and subgrid-scale mixing. This indicates that the use of large eddy simulation to study mixing in stratocumulus boundary layers needs to account for both sources of mixing.