scholarly journals Understanding the drivers of marine liquid-water cloud occurrence and properties with global observations using neural networks

2017 ◽  
Author(s):  
Hendrik Andersen ◽  
Jan Cermak ◽  
Julia Fuchs ◽  
Reto Knutti ◽  
Ulrike Lohmann
Keyword(s):  
Neural Networks ◽  
Liquid Water ◽  
Meteorological Parameters ◽  
Reanalysis Data ◽  
Main Determinant ◽  
Boundary Layer Height ◽  
Water Cloud ◽  
Aerosol Cloud Interactions ◽  
Water Amount

Abstract. The role of aerosols, clouds and their interactions with radiation remain among the largest unknowns in the climate system. Even though the processes involved are complex, aerosol-cloud interactions are often analyzed by means of bivariate relationships. In this study, 15 years (2001–2015) of monthly satellite-retrieved nearly-global aerosol products are combined with reanalysis data of various meteorological parameters to predict satellite-derived marine liquid-water cloud occurrence and properties by means of regionally-specific artificial neural networks. The statistical models used are shown to be capable of predicting clouds, especially in regions of high cloud variability. At this monthly scale, lower tropospheric stability is shown to be the main determinant of cloud fraction and droplet size, especially in stratocumulus regions, while boundary layer height controls the liquid-water amount and thus the optical thickness of clouds. While aerosols show the expected impact on clouds, at this scale they are less relevant than some meteorological factors. Global patterns of the derived sensitivities point to regional characteristics of aerosol and cloud processes.

scholarly journals Understanding the drivers of marine liquid-water cloud occurrence and properties with global observations using neural networks

2017 ◽  
Vol 17 (15) ◽  
pp. 9535-9546 ◽  
Author(s):  
Hendrik Andersen ◽  
Jan Cermak ◽  
Julia Fuchs ◽  
Reto Knutti ◽  
Ulrike Lohmann
Keyword(s):  
Neural Networks ◽  
Liquid Water ◽  
Meteorological Parameters ◽  
Reanalysis Data ◽  
Main Determinant ◽  
Boundary Layer Height ◽  
Water Cloud ◽  
Aerosol Cloud Interactions ◽  
Water Amount

Abstract. The role of aerosols, clouds and their interactions with radiation remain among the largest unknowns in the climate system. Even though the processes involved are complex, aerosol–cloud interactions are often analyzed by means of bivariate relationships. In this study, 15 years (2001–2015) of monthly satellite-retrieved near-global aerosol products are combined with reanalysis data of various meteorological parameters to predict satellite-derived marine liquid-water cloud occurrence and properties by means of region-specific artificial neural networks. The statistical models used are shown to be capable of predicting clouds, especially in regions of high cloud variability. On this monthly scale, lower-tropospheric stability is shown to be the main determinant of cloud fraction and droplet size, especially in stratocumulus regions, while boundary layer height controls the liquid-water amount and thus the optical thickness of clouds. While aerosols show the expected impact on clouds, at this scale they are less relevant than some meteorological factors. Global patterns of the derived sensitivities point to regional characteristics of aerosol and cloud processes.

scholarly journals Continuos Monitoring of Liquid Water Clouds and Aerosols with Dual-FOV Lidar Polarization Technique

2020 ◽  
Vol 237 ◽  
pp. 07005
Author(s):  
Cristofer Jimenez ◽  
Albert Ansmann ◽  
Ronny Engelmann ◽  
Patric Seifert ◽  
Robert Wiesen ◽  
...  
Keyword(s):  
Liquid Water ◽  
Cloud Properties ◽  
A Value ◽  
Scattering Technique ◽  
Polarization Technique ◽  
Water Cloud ◽  
Aerosol Cloud Interactions ◽  
Short Time ◽  
Lidar Observations ◽  
Aerosol Extinction Coefficient

In this work we evaluate the possibilities to assess aerosol-cloud interactions in short time scales (2 min.) on an observational base. Retrievals of the cloud effective radius and number concentration in a liquid-water cloud by using the multiple scattering technique Dual-FOV Polarization lidar, together with the aerosol extinction coefficient in the boundary layer has shown a correspondence between the aerosol and cloud properties in the 6 hours case presented, obtaining a value of ACIN = 0.76 ± 0.29, which corroborates the potential of lidar observations to study the relation between aerosols and clouds on small scales.

Technique of scientific and technical forecasting using neural networks

2018 ◽  
pp. 103-110
Author(s):  
V. V. Nefedev
Keyword(s):  
Mathematical Modeling ◽  
Neural Networks ◽  
Artificial Neural Networks ◽  
Original Method ◽  
Forecasting Methods ◽  
Expert Assessments ◽  
Artificial Neural

For the definition and implementation of breakthrough technologies the most important is the role of scientific and technical forecasting. Well-known forecasting methods based on extrapolation, expert assessments and mathematical modeling are not universal and have a number of significant disadvantages. The article proposes an original method of scientific and technical forecasting based on the use of the methodology of artificial neural networks. 

The Role of Regularization in Overparameterized Neural Networks*

2020 ◽  
Author(s):  
Siddhartha Satpathi ◽  
Harsh Gupta ◽  
Shiyu Liang ◽  
R Srikant
Keyword(s):  
Neural Networks

scholarly journals Seasonal predictability of Mediterranean weather regimes in the Copernicus C3S systems

2021 ◽  
Author(s):  
Ignazio Giuntoli ◽  
Federico Fabiano ◽  
Susanna Corti
Keyword(s):  
Mediterranean Region ◽  
Climate Models ◽  
Reanalysis Data ◽  
Seasonal Predictability ◽  
Economic Implications ◽  
Weather Regimes ◽  
Weather Patterns ◽  
The Mediterranean ◽  
Good Agreement

AbstractSeasonal predictions in the Mediterranean region have relevant socio-economic implications, especially in the context of a changing climate. To date, sources of predictability have not been sufficiently investigated at the seasonal scale in this region. To fill this gap, we explore sources of predictability using a weather regimes (WRs) framework. The role of WRs in influencing regional weather patterns in the climate state has generated interest in assessing the ability of climate models to reproduce them. We identify four Mediterranean WRs for the winter (DJF) season and explore their sources of predictability looking at teleconnections with sea surface temperature (SST). In particular, we assess how SST anomalies affect the WRs frequencies during winter focussing on the two WRs that are associated with the teleconnections in which the signal is more intense: the Meridional and the Anticyclonic regimes. These sources of predictability are sought in five state-of-the-art seasonal forecasting systems included in the Copernicus Climate Change Services (C3S) suite finding a weaker signal but an overall good agreement with reanalysis data. Finally, we assess the ability of the C3S models in reproducing the reanalysis data WRs frequencies finding that their moderate skill increases during ENSO intense years, indicating that this teleconnection is well reproduced by the models and yields improved predictability in the Mediterranean region.

The Main Sequence of Human Optokinetic Afternystagmus (OKAN)

2009 ◽  
Vol 101 (6) ◽  
pp. 2889-2897 ◽  
Author(s):  
Andre Kaminiarz ◽  
Kerstin Königs ◽  
Frank Bremmer
Keyword(s):  
Neural Networks ◽  
Eye Movements ◽  
Main Sequence ◽  
Critical Role ◽  
Saccade Target ◽  
Control Mechanisms ◽  
Visually Guided ◽  
Background Characteristics ◽  
Optokinetic Afternystagmus

Different types of fast eye movements, including saccades and fast phases of optokinetic nystagmus (OKN) and optokinetic afternystagmus (OKAN), are coded by only partially overlapping neural networks. This is a likely cause for the differences that have been reported for the dynamic parameters of fast eye movements. The dependence of two of these parameters—peak velocity and duration—on saccadic amplitude has been termed “main sequence.” The main sequence of OKAN fast phases has not yet been analyzed. These eye movements are unique in that they are generated by purely subcortical control mechanisms and that they occur in complete darkness. In this study, we recorded fast phases of OKAN and OKN as well as visually guided and spontaneous saccades under identical background conditions because background characteristics have been reported to influence the main sequence of saccades. Our data clearly show that fast phases of OKAN and OKN differ with respect to their main sequence. OKAN fast phases were characterized by their lower peak velocities and longer durations compared with those of OKN fast phases. Furthermore we found that the main sequence of spontaneous saccades depends heavily on background characteristics, with saccades in darkness being slower and lasting longer. On the contrary, the main sequence of visually guided saccades depended on background characteristics only very slightly. This implies that the existence of a visual saccade target largely cancels out the effect of background luminance. Our data underline the critical role of environmental conditions (light vs. darkness), behavioral tasks (e.g., spontaneous vs. visually guided), and the underlying neural networks for the exact spatiotemporal characteristics of fast eye movements.

Role of noises in neural networks

1995 ◽  
Vol 52 (6) ◽  
pp. 6593-6606 ◽  
Author(s):  
Sergio Albeverio ◽  
Jianfeng Feng ◽  
Minping Qian
Keyword(s):  
Neural Networks
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