Meteorological-physical Limitations of Icing in the Atmosphere

The icing hazard can, in most cases, be avoided by correct execution of the flights according to meteorological viewpoints and by meteorologically correct navigation (horizontal and, above all, vertical). The zones of icing hazard are usually narrowly confined. Their location can be ascertained with, in most cases, sufficient accuracy before take-off

The Method of Applied Systems Analysis

The International Institute for Applied Systems Analysis is preparing a "Handbook of Systems Analysis," which will appear in three volumes: Volume 1, "Overview," is aimed at a widely varied audience of producers and users of systems analysis; Volume 2, "Methods," is aimed at systems analysts who need basic knowledge of methods in which they are not expert; the volume contains introductory overviews of such methods; Volume 3, "Cases," contains descriptions of actual systems analyses that illustrate the methods and diversity of systems analysis. Volume 1 will have ten chapters: 1) The context, nature, and use of systems analysis; 2) Applied systems analysis: a genetic approach; 3) Examples of systems analysis; 4) The method of applied systems analysis: finding a solution; 5) Formulating problems for systems analysis; 6) Generating alternatives for systems analysis; 7) Estimating and predicting consequences; 8) Guidance for decision; 9) Implementation; 10) Principles of good practice. To these ten chapters will be added a glossary of systems analysis terms and a bibliography of basic books in the field. This Working Paper is the current draft of Chapter 4. A word about the format of this Working Paper. In order to make the text of each chapter easily amended, it has been entered into the IIASA computer, from which the current version can be reproduced in a few minute's time whenever needed. This Working Paper was produced from the version current on the date shown on each page

Multilevel Structures for On-Line Dynamic Control

The paper presents basic ideas of three of the possible structures of hierarchical control for a dynamic system. All these structures are closed-loop, that is, they make use of feedback in form of the state measured in the controlled system. Local decision units and a supremal unit (coordinator) exist in each of the hierarchical structures, but they differ in the tasks assigned to each level. The price coordination method allows for relative autonomy of the local units, which are being asked to solve appropriate short-horizon, dynamic problems in a repetitive way. In the other two structures the local problems are non-dynamical, but would be much less natural for a human decision maker

Hierarchical Control Systems: An Introduction

The purpose of this paper is to describe the main concepts, ideas and operating principles of hierarchical control systems. The mathematical treatment is rather elementary; the emphasis of the paper is on motivation for using hierarchical control structures as opposed to centralized control. The paper starts with a discussion of multilayer control hierarchies, i.e. hierarchies where either the functions or the time horizons of the subsequent layers of control are different. Some attention has been paid, in this part, to the question of structural choices such as designation of control variables and the selection of the time horizons. Next part of the paper treats decomposition and coordination in steady-state control: direct coordination, penalty function coordination and price coordination are discussed. The focus is on model-reality differences, that is on finding structures and operating principles that would be relatively insensitive to disturbances. The last part of the paper gives a brief presentation of the broad and still developing area of dynamic multilevel control. It was possible, within the restricted space, to show the three main structural principles of this kind of control and to provide for a comparison of their properties. A list of selected references is enclosed with the paper

Handbook of Systems Analysis: Volume 1. Overview. Chapter 4. The Methods of Applied Systems Analysis: An Introductory Overview

The International Institute for Applied Systems Analysis is preparing a Handbook of Systems Analysis, which will appear in three volumes: Volume 1: Overview is aimed at a widely varied audience of producers and users of systems analysis studies. Volume 2: Methods is aimed at systems analysts and other members of systems analysis teams who need basic knowledge of methods in which they are not expert; this volume contains introductory overviews of such methods. Volume 3: Cases contains descriptions of actual systems analyses that illustrate the diversity of the contexts and methods of systems analysis. Drafts of the material for Volume 1 are being widely circulated for comment and suggested improvement. This Working Paper is the current draft of Chapter 4. Correspondence is invited. Volume 1 will consist of the following ten chapters: 1. The context, nature, and use of systems analysis 2. The genesis of applied systems analysis; 3. Examples of applied systems analysis 4. The methods of applied systems analysis: An introduction and overview 5. Formulating problems for systems analysis 6. Objectives, constraints, and alternatives 7. Predicting the consequences: Models and modeling 8. Guidance for decision 9. Implementation 10. The practice of applied systems analysis To these ten chapters will be added a glossary of systems analysis terms and a bibliography of basic works in the field

Cloud feedback mechanisms and their representation in global climate models

Cloud feedback – the change in top-of-atmosphere radiative flux resulting from the cloud response to warming – constitutes by far the largest source of uncertainty in the climate response to CO2 forcing simulated by global climate models (GCMs). We review the main mechanisms for cloud feedbacks, and discuss their representation in climate models and the sources of inter-model spread. Global-mean cloud feedback in GCMs results from three main effects: (1) rising free- tropospheric clouds (a positive longwave effect); (2) decreasing tropical low cloud amount (a positive shortwave effect); (3) increasing high-latitude low cloud optical depth (a negative shortwave effect). These cloud responses simulated by GCMs are qualitatively supported by theory, high-resolution modeling, and observations. Rising high clouds are consistent with the Fixed Anvil Temperature (FAT) hypothesis, whereby enhanced upper-tropospheric radiative cooling causes anvil cloud tops to remain at a nearly fixed temperature as the atmosphere warms. Tropical low cloud amount decreases are driven by a delicate balance between the effects of vertical turbulent fluxes, radiative cooling, large-scale subsidence, and lower-tropospheric stability on the boundary-layer moisture budget. High-latitude low cloud optical depth increases are dominated by phase changes in mixed- phase clouds. The causes of inter-model spread in cloud feedback are discussed, focusing particularly on the role of unresolved parameterized processes such as cloud microphysics, turbulence, and convection

A Sample Glossary of Systems Analysis

Every activity -- and systems analysis is no exception tends to develop its own vocabulary. Indeed, systems analysis, because of its interdisciplinary nature, has been more prone than most not only to invent new words for new concepts but also -- and more often -- to borrow established terms from the disciplines it employs and to change their meaning, sometimes slightly, sometimes grossly, sometimes inconsistently. The result of this can be confusion, misunderstanding, and failure of communication. This glossary is an attempt at resolving part of the ambiguity. The glossary, as it stands now, is tentative. It has been prepared for the preliminary version of the Handbook of Applied Systems Analysis, and the terms included are those used in the Handbook

Control and Coordination in Hierarchical Systems

This book presents the applied theory of control and cooordination in hierarchical systems which are those where decision making has been divided in a certain way. It concentrates on various aspects of optimal control in large scale systems and covers a range of topics from multilevel methods for optimizing by interactive feedback procedures to methods for sequential, hierarchical control in large dynamic systems

Aerosol Mixing State: Measurements, Modeling, and Impacts

Atmospheric aerosols are complex mixtures of different chemical species, and individual particles exist in many different shapes and morphologies. Together, these characteristics contribute to the aerosol mixing state. This review provides an overview of measurement techniques to probe aerosol mixing state, discusses how aerosol mixing state is represented in atmospheric models at different scales, and synthesizes our knowledge of aerosol mixing state’s impact on climate‐relevant properties, such as cloud condensation and ice nucleating particle concentrations, and aerosol optical properties. We present these findings within a framework that defines aerosol mixing state along with appropriate mixing state metrics to quantify it. Future research directions are identified, with a focus on the need for integrating mixing state measurements and modeling.Key PointsWe define aerosol mixing state and connect it to the physicochemical properties of aerosol particlesWe discuss existing measurements and models to understand chemical and physicochemical mixing stateWe explain the connection between aerosol mixing state and climate‐relevant aerosol propertiesPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150540/1/rog20184_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150540/2/rog20184.pd