Unified Model User Guide Document Version: 2 Date of Issue: December 22, 1998 Unified Model Version: 4.4 The Meteorological Office London Road, Bracknell Berkshire, RG12 2SZ United Kingdom c Crown Copyright 1998 This document has not been published. Permission to quote from it must be obtained from the Head of Numerical Modelling at the above address. ii iii Contents List of Figures v List of Tables vi Preface vii 1 Introduction 1 1.1TheUnifiedModel........................................ 1 1.2 The History of the Unified Model . 12 2 Understanding the Unified Model 20 2.1AtmosphericPhysics....................................... 20 2.2AtmosphericDynamics...................................... 27 2.3OceanDynamicsandPhysics................................... 29 3 Code Management and Structure 33 3.1 Managing and Modifying Source Code . 33 3.2UMRoutines........................................... 39 3.3CompilationSystem........................................ 41 3.4MPPCapability.......................................... 58 3.5 Atmosphere Model Control Code . 63 4 Using the Unified Model 71 4.1 The Unified Model User Interface (UMUI) . 71 4.2GettingStarted.......................................... 81 4.3Reconfiguration.......................................... 88 4.4ChangingResolution....................................... 94 4.5AtmosphericTracers....................................... 99 4.6SelectingaNewLAMArea....................................102 iv CONTENTS 4.7ScienceOptions..........................................108 4.8 Assimilation in the Atmosphere Model . 111 4.9 Ancillary and Boundary Files . 115 4.10OceanModel...........................................123 4.11SlabModel............................................131 4.12 Atmosphere-Ocean Coupled Models . 137 4.13 OASIS Coupling Between Models . 141 4.14 Diagnostic Output (STASH) . 142 4.15ClimateMeaning.........................................147 4.16 Automatic Post-Processing for Climate Runs . 151 4.17FileUtilities............................................156 4.18Troubleshooting..........................................157 A The Portable UM 164 A.1Introduction............................................164 A.2PortingtheUM..........................................165 B The UK Met. Office UM 166 B.1FileTransfer............................................166 B.2OperationalArchives.......................................174 B.3 Obtaining Data from the ECMWF Archives . 181 Acronyms 185 References 187 v List of Figures 1.1 The main components of the Unified Model system . 2 1.2 The skill of Met Office operational global forecasts as measured by the NWP index. The index increases as the skill of the forecasts improves. It is calculated by normalising the root mean square (rms) error of the model against persistence and forming a weighted average of key forecast fields. The Unified Model was introduced into operational service in June 1991. 5 1.3 A 12 hour forecast of precipitation intensity obtained using a high resolution (17Km) regional configuration of the Unified Model (right). The observed precipitation as measured by the UK radar network is also shown (left). 5 1.4 Temperature anomaly at level 5 as analysed by FOAM . 6 1.5 A prediction of global temperature change in summer for the middle of next century, using theHadCM2coupledmodel................................... 7 1.6 Time series of winds over the equator, analysed using the stratospheric configuration of the Unified Model. The winds show a clear Quasi-Biennial Oscillation in the stratosphere and a Semi-Annual Oscillation near the stratopause. 7 1.7 The main navigation window of the UMUI. Nodes in the tree (left) may be expanded and collapsed. In this example, the atmospheric model node is expanded. Selected nodes are opened up to display windows (right). 8 1.8 A regional integration domain and grid. Initial data may be interpolated onto such domains viathereconfigurationmodule................................... 9 4.1 A simple example input panel from the UMUI showing entry boxes, a check box, a table widget and a pair of radiobuttons. The three buttons at the bottom of the window are common to all panels. ‘Help’ brings up local help for the window, ‘Close’ and ‘Abandon’ close the window with or without saving changes. 74 4.2FilterPop-UpWindow...................................... 83 4.3CopyWindow........................................... 83 vi List of Tables 1.1 Global configurations of the Unified Model used for production and research at the Met Office 2 1.2UnifiedModelVersions...................................... 13 2.1 Principle differences between the UKMO land surface scheme and MOSES I . 26 4.1UnifiedModelSections......................................109 4.2FileUtilities............................................156 vii Preface This document is the User Guide for the Unified Model (UM). It gives basic information on how to use the model and includes references to relevant UM Documentation Papers (UMDPs) where more detailed information is required. Chapter 1 provides the introduction. It gives an overview description of the UM and its development history. Chapter 2 contains information describing various aspects of the Unified Model. It is intended to help explain how the UM works and describe some of its features but does not explain how to use it. Chapter 3 contains information about the UM source code. This includes information on its structure, management and compila- tion. The main part of the User Guide is chapter 4. It contains instructions on how to use various parts of the UM and how to perform particular tasks. The User Guide is intended for use both by users at the Met. Office and external users of the UM. It also contains additional information relating to the particular set up at the Met. Office. Where information is specific to one set of users it has been put into the appropriate appendix (appendix A for the Portable UM and appendix B for Met. Office specific information). This document was written in LATEX and is available in both HTML and PostScript forms. The HTML form contains links to allow easy navigation around the document and also out to external documents (such as UMDPs, source code listings, etc). External users will find that some of these links will not work since they are specific to the Met. Office or have not been configured. If you have any contributions, corrections, or any other feedback concerning this document please contact the editor by emailing to [email protected]. viii CHAPTER 0. PREFACE 1 Chapter 1 Introduction 1.1 The Unified Model Author: Anette Van der Wal, Last Updated: 1 Jun 98 1.1.1 Overview The Unified Model is the name given to the suite of atmospheric and oceanic numerical modelling software developed and used at the Met Office. The formulation of the model supports global and regional domains and is applicable to a wide range of temporal and spatial scales that allow it to be used for both numerical weather prediction and climate modelling as well as a variety of related research activities. The Unified Model was introduced into operational service in 1991. Since then, both its formulation and capabilities have been substantially enhanced. The modelling system is designed so that it can be run in atmosphere-only, ocean-only or in coupled mode. A number of sub-models are also available which may be used in place of or in addition to the main models. These include a simplified model of the ocean, known as the slab model, and models to simulate the thermo- dynamic and dynamic motion of sea ice. A typical run of the system consists of an optional period of data assimilation followed by a prediction phase. Forecasts from a few hours to a few days ahead are required for numerical weather prediction while for climate modelling the prediction phase may be for tens, hundreds or even thousands of years. The choice of horizontal and vertical resolution is arbitrary and may be varied by the user. In practice, the resolution is constrained by the available computing power and a number of stan- dard resolutions tend to be used (see table 1.1). A separate reconfiguration module allows model data to be optionally interpolated to a new grid or area prior to the start of a run. This applies to the atmosphere only. A range of ancillary data may be incorporated into the model as a run progresses. The options range from lat- eral boundary forcing information for regional configurations to the periodic updating of fields such as ozone concentration to allow for the effects of seasonal variations, and surface forcing for ocean-only configurations. Prognostic, diagnostic and derived fields of data may be output on a time-step by time-step basis for inspection and further analysis, or as forcing information for sub-models such as a sea-state prediction model. Time- meaned or accumulated quantities may also be specified. The wide range of options available within the Unified Model system means that a large number of parameters need to be defined in order to specify and control a particular model configuration. A user-friendly X-Windows based user interface has been developed to make this task much easier. By use of interactive windows, a user may control parameters such as model resolution, the date and time of the initial data, the length of forecast, the choice of output diagnostics and so on. The user may also control the scientific content of the model by selecting from a library of alternative representations of the physical processes. 2 CHAPTER 1. INTRODUCTION Application Status Version Resolution Grid Levels