Chapter 1: Overview
Introduction
The Advanced Research WRF (ARW) modeling system has been in development for the past few years. The current release is Version 3, available since April 2008. The ARW is designed to be a flexible, state-of-the-art atmospheric simulation system that is portable and efficient on available parallel computing platforms. The ARW is suitable for use in a broad range of applications across scales ranging from meters to thousands of kilometers, including:
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简介
Advanced Research WRF (ARW)模式系统在过去的数年中得到了发展。最近公布了第三版，从2008年4月开始可供使用。ARW是灵活的，最先进的大气模拟系统，它易移植，并且有效的应用于各种操作系统。ARW适用于从米到成千上万公里尺度的各种天气系统的模拟，它的功能包括：
Idealized simulations (e.g. LES, convection, baroclinic waves) Parameterization research Data assimilation research Forecast research Real-time NWP
Coupled-model applications Teaching
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理想化模拟（如，LES，对流，斜压波） 参数化研究 数据同化研究 预报研究 实时数值天气预报 耦合模式应用 教学
The Mesoscale and Microscale Meteorology Division of NCAR is currently maintaining and supporting a subset of the overall WRF code (Version 3) that includes:
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WRF Software Framework (WSF)
Advanced Research WRF (ARW) dynamic solver, including one-way, two-way nesting and moving nest. The WRF Preprocessing System (WPS)
WRF Variational Data Assimilation (WRF-Var) system which currently supports 3DVAR capability Numerous physics packages contributed by WRF partners and the research community Several graphics programs and conversion programs for other graphics tools
And these are the subjects of this document.
The WRF modeling system software is in the public domain and is freely available for community use.
NCAR的中尺度以及微尺度气象部门最近维护以及支持整个WRF（第三版）的代码的子集，其中包括：
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WRF软件框架
Advanced Research WRF (ARW)动力求解方法，包括单向，双向嵌套以及移动嵌套 预处理系统
WRF多种数据同化系统（WRF-Var），该系统还支持3维同化能力 为WRF合作伙伴以及研究论坛提供的数值物理包. 一些画图程序和转换适合其他画图工具的程序
这也是本文档的主题。
WRF模式系统软件现在是公开以及免费使用的。?
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As shown in the diagram, the WRF Modeling System consists of these major programs:
The WRF Preprocessing System (WPS)? WRF-Var? ARW solver?
Post-processing & Visualization tools?
如图所示，WRF模式系统包括如下的主要部分： WRF预处理系统? WRF参数同化系统? ARW求解程序? 后处理以及可视化工具 WPS
This program is used primarily for real-data simulations. Its functions include 1) defining simulation domains; 2) interpolating terrestrial data (such as terrain, landuse, and soil types) to the simulation domain; and 3) degribbing and interpolating meteorological data from another model to this simulation domain. Its main features include:
·GRIB 1/2 meteorological data from various centers around the world
·Map projections for 1) polar stereographic, 2) Lambert-Conformal, 3) Mercator and 4) latitude-longitude ·Nesting
·User-interfaces to input other static data as well as met data
这个程序的主要用于实时数值模拟。其中包括：1）定义模拟区域；2）插值地形数据（如地势，土地类型，以及土壤类型）到模拟区域；3）从其他模式结果中细致网格以及插值气象数据到此模拟区域。它的主要特点包括：
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GRIB 1/2 格式全球格点气象数据
地图投影有1）极地投影，2）兰伯特-保角投影，3）麦卡托投影以及4）经纬度投影嵌套 由用户接口输入其他数据及met 数据
WRF-Var
This program is optional, but can be used to ingest observations into the interpolated analyses created by WPS. It can also be used to update WRF model's initial condition when WRF model is run in cycling mode. Its main features are as follows.
·? ?? ?It is based on incremental variational data assimilation technique
·? ?? ?Conjugate gradient method is utilized to minimized the cost function in analysis control variable space ·? ?? ?Analysis is performed on un-staggered Arakawa A-grid
·? ?? ?Analysis increments are interpolated to staggered Arakawa C-grid and it gets added to the background (first guess) to get final analysis at WRF-model grid
·? ?? ?Conventional observation data input may be supplied both in ASCII or “PREPBUFR” format via “obsproc” utility ·? ?? ?Multiple radar data (reflectivity & radial velocity) input is supplied through ASCII format
·? ?? ?Horizontal component of the background (first guess) error is represented via recursive filter (for regional) or power spectrum (for global). The vertical component is applied through projections on climatologically generated averaged eigenvectors and its corresponding eigenvalues
·? ?? ?Horizontal and vertical background errors are non-separable. Each eigen vector has its own horizontal climatologically determined length scale
·? ?? ?Preconditioning of background part of the cost function is done via control variable transform U defined as B= UUT ·? ?? ?It includes “gen_be” utility to generate the climatological background error covariance estimate via the NMC-method or ensemble perturbations
·? ?? ?A utility program to update WRF boundary condition file after WRF-Var?
该程序是可选择的，但可用于将观测数据融入到WPS所产生的插值分析中。它还可以在WRF模式处在循环模式运行时，用于更新WRF模式的初始条件.它的主要特点如下：
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它是基于增量变分数据同化技术上而产生出来的 在分析控制变量空间,用共轭梯度法最小化成本函数 非交错的 Arakawa A网格分析
增量分析插值到Arakawa C网格,以及附加到背景场（第一猜测场）以得到WRF模式格点的最终分析 通过使用“obsproc ”工具,可以输入ASCII或者“PREPEUFR”格式的常规观测数据 复合雷达数据（反射率与雷达速度）以ASCII格式输入
背景场（初估计场）的水平分量误差通过递归滤波器（区域范围）或能量谱（全球范围）表现。垂直分量则通过气候学的平均特征向量以及其对应的特征值反映。
水平与垂直背景场误差是不可分割的。每个特征向量的都有各自的水平气候学尺度。 背景场的预处理函数是通过控制变量转换U，其定义为B=UU^T
它包括通过NMC法或整体摄动法，用“gen_be”程序产生气候学背景场误差协方差估计 在WRF-Var后，用程序更新WRF的边界条件文件 ARW Solver