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第1行： − + − 【终稿】一次850mbar处地势高度和温度的96小时预报|链接=Special:FilePath/GFS_850_MB.PNG]]+ − An '''atmospheric model''' is a [[mathematical model]] constructed around the full set of [[primitive equations|primitive]] [[Dynamical systems theory|dynamical equations]] which govern atmospheric motions. It can supplement these equations with [[Parametrization (climate)|parameterizations]] for [[Turbulence|turbulent]] diffusion, [[radiation]], [[moist processes]] ([[clouds]] and [[precipitation (meteorology)|precipitation]]), [[heat transfer|heat exchange]], [[soil]], vegetation, surface water, the [[Kinematics|kinematic]] effects of [[terrain]], and convection. Most atmospheric models are numerical, i.e. they discretize equations of motion. They can predict microscale phenomena such as [[tornadoes]] and [[Eddy covariance|boundary layer eddies]], sub-microscale turbulent flow over buildings, as well as synoptic and global flows. The horizontal domain of a model is either ''global'', covering the entire [[Earth]], or ''regional'' (''limited-area''), covering only part of the Earth. The different types of models run are thermotropic, [[barotropic]], hydrostatic, and nonhydrostatic. Some of the model types make assumptions about the atmosphere which lengthens the time steps used and increases computational speed. − An atmospheric model is a mathematical model constructed around the full set of primitive dynamical equations which govern atmospheric motions. It can supplement these equations with parameterizations for turbulent diffusion, radiation, moist processes (clouds and precipitation), heat exchange, soil, vegetation, surface water, the kinematic effects of terrain, and convection. Most atmospheric models are numerical, i.e. they discretize equations of motion. They can predict microscale phenomena such as tornadoes and boundary layer eddies, sub-microscale turbulent flow over buildings, as well as synoptic and global flows. The horizontal domain of a model is either global, covering the entire Earth, or regional (limited-area), covering only part of the Earth. The different types of models run are thermotropic, barotropic, hydrostatic, and nonhydrostatic. Some of the model types make assumptions about the atmosphere which lengthens the time steps used and increases computational speed.+ − 大气模式是围绕控制大气运动的一整套原始动力学方程建立的数学模式。它可以用湍流扩散、辐射、湿过程(云和降水)、热交换、土壤、植被、地表水、地形的运动学效应和对流等参数化来补充这些方程。大多数大气模型都是数字化的，例如。他们把运动方程分开。他们可以预测微尺度现象，例如龙卷风和边界层涡旋，建筑物上空的亚微尺度湍流，以及天气和全球气流。模型的水平域要么是全球性的，覆盖了整个地球; 要么是区域性的，只覆盖了地球的一部分。不同类型的模式运行是热力学，正压，流体静力学和非流体静力学。一些模型类型对大气层做出假设，从而延长了使用的时间步骤，提高了计算速度。 − 【终稿】大气模式是围绕控制大气运动的一整套原始的动力学方程所建立的数学模型。它可以通过湍流扩散、辐射、湿过程（云和降水）、热交换、土壤、植被、地表水、地形的动力学效应和对流等的参数化来补充这些方程。大多数大气模式是基于数值方法的，即将运动方程离散化。它们可以预测微尺度的现象，例如龙卷风、边界层的涡旋、流经建筑物上方的亚微尺度湍流，以及天气气流、全球气流。模式的水平区域全球性的，覆盖整个地球，也可以是区域性的（有限区域的），只覆盖部分地球。模式运行的不同类型包括热致的、正压的、流体静力学的和非流体静力学的。部分类型的模式对大气进行了一些假设，从而加长了时间步长并提高计算速度。+ + − Forecasts are computed using mathematical equations for the physics and dynamics of the atmosphere. These equations are nonlinear and are impossible to solve exactly. Therefore, numerical methods obtain approximate solutions. Different models use different solution methods. Global models often use [[spectral method]]s for the horizontal dimensions and [[Finite difference method|finite-difference methods]] for the vertical dimension, while regional models usually use finite-difference methods in all three dimensions. For specific locations, [[model output statistics]] use climate information, output from [[numerical weather prediction]], and current [[surface weather observation]]s to develop statistical relationships which account for model bias and resolution issues. − Forecasts are computed using mathematical equations for the physics and dynamics of the atmosphere. These equations are nonlinear and are impossible to solve exactly. Therefore, numerical methods obtain approximate solutions. Different models use different solution methods. Global models often use spectral methods for the horizontal dimensions and finite-difference methods for the vertical dimension, while regional models usually use finite-difference methods in all three dimensions. For specific locations, model output statistics use climate information, output from numerical weather prediction, and current surface weather observations to develop statistical relationships which account for model bias and resolution issues. − 预报是利用大气物理和动力学的数学方程式计算出来的。这些方程是非线性的，不可能精确求解。因此，数值方法可以得到近似解。不同的模型使用不同的求解方法。全球模型通常采用谱方法计算水平维数，有限差分方法计算垂直维数，而区域模型通常采用三维有限差分方法。对于特定的位置，模型输出统计使用气候信息、数值天气预报气象观测数据和当前地面天气观测数据来建立统计关系，以解释模型偏差和分辨率问题。+ − − 【终稿】预报是使用大气物理和动力学方程计算得来的。这些方程是非线性的，无法获得准确解。因此只能使用数值方法获得近似解。不同的模式使用不同的求解方法。全球模式通常在水平维度上采用谱方法，而在垂直维度采用有限差分法；而区域模式通常在三个维度均使用有限差分法。对于特定的位置，模式的输出统计使用气候信息、数值天气预测结果以及当前地表天气观测数据来建立统计关系，以解释模式偏差和分辨率问题。 − − == Types 类型 == − The main assumption made by the '''thermotropic''' model is that while the magnitude of the [[thermal wind]] may change, its direction does not change with respect to height, and thus the [[Baroclinity|baroclinicity]] in the atmosphere can be simulated using the {{convert|500|mb|inHg|adj=on |abbr=on |lk=on}} and {{convert|1000|mb|inHg|adj=on|abbr=on}} [[geopotential height]] surfaces and the average thermal wind between them.<ref>{{cite book|last= Gates|first=W. Lawrence|title=Results Of Numerical Forecasting With The Barotropic And Thermotropic Atmospheric Models|date=August 1955|publisher=Air Force Cambridge Research Laboratories|location=[[Hanscom Air Force Base]]|url=http://handle.dtic.mil/100.2/AD101943}}</ref><ref>{{cite journal |last=Thompson|first=P. D.|author2=W. Lawrence Gates|title=A Test of Numerical Prediction Methods Based on the Barotropic and Two-Parameter Baroclinic Models|journal=[[Journal of the Atmospheric Sciences|Journal of Meteorology]]| date=April 1956 |volume=13|issue=2|pages=127–141 |doi= 10.1175/1520-0469(1956)013<0127:ATONPM>2.0.CO;2 |issn=1520-0469|bibcode = 1956JAtS...13..127T |doi-access=free}}</ref> − − The main assumption made by the thermotropic model is that while the magnitude of the thermal wind may change, its direction does not change with respect to height, and thus the baroclinicity in the atmosphere can be simulated using the and geopotential height surfaces and the average thermal wind between them. − − = = = = = 由热带模式作出的主要假设是，虽然热风的大小可能改变，但其方向不随高度而改变，因此大气的斜压性可以利用位势高度表面和它们之间的平均热风来模拟。 − − 【终稿】由热致模式作出的主要假设是，热风的大小可以改变，但方向不随高度变化，因此大气的斜压性可以用位势高度面和它们之间的平均热风来模拟。
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[[File:GFS 850 MB.PNG|right|250px|thumb|A 96-hour forecast of 850 [[millibar|mbar]] [[geopotential height]] and [[temperature]] from the [[Global Forecast System]]
[[File:GFS 850 MB.PNG|right|250px|thumb|一次850mbar处地势高度和温度的96小时预报]]
'''大气模式 atmospheric model'''是围绕控制大气运动的一整套原始的动力学方程所建立的数学模型。它可以通过[[湍流]]扩散、[[辐射]]、[[湿过程]]（云和降水）、[[热交换]]、土壤、植被、地表水、地形的动力学效应和对流等的参数化来补充这些方程。大多数大气模式是基于数值方法的，即将运动方程离散化。它们可以预测微尺度的现象，例如龙卷风、边界层的涡旋、流经建筑物上方的亚微尺度湍流，以及天气气流、全球气流。模式的水平区域全球性的，覆盖整个地球，也可以是区域性的（有限区域的），只覆盖部分地球。模式运行的不同类型包括热致的、正压的、流体静力学的和非流体静力学的。部分类型的模式对大气进行了一些假设，从而加长了时间步长并提高计算速度。
预报是使用大气物理和动力学方程计算得来的。这些方程是非线性的，无法获得准确解。因此只能使用数值方法获得近似解。不同的模式使用不同的求解方法。全球模式通常在水平维度上采用谱方法，而在垂直维度采用有限差分法；而区域模式通常在三个维度均使用有限差分法。对于特定的位置，模式的输出统计使用气候信息、[[数值天气预测]]结果以及当前[[地表天气观测]]数据来建立统计关系，以解释模式偏差和分辨率问题。
== 类型 ==
The main assumption made by the '''thermotropic''' model is that while the magnitude of the [[thermal wind]] may change, its direction does not change with respect to height, and thus the [[Baroclinity|baroclinicity]] in the atmosphere can be simulated using the {{convert|500|mb|inHg|adj=on |abbr=on |lk=on}} and {{convert|1000|mb|inHg|adj=on|abbr=on}} [[geopotential height]] surfaces and the average thermal wind between them.
【终稿】由热致模式作出的主要假设是，[[热风]]的大小可以改变，但方向不随高度变化，因此大气的斜压性可以用位势高度面和它们之间的平均热风来模拟。<ref>{{cite book|last= Gates|first=W. Lawrence|title=Results Of Numerical Forecasting With The Barotropic And Thermotropic Atmospheric Models|date=August 1955|publisher=Air Force Cambridge Research Laboratories|location=[[Hanscom Air Force Base]]|url=http://handle.dtic.mil/100.2/AD101943}}</ref><ref>{{cite journal |last=Thompson|first=P. D.|author2=W. Lawrence Gates|title=A Test of Numerical Prediction Methods Based on the Barotropic and Two-Parameter Baroclinic Models|journal=[[Journal of the Atmospheric Sciences|Journal of Meteorology]]| date=April 1956 |volume=13|issue=2|pages=127–141 |doi= 10.1175/1520-0469(1956)013<0127:ATONPM>2.0.CO;2 |issn=1520-0469|bibcode = 1956JAtS...13..127T |doi-access=free}}</ref>
'''Barotropic''' models assume the atmosphere is nearly [[barotropic]], which means that the direction and speed of the [[geostrophic wind]] are independent of height. In other words, no vertical [[wind shear]] of the geostrophic wind. It also implies that thickness contours (a proxy for temperature) are parallel to upper level height contours. In this type of atmosphere, [[high-pressure area|high]] and [[low-pressure area|low pressure area]]s are centers of warm and cold temperature anomalies. Warm-core highs (such as the [[subtropical ridge]] and Bermuda-Azores high) and [[cold-core low]]s have strengthening winds with height, with the reverse true for cold-core highs (shallow arctic highs) and warm-core lows (such as [[tropical cyclone]]s).<ref>{{cite book|title=Atmospheric Science: An Introductory Survey|author1=Wallace, John M. |author2=Peter V. Hobbs |name-list-style=amp |year=1977|isbn=978-0-12-732950-5|publisher=Academic Press, Inc.|pages=384–385}}</ref> A barotropic model tries to solve a simplified form of [[atmospheric dynamics]] based on the assumption that the atmosphere is in [[geostrophic balance]]; that is, that the [[Rossby number]] of the air in the atmosphere is small.<ref>{{cite book|last=Marshall|first=John|title=Atmosphere, ocean, and climate dynamics : an introductory text|year=2008|publisher=Elsevier Academic Press|location=Amsterdam|isbn=978-0-12-558691-7|author2=Plumb, R. Alan|pages=109–12|chapter=Balanced flow}}</ref> If the assumption is made that the atmosphere is [[divergence-free]], the [[curl (mathematics)|curl]] of the [[Euler equations (fluid dynamics)|Euler equations]] reduces into the [[barotropic vorticity equation]]. This latter equation can be solved over a single layer of the atmosphere. Since the atmosphere at a height of approximately {{convert|5.5|km|mi}} is mostly divergence-free, the barotropic model best approximates the state of the atmosphere at a [[geopotential height]] corresponding to that altitude, which corresponds to the atmosphere's {{convert|500|mb|inHg|abbr=on}} pressure surface.<ref name="Charney 1950" /><!-- also solved as a stream function, need to find a reference for that -->
'''Barotropic''' models assume the atmosphere is nearly [[barotropic]], which means that the direction and speed of the [[geostrophic wind]] are independent of height. In other words, no vertical [[wind shear]] of the geostrophic wind. It also implies that thickness contours (a proxy for temperature) are parallel to upper level height contours. In this type of atmosphere, [[high-pressure area|high]] and [[low-pressure area|low pressure area]]s are centers of warm and cold temperature anomalies. Warm-core highs (such as the [[subtropical ridge]] and Bermuda-Azores high) and [[cold-core low]]s have strengthening winds with height, with the reverse true for cold-core highs (shallow arctic highs) and warm-core lows (such as [[tropical cyclone]]s).<ref>{{cite book|title=Atmospheric Science: An Introductory Survey|author1=Wallace, John M. |author2=Peter V. Hobbs |name-list-style=amp |year=1977|isbn=978-0-12-732950-5|publisher=Academic Press, Inc.|pages=384–385}}</ref> A barotropic model tries to solve a simplified form of [[atmospheric dynamics]] based on the assumption that the atmosphere is in [[geostrophic balance]]; that is, that the [[Rossby number]] of the air in the atmosphere is small.<ref>{{cite book|last=Marshall|first=John|title=Atmosphere, ocean, and climate dynamics : an introductory text|year=2008|publisher=Elsevier Academic Press|location=Amsterdam|isbn=978-0-12-558691-7|author2=Plumb, R. Alan|pages=109–12|chapter=Balanced flow}}</ref> If the assumption is made that the atmosphere is [[divergence-free]], the [[curl (mathematics)|curl]] of the [[Euler equations (fluid dynamics)|Euler equations]] reduces into the [[barotropic vorticity equation]]. This latter equation can be solved over a single layer of the atmosphere. Since the atmosphere at a height of approximately {{convert|5.5|km|mi}} is mostly divergence-free, the barotropic model best approximates the state of the atmosphere at a [[geopotential height]] corresponding to that altitude, which corresponds to the atmosphere's {{convert|500|mb|inHg|abbr=on}} pressure surface.<ref name="Charney 1950" /><!-- also solved as a stream function, need to find a reference for that -->