Question

您想知道在Metpy中如何进行散度计算吗？我们知道，在Grads中，发散度的计算是通过有限差分法进行的，如下所示：

data_frame_Rate_Table<- data.frame(Policy_Class = c("red", "white","blue"),
    Rate=c(3,9,19),"Factor_1"= 1:3,Factor_2=7:9, stringsAsFactors = FALSE)

data_frame_Policyholders <- data.frame(Policy_number . = 1:10,
  Policy_Class=rep(c("red","red","white","blue","blue"),2),
  Risk=c(rep("High",5),rep("Low",5)), 
  Lapse=rep(c("Y","N"),5), stringsAsFactors = FALSE)

但是，在Metpy中，我没有找到如何进行这种差异计算的任何详细信息（就像在Grads中一样）。

Answer 1

MetPy中的散度是通过使用MetPy中的first_derivative函数来计算的，该函数基于中心（除了边缘点之外）将dudx和dvdy相加。如果您将metpy.calc.divergence或metpy.calc.first_derivative传递给带有坐标/投影信息的Xarray.Dataset，它将计算出变化的网格上的散度。否则，您需要提供网格间距。有关散度函数和坐标数组处理的更多信息，请参见https://unidata.github.io/MetPy/latest/_modules/metpy/calc/kinematics.html#divergence和https://unidata.github.io/MetPy/latest/api/generated/metpy.calc.first_derivative.html#metpy.calc.first_derivative。

Answer 2

MetPy的散度计算（metpy.calc.divergence）内部使用三点差分first_derivative函数以笛卡尔形式计算散度，

$\nabla \cdot V = \frac{\partial u}{\partial x} + \frac{\partial v}{\partial y}$

As referenced in the MetPy documentation，它根据Bowen and Smith（2005）的公式显式处理不规则间距。但是，当前的MetPy计算中不包括GrADS包含的最终坐标校正项/C:/Users/%d0%90%d0%bb%d1%8c%d1%84%d0%b0/eclipse-workspace/Piskostroi/bin/application/Voshel.fxml at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601) at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2571) at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441) at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2409) at application.ControllerMine.lambda$0(ControllerMine.java:62) at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191) at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74) at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49) at javafx.event.Event.fireEvent(Event.java:198) at javafx.scene.Node.fireEvent(Node.java:8411) at javafx.scene.control.Button.fire(Button.java:185) at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182) at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96) at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89) at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218) at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238) at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191) at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56) at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114) at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74) at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54) at javafx.event.Event.fireEvent(Event.java:198) at javafx.scene.Scene$MouseHandler.process(Scene.java:3757) at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485) at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762) at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494) at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394) at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295) at java.security.AccessController.doPrivileged(Native Method) at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$358(GlassViewEventHandler.java:432) at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389) at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431) at com.sun.glass.ui.View.handleMouseEvent(View.java:555) at com.sun.glass.ui.View.notifyMouse(View.java:937) at com.sun.glass.ui.win.WinApplication._runLoop(Native Method) at com.sun.glass.ui.win.WinApplication.lambda$null$152(WinApplication.java:177) at java.lang.Thread.run(Unknown Source) Caused by: java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at sun.reflect.misc.Trampoline.invoke(Unknown Source) at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at sun.reflect.misc.MethodUtil.invoke(Unknown Source) at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2566) ... 50 more Caused by: java.lang.NullPointerException at application.ControllerVxod.initialize(ControllerVxod.java:21) ... 60 more（这是an open issue on GitHub的一部分）。

如何计算Metpy中的散度？

2 个答案: