**uv2dvG_Wrap**calculates the divergence via spherical harmonics and maintain meta data

**dv2uvg**calculates the divergent wind components via spherical harmonics**uv2vrG_Wrap**computes the vorticity via spherical harmonics and maintain meta data**vr2uvg**computes the rotational wind components via spherical harmonics**uv2dv_cfd**computes the divergence via centerd finite differences**uv2vr_cfd**computes the vorticity via centerd finite differences

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# NCL: Divergent and Rotational Wind Components

**uv2dvG**) and centered finite differences

**uv2dv_cfd**. These functions require the grids to be rectilinear. All spherical harmonic function require global grids. The centered finite difference function(s) can be used on limited area grids and allow missing values (_FillValue).

**local vorticity tendency**using spherical harmonics. Spherical harmonics are used to produce highly accurate gradients. Based upon scale analysis, the synoptic scale local vorticity tendency can be calculated using the two terms shown in the rightmost figure. The reference in the

**wind_6.ncl**script provides additional information. The original code design was to plot an EOF ONLY if it was significant (see:

**). However, for this example, those code lines are commented to illustrate what the EOF plots would look like. Also, only one EOF plot is presented.**

**eofunc_north****VIMFC**). VIMFC has a high correlation with frontal and convective activity. Positive values indicate net precipitation.

The following equation is implemented within
mfc_div_1.ncl

This example uses **uv2dvF_Wrap** [**uv2dvF**]
because the grid is a global fixed grid. For global gaussian,
**uv2dvG_Wrap** [**uv2dvG**] should be used.
For a regional grid **uv2dv_cfd** should be used.

**MFC**equation can be partitioned as follows:

TheMFC => Moisture Flux ConvergenceMFC_advect= -(u*(dq/dx)+v*(dq/dy)) ; advect moisture termMFC_conv= -q*((du/dx)+(dv/dy) ) ; [con/div]ergence termMFC=MFC_advect+MFC_conv

**MFC_advect**can be derived using

**advect_variable**for global rectilinear grids or

**advect_variable_cfd**for regional rectilinear grids

The **MFC_conv** can be derived using: **uv2dvF_Wrap** or
**uv2dvG_Wrap** for global rectilinear grids
or **uv2dv_cfd** for regional rectilinear grids.
Then, multiply the derived quantity by specific humidity [q].

This example uses daily mean data from NOAA/OAR/ESRL PSD, Boulder, Colorado, USA. Specifically,
**NCEP_Reanalysis 2**
daily mean data spanning 3-9 April 1993.

This is a **test script**. It is not fully tested. The returned quantities are:

q1 = (dT/dt) - [omega*static_stability - V.grad(T)] ; K/day q2 = -[(dH/dt) + V.grad(H) +omega*(dH/dp)] ; g/(kg-Pa) and Q1 = Cp*q1 ; apparent Heat Source Q2 = Lc*q2 ; apparent Moisture Sink