# atmoshwm

Implement horizontal wind model

## Syntax

``wind = atmoshwm(latitude,longitude,altitude)``
``wind = atmoshwm(latitude,longitude,altitude,Name,Value)``

## Description

example

````wind = atmoshwm(latitude,longitude,altitude)` implements the U.S. Naval Research Laboratory Horizontal Wind Model (HWM™) routine to calculate the meridional and zonal components of the wind for one or more sets of geographic coordinates: `latitude`, `longitude`, and `altitude`. ```

example

````wind = atmoshwm(latitude,longitude,altitude,Name,Value)` uses additional options specified by one or more `Name,Value` pair arguments.```

## Examples

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This example shows how to calculate the total horizontal wind model for a latitude of 45 degrees south, longitude of 85 degrees west, and altitude of 25,000 m above mean sea level (msl). The date is the 150th day of the year, at 11 am UTC, using an Ap index of 80. The horizontal model version is 14.

`w = atmoshwm(-45,-85,25000,'day',150,'seconds',39600,'apindex',80,'model','total', 'version', '14')`
```w = 1×2 3.2874 25.8735 ```

Calculate the quiet horizontal wind model for a latitude of 50 degrees north, two altitudes of 100,000 m and 150,000 m above msl, and a longitude of 20 degrees west. The date is midnight UTC of January 30. The default horizontal model version is 14.

`w = atmoshwm([50;50],[-20;-20],[100000;150000],'day',[30;30])`
```w = -42.9350 -40.3693 29.1106 0.6253```

Calculate the disturbed horizontal wind model for an altitude of 150,000 m above msl at latitude 70 degrees north, longitude 65 degrees west. The date is midnight UTC of June 15. The default horizontal model version is 14.

`dw = atmoshwm(70,-65,150000,'day',166,'model','disturbance')`
```dw = 1.7954 -1.7130```

## Input Arguments

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Geodetic latitudes, in degrees, specified as a scalar or M-by-1 array.

Example: -45

Data Types: `double`

Geodetic longitudes, in degrees, specified as a scalar or M-by-1 array.

Example: -85

Data Types: `double`

Geopotential heights, in meters, within the range of 0 to 500 km, specified as a scalar or M-by-1 array. Values are held outside the range 0 to 500 km.

Example: 25000

Data Types: `double`

### Name-Value Arguments

Specify optional pairs of arguments as `Name1=Value1,...,NameN=ValueN`, where `Name` is the argument name and `Value` is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose `Name` in quotes.

Example: `'apindex',80,'model','total'` specifies that the total horizontal wind model be calculated for an Ap index of 80.

Ap index for the Coordinated Universal Time (UTC) at which `atmoshwm` evaluates the model, specified as an M-by-1 array of zeroes, a scalar, or an M-by-1 array. M is the number of requested geographic coordinates. Select the index from the NOAA National Geophysical Data Center, which contains three-hour interval geomagnetic disturbance index values. If the Ap index value is greater than zero, the model evaluation accounts for magnetic effects.

Specify the Ap index as a value from 0 through 400. Specify an Ap index value for only the disturbance or total wind model type.

Data Types: `double`

Day of year in UTC. Specify the day as a value from 1 through 366 (for a leap year), specified as an M-by-1 array of zeroes, a scalar, or an M-by-1 array. Values are wrapped to within 1 to 366 days.

Data Types: `double`

Elapsed seconds since midnight for the selected day, in UTC, specified as specified as an M-by-1 array of zeroes, a scalar, or an M-by-1 array.

Specify the seconds as a value from 0 through 86,400. Values are wrapped to within 0 to 86400 seconds.

Data Types: `double`

Horizontal wind model type for which to calculate the wind components. This setting applies to all the sets of geophysical data in M.

• `'quiet'`

Calculates the horizontal wind model without the magnetic disturbances. Quiet model types do not account for Ap index values. For this model type, do not specify an Ap index value.

• `'disturbance'`

Calculates the effect of only magnetic disturbances in the wind. For this model type, specify Ap index values greater than or equal to zero.

• `'total'`

Calculates the combined effect of the quiet and magnetic disturbances. for this model type, specify Ap index values greater than or equal to zero.

Data Types: `char` | `string`

Function behavior when inputs are out of range, specified as one of these values. This type applies to all the sets of geophysical data in M.

ValueDescription
`'None'`No action.
`'Warning'`Warning in the MATLAB® Command Window, model simulation continues.
`'Error'`MATLAB returns an exception, model simulation stops.

Data Types: `char` | `string`

Implements specified horizontal wind model type.

• `'14'`

Horizontal Wind Model 14.

• `'07'`

Horizontal Wind Model 07.

Data Types: `char` | `string`

## Output Arguments

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Meridional and zonal wind components of the horizontal wind model, returned as an M-by-2 array, in m/s.

## Version History

Introduced in R2016b

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