Struct measurements::humidity::Humidity

pub struct Humidity { /* private fields */ }

The Humidity struct can be used to deal with relative humidity in air in a common way. Relative humidity is an important metric used in weather forecasts.

Relative humidity (as a ratio and percentage) and conversions between relative humidity and dewpoint are supported. It also provides calculations giving vapour pressure and absolute humidity.

Relative humidity gives the ratio of how much moisture the air is holding to how much moisture it could hold at a given temperature. Here we use the technical definition of humidity as ratio of the actual water vapor pressure to the equilibrium vapor pressure (often called the “saturation” vapor pressure).

For dewpoint calculations, we use the algorithm commonly known as the Magnus formula, with coefficients derived by Alduchov and Eskridge (1996), which gives resonable accuracy (vapour pressure error < 0.2%) for temperatures between 0 deg C, and 50 deg C.

Example:

    //  calculate the dewpoint from the relative humidity
    use measurements::{Humidity,Temperature};

    let humidity = Humidity::from_percent(85.0);
    let temp = Temperature::from_celsius(18.0);
    let dewpoint = humidity.as_dewpoint(temp);
    println!("At {} humidity, air at {} has a dewpoint of {}", humidity, temp, dewpoint);

Implementations

impl Humidity

pub fn from_percent(percent: f64) -> Self

Create a new Humidity from a floating point value percentage (i.e. 0.0% to 100.0%)

pub fn from_ratio(relative_humidity: f64) -> Self

Create a new Humidity from a floating point value ratio (i.e. 0.0 to 1.0)

pub fn as_ratio(&self) -> f64

Convert this relative humidity to a value expressed as a ratio (i.e. 0.0 to 1.0)

pub fn as_percent(&self) -> f64

Convert this relative humidty to a value expressed as a percentage (i.e. 0.0% to 100.0%)

pub fn as_dewpoint(&self, temp: Temperature) -> Temperature

Calculates Dewpoint from humidity and air temperature using the Magnus-Tetens approximation, with coefficients derived by Alduchov and Eskridge (1996). The formulas assume

pub fn as_vapor_pressure(&self, temp: Temperature) -> Pressure

Calculates the actual vapour pressure in the air, based on the air temperature and humidity at standard atmospheric pressure (1013.25 mb), using the Buck formula (accurate to +/- 0.02% between 0 deg C and 50 deg C)

pub fn as_absolute_humidity(&self, temp: Temperature) -> Density

Calculates the absolute humidity (i.e. the density of water vapor in the air (kg/m3)), using the Ideal Gas Law equation.

pub fn from_dewpoint(dewpoint: Temperature, temp: Temperature) -> Humidity

Calculates humidity from dewpoint and air temperature using the Magnus-Tetens Approximation, with coefficients derived by Alduchov and Eskridge (1996). The formulas assume

Trait Implementations

impl Clone for Humidity

fn clone(&self) -> Humidity

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Humidity

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Humidity

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Measurement for Humidity

fn as_base_units(&self) -> f64

Get this quantity in the base units

fn from_base_units(relative_humidity: f64) -> Self

Create a new quantity from the base units

fn get_base_units_name(&self) -> &'static str

Return the base unit for this type, as a string. For example “kilograms”

fn get_appropriate_units(&self) -> (&'static str, f64)

Returns a string containing the most appropriate units for this quantity, and a floating point value representing this quantity in those units. Useful when, for example, a length might be in millimeters if it is very small, or kilometers when it is very large.

fn pick_appropriate_units(
    &self,
    list: &[(&'static str, f64)]
) -> (&'static str, f64)

Given a list of units and their scale relative to the base unit, select the most appropriate one.

impl PartialEq<Humidity> for Humidity

fn eq(&self, other: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl PartialOrd<Humidity> for Humidity

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for Humidity

impl Eq for Humidity