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Added volume.

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Simon Brooke 2026-08-12 11:52:38 +01:00
parent 115e3d65b5
commit ce32cd285e
6 changed files with 90 additions and 20 deletions
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12
README.md
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@ -13,10 +13,8 @@ I'm using this code to explore human survivability given global warming. The fol
3. [Extreme Heat](https://www.journeyman.cc/blog/posts-output/2026-07-31-Extreme-Heat/)
4. [Analysis of 2026 heatwaves UK](https://www.journeyman.cc/blog/posts-output/2026-08-04-Analysis-of-2026-heatwaves-UK/)
## Status
Alpha-quality code. It more or less works but it isn't at all polished.
## General architecture
@ -26,16 +24,18 @@ Alpha-quality code. It more or less works but it isn't at all polished.
The 'packet', in the terminology of this library, is a map which has bindings
for some of the following keywords:
1. `:absolute-humidity`
1. `:absolute-humidity` *grammes per metre<sup>3</sup>.*
2. `:actual-vapour-pressure` *not yet implemented*
1. `:dew-point` *not yet implemented*
2. `:pressure-pascals`
3. `:pressure-millibars`
4. `:saturation-vapour-pressure`
5. `:relative-humidity`
6. `:temperature` *assumed to be celsius*
4. `:saturation-vapour-pressure` *Pascals*
5. `:relative-humidity` *percentage, 0...100.*
6. `:temperature` *assumed to be &deg; Celsius*
7. `:temperature-celsius`
8. `:temperature-kelvin`
9. `:volume` *in metres<sup>3</sup>, relative to 1 at standard temperature and pressure.*
10. `:wet-bulb-temperature` *in &deg; Celsius.*
These keywords represent variables in the pressure equations, and they are all
to a degree inter-related; so if you have (or can assume) some of them, you can

4
src/humidity/actual_vp.clj
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@ -1,4 +1,6 @@
(ns humidity.actual-vp)
(ns ^{:author "simon"
:authority "https://www.weather.gov/media/epz/wxcalc/vaporPressure.pdf"
:doc "Compute actual vapour pressure."} humidity.actual-vp)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

8
src/humidity/core.clj
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@ -6,6 +6,7 @@
[humidity.relative :refer [rel-humidity]]
[humidity.saturation-vp :refer [saturation-vp]]
[humidity.utils :refer [?assoc]]
[humidity.volume :refer [volume-fn]]
[humidity.wet-bulb :as wb]))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@ -33,7 +34,8 @@
"Resolve humidity equations given the data in this packet."
[& {:keys [absolute-humidity pressure-pascals pressure-millibars
relative-humidity saturation-vapour-pressure temperature
temperature-celsius temperature-kelvin wet-bulb-temperature] :as packet}]
temperature-celsius temperature-kelvin volume
wet-bulb-temperature] :as packet}]
(println packet)
(if temperature (resolve-humidity
(assoc (dissoc packet :temperature)
@ -46,7 +48,8 @@
(* pressure-millibars 100) Pa))
:pressure-millibars (when-not pressure-millibars
(if pressure-pascals
(/ pressure-pascals 100) (/ Pa 100)))
(float (/ pressure-pascals 100))
(float (/ Pa 100))))
:relative-humidity (when-not relative-humidity
(rel-humidity packet))
:saturation-vapour-pressure (when-not saturation-vapour-pressure
@ -59,6 +62,7 @@
(and temperature-celsius
(not temperature-kelvin))
(+ temperature-celsius celsius-offset))
:volume (when-not volume (volume-fn packet))
:wet-bulb-temperature (when-not wet-bulb-temperature
(wb/wet-bulb-temperature packet)))))

22
src/humidity/volume.clj Normal file
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@ -0,0 +1,22 @@
(ns ^{:author "simon"
:authority "https://en.wikipedia.org/wiki/Gas_laws"
:doc "In computing the relative humidity of air after it has warmed, I need
to account for the change in volume. By Charles' Law, given stable
pressure, volume is proportinal to absolute temperature (i.e. V=Tk, where K
is a constant). However, the sources I have read do not give that constant,
for air. But seeing what I'm interested in is that amount of air which is
contained in a cubic metre at standard temperature and pressure, then *I
think* I can just take (temperature-kelvin/celsius-offset) as the temperature
component.
Gay-Lussac's law says pretty much the same for pressure, so again *I think* I
can take (pressure-pascals/Pa) as the pressure component."} humidity.volume
(:require [humidity.constants :refer [celsius-offset Pa]]))
(defn volume-fn
"Compute the volume, in m<sup>3</sup> of a quantity of air which would be
1m<sup>3</sup> at standard temperature and pressure, given temperature in
&deg; Kelvin and pressure in Pascals."
[& {:keys [temperature-kelvin pressure-pascals]}]
(when (and temperature-kelvin pressure-pascals)
(* (/ temperature-kelvin celsius-offset) (/ pressure-pascals Pa))))

23
test/humidity/core_test.clj
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@ -1,7 +1,7 @@
(ns humidity.core-test
(:require
[clojure.test :refer [deftest is testing]]
[humidity.core :refer [resolution]]))
[clojure.test :refer [deftest is testing]]
[humidity.core :refer [resolution]]))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;
@ -27,12 +27,13 @@
(deftest resolution-test
(testing "resolution")
(let [expected {:relative-humidity 100,
:temperature-celsius 35,
:pressure-pascals 101325,
:pressure-millibars 4053/4,
:saturation-vapour-pressure 5622.488734516426,
:temperature-kelvin 308.15,
:absolute-humidity 3953.618101887827}
packet {:relative-humidity 100 :temperature-celsius 35}
actual (resolution packet)]
(is (= actual expected))))
:temperature-celsius 35,
:pressure-pascals 101325,
:pressure-millibars 1013.25,
:saturation-vapour-pressure 5622.488734516426,
:temperature-kelvin 308.15,
:absolute-humidity 3953.618101887827,
:volume 1.1281347245103424}
packet {:relative-humidity 100 :temperature-celsius 35}
actual (resolution packet)]
(is (= actual expected))))

41
test/humidity/volume_test.clj Normal file
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@ -0,0 +1,41 @@
(ns humidity.volume-test
(:require [clojure.test :refer [deftest is testing]]
[humidity.constants :refer [celsius-offset Pa]]
[humidity.volume :refer [volume-fn]]))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;
;;; Copyright (C) 2026 Simon Brooke
;;;
;;; This program is free software; you can redistribute it and/or
;;; modify it under the terms of the GNU General Public License
;;; as published by the Free Software Foundation; either version 2
;;; of the License, or (at your option) any later version.
;;;
;;; This program is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program; if not, write to the Free Software
;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
;;; USA.
;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(deftest relative-humidity-test
(testing "definitional"
(let [min-expected 0.99
max-expected 1.01
actual (volume-fn :pressure-pascals Pa :temperature-kelvin celsius-offset)]
(is (< min-expected actual max-expected))))
(testing "Example from metoffice 26th May data."
(let [min-expected 1.14
max-expected 1.15
actual (volume-fn :pressure-pascals 102600 :temperature-kelvin (+ 35.1 celsius-offset))]
(is (< min-expected actual max-expected)))
(testing "Missing data returns nil"
(let [expected nil
actual (volume-fn :pressure-pascals 102600 :temperature-celsius 35.1)]
(is (= actual expected))))))