From 0aad130001bbc71c9a362e9cfc6774bdf7b03375 Mon Sep 17 00:00:00 2001
From: XANTRONIX Industrial <xan@xantronix.com>
Date: Wed, 5 Mar 2025 00:34:23 -0500
Subject: [PATCH] Initial implementation of moist_lapse_rate()
---
lib/xmet/thermo.py | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/lib/xmet/thermo.py b/lib/xmet/thermo.py
index cfefcac..540ad00 100644
--- a/lib/xmet/thermo.py
+++ b/lib/xmet/thermo.py
@@ -1,6 +1,9 @@
LAPSE_RATE_DRY = 9.8 / 1000 # degrees C per km
LAPSE_RATE_MOIST = 4.0 / 1000
+def kelvin(c: float) -> float:
+ return 273.15 + c
+
def vapor_pressure(dewpoint: float) -> float:
"""
Return the pressure of vapor in a parcel of a given dewpoint.
@@ -56,3 +59,15 @@ def lapse(temp: float, delta: float, rate=LAPSE_RATE_DRY) -> float:
given increase in height (in meters).
"""
return temp - (rate * delta)
+
+def moist_lapse_rate(temp: float, dewpoint: float, pressure: float) -> float:
+ g = 9.8076
+ Hv = 2501000
+ r = mixing_ratio(dewpoint, pressure)
+ Rsd = 287
+ Rsw = 461.5
+ Cpd = 1003.5
+ T = kelvin(temp)
+
+ return g * (1 + (Hv * r) / (Rsd * T)) \
+ / (Cpd + ((Hv**2 * r) / (Rsw * T**2)))