From 929e6b4351638905500c9635dfd309bd42eb99c4 Mon Sep 17 00:00:00 2001
From: XANTRONIX Industrial <xan@xantronix.com>
Date: Tue, 4 Mar 2025 22:57:01 -0500
Subject: [PATCH] Hardcode lapse() to perform dry lapse
---
lib/xmet/skew_t.py | 13 ++++---------
lib/xmet/thermo.py | 12 ++++++------
2 files changed, 10 insertions(+), 15 deletions(-)
diff --git a/lib/xmet/skew_t.py b/lib/xmet/skew_t.py
index 5e05c9e..d41f41a 100644
--- a/lib/xmet/skew_t.py
+++ b/lib/xmet/skew_t.py
@@ -4,8 +4,7 @@ import cairo
from typing import Callable
from xmet.sounding import Sounding
-from xmet.thermo import pressure_height, lapse, \
- LAPSE_RATE_MOIST, LAPSE_RATE_DRY
+from xmet.thermo import pressure_height, lapse
PRESSURE_MAX = 1050 # millibar
PRESSURE_MIN = 100
@@ -22,9 +21,6 @@ TEMP_CENTER = 0 # degrees C
TEMP_STEP = 5
TEMP_STEP_COUNT = math.ceil(TEMP_RANGE / TEMP_STEP)
-LAPSE_RATE_DRY = 9.8 / 1000 # degrees C per 1000m
-LAPSE_RATE_MOIST = 4.0 / 1000
-
def clamp(value, lowest, highest):
if value < lowest:
return lowest
@@ -108,8 +104,7 @@ class SkewTGraph():
x: float,
y: float,
start_temp: float,
- start_pressure: float,
- lapse_rate: float):
+ start_pressure: float):
start_height = pressure_height(start_pressure)
sx_last = None
sy_last = None
@@ -118,7 +113,7 @@ class SkewTGraph():
while pressure >= PRESSURE_MIN:
height = pressure_height(pressure)
- temp_cur = lapse(start_temp, lapse_rate, height - start_height)
+ temp_cur = lapse(start_temp, height - start_height)
sx, sy = self.sample_to_screen(temp_cur, pressure)
@@ -140,7 +135,7 @@ class SkewTGraph():
cr.set_source_rgba(1.0, 0.2, 0, 0.2)
for temp in range(-140, 140, 10):
- self.draw_adiabat(cr, x, y, temp, PRESSURE_MAX, LAPSE_RATE_DRY)
+ self.draw_adiabat(cr, x, y, temp, PRESSURE_MAX)
cr.restore()
diff --git a/lib/xmet/thermo.py b/lib/xmet/thermo.py
index 23acabb..f8c2c62 100644
--- a/lib/xmet/thermo.py
+++ b/lib/xmet/thermo.py
@@ -1,5 +1,5 @@
-LAPSE_RATE_MOIST = 4.0 # degrees C per km
-LAPSE_RATE_DRY = 9.8
+LAPSE_RATE_DRY = 9.8 / 1000 # degrees C per km
+LAPSE_RATE_MOIST = 4.0 / 1000
def vapor_pressure(dewpoint: float) -> float:
"""
@@ -50,9 +50,9 @@ def pressure_height(pressure: float) -> float:
"""
return (1 - (pressure / 1013.25) ** 0.190284) * 145366.45 * 0.3048
-def lapse(temp: float, rate: float, delta: float) -> float:
+def lapse(temp: float, delta: float) -> float:
"""
- Return the temperature of a parcel cooled at either the dry or moist lapse
- rate for a given increase in height (in meters).
+ Return the temperature of a parcel cooled at the dry lapse rate for a
+ given increase in height (in meters).
"""
- return temp - (rate * delta)
+ return temp - (LAPSE_RATE_DRY * delta)