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Hardcode lapse() to perform dry lapse

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This commit is contained in:
XANTRONIX 2025-03-04 22:57:01 -05:00
parent 706a1cf41e
commit 929e6b4351
2 changed files with 10 additions and 15 deletions
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13
lib/xmet/skew_t.py
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@ -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()

12
lib/xmet/thermo.py
View file

@ -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)