From 706a1cf41e4a2cc3f855a6ff301c8084ce039184 Mon Sep 17 00:00:00 2001
From: XANTRONIX Industrial <xan@xantronix.com>
Date: Tue, 4 Mar 2025 21:52:00 -0500
Subject: [PATCH] Implement rendering of dry adiabats
---
lib/xmet/skew_t.py | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
diff --git a/lib/xmet/skew_t.py b/lib/xmet/skew_t.py
index c45adf0..5e05c9e 100644
--- a/lib/xmet/skew_t.py
+++ b/lib/xmet/skew_t.py
@@ -4,6 +4,8 @@ import cairo
from typing import Callable
from xmet.sounding import Sounding
+from xmet.thermo import pressure_height, lapse, \
+ LAPSE_RATE_MOIST, LAPSE_RATE_DRY
PRESSURE_MAX = 1050 # millibar
PRESSURE_MIN = 100
@@ -101,6 +103,47 @@ class SkewTGraph():
cr.restore()
+ def draw_adiabat(self,
+ cr: cairo.Context,
+ x: float,
+ y: float,
+ start_temp: float,
+ start_pressure: float,
+ lapse_rate: float):
+ start_height = pressure_height(start_pressure)
+ sx_last = None
+ sy_last = None
+
+ pressure = start_pressure
+
+ while pressure >= PRESSURE_MIN:
+ height = pressure_height(pressure)
+ temp_cur = lapse(start_temp, lapse_rate, height - start_height)
+
+ sx, sy = self.sample_to_screen(temp_cur, pressure)
+
+ if sx_last is not None:
+ cr.move_to(x + sx, y + sy)
+ cr.line_to(x + sx_last, y + sy_last)
+ cr.stroke()
+
+ sx_last = sx
+ sy_last = sy
+
+ pressure -= 10.0
+
+ def draw_adiabats(self,
+ cr: cairo.Context,
+ x: float,
+ y: float):
+ cr.save()
+ 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)
+
+ cr.restore()
+
def draw_sounding(self,
cr: cairo.Context,
x: float,
@@ -149,6 +192,7 @@ class SkewTGraph():
self.draw_isotherms(cr, x, y)
self.draw_isobars(cr, x, y)
+ self.draw_adiabats(cr, x, y)
cr.set_source_rgb(1, 0, 0)
self.draw_sounding(cr, x, y, sounding, lambda s: s.temp)