feat(plotly): implement skewt-logp-atmospheric (#7563)

## Implementation: `skewt-logp-atmospheric` - python/plotly

Implements the **python/plotly** version of `skewt-logp-atmospheric`.

**File:**
`plots/skewt-logp-atmospheric/implementations/python/plotly.py`

**Parent Issue:** #3802

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/anyplot/actions/runs/26196176895)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Markus Neusinger <2921697+MarkusNeusinger@users.noreply.github.com>

Author: github-actions[bot]

plots/skewt-logp-atmospheric/implementations/python/plotly.py

@@ -0,0 +1,305 @@
+""" anyplot.ai
+skewt-logp-atmospheric: Skew-T Log-P Atmospheric Diagram
+Library: plotly 6.7.0 | Python 3.13.13
+Quality: 87/100 | Updated: 2026-05-21
+"""
+
+import os
+
+import numpy as np
+import plotly.graph_objects as go
+
+
+# Theme tokens
+THEME = os.getenv("ANYPLOT_THEME", "light")
+PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
+ELEVATED_BG = "#FFFDF6" if THEME == "light" else "#242420"
+INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
+INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
+GRID = "rgba(26,26,23,0.10)" if THEME == "light" else "rgba(240,239,232,0.10)"
+
+BRAND = "#009E73"  # Okabe-Ito pos 1 — temperature profile
+C_DEWPT = "#D55E00"  # Okabe-Ito pos 2 — dewpoint profile
+
+# Reference line colors: subtle, theme-adaptive
+C_ISO = "rgba(80,80,80,0.22)" if THEME == "light" else "rgba(180,180,180,0.28)"
+C_DRY = "rgba(213,94,0,0.22)" if THEME == "light" else "rgba(213,94,0,0.38)"
+C_MOIST = "rgba(0,114,178,0.22)" if THEME == "light" else "rgba(0,114,178,0.38)"
+C_MIX = "rgba(0,158,115,0.22)" if THEME == "light" else "rgba(0,158,115,0.38)"
+
+# Skew-T transform: °C shift per log10 decade of pressure from 1000 hPa
+SKEW = 30.0
+
+
+def skew_x(T, P):
+    return T + SKEW * np.log10(1000.0 / P)
+
+
+# Atmospheric constants
+Rd = 287.05  # J/(kg·K)
+Cp = 1004.0  # J/(kg·K)
+Lv = 2.5e6  # J/kg
+Rv = 461.5  # J/(kg·K)
+Rd_Cp = Rd / Cp  # ≈ 0.2854
+
+
+def moist_adiabat(T0_C, P_start=1000.0, P_end=100.0, n=150):
+    """Integrate moist adiabat from P_start to P_end starting at T0_C."""
+    P = np.linspace(P_start, P_end, n)
+    T = np.zeros(n)
+    T[0] = T0_C
+    for i in range(1, n):
+        T_K = T[i - 1] + 273.15
+        es = 6.112 * np.exp(17.67 * T[i - 1] / (T[i - 1] + 243.5))
+        rs = 0.622 * es / max(P[i - 1] - es, 0.001)
+        num = Rd * T_K + Lv * rs
+        den = P[i - 1] * (Cp + Lv**2 * rs / (Rv * T_K**2))
+        T[i] = T[i - 1] + (num / den) * (P[i] - P[i - 1])
+    return P, T
+
+
+# Data: synthetic warm-moist sounding, US Great Plains summer
+pressure = np.array(
+    [1000, 975, 950, 925, 900, 850, 800, 750, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 200, 150, 100]
+)
+temperature = np.array(
+    [
+        32.0,
+        29.0,
+        26.0,
+        23.0,
+        20.5,
+        16.0,
+        11.0,
+        6.0,
+        2.0,
+        -3.5,
+        -8.5,
+        -15.0,
+        -21.5,
+        -29.0,
+        -37.5,
+        -48.0,
+        -56.0,
+        -62.0,
+        -64.5,
+        -68.0,
+        -73.0,
+    ]
+)
+dewpoint = np.array(
+    [
+        24.0,
+        22.0,
+        20.5,
+        18.0,
+        14.5,
+        9.0,
+        2.5,
+        -5.0,
+        -13.0,
+        -23.0,
+        -33.0,
+        -43.0,
+        -53.0,
+        -62.0,
+        -70.0,
+        -76.0,
+        -81.0,
+        -84.0,
+        -86.0,
+        -88.0,
+        -90.0,
+    ]
+)
+
+# Lifting Condensation Level (LCL) — surface parcel T=32°C, Td=24°C
+# At DALR=9.8°C/km and dewpoint cooling ~1.8°C/km, they meet at z≈1 km ≈ 900 hPa
+LCL_P = 900.0
+LCL_T = 22.0
+
+# Pressure array for reference lines
+P_ref = np.linspace(100.0, 1000.0, 200)
+
+fig = go.Figure()
+
+# --- Reference lines (background layer) ---
+
+# Isotherms (constant temperature, appear as diagonal lines when skewed)
+for idx, T_iso in enumerate(range(-50, 55, 10)):
+    fig.add_trace(
+        go.Scatter(
+            x=skew_x(T_iso * np.ones_like(P_ref), P_ref),
+            y=P_ref,
+            mode="lines",
+            line=dict(color=C_ISO, width=0.8),
+            legendgroup="iso",
+            showlegend=(idx == 0),
+            name="Isotherms",
+            hoverinfo="skip",
+        )
+    )
+
+# Dry adiabats (constant potential temperature θ)
+for idx, theta in enumerate(range(290, 430, 10)):
+    T_dry = theta * (P_ref / 1000.0) ** Rd_Cp - 273.15
+    mask = (T_dry > -55) & (T_dry < 55)
+    x_d = np.where(mask, skew_x(T_dry, P_ref), np.nan)
+    if not np.all(np.isnan(x_d)):
+        fig.add_trace(
+            go.Scatter(
+                x=x_d,
+                y=P_ref,
+                mode="lines",
+                line=dict(color=C_DRY, width=0.8),
+                legendgroup="dry",
+                showlegend=(idx == 0),
+                name="Dry Adiabats",
+                hoverinfo="skip",
+            )
+        )
+
+# Moist adiabats (saturated adiabatic lapse rate, numerically integrated)
+for idx, T0 in enumerate(range(-10, 45, 10)):
+    P_m, T_m = moist_adiabat(T0)
+    fig.add_trace(
+        go.Scatter(
+            x=skew_x(T_m, P_m),
+            y=P_m,
+            mode="lines",
+            line=dict(color=C_MOIST, width=0.8, dash="dot"),
+            legendgroup="moist",
+            showlegend=(idx == 0),
+            name="Moist Adiabats",
+            hoverinfo="skip",
+        )
+    )
+
+# Mixing ratio lines (constant water vapor mixing ratio)
+for idx, r_gkg in enumerate([1, 2, 4, 8, 16]):
+    r = r_gkg / 1000.0
+    es = r * P_ref / (r + 0.622)
+    with np.errstate(divide="ignore", invalid="ignore"):
+        log_r = np.log(es / 6.112)
+        T_mix = 243.5 * log_r / (17.67 - log_r)
+    mask = np.isfinite(T_mix) & (T_mix > -50) & (T_mix < 35)
+    x_mix = np.where(mask, skew_x(T_mix, P_ref), np.nan)
+    fig.add_trace(
+        go.Scatter(
+            x=x_mix,
+            y=P_ref,
+            mode="lines",
+            line=dict(color=C_MIX, width=0.8, dash="dash"),
+            legendgroup="mix",
+            showlegend=(idx == 0),
+            name="Mixing Ratio",
+            hoverinfo="skip",
+        )
+    )
+
+# --- Atmospheric sounding profiles ---
+
+# Dewpoint (dashed blue)
+fig.add_trace(
+    go.Scatter(
+        x=skew_x(dewpoint, pressure),
+        y=pressure,
+        mode="lines+markers",
+        name="Dewpoint",
+        line=dict(color=C_DEWPT, width=2.5, dash="dash"),
+        marker=dict(color=C_DEWPT, size=7),
+        customdata=np.column_stack([dewpoint, pressure]),
+        hovertemplate="%{customdata[1]:.0f} hPa | Td: %{customdata[0]:.1f}°C<extra></extra>",
+    )
+)
+
+# Temperature (solid green, Okabe-Ito pos 1)
+fig.add_trace(
+    go.Scatter(
+        x=skew_x(temperature, pressure),
+        y=pressure,
+        mode="lines+markers",
+        name="Temperature",
+        line=dict(color=BRAND, width=3.0),
+        marker=dict(color=BRAND, size=7),
+        customdata=np.column_stack([temperature, pressure]),
+        hovertemplate="%{customdata[1]:.0f} hPa | T: %{customdata[0]:.1f}°C<extra></extra>",
+    )
+)
+
+# --- Layout ---
+
+# x-axis ticks: at P=1000 hPa, skew=0 so tick position = actual temperature
+tick_T = list(range(-50, 55, 10))
+
+fig.update_layout(
+    autosize=False,
+    paper_bgcolor=PAGE_BG,
+    plot_bgcolor=PAGE_BG,
+    title=dict(
+        text="skewt-logp-atmospheric · python · plotly · anyplot.ai",
+        font=dict(size=16, color=INK),
+        x=0.5,
+        xanchor="center",
+    ),
+    xaxis=dict(
+        title=dict(text="Temperature (°C)", font=dict(size=12, color=INK)),
+        tickfont=dict(size=10, color=INK_SOFT),
+        linecolor=INK_SOFT,
+        zeroline=False,
+        showgrid=False,
+        tickmode="array",
+        tickvals=[float(t) for t in tick_T],
+        ticktext=[f"{t}°" for t in tick_T],
+        range=[-50.0, 75.0],
+    ),
+    yaxis=dict(
+        title=dict(text="Pressure (hPa)", font=dict(size=12, color=INK)),
+        tickfont=dict(size=10, color=INK_SOFT),
+        gridcolor=GRID,
+        linecolor=INK_SOFT,
+        zeroline=False,
+        type="log",
+        range=[3.0, 2.0],  # log10(1000)=3 at bottom → 1000 hPa, log10(100)=2 at top
+        tickmode="array",
+        tickvals=[100, 150, 200, 250, 300, 400, 500, 600, 700, 850, 925, 1000],
+        ticktext=["100", "150", "200", "250", "300", "400", "500", "600", "700", "850", "925", "1000"],
+        showgrid=True,
+    ),
+    legend=dict(
+        bgcolor=ELEVATED_BG,
+        bordercolor=INK_SOFT,
+        borderwidth=1,
+        font=dict(size=10, color=INK_SOFT),
+        x=0.02,
+        y=0.98,
+        xanchor="left",
+        yanchor="top",
+    ),
+    margin=dict(l=80, r=40, t=80, b=60),
+    annotations=[
+        dict(
+            x=skew_x(LCL_T, LCL_P),
+            y=LCL_P,
+            xref="x",
+            yref="y",
+            text="LCL ≈ 900 hPa",
+            showarrow=True,
+            arrowhead=2,
+            arrowcolor=INK_SOFT,
+            arrowwidth=1.5,
+            ax=55,
+            ay=-30,
+            font=dict(size=10, color=INK),
+            bgcolor=ELEVATED_BG,
+            bordercolor=INK_SOFT,
+            borderwidth=1,
+            borderpad=4,
+            opacity=0.9,
+        )
+    ],
+)
+
+# Save
+fig.write_image(f"plot-{THEME}.png", width=800, height=450, scale=4)
+fig.write_html(f"plot-{THEME}.html", include_plotlyjs="cdn")