earths 0.0.4

High-fidelity Earth simulation engine — orbit, atmosphere, geology, hydrology, biosphere, terrain, lighting, rendering, satellites, and temporal systems with full scientific coupling
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173

#[derive(Debug, Clone, Copy, PartialEq)]
pub enum CloudType {
    Cumulus,
    Stratus,
    Cirrus,
    Cumulonimbus,
    Altocumulus,
    Stratocumulus,
    Nimbostratus,
}

pub struct CloudLayer {
    pub cloud_type: CloudType,
    pub base_altitude_m: f64,
    pub thickness_m: f64,
    pub coverage: f64,
    pub density: f64,
    pub wind_speed_m_s: f64,
    pub wind_direction: [f64; 2],
    pub droplet_radius_um: f64,
    pub ice_fraction: f64,
}

impl CloudLayer {
    pub fn cumulus() -> Self {
        Self {
            cloud_type: CloudType::Cumulus,
            base_altitude_m: 2_000.0,
            thickness_m: 1_500.0,
            coverage: 0.4,
            density: 0.3,
            wind_speed_m_s: 8.0,
            wind_direction: [1.0, 0.0],
            droplet_radius_um: 10.0,
            ice_fraction: 0.0,
        }
    }
    pub fn stratus() -> Self {
        Self {
            cloud_type: CloudType::Stratus,
            base_altitude_m: 500.0,
            thickness_m: 500.0,
            coverage: 0.7,
            density: 0.5,
            wind_speed_m_s: 5.0,
            wind_direction: [0.7, 0.7],
            droplet_radius_um: 8.0,
            ice_fraction: 0.0,
        }
    }
    pub fn cirrus() -> Self {
        Self {
            cloud_type: CloudType::Cirrus,
            base_altitude_m: 8_000.0,
            thickness_m: 1_000.0,
            coverage: 0.3,
            density: 0.05,
            wind_speed_m_s: 30.0,
            wind_direction: [1.0, 0.2],
            droplet_radius_um: 25.0,
            ice_fraction: 1.0,
        }
    }
    pub fn cumulonimbus() -> Self {
        Self {
            cloud_type: CloudType::Cumulonimbus,
            base_altitude_m: 1_000.0,
            thickness_m: 12_000.0,
            coverage: 0.15,
            density: 0.8,
            wind_speed_m_s: 15.0,
            wind_direction: [0.5, 0.5],
            droplet_radius_um: 14.0,
            ice_fraction: 0.3,
        }
    }
    pub fn stratocumulus() -> Self {
        Self {
            cloud_type: CloudType::Stratocumulus,
            base_altitude_m: 600.0,
            thickness_m: 800.0,
            coverage: 0.6,
            density: 0.4,
            wind_speed_m_s: 6.0,
            wind_direction: [0.8, 0.3],
            droplet_radius_um: 9.0,
            ice_fraction: 0.0,
        }
    }
    pub fn nimbostratus() -> Self {
        Self {
            cloud_type: CloudType::Nimbostratus,
            base_altitude_m: 1_500.0,
            thickness_m: 3_000.0,
            coverage: 0.85,
            density: 0.6,
            wind_speed_m_s: 10.0,
            wind_direction: [0.6, 0.4],
            droplet_radius_um: 12.0,
            ice_fraction: 0.1,
        }
    }
}

pub struct CloudSystemEndpoint {
    pub layers: Vec<CloudLayer>,
}

impl CloudSystemEndpoint {
    pub fn earth_default() -> Self {
        Self {
            layers: vec![
                CloudLayer::cumulus(),
                CloudLayer::stratus(),
                CloudLayer::cirrus(),
                CloudLayer::stratocumulus(),
            ],
        }
    }
    pub fn earth_stormy() -> Self {
        Self {
            layers: vec![
                CloudLayer::cumulonimbus(),
                CloudLayer::nimbostratus(),
                CloudLayer::stratus(),
            ],
        }
    }

    pub fn sample_density(&self, sample_alt: f64) -> f64 {
        self.layers
            .iter()
            .map(|l| {
                let alt_dist = (sample_alt - l.base_altitude_m).abs();
                let sigma = l.thickness_m * 0.5;
                let weight = (-0.5 * (alt_dist / sigma.max(1.0)).powi(2)).exp();
                let mie_size_factor = l.droplet_radius_um / 10.0;
                let phase_contrib = l.ice_fraction * 0.7 + (1.0 - l.ice_fraction) * 1.0;
                l.density * l.coverage * weight * mie_size_factor * phase_contrib
            })
            .sum::<f64>()
            / self.layers.len().max(1) as f64
    }

    pub fn wind_transport(&self) -> f64 {
        self.layers
            .iter()
            .map(|l| {
                let wind_dir_len = l.wind_direction[0].hypot(l.wind_direction[1]);
                l.wind_speed_m_s * wind_dir_len.max(0.01) * l.coverage
            })
            .sum::<f64>()
            / self.layers.len().max(1) as f64
    }

    pub fn optical_depth(&self) -> f64 {
        self.layers
            .iter()
            .map(|l| {
                let lwc = 0.3 * l.density;
                let r_eff = l.droplet_radius_um * 1e-6;
                let rho_w = 1000.0;
                let tau = 1.5 * 2.0 * lwc * l.thickness_m * l.coverage / (rho_w * r_eff);
                let ice_correction = 1.0 - 0.15 * l.ice_fraction;
                tau * ice_correction
            })
            .sum()
    }

    pub fn total_thickness(&self) -> f64 {
        self.layers.iter().map(|l| l.thickness_m * l.coverage).sum()
    }
}