initial commit - really rough calculations based on temp & relative h…

…umidity
babattles · Feb 21, 2023 · 8baef24 · 8baef24
commit 8baef24
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diff --git a/crust/crust.go b/crust/crust.go
@@ -0,0 +1,53 @@
+package crust
+
+import (
+	"github.com/babattles/snoqualmie-crust-calculator/inversion"
+	"github.com/babattles/snoqualmie-crust-calculator/models"
+	"github.com/babattles/snoqualmie-crust-calculator/sun"
+)
+
+type CrustConfidence string
+
+const (
+	CrustYes CrustConfidence = "yes"
+	CrustNo CrustConfidence = "no"
+	CrustMaybe CrustConfidence = "maybe"
+)
+
+// returns an array of bools where the index is true when there likely
+// exists a sun crust based on temperature inversions & sun effect
+func FindSunCrust(data []models.WeatherStationData) []CrustConfidence {
+	res := make([]CrustConfidence, len(data))
+	inversionsBelow := inversion.FindInversionsBelow(data)
+	sunExposures := sun.FindSunEffect(data)
+	for i, layer := range(data) {
+		gotSun := sunExposures[i]
+		inversionBelow := inversionsBelow[i]
+
+		// if there was a temperature inversion detected below
+		// AND this layer might have recieved sun exposure
+		// AND the temperature is above freezing
+		// there is very likely a sun crust
+		// NOTE: this assumption is likely to upset many people
+		if inversionBelow && 
+		gotSun && 
+		!layer.BelowFreezing() {
+			res[i] = CrustYes
+			continue
+		}
+
+		// because our sun exposure estimate isn't perfect, we provide a maybe if we can't 
+		// guess more precisely because we detected an inversion
+		// so if the layer might have received sun exposure 
+		// AND is above freezing, it might have a crust
+		// NOTE: this check assumes mid-winter conditions that will return this layer to freezing at some point
+		// YMMV
+		if gotSun && !layer.BelowFreezing() {
+			res[i] = CrustMaybe
+			continue
+		}
+
+		res[i] = CrustNo
+	}
+	return res
+}
diff --git a/crust/crust_test.go b/crust/crust_test.go
@@ -0,0 +1,155 @@
+package crust_test
+
+import (
+	"testing"
+
+	"github.com/babattles/snoqualmie-crust-calculator/crust"
+	"github.com/babattles/snoqualmie-crust-calculator/models"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFindSunCrust(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name string
+		data []models.WeatherStationData
+		expected []crust.CrustConfidence
+	}{
+        {
+			name: "no inversions - no clouds - all above freezing - all maybes",
+			data: []models.WeatherStationData{
+				{
+					ElevationFt: 0,
+					TemperatureF: 36,
+					RelativeHumidityPercent: 0,
+				},
+				{
+					ElevationFt: 500,
+					TemperatureF: 34,
+					RelativeHumidityPercent: 0,
+				},
+				{
+					ElevationFt: 1000,
+					TemperatureF: 32,
+					RelativeHumidityPercent: 0,
+				},
+			},
+			expected: []crust.CrustConfidence{crust.CrustMaybe, crust.CrustMaybe, crust.CrustMaybe},
+		},
+		{
+			name: "no inversions - all clouds - all above freezing - all nos",
+			data: []models.WeatherStationData{
+				{
+					ElevationFt: 0,
+					TemperatureF: 36,
+					RelativeHumidityPercent: 100,
+				},
+				{
+					ElevationFt: 500,
+					TemperatureF: 34,
+					RelativeHumidityPercent: 100,
+				},
+				{
+					ElevationFt: 1000,
+					TemperatureF: 32,
+					RelativeHumidityPercent: 100,
+				},
+			},
+			expected: []crust.CrustConfidence{crust.CrustNo, crust.CrustNo, crust.CrustNo},
+		},
+		{
+			name: "no inversions - no clouds - all below freezing - all nos",
+			data: []models.WeatherStationData{
+				{
+					ElevationFt: 0,
+					TemperatureF: 28,
+					RelativeHumidityPercent: 0,
+				},
+				{
+					ElevationFt: 500,
+					TemperatureF: 26,
+					RelativeHumidityPercent: 0,
+				},
+				{
+					ElevationFt: 1000,
+					TemperatureF: 24,
+					RelativeHumidityPercent: 0,
+				},
+			},
+			expected: []crust.CrustConfidence{crust.CrustNo, crust.CrustNo, crust.CrustNo},
+		},
+		{
+			name: "all inversions & all clouds - no crusts",
+			data: []models.WeatherStationData{
+				{
+					ElevationFt: 0,
+					TemperatureF: 30,
+					RelativeHumidityPercent: 100,
+				},
+				{
+					ElevationFt: 500,
+					TemperatureF: 32,
+					RelativeHumidityPercent: 100,
+				},
+				{
+					ElevationFt: 1000,
+					TemperatureF: 34,
+					RelativeHumidityPercent: 100,
+				},
+			},
+			expected: []crust.CrustConfidence{crust.CrustNo, crust.CrustNo, crust.CrustNo},
+		},
+		{
+			name: "all inversions - no clouds - all below freezing - no crusts",
+			data: []models.WeatherStationData{
+				{
+					ElevationFt: 0,
+					TemperatureF: 12,
+					RelativeHumidityPercent: 0,
+				},
+				{
+					ElevationFt: 500,
+					TemperatureF: 20,
+					RelativeHumidityPercent: 0,
+				},
+				{
+					ElevationFt: 1000,
+					TemperatureF: 30,
+					RelativeHumidityPercent: 0,
+				},
+			},
+			expected: []crust.CrustConfidence{crust.CrustNo, crust.CrustNo, crust.CrustNo},
+		},
+		{
+			name: "all inversions - no clouds - one below freezing - two crusts",
+			data: []models.WeatherStationData{
+				{
+					ElevationFt: 0,
+					TemperatureF: 30,
+					RelativeHumidityPercent: 0,
+				},
+				{
+					ElevationFt: 500,
+					TemperatureF: 32,
+					RelativeHumidityPercent: 0,
+				},
+				{
+					ElevationFt: 1000,
+					TemperatureF: 34,
+					RelativeHumidityPercent: 0,
+				},
+			},
+			expected: []crust.CrustConfidence{crust.CrustNo, crust.CrustYes, crust.CrustYes},
+		},
+    }
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			tc := tc
+			res := crust.FindSunCrust(tc.data)
+			assert.Equal(t, tc.expected, res)
+		})
+	}
+}
diff --git a/go.mod b/go.mod
@@ -0,0 +1,10 @@
+module github.com/babattles/snoqualmie-crust-calculator
+
+go 1.20
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/testify v1.8.1 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
diff --git a/go.sum b/go.sum
@@ -0,0 +1,16 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
+github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/inversion/inversion.go b/inversion/inversion.go
@@ -0,0 +1,64 @@
+package inversion
+
+import (
+	"errors"
+
+	"github.com/babattles/snoqualmie-crust-calculator/models"
+)
+
+var (
+	ErrImproperElevationOrdering = errors.New("improper elevation ordering")
+)
+
+type InversionData struct {
+	LowerElevationFt int
+	HigherElevationFt int
+	InversionPresent bool
+}
+
+// for each elevation band, return if there was an inversion between it and the above elevation band
+// (the uppermost elevation band will always be false)
+func FindInversionsAbove(data []models.WeatherStationData) []bool {
+	// sort first for peace of mind
+	models.SortByElevation(data)
+
+	res := make([]bool, len(data))
+	for i, layer := range(data) {
+		// uppermost layer
+		if i == len(data) - 1 {
+			res[i] = false
+			return res
+		}
+
+		res[i] = temperatureInversionExists(layer, data[i+1])
+	}
+
+	return res
+}
+
+// for each elevation band, return if there was an inversion between it and the elevation band below
+// (the lowest elevation band will always be false)
+func FindInversionsBelow(data []models.WeatherStationData) []bool {
+	// sort first for peace of mind
+	models.SortByElevation(data)
+
+	res := make([]bool, len(data))
+	for i := len(data)-1; i >= 0; i-- {
+		// lowest layer
+		if i == 0 {
+			res[i] = false
+			return res
+		}
+
+		res[i] = temperatureInversionExists(data[i-1], data[i])
+	}
+
+	return res
+}
+
+// calculates if there was a temperature inversion between two elevation bands
+func temperatureInversionExists(
+	lowerBand models.WeatherStationData, higherBand models.WeatherStationData,
+) bool {
+	return higherBand.TemperatureF > lowerBand.TemperatureF
+}