EVALUATION OF ULTRASONIC SNOW DEPTH SENSORS FOR

3,41

MB

AUTOMATED SURFACE OBSERVING SYSTEMS (ASOS)

134

stron

6382

ID

Colorado State University

2005

rok

Table of Contents

Title Page i

Signature Page . ii

Abstract iii

Acknowledgements.v

List of Figures and Tables.

Chapter 1: Introduction and Background.1

1.1 Introduction1

1.1.1 Traditional Snow Measurements 2

1.1.2 Challenges of Snow Measurements 3

1.2 Background5

1.2.1 Review of Literature .5

1.2.2 Automation of Snow Measurements.6

1.2.2.1 Snow Pillows .7

1.2.2.2 Ultrasonic Snow Depth Sensors.7

1.3 Objectives .10

Chapter 2: Site Descriptions 13

2.1 Site Construction.13

2.2 Climate Classification.15

Chapter 3: Methods18

3.1 Data Collection .18

3.1.1 Manual Data18

3.1.2 Automated Data 21

3.2 Quality Assurance/Quality Control (QA/QC) 21

3.2.1 Sensor QA/QC 22

3.2.2 Manual Data QA/QC 24

3.3 Factors Affecting Sensor Performance .25

3.4 Comparison of Sensor Snow Depth to Manual Snow Depth25

3.5 Six Hour Snowfall Algorithm.26

3.5.1 Calculation of Snowfall 26

3.5.1.1 Five Minute Snowfall Algorithm (5MSA) 27

3.5.1.2 Sixty Minute Snowfall Algorithm (60MSA) .27

3.5.2 Compaction .28

3.5.3 Statistics Used for Algorithm Assessment .30

Chapter 4: Results35

4.1 Characteristics of Snow Sensor Data35

4.1.1 Large Amplitude Variability: Qualitative Analysis35

4.1.2 Large Amplitude Variability: Quantitative Analysis36

4.1.3 Small Amplitude Variability.37

4.2 Climate Factors Affecting Sensor Performance .39

4.2.1 Snow Crystal Type39

4.2.2 Presence of Blowing/Drifting Snow .40

4.2.3 Intense Snowfall40

4.2.4 Wind Speed.41

4.2.5 Uneven Snow Surface.41

4.2.6 Extreme Cold Temperatures .42

4.3 Comparison of Automated and Manual Snow Depth .42

4.3.1 Sensor Comparison to Depth at Sensors.43

4.3.2 Sensor Comparison to Total Snow Depth.46

4.4 Six Hour Snowfall Algorithm.48

4.4.1 Five Minute Snowfall Algorithm (5MSA) .50

4.4.2 Sixty Minute Snowfall Algorithm (60MSA) 51

Chapter 5: Discussion 64

5.1 Characteristics of Snow Sensor Data64

5.1.1 Large Amplitude Variability.64

5.1.2 Small Amplitude Variability.65

5.2 Factors Affecting Sensor Performance .66

5.2.1 Snow Crystal Type66

5.2.2 Presence of Blowing/Drifting Snow .67

5.2.3 Intense Snowfall67

5.2.4 Wind Speed.68

5.2.4.1 Snow Fences .68

5.2.5 Uneven Snow Surface.69

5.2.6 Extreme Cold Temperatures 70

5.2.7 Summary 70

5.3 Comparison of Automated and Manual Snow Depth .71

5.3.1 Sensor Comparison to Depth at Sensors 71

5.3.2 Sensor Comparison to Total Snow Depth.72

5.4 Six Hour Snowfall Algorithm.74

5.4.1 Five Minute Snowfall Algorithm (5MSA) .74

5.4.2 Sixty Minute Snowfall Algorithm (60MSA) 75

Chapter 6: Conclusions and Recommendations. .81

6.1 Conclusions.81

6.1.1 Develop a reliable method of quality assurance/quality control (QA/QC) 81

6.1.2 Identify factors affecting sensor performance 82

6.1.3 Compare manual measurements of snow depth to each ultrasonic depth sensor.83

6.1.3.1.Se

nsor Comparison to Depth at Sensors83

6.1.3.2 Sensor Comparison to Total Snow Depth83

6.2 Recommendations.84

Literature Cited 86

Appendix A 89

Appendix B .94

Appendix C 96

Appendix D 105

Appendix E 121