Rainfall Effects

Topics: Radar, Weather radar, Rain Pages: 67 (22200 words) Published: August 23, 2013
ISWS/CIR-146/80

Circular 146
STATE OF ILLINOIS ILLINOIS INSTITUTE OF NATURAL RESOURCES

Rainfall Prediction-Measurement Systems and Rainfall Design Information for Urban Areas by STANLEY A. CHANGNON, JR., FLOYD A. HUFF, JOHN L. VOGEL, DAVID A. BRUNKOW, and DONALD W. STAGGS

ILLINOIS STATE WATER SURVEY
CHAMPAIGN

1980

-i-

CONTENTS

Page SYSTEM FOR REAL-TIME PREDICTION AND MONITORING OF PRECIPITATION OVER URBAN AREAS INTRODUCTION Components Philosophy 1 1 5 7 7 11 11 12 12

RADAR PRECIPITATION MEASUREMENT Radar System Antenna Transmitter Receiver

Reflectivity Processor Site Selection Horizon Ground Targets ....

15 15 15

Access and Utilities Computers and Programming RAINGAGE NETWORK

Surveil lance Area

Federal Communications Commission License

16

16 16 18 19 20 23 24 19

Types of Precipitation Gages Density Requirements for Radar-Rainfall Systems Mean Precipitation Pattern Analysis Detection and Areal Extent Installation Procedures

Siting

21 ■.

Density Requirements for Hydrologic Design Data

25 25 25

24

Rain Cell Analysis Operational Use

26

-ii-

Page COMMUNICATION SYSTEMS Radar-Raingage Communications Dedicated Land-Line Telemetered Data Link Dial Land-Line 27 27 27 27

Interrogated-Beacon Data Link

27

27 28 30

Radar System to User Communication DATA ANALYSIS AND INTERPRETATION System Analysis and Interpretation Long-Range Prediction Future Expansion of the System HYDROMETEOROLOGICAL PROPERTIES OF CONVECTIVE STORMS Relation Between Point and Areal Mean Rainfall Frequencies Time Between Successive Heavy Storms Introduction

33 35 35

30

34

Antecedent Rainfall Distribution .

36

36

Orientation and Movement of Heavy Storm Heavy Raincell Characteristics

Synoptic Weather Conditions Associated with Heavy Rainstorms ....

40 45

37

44

Temporal Rainfall Distribution Within Storms Spatial Distribution of Storm Rainfall REFERENCES APPENDIX A

48

50

55 62

-iii-

LIST OF TABLES

Table 1 2 3 4 5 6 7 Radar reflectivity, rainfall rate relationships from drop size spectra FCC table of frequency allocations, definitions, and footnotes . Listing of telemetered gages and their characteristics

Page 9 17 22

Rainfall sampling requirements for design and operation of urban hydrologic systems 26 Three communications options Ratio of areal mean to point rainfall frequencies in heavy storms Probability distributions of antecedent rainfall for 1 to 10 days on selected areas in storms producing rainfall of 1 inch or more Frequency distribution of heavy rainstorm orientations . . . . . . Typical distribution of synoptic storm types associated with urban flash floods in the Midwest Comparison of water yield between urban-effect (U) and no effect (C) raincells amount the heaviest cells during 1971-1975 at St. Louis Medians in cells having mean rainfall of 6 mm (0.25 in) or more Frequency of heavy raincell movements in the St. Louis region .. Differences between Figure 8 and specific area curves Ratio of maximum to mean rainfall on 400 mi2,,,,,,,,,,,,,, 29 37

38 41 45

8 9 10

46 47 47 50 52

11 12 13 14

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LIST OF FIGURES

Figure 1 2 3 4 5 6 7 8 9 Study area and facilities for Chicago Hydrometeorology Area Project Radar-rainfall monitoring scheme developed in CHAP Radar range height Time between successive rainstorms Major types of storm patterns Mean shape factor Time distribution of point rainfall Time distribution of area rainfall Average area-depth relation for 3-hour, 10-year storm at Chicago

Page 3 6 13 39 42 43 49 49 54

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For this report it was decided to use the English system of units since the primary audience would be engineers, many of whom still use the English system rather than the International System of Units (SI). The following multiplicative factors may be used to convert from the English to the SI system. Multiples for Converting from English to SI Units.

English Feet...
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