Double Rain Gauge Network, Iowa


This data set includes rainfall data from 25 sites in Iowa, centered on the Iowa City Municipal Airport. The collection sites form an approximately regular grid with spacing of 5 km. At each site there are two tipping bucket rain gauges. Data were collected between June 2002 and November 2003. The network is a collaborative effort between NASA, NOAA, the University of Maryland, and the University of Iowa. The experiment was designed to validate the AMSR-E rainfall measurements.

The Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) is a mission instrument launched aboard NASA's Aqua Satellite on 4 May 2002. AMSR-E validation studies linked to rainfall experiments are designed to evaluate the accuracy of AMSR-E precipitation data.

Citing These Data

Krajewski, W. F. 2004. Double Rain Gauge Network, Iowa. [indicate subset used]. Boulder, Colorado USA: NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: 10.5067/2BC7FR1I6HLS.

Overview Table

Category Description
Data format ASCII text files
Spatial coverage 41.5°N, 91.5°W
Temporal coverage and resolution 18 June 2002 through 13 November 2003. Measurements were taken every minute, then averaged to every five minutes.
File naming convention Files are named after the study sites. For example, "SITE12.dat."
File size File sizes range from 2.69 MB to 3.51 MB.
Parameter(s) Rainfall amount.
Procedures for obtaining data Data are available via FTP and HTTPS.

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments

Investigator(s) Name and Title

Witold F. Krajewski
IIHR-Hydroscience & Engineering
University of Iowa

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services


Investigators and others who worked with this data include Anton Kruger, Ralph Ferraro, and Grzegorz J. Ciach of the IIHR-Hydroscience & Engineering department of the University of Iowa, and Jeffrey McCollum of the University of Maryland. This research was done under NASA Grant Number NAG5-11969.

2. Detailed Data Description


Data files are ASCII text files.

File Naming Convention

Files are named after the study sites. For example, SITE12.dat.

File Size

File sizes range from 2.69 MB to 3.51 MB.

Spatial Coverage

Southernmost Latitude: 41.5° N
Northernmost Latitude: 41.75° N
Westernmost Longitude: 91.75° W
Easternmost Longitude: 91.5° W

Temporal Coverage

18 June 2002 through 13 November 2003. Different data files cover different time periods. The table below shows the start and end dates for each site.

Site number Start date End date
1 8/13/02 11/12/03
2 8/11/02 11/12/03
3 09/19/02 11/12/03
4 8/11/02 11/12/03
5 8/11/02 11/12/03
6 8/11/02 11/12/03
7 8/11/02 11/12/03
8 8/11/02 11/12/03
9 8/11/02 11/12/03
10 6/18/02 11/12/03
11 6/20/02 11/12/03
12 8/18/02 11/20/03
13 8/15/02 11/11/03
14 8/12/02 11/12/03
15 9/14/02 11/13/03
16 8/12/02 11/12/03
17 8/15/02 11/13/03
18 8/15/02 11/12/03
19 8/15/02 9/26/03
20 8/14/02 11/12/03
21 6/21/02 11/12/03
22 6/21/02 11/12/03
23 6/18/02 11/12/03
24 8/18/02 11/12/03
25 10/17/02 11/13/03

Temporal Resolution

Data files contain readings in five minute intervals.

Parameter or Variable

Parameter Description

Rainfall is measured by two tipping bucket rain gauges. Each data file consists of three columns:

  1. Date (yyymmdd)
  2. Time (hh:mm:ss) UTC
  3. recorded rain rate in mm

Unit of Measurement

Rainfall amount (in mm) from tipping bucket gauge.

Parameter Source

The network consists of 25 dual tipping bucket rain gauge platforms.

Sample Data Record

The following sample is taken from the "SITE04.dat" file.

20020811  15:15:00	0.00
20020811  15:20:00	12.43
20020811  15:25:00	5.69
20020811  15:30:00	0.43
20020811  15:35:00	0.00

Error Sources

Raw data were taken in one-minute intervals, and processed into five-minute rain accumulations. Although such short time scale accumulations are associated with significant random error, providing data on a five-minute basis provides flexibility in selecting the time interval for analysis. This is particularly important for evaluation of remote sensing products. The random error of the tipping bucket rain gauge data decreases with time accumulation scale. It is negligible for scales longer than about 15 minutes.

Quality Assessment

The investigators guarantee quality between 1 April and 13 November, 2003.

3. Data Access and Tools

Data Access

Data are available via FTP and HTTPS.


Total volume of data files is 78.72 MB.

Related Data Collections

4. Data Acquisition and Processing

Sensor or Instrument Description

The network consists of 25 dual tipping-bucket rain gauge platforms. Please see IIHR- Hydroscience and Engineering to learn more.

Processing Steps

After quality control of the raw data from the tipping buckets, investigators used the tip interpolation method (Ciach 2002) to calculate rain rate. The rain rate values in the third column of the data files are the average of the two tipping-bucket rain gauges on the platform. Because of the way a tipping-bucket operates, data were recorded data only when the buckets tipped (when they contained moisture).

5. References and Related Publications

Ciach, G. J. 2003. Local random errors in tipping-bucket rain gauge measurements. Journal of Atmospheric and Oceanic Technology 20 (5) (May): 752-759.

Krajewski, W.F., G.J. Ciach and E. Habib. 2003. An analysis of small-scale rainfall variability in different climatological regimes. Hydrologic Science Journal 48: 151-162.

Habib, E., W.F. Krajewski, and A. Kruger. 2001. Sampling errors of fine resolution tipping-bucket rain gauge measurements. Journal of Hydrologic Engineering 6 (2): 159-166.

Habib, E., W.F. Krajewski, V. Nespor, and A. Kruger. 1999. Numerical simulation studies of raingage data correction due to wind effect. Journal of Geophysical Research-Atmospheres Research 104 (D16): 19, 723 - 19, 734.

Krajewski, W.F., Kruger, A., and V. Nespor. 1998. Experimental and numerical studies of small-scale rainfall measurements and variability. Water Science and Technology 37 (11): 131-138.

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

AMSR-E Advanced Microwave Scanning Radiometer - Earth Observing System
FTP File Transfer Protocol
IIHR Iowa Institute of Hydraulic Research
NASA National Aeronautics and Space Administration
NOAA National Oceanic and Atmospheric Administration

Document Creation Date

February 2004

Document URL