CAMEX-4 MIPS Ceilometer

Table of Contents

Introduction

The University of Alabama in Huntsville (UAH) Mobile Integrated Profiling System (MIPS) includes a 915 MHz Doppler profiler, lidar ceilometer, 12 channel microwave profiling radiometer, Doppler Sodar, Radio Acoustic Sounding System (RASS), Field Mills, and surface observing stations.

This dataset consists of data from the MIPS ceilometer.

The Vaisala CT25K Laser Ceilometer is a general-purpose cloud height sensor employing LIDAR (Light Detection and Ranging) technology for detection of clouds, precipitation and other obstructions to vision. The CT25K provides reliable determination of cloud height up to 25,000 feet (7.5 km) thus covering most heights where dense clouds appear.

Specific information about this instrument may be found on the Vaisala web site.

Data is in a space delimited data file. A data file is created for each day (mission) and is of the form:

c4gmipsclo_2001.ddd.dat

where c4gmipsclo represents CAMEX4 ground station MIPS ceilometer, 2001.ddd is the four digit year and day of year. These data are easily imported into a spreadsheet, and an example of such an extraction is shown below.

NOTE: In this example, the first column (in red) has been added for line reference purposes only, and does NOT appear in the dataset.

1. Time (UTC) and date in HH:MM:SS MM/DD/YYYY. This example was collected at 16:55:08 on 08/05/2001. It represents only one vertical sounding, and those are collected about once every fifteen seconds. The next would be at 16:55:23, then 16:55:38, etc.

2. This is a bit complicated, and yields information about the backscatter, cloudbases, and visibility as follows:

Line 2 reads: 30 01230 12340 23450 FEDCBA98 where:

3 First digit of line: Status of detection as follows:

0 No significant backscatter
1 One cloud base detected
2 Two cloud bases detected
3 Three cloud bases detected
4 Full obscuration determined but no cloud base detected
5 Some obscuration detected but determined to be transparent

0 Second digit of line: Warnings and Alarm information as follows:

0 Self-check OK
W At least one Warning active, no Alarms
A At least one Alarm active

01230

If Detection Status is 1, 2 or 3: Lowest cloud base height
If Detection Status is 4: Vertical Visibility as calculated
If Detection Status is 0 or 5: /////

12340

If Detection Status is 2 or 3: Second lowest cloud base height
If Detection Status is 4: Highest signal detected
If Detection Status is 0, 1 or 5: /////

23450

If Detection Status is 3: Highest cloud base height
If Detection Status is 0, 1, 2, 4, 5: /////

FEDCBA98

Alarm (A), Warning (W), and Internal Status information. Each
character is a hexadecimal representation of four bits, altogether 32 bits
(b00-b31), with the following breakdown. Interpretation as follows:

F

b31 Laser temperature shut-off (A)
b30 Laser failure (A)
b29 Receiver failure (A)
b28 Voltage failure (A)

E

b27 (spare) (A)
b26 (spare) (A)
b25 (spare) (A)
b24 (spare) (A)

D

b23 Window contaminated (W)
b22 Battery low (W)
b21 Laser power low (W)
b20 Laser temperature high or low (W)

C

b19 Internal temperature high or low (W)
b18 Voltage high or low (W)
b17 Relative Humidity is > 85 % (option) (W)
b16 Receiver optical cross-talk
compensation poor (W)

B

b15 Fan suspect (W)
b14 (spare) (W)
b13 (spare) (W)
b12 (spare) (W)

A

b11 Blower is ON
b10 Blower heater is ON
b09 Internal heater is ON
b08 Units are METERS if ON, else FEET

9

b07 Polling mode is ON
b06 Working from battery
b05 Single sequence mode is ON
b04 Manual settings are effective

8

b03 Tilt angle is > 45 degrees
b02 (spare)
b01 (spare)
b00 (spare)

For example, if the battery voltage is too low, a warning is given and the second line appears as

0W ///// ///// ///// 00400300

In this example the internal heater is on and units are meters.

Line 3 contains information about the instrument and its output as follows:

Line 3: Example 100 N 101 +32 102 215 -2 744 LF7HN1 68

Measurement parameters are mostly in engineering units. Plus and minus signs are possible. Out-of-Range is indicated by slashes (/////). Contents:

100 Parameter SCALE, 100 (%) is normal (0 ... 999 possible)
N measurement mode; N = Normal, C = Close range
53 laser pulse energy, 0f nominal factory setting (0 ... 999)
+32 laser temperature degrees C (-50...+99)
102 receiver sensitivity, 0f nominal factory setting (0 ... 999)
215 window contamination, millivolts at internal ADC input (0 ... 2500)
-2 tilt angle, degrees from vertical (-15...+90)
744 background light, millivolts at internal ADC input (0 ... 2500)
LF7HN1 measurement parameters coded:
(pulse Long/Short, freq F, pulse qty 47+1, gain High/Low, bandwidth Narrow/Wide, sampling 10/20 MHz)
68 SUM of detected and normalized backscatter, 0 ... 999. Multiplied by scaling factor times 104. At scaling factor 100 the SUM range 0 ... 999 corresponds to integrated backscatter 0 ... 0.0999 srad-l

Line 4-19: The first field is height of the first gate reported on that line divided by 100. The next 16 fields are data at successive gates. The data are range and sensitivity normalized backscatter, units (10000·srad·km)-1

The data producer is:

Dr. Kevin Knupp
UAH 320 Sparkman Dr.
Huntsville, AL  35805

To order these data or for further information, please contact:

Global Hydrology Resource Center
User Services
320 Sparkman Drive
Huntsville, AL 35805
Phone: 256-961-7932
E-mail: support-ghrc@earthdata.nasa.gov
Web: http://ghrc.nsstc.nasa.gov/