NCAR Airborne Instrumentation Inventory

1. INSTRUMENT IDENTIFICATION

Instrument Designation:
Total Actinic Flux Measurement for the Determination of Photolysis Rates

Instrument Acronym:


Instrument Measurements:

a) Trace Gas


b) Cloud Physics/Aerosol


c) Radiation/Optical/Electrical
Total Actinic Flux 280-420 nm
Photolysis rates of O3, NO2, CH2O, HONO, H2O2, acetone and possibly others

d) Additional Capabilities
extended wavelength range
separate downwelling and upwelling radiation components

Resource Person/Developer:
Name: Rick Shetter
Affiliation: NCAR/ACD
Phone: (303) 497-1480
Email: shetter@ucar.edu

Principle of Measurement:
Collection of atmospheric radiation by a quartz collector with nearly uniform response from entire hemisphere followed by a fiber optic coupled double monochrometer determination of wavelength dependant intensities.

In situ/Remote/Flux Measurement:

2. INSTRUMENT APPLICATION

Scientific questions to be answered:
Photolysis rate measurements in photochemistry experiments provide the dominant OH source term, NOx partitioning, free radical sources, and other important inputs for chemical modeling. Actinic Flux as a function of wavelength in and around clouds and aerosols comparison with radiative transfer theory used in models

Field projects in which the instrument has been used:
NASA PEM-Tropics
NASA SONEX

Publications describing the instrument, applications and field project results:
in preparation

3. Instrument Deployment

Altitude:
ground to max alittude of DC-8
Could be adapted for stratospheric aircraft

Aircraft Platform:
Currently NASA DC-8

Inlet Configuration/Location:
Zenith (DC-8 #1)and Nadir (DC-8 #2) ports away from interferences with hemispherical field of view.

Calibration/Cross Calibration:
Lab calibration with NIST traceable QTH lamps
Field calibrations before and after flight with secondary QTH standards
Cross calibration with existing ACD chemical actinometers for jO3 and jNO2 a ground based site (Marshall field site)

Operator Requirements:
Currently 1 operator
Development underway to eliminate operator intervention during flight

Data Collection:
self

Post-flight Data Validation, Processing, Hours per Flight Hour etc.
Flight data processed into photolysis rates within 24 hours
Post flight instrument calibration ~2 hours

Physical Characteristics:
Dimensions: 24 inches of 19 inch rack mount
Weight: <100 lbs
Power: <3 amps 110 volt power
Other: Zenith and nadir mounts

4. Instrument Performance

Linear Range:
~6-7 orders of magnitude

Response Time:
~10-30 sec for 280-420 nm spectrum

Detection Limits:
jO3 1X10-8 sec -1
jNO2 3X10-8 sec-1
jHONO 1X10-8 sec -1
jCH2O 1X10-9 sec -1

Accuracy:
~ 5-8% at 1 sigma

Precision:
<3%

Limitations (such as altitude, airspeed, etc.)

5. Alternative Techniques

6.Status/Plans

7. Comments