preliminary results from the prototype thin-cloud rotating shadowband radiometer
DESCRIPTION
Motor. Motor. MFRSR Head. 1 broadband channel, 6 narrow channels 415, 500, 610, 670, 870 & 940nm. Preliminary Results from the Prototype Thin-Cloud Rotating Shadowband Radiometer. M.J. Bartholomew*, R.M. Reynolds + , A. Vogelmann*, R. Edwards, S. Smith*, and Q.-L. Min^ - PowerPoint PPT PresentationTRANSCRIPT
Preliminary Results from the Prototype Thin-Cloud Rotating Shadowband Radiometer
M.J. Bartholomew*, R.M. Reynolds+, A. Vogelmann*, R. Edwards, S. Smith*, and Q.-L. Min^*Brookhaven National Laboratory, Upton, NY
+ Remote Measurements and Research Company, Seattle, WA^State University of New York, Albany
ReferencesMarchland, R., T. P. Ackerman, E. R. Westwater, S. A. Clough, K. Cady-Periera,
and J. C. Liljegren, 2003: An assessment of microwave absorption models and retrievals of cloud liquid water using clear-sky data, J.
Geophys. Res, 108(D24), 4773, doi:10.1029/2003JD003843.Min, Q.-L., and M. Duan , 2005: Simultaneously retrieving cloud optical depth and
effective radius for optically thin clouds, J. Geophys. Res., 110(D21201), doi:10.1029/2005JD006136.
Future Plans- Complete installation at SGP, make observations there and carry out intercomparisons with other ARM instruments.
Acknowledgements- This project received ACRF funding and help from the ARM Operations staff at SGP. We wish to extend a special thank you to SGP Operations staff members Dan Nelson, Craig Webb and Rod Soper
Solar Aureole = Total Hemispheric Irradiance – Observed Partially Occulted Irradiance
2. Design
1. Background and Theory
3. Some Preliminary Observations
1 broadband channel, 6 narrow channels 415, 500, 610, 670, 870 & 940nm
MFRSR Head
Motor Motor
Figure 1
Figure 2a
RMRC0Remote Measurements
& Research
Thin clouds prevalent and accuracies are low for their liquid water path (LWP),effective radius (Reff) and cloud optical depth (COD)- At SGP 50% of clouds have LWP less than 100gm-2, mode 40gm-2
- current microwave radiometer LWP retrieval accuracy, +- 20gm-2
- Marchland et al., 2003Surface irradiance calculations, Figure 1, suggest that a LWP uncertainty of 20gm-2 causes an error of greater than 100W/m2 in total hemispheric irradiance for an atmosphere with a 1 km thick cloud layer (45 degree incidence angle) with 40gm-2 (Min and Duan, 2005)Observations of solar aureole, Figures 2a and b, may lead to simultaneous retrievals of LWP, Reff, and COD with the following expected accuracies
LWP, 2gm-2
Reff, 10%COD, 2%- Min and Duan, 2005
Requires a scanning resolution of 1 degree +-15 degrees of the sun
Figure 2b
25cm R
10cm R
Testing at BNL
On roof of Radiometer Calibration Facility at SGP, 1/2008Image courtesy of Dan Nelson
Solar Aureole
Total Hemispheric Irradiance
Observed Partially Occulted Irradiance
Thick Cloud Thin Cloud