Clear-Sky Model and Measurement Comparisons from the First Diffuse Irradiance IOP - Fall 2001
Powell, D.(a), Kato, S.(b), Haeffelin, M.(c), and Dubovik, O.(d), Pacific Northwest National Laboratory (a), Hampton University (b), Laboratoire de Meteorologie Dynamique (c), NASA/Goddard Space Flight Center (d)
Twelfth Atmospheric Radiation Measurement (ARM) Science Team Meeting
In the fall of 2001 the central facility of the ARM SGP site was the location of the first diffuse irradiance IOP. Simultaneous measurements were obtained over a one-month period from more than a dozen radiometers of varying design and manufacturer. The focus of this IOP was to evaluate and compare the different instruments and calibration techniques and inevitably to move towards reducing the uncertainty associated with the diffuse measurement. Relevant to this goal is tracking the ability of radiative transfer models to simulate accurately diffuse shortwave irradiance. Previous studies of clear-sky cases at the SGP site have found model calculations are consistently higher than the measured diffuse irradiance (where corrections for IR loss have been applied). The source of this discrepancy is a subject of much debate. We present a comparison of modeled and measured diffuse irradiance for selected clear-sky cases during the diffuse irradiance IOP. Model inputs are obtained from sounding and instrument measurements at the SGP site. Additionally, multiple models are employed in this study. Our results are consistent with the previous studies with model computations typically exceeding the measured diffuse values by 10 to 15 Wm-2. We are investigating what is causing this difference.
Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).
