Critical Evaluation of the ISCCP Simulator Using Ground-Based Remote Sensing Data

Journal Article · Mon Nov 02 04:00:00 EST 2009 · Journal of Climate

OSTI ID:1020324

Mace, G G; Houser, S; Benson, S; Klein, S A; Min, Q

Given the known shortcomings in representing clouds in Global Climate Models (GCM) comparisons with observations are critical. The International Satellite Cloud Climatology Project (ISCCP) diagnostic products provide global descriptions of cloud top pressure and column optical depth that extends over multiple decades. The necessary limitations of the ISCCP retrieval algorithm require that before comparisons can be made between model output and ISCCP results the model output must be modified to simulate what ISCCP would diagnose under the simulated circumstances. We evaluate one component of the so-called ISCCP simulator in this study by comparing ISCCP and a similar algorithm with various long-term statistics derived from the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Climate Research Facility ground-based remote sensors. We find that were a model to simulate the cloud radiative profile with the same accuracy as can be derived from the ARM data, then the likelihood of that occurrence being placed in the same cloud top pressure and optical depth bin as ISCCP of the 9 bins that have become standard ranges from 30% to 70% depending on optical depth. While the ISCCP simulator improved the agreement of cloud-top pressure between ground-based remote sensors and satellite observations, we find minor discrepancies due to the parameterization of cloud top pressure in the ISCCP simulator. The primary source of error seems to be related to discrepancies in visible optical depth that are not accounted for in the ISCCP simulator. We show that the optical depth discrepancies are largest when the assumptions necessary for plane parallel radiative transfer optical depths retrievals are violated.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 1020324
• Report Number(s): LLNL-JRNL-419342
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Vol. 24; ISSN 0894-8755; ISSN JLCLEL
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ACCURACY
ALGORITHMS
CLIMATE MODELS
CLIMATES
CLOUDS
EVALUATION
RADIANT HEAT TRANSFER
RADIATIONS
REMOTE SENSING
SATELLITES
SENSORS
SIMULATORS
STATISTICS