MAGIC Radiative Flux Compared to NASA Clouds and the Earth’s Radiant Energy Systems (CERES) SYN1Deg Radiative Transfer Calculations

 

Authors

David A Rutan — Science Systems and Applications. Inc./NASA - LRC
Seiji Kato — NASA - Langley Research Center
Fred G Rose — Science Systems and Applications. Inc./NASA - LRC

Category

Radiation

Description

From Oct 2012 to Sep 2013, the second ARM Mobile Facility (AMF2) was deployed on the container ship Spirit for the Marine ARM GPCI Investigation of Clouds (MAGIC) field campaign. The Spirit ran between Los Angeles, CA, and Honolulu, HI, making approximately 20 round trips while AMF2 measured clouds, precipitation, aerosols, and atmospheric radiation. MAGIC also included surface meteorological variables and atmospheric profiles from weather balloons launched at approximate six-hour intervals. The Clouds and the Earth’s Radiant Energy System (CERES) Synoptic (SYN1deg) product provides climate quality global 3-hourly 1°x1°gridded top of atmosphere, in atmosphere, and surface radiant fluxes. In atmosphere and surface fluxes are computed hourly using a radiative transfer code based on input from Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS), 3-hourly geostationary (GEO) imager data, and meteorological assimilation data from the Goddard Earth Observing System. The GEO visible and infrared imager calibration is tied to MODIS to ensure uniform MODIS-like cloud properties across all satellite cloud data sets. To compare SYN1deg to MAGIC observations we isolate the average MAGIC observations within a grid box ensuring the ship moves across the entire longitudinal axis. The ship can cross a grid box in less than two hours. Hour average observations are compared to hourly calculations from SYN1deg data processing. Results from 6 months of comparisons show a positive bias (calculation-observation) in shortwave (SW), daytime only, of 16W (4.4%) out of an average observed value of 366W. The longwave (LW) bias is smaller, 2W (0.5%), out of an average observed value of 369W. Standard deviations of the differences were larger for the SW comparisons. MAGIC SW bias is high relative to comparisons from two long-term buoys, the N. Tropical Atlantic Site and the Hawaii Time Series Buoy (from Woods Hole Oceanographic Institute WHOI) whose biases were 1.4% and 2.1% respectively. MAGIC biases are smaller than a third WHOI buoy, the STRATUS buoy, in the marine stratus region off the west coast of Chile where bias with respect to SYN1deg product is 8.5%. MAGIC data will allow us to investigate the effect of ship motion on the comparisons and compare meteorological, cloud, and aerosol inputs to the SYN1deg product by comparing sonde data to the input GEOS profiles and observed cloud and aerosol properties from the ship to inputs used in flux computations.