CloudSat/VIIRS CBH Validation Activities at CIRA Curtis Seaman, Yoo-Jeong Noh, Steve Miller, Dan Lindsey 10 September 2012

Accomplishments Coordinated with CloudSat Data Processing Center to provide CloudSat data – Operational CloudSat data remains (as yet) unavailable to the public – Acquired 2 months of data during CloudSat/NPP matchup time periods (February and May 2012) Acquired parallax-corrected VIIRS Intermediate Products for each matchup time period Acquired and successfully installed software developed at CIMSS to identify matching CloudSat profiles/VIIRS pixels Developed software to analyze/compare CloudSat CBH/CTH with VIIRS – Developed framework to compare CBH/CTH matchup statistics – Compared CBH/CTH as a function of VIIRS COT, cloud phase, cloud height – Identified areas where further investigation is needed to understand retrieval behavior and suggest improvement Began creation of CloudSat/VIIRS matchup data set (HDF) to be run operationally when CloudSat data is officially released to public

Accomplishments/DRs Identified possible CTH retrieval issue with clouds near the tropopause – CBH retrieval requires accurate CTH retrieval

CBH Retrieval Algorithm Performance Summary VIIRS Cloud Base Height (CBH) compared with CloudSat, shows only marginal skill – Scatterplot shows large spread in retrieval – R 2 correlation value of globally CBH algorithm depends on numerous retrievals that must be correct before CBH can be retrieved – Cloud top temperature, optical thickness, effective particle size, cloud top height – Errors in these retrievals impact CBH retrieval Difficulty implementing changes in upstream retrievals hampers improvements to CBH retrieval Possibility to develop CBH/CTH retrieval in PATMOS-x where changes to algorithm would be easier to test/implement

Results – VIIRS vs. CloudSat for May 2012 CloudSat must be within 1500 km and 15 minutes of Suomi-NPP for a “matchup period” typically occurs for a ~4.5 hour period every three days CloudSat only collects data during daytime

Results – VIIRS CBH compared with CloudSat 1 month of data shown – All clouds included Scatterplot (left) and 2D histogram (density of points) of VIIRS CBH vs Cloudsat for all clouds Histogram uses a logarithmic scale There is a large spread in CBH retrievals between CloudSat and VIIRS Primary goal in the short term is to identify causes of this spread

Results – VIIRS CBH/CTH compared with CloudSat 1 month of data shown – All clouds included Notes: top black line represents all clouds; colored lines represent histograms for optical thickness bins (see color table); Error is defined as (CloudSat) – (VIIRS) so negative value means VIIRS CBH or CTH was higher than CloudSat CBHCTH

Results – VIIRS CBH/CTH compared with CloudSat 1 month of data shown – Cirrus clouds only Large variation in VIIRS CBH (left) for CloudSat profiles that indicate clouds near the surface Is the VIIRS CTH (right) pinned to the tropopause? Similar patterns seen for “Cirrus”, “Overlap” and “Opaque Ice”

Results – VIIRS CBH/CTH compared with CloudSat 1 month of data shown – Water clouds only Why do so many “water” clouds have CloudSat CBH/CTH values above 10 km MSL? Is this a VIIRS problem or a CloudSat problem? Most of these clouds have a high VIIRS cloud optical thickness It is expected that the retrievals would perform better in optically thick clouds

Issues/Challenges/Setbacks Availability of CloudSat data has been a limitation – CloudSat data products not operationally available – CloudSat data available only during daytime when satellite is turned on – No problem getting VIIRS data thanks to PEATE VIIRS CBH retrievals are dependent on a wide variety of cloud property retrievals that need to be accurate to get the correct CBH – For example: cloud top temperature, cloud optical thickness, effective particle size, cloud phase and cloud top height – Issues in these retrievals need to be resolved before CBH retrievals can be improved

FY13 Plans Continue analysis of CBH and CTH retrievals from both CloudSat and VIIRS and indentify where retrievals perform best – Compare land vs. ocean retrievals – Use recently developed CloudSat precipitation product to separate precip from clouds – Use combined CloudSat/CALIPSO products when they become available to improve CBH/CTH retrievals of optically thin clouds Continue development of CloudSat/VIIRS matchup database and run it operationally on PEATE Develop a VIIRS CBH/CTH retrieval based on PATMOS-x that can be run locally, and would be easier to adjust as our knowledge of the retrieval increases