Inter-Comparisons between Radiometric and Geometric Cloud Top Height Products

Houria Madani1, James L. Carr1, Andrew Heidinger2, and Steve Wanzong3

1: Carr Astronautics, Greenbelt, Maryland (email: hmadani@carrastro.com)2: NOAA/NESDIS STAR, Madison, Wisconsin

3: Cooperative Institute for Meteorological Satellite Studies (CIMSS), University of Wisconsin-Madison, Madison, Wisconsin, USA

INTRODUCTION

Knowledge of cloud properties, such as cloud top height, is important for climate studies and weather prediction. This paper describes a comparison between two GOES Cloud Top Height (CTH) products: (1) Stereo-CTH using stereo parallax and (2) operational cloud top height products obtained using the Algorithm Working Group Cloud Height Algorithm (ACHA) which is based on Extended CLAVR (CLAVR-x), NOAA's operational cloud processing system for the AVHRR. Validation of both CTH products is performed with Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data.

STEREO-CTH ALGORITHM SUMMARY

The Stereo-CTH product is based on matching features seen in images of the same spectral bands acquired quasi-simultaneously by satellites from two or more different vantage points. The CTH is derived from the observed parallax between pairs of satellites. In this case, we have access to three GOES satellites.•GOES-E and GOES-W images are remapped to the Central satellite geometry.•Sites are defined every 10 pixels in NS and EW directions resulting in a CTH product with a nominal horizontal resolution of 10km NS and 6km EW or half that for a 2012-Oct-25 18:45 image of Hurricane Sandy.

•Retrieved heights under clear skies can be compared against known terrain heights to calibrate biases (caused by residual mapping errors) to apply everywhere and improve the accuracy of the product.

•Processing can be real time and potentially mix geostationary and polar data.

The RGB composite image (left) above shows where 3-satellite and 2-satellite products can be obtained.

STEREO-CTH VS. CALIPSO

Stereo-CTH and CALIPSO are co-located but not always simultaneous. The two products agree well for the 2012-Oct-24 19:15 and 19:45 GOES images, but not always the top layer; in the third case (image and plot at far right) there is more discrepancy between the two products; this is likely due to cloud transport.

CLAVR-X CTH VS. CALIPSO

Stereo-CTH, CLAVR-x, and CALIPSO products compare well. Stereo-CTH and CLAVR-x complement each other, as they often measure different layers, providing a richer description of cloud structure. Stereo-CTH has unique value for Cloud Motion Wind height assignments and can be implemented in real time.

Poster A33E-0220

CLAVR-X AND CALIPSO VS. STEREO-CTH

Large differences between Stereo-CTH and CALIPSO CTH from Layer 1 occur where there is more than one cloud layer..

CLAVR-x vs. Stereo-CTH A linear relationship is seen for about 75% of the data. Discrepancies are seen in the remaining 25%:• CLAVR-x values larger than Stereo-CTH values when acha_quality = 79 (Beta

retrieval is degraded) and acha_quality = 95 (Tc and Beta retrievals are degraded).

SUMMARY

CALIPSO vs. Stereo-CTHSimilar behavior as seen for CALVR-x vs. Stereo:• Most of the data falls on the y = x line.• CALIPSO values from 1st cloud layer are sometimes larger than Stereo-CTH but 2nd

layer matches; likely due to semi-transparency.

The RGB composite image (left) shows where three-satellite and two-satellite products can be obtained.

CLAVR-x CTH compared to CALIPSO shows a behavior similar to that of Stereo-CTH.

Stereo-CTH (km)0 2 4 6 8 10 12 14 16 18

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CLAVR-x CTH vs Stereo-CTH as a Function of ACHA QualityImage of 2015-Oct-24 19:15

qual = 001qual = 031qual = 079qual = 095

qual = 111qual = 127

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CLAVR-x CTH vs. Stereo-CTH as a function of ACHA QualityImage of 2012-Oct-24 19:15

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CALIPSO CTH and CBH first 2 Cloud Layers vs. Stereo-CTH2015-Oct-24 19:15 and 19:45 Combined data

CTH Layer 1CTH Layer 2CBH Layer 1

CBH Layer 2y = x line

CALIPSO CTH and CBH First 2 Cloud Layers vs. Stereo-CTH2012-Oct-24 19:15 and 19:45 Combined Data

Latitude (degrees)

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CALIPSO Cloud Height (Base to Top) and Stereo-CTH2012-Oct-25 18:45

CALIPSO Top Layer 1CALIPSO Base Layer 1CALIPSO Top Layer 2CALIPSO Base Layer 2Stereo

Latitude (degrees)

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CALIPSO Cloud Height (Base to Top) and Stereo-CTH2012-Oct-24 19:45

CALIPSO Top Layer 1CALIPSO Base Layer 1CALIPSO Top Layer 2CALIPSO Base Layer 2Stereo

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CALIPSO Cloud Height (Base to Top) and Stereo-CTH2012-Oct-24 19:15

CALIPSO Top Layer 1CALIPSO Base Layer 1CALIPSO Top Layer 2CALIPSO Base Layer 2Stereo

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Difference between Calipso and Stereo for Different Cloud Layers2012-Oct-24 19:15

All locationsLocations with more than 1 layer

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Difference between Calipso and Stereo for Different Cloud Layers2012-Oct-24 19:45

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Latitude (degrees)

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Difference between Calipso and Stereo for Different Cloud Layers2012-Oct-25 18:45

All locationsLocations with more than 1 layer