Application of Cloudnet data in the validation of SCIAMACHY cloud height products

Ping Wang Piet Stammes

KNMI, De Bilt, The Netherlands

CESAR Science day, 19 June, 2013

Overview

• SCIAMACHY cloud products

• Cloud retrieval algorithms from O2 A band

• Validation data sets • Results• Summary

SCIAMACHY cloud products• ESA L2 (v5.02)Cloud top height and Cloud optical thickness are retrieved from SACURA. Cloud optical thickness is only retrieved for thick clouds, > 5. Cloud fraction is retrieved from PMDs (OCRA).

• FRESCO (v6)Effective cloud fraction and cloud height are retrieved from FRESCO. The cloud height is close to the middle of the cloud. FRESCO: Fast Retrieval Scheme for Clouds from the Oxygen A band

FRESCO cloud algorithms

Lambertian cloud model

Cloud data sets of SCIAMACHY

Data: ESA level-2, version 5.02, FRESCO, version 6

• Intercomparison data set - one orbit per month from 2002 to 2012, including 4 full day of data (~160 orbits).

• Validation data set - SCIAMACHY overpass pixels at Cabauw (2003- 2005) and Lindenberg (2005-2012). (~700 measurements)

Distributions of the differences (L2 –FRESCO)

Mean difference -0.0225 Standard deviation 0.100

Mean difference 0.609 km Standard deviation 2.16 km

Cloud fraction Cloud height

Cloudnet data

Instruments:

Radar : large particles such as rain and drizzle drops, ice particles, and insectsLidar : higher concentrations of smaller particles, such as cloud droplets, aerosol, supercooled liquid layers Microwave radiometer: liquid water pathRain gauge: precipitation

Cloudnet cloud top height, cloud base height and target categorization data are selected for one hour, centered at SCIAMACHY overpass time.

Illingworth et al., BAMS, 2007. http://www.cloud-net.org

Cloudnet categorization product

Ice cloud

Water cloud

height grid time resolution

Cabauw: 0.253-11.5km, 90m (126 levels), 15s (240 /hr) Lindenberg: 0.355-15.2km, 30m (495 levels), 30s (120 /hr)

Cloud top

Cloud base

Cloudnet categorization product

Ice cloud

Water cloud

height grid time resolution

Cabauw: 0.253-11.5km, 90m (126 levels), 15s (240 /hr) Lindenberg: 0.355-15.2km, 30m (495 levels), 30s (120 /hr)

Cloud top

Cloud base

Cloud top of ESA L2 vs. Cloudnet: single layer clouds

All clouds

water clouds

ice clouds

Color scale: ESA L2 cloud fraction

All clouds

ice clouds

water clouds

Cloud height of FRESCO vs. Cloudnet cloud top: single layer clouds

Color scale: FRESCO effective cloud fraction

SCIA cloud heights and Cloudnet cloud boundaries: single layer clouds, ceff>0.1

SCIAMACHY and Cloudnet cloud heights: single layer clouds, ceff>0.1

SCIAMACHY cloud height vs. Cloudnet cloud top: multi-layer clouds

ESA L2 cloud top height

FRESCO cloud height

SCIAMACHY and Cloudnet cloud heights: Multi-layer clouds

Summary (1)SCIAMACHY ESA L2 v5.02 cloud fractions are similar to FRESCO v6 effective cloud fractions. For the selected data from 200210 to 201204, the mean difference is -0.0225 and the standard deviation is 0.10.

SCIAMACHY ESA L2 v5.02 cloud top height is higher than FRESCO cloud height. The mean difference of cloud heights is 0.609 km with a standard deviation of 2.16 km for pixels without snow/ice.

Summary (2)We compared ESA L2 and FRESCO cloud heights with Cloudnet products for 220 single layer cloud cases in 2003-2011.

For single layer clouds, ESA L2 cloud top height is close to lidar/radar cloud top height for clouds at 3-7 km.FRESCO cloud height is close to lidar/radar cloud middle height for clouds below 5 km.

Acknowledgment

We would like to thank Henk Klein-Baltink (KMNI) for helpful discussions.

We acknowledge the Cloudnet project (European Union contract EVK2-2000-00611) for providing the target classification and cloud boundaries, which was produced by the University of Reading using measurements from Cabauw and Lindenberg.