UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Synergy of stereo cloud top height and ORAC optimal estimation cloud retrieval: evaluation and application to AATSR

Fisher, D; Poulsen, CA; Thomas, GE; Muller, J-P; (2015) Synergy of stereo cloud top height and ORAC optimal estimation cloud retrieval: evaluation and application to AATSR. Atmospheric Measurement Techniques Discussions , 8 (5) pp. 5283-5327. 10.5194/amtd-8-5283-2015. Green open access

[thumbnail of amtd-8-5283-2015.pdf]
Preview
Text
amtd-8-5283-2015.pdf - Published Version

Download (2MB) | Preview

Abstract

In this paper we evaluate the retrievals of cloud top height when stereo derived heights are combined with the radiometric cloud top heights retrieved from the ORAC (Optimal Retrieval of Aerosol and Cloud) algorithm. This is performed in a mathematically rigorous way using the ORAC optimal estimation retrieval framework, which includes the facility to use independent a priori information. Key to the use of a priori information is a characterisation of their associated uncertainty. This paper demonstrates the improvements that are possible using this approach and also considers their impact on the microphysical cloud parameters retrieved. The AATSR instrument has two views and three thermal channels so is well placed to demonstrate the synergy of the two techniques. The stereo retrieval is able to improve the accuracy of the retrieved cloud top height when compared to collocated Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), particularly in the presence of boundary layer inversions and high clouds. The impact on the microphysical properties of the cloud such as optical depth and effective radius was evaluated and found to be very small with the biggest differences occurring over bright land surfaces and for high clouds. Overall the cost of the retrievals increased indicating a poorer radiative fit of radiances to the cloud model, which currently uses a single layer cloud model. Best results and improved fit to the radiances may be obtained in the future if a multi-layer model is used.

Type: Article
Title: Synergy of stereo cloud top height and ORAC optimal estimation cloud retrieval: evaluation and application to AATSR
Open access status: An open access version is available from UCL Discovery
DOI: 10.5194/amtd-8-5283-2015
Publisher version: http://dx.doi.org/10.5194/amtd-8-5283-2015
Language: English
Additional information: © Author(s) 2015. This work is distributed under the Creative Commons Attribution 3.0 License.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/1475218
Downloads since deposit
122Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item