Oxford-RAL Retrieval of Aerosol and Cloud (ORAC)
Introduction
This page provides an overview of the work performed at the
University of Oxford and the Rutherford Appleton Laboratory on the
Oxford-RAL Retrieval of Aerosol and Cloud (ORAC) algorithm. The
project is lead by Dr R.G. Grainger of the University of
Oxford.
Current members of the
ORAC Science Team are
- Mr C. Arnold
- Dr E. Carboni
- Ms H. Huang
- Dr C. Poulson
- Dr R. Siddans
- Mr A. Smith
- Dr G. Thomas
| Other significant contributers
to ORAC include
- Dr E. Campmany
- Dr S. Dean
- Dr G. Ewen
- Dr B. Lawrence
- Dr S. Marsh
- Dr A. Sayer
- Mr P. Watts
|
Algorithm
The Oxford-RAL Retrieval of Aerosol and Cloudis an optimal
estimation scheme that determines aerosol and cloud properties from multispectral imagery [Thomas et al., 2010a,b, Poulsen et al., in press, Sayer et al., 2011]. The
scheme uses Discrete Ordinates Radiative Transfer (DISORT) [Stammes et
al., 1988] to model the top of atmosphere radiance as a function of
the properties of a plane parallel cloud layer or aerosol with an
assumed height distribution. The optimal estimation framework fits the
radiance in all channels by varying all retrieved parameters
simultaneously, while taking a priori information into account. The
scheme also provides error estimates on all retrieved quantities.
The code has been applied to measurements by ATSR-2, AATSR and
MSG-SEVIRI. The following is a description of the ATSR-2 nadir view
retrieval. Cloud properties are retrieved using the 0.67, 0.87,
1.6, 11 and 12 µm channels and the derived products are optical depth
at 0.55 µm, effective radius, liquid water path, cloud top height,
pressure and temperature and the fraction of each pixel filled with
cloud. Aerosol properties are retrieved using the 0.67, 0.87 and 1.6
µm channels and the products are 0.55 µm optical depth and effective
radius.
Product Availability ORAC has been applied to ATSR-2
data collected from 1995-2001 as part of the GRAPE project. Version 2
data is currently being prepared and is available from the BADC
with the
dataset name "CWVC - Global Retrieval of ATSR Cloud Parameters and
Evaluation (GRAPE)". (See also GRAPE)
Funding
The development and implementation of the code has been funded by a number of studies:
ORAC Meeting Dates for 2011
| Date | Location |
|---|
| 11/1 | Oxford |
| 8/2 | RAL |
| 8/3 | Oxford |
| 12/4 | RAL |
| 10/5 | Oxford
| | 14/6 | RAL |
| 12/7 | Oxford |
| 9/8 | RAL |
| 13/9 | Oxford |
| 11/10 | RAL |
| 8/11 | Oxford |
| 13/12 | RAL |
Maintained by Don Grainger
|
