Acquiring the HALOE L2 data held at the BADC

This file contains background information to help you get the HALOE L2 data held at the BADC.

Before you start
Checking and Transferring Data from the BADC
File name convention
Reading the data files

The HALOE level 2 data was supplied to the BADC in IEEE binary files by the instrument team at NASA Langley. These files should be readable on most Unix platforms using the software provided, but note that if you want to read the data using a DEC alpha machine running Digital Unix, then you will have to compile the routines using the - convert big_endian option.

Since the dataset is restricted, you need to apply for access to the HALOE Level 2 data .

1. Before you start

You will need gzip installed on your local system to uncompress the data files and software packages - the source code is available from software archives. You will also need to know how to use gzip and tar once you have the files on your system.

2. Checking and Transferring Data from the BADC

All data and software is located beneath the directory /badc/haloe/. Here you will find a README file and the following subdirectories:

data/haloel2/ - contains the HALOE Level 2 data files.
doc - contains HALOE documentation.
software/haloel2/ - contains the example read routines and any 3rd party software available to read HALOE Level 2 data.

Check whether the data you require is available by browsing the HALOE L2 data directories.

3. File name convention

The file name convention adopted is as follows: HALOE_Ll_Sssss_Ddddd.Vvvvv_Ccc_xxxx,

where:

l is the UARS processing level (e.g. 2),
ssss is the subtype or parameter,
dddd is the UARS acquisition day (0001 = 12 September 1991),
vvvv is the data version number (e.g. 18 or 19),
cc is the data version cycle number, and
xxxx is the file extension (PROD for the binary files).

4. Reading the data files

4.1 The file structure

Level 2 data are organized into one file per day. Each daily file contains data for all constituents for the sunrise and sunset events in the day (typically 29 or 30 in total). An overview of the file structure is shown below. Formal file specifications can be found in the HALOE level 2 documentation.
At the beginning of each file, there is a block of summary information. The files are then organized sequentially by event. The data from the event is arranged into a standard header containing the level 1 data used in the level 2 retrievals, and a data block containing the level 2 results of the retrieval.
Schematically the file has the following structure :
 ______________________________
|                              |
|    Day Summary Block         |
|______________________________|
|                              |
|Profile 1 : Level 1 Header    |
|______________________________|
|                              |
|Profile 1 : Level 2 Data Block|
|______________________________|
|                              |
|Profile 2 : Level 1 Header    |
|______________________________|
|                              |
|Profile 2 : Level 2 Data Block|
|______________________________|
          .
          .
          .
         etc
4.2 The Access Routines

A set of FORTRAN subroutines to read the data are available from the HALOE software directory at the BADC. These are the routines supplied by the instrument team at NASA Langley which should compile and run on the majority of platforms.
A set of access routines written in IDL at the BADC is also available.
4.3 Third Party Software

In the software directories for the HALOE Level 2 data, there is a subdirectory for 3rd Party software. If you develop software to use with the HALOE Level 2 data, then we encourage you to let us have a copy so that we can make it available to other researchers.