The Cambridge Chemical Assimilation Data were produced in the framework of the Enhanced atmospheric constituents data assimilation project (PI: David Lary) under the Assimilation of Remote-sensed Data for Applications in the Atmospheric and Oceanographic Sciences (ARDAAOS) NERC thematic programme.

The ever-increasing quantity and availability of observational data allows us to develop more accurate and more detailed atmospheric models than ever before. Unfortunately there is a drawback to having this amount of readily accessible information, namely the time that must necessarily be invested in sorting and extracting the required data. Given that different datasets are invariably presented in different file formats this process is usually performed from scratch each time, especially when data from more than one set is required. This data is designed to combat this problem by using:

• A common file format
• Flexible database import & export
• Rapid searching of large datasets

To gain access to this dataset, please apply for access to the Cambridge Chemical Assimilation data. The application includes the Met Office Agreement to completed online - you will receive email confirmation when access has been granted.

The file format is a column-based plain text file with one file for each day of observations from each instrument. The data usually consist of the date, time and location of the measurement along with the measurement itself and an estimate of the error on that value. In addition to these we add several other quantities describing the atmosphere at that location and time. The full list is given in the table below. Those quantities marked with an asterisk (*) are used as co-ordinates and may be used to specify limits in the search process.

The Assimilation of Remote-sensed Data for Applications in the Atmospheric and Oceanographic Sciences (ARDAAOS) Programme was a NERC thematic research programme directed at developing and promoting the expertise of the UK scientific community in the area of assimilation techniques applied to remote-sensed atmospheric and oceanographic data. The programme started in 1998 and ended in 2003. For further details of the programme see the ARDAAOS web page.

General queries about the data should be directed to BADC Support.