ACE-MAESTRO Data Version 1.2 June 9, 2006 ================================================================================ 1. A description of the versions A version change is caused by these factors: 1) major forward model and/or retrieval algorithm changes; 2) Input data changes such as version changes of the input ACE-FTS retrieved pressure and temperature (p,T) profile data; 3) Changes of the tuning instrument parameters. So far three data products were generated: Version 1.0: The first MAESTRO data product covers the period from Feb 2004 to May 2005. This version utilized various versions of ACE-FTS retrieved p,T profiles, e.g. versions 1, 2.0, 2.1, 2.2. Version 1.1: This data set was produced uniformly based on version 2.2 of FTS p,T profiles and covers the period from Feb 2004 to Feb 2006. In the future this version will no longer be processed. Users are encouraged to use version 1.2 instead. Version 1.2: This data product was also based on uniform version 2.2 of FTS p,T profiles. Comparing to version 1.1 it utilized an optimal set of instrument parameters in time shift, UV spectrometer angle shift and VISIBLE spectrometer angle shift. The three shifts are relative to the ACE-FTS instrument. Version 1.2 is currently at on-going processing stage. Nitrogen dioxide (NO2) and ozone (O3) mixing ratios as well as UV and VISIBLE optical depth are the routine products. Data descriptions are given in section 2 and 3. Section 4 describes the ancillary data such as longitude and latitude information. ================================================================================ 2. Mixing ratio data Six mixing ratio data products were generated in version 1.2. The files are stored in directories like \2004_02, etc. One directory stores approximately one month of data. Note that one directory of certain month may contain data from other months. The date and time can be determined fully by the file name rather than reflected by the directory name. The data types can be identified in terms of the fixed sub-strings in the file names. 1) _uno2_: NO2 profile retrieved from the UV spectrometer at the measurement tangent altitudes. 2) _uno2g_: NO2 profile interpolated at the regular tangent height grid from the _uno2_ profile 1). 3) _uo3_: O3 profile retrieved from the UV spectrometer at the measurement tangent altitudes. 4) _uo3g_: O3 profile interpolated at the regular tangent height grid from the _uo3_ profile 3). 5) _vo3_: O3 profile retrieved from the VISIBLE spectrometer at the measurement tangent altitudes. 6) _vo3g_: O3 profile interpolated at the regular tangent height grid from the _vo3_ profile 5). 2.1 File naming convention of the mixing ratio data A file name is composed of following information: orbit number, data type, date and time. For example, "ss2825_uno2_040220_185958_27.dat" reads: "SunSet Orbit ss2825, UV retrieved NO2, measurement starting at 2004/02/20, 18:59:58UTC, using action table 27". Among these items, the action table number is irrelevant to general users. The file names after Aug. 10, 2005 18:10UTC have an additional 'B' character before the two-digit action table number. This denotes the phase "B" measurement after that time when MAESTRO adopted a new measurement scheme by doubling the sampling rate for the interesting altitude range. For the SunRise data, the first two letters are "sr". 2.2 Formats of the mixing ratio data Data formats for products at measurement points and interpolated grids are slightly different: 1) At measurement points Rows 1-10: Ten header lines, indicating the program version and the date. Just skip them. Follows are 6-column rows: -Index: Number of the data count. -Heights: The MAESTRO measurement tangent height estimated from the FTS tangent height. Additional 3 grid points at 654km, 100km and 0km were also included. -Nitrogen_Dioxide or Ozone: The retrieved Volume Mixing Ratio (VMR) in ppv (parts per volume). The values at 654km, 100km, and 0km were obtained from the first guess. -Error: The unitless fractional error transformed from instrument noise through the spectral fitting code and profile retrieval. This is essentially the random noise and does not contain the systematic error component. -Ret: Flag for retrieved with 1, or not retrieved with 0. -Time: Elapsed seconds in the day. 2) At interpolated regular grid Rows 1-10: Ten header lines, indicating the program version and the date. Just skip them. Follows are 5-column rows: -Index: Number of the data count. -Heights: A regular grid of the tangent height from 0km to 100km with the interval of 0.5km. -Nitrogen_Dioxide or Ozone: Logarithmically interpolated Volume Mixing Ratio (VMR) in ppv from the measurement points as given by product 1). -Error: Unitless fractional error interpolated from the measurement points. -Retrieved?: Flag for retrieved with 1, or not retrieved with 0. ================================================================================ 3. The optical depth data The optical depth data are produced as a routine product. They are stored in directories od_h\2004_02\ ... on monthly basis. Like the mixing ratio data the date and time can be determined fully by the file name. 3.1 The file naming convention of the optical depth data The optical depth data have two files for each measurement. One is for UV, the other for VISIBLE. The naming convention is similar to the mixing ratio files. For example, "ss2826_odu_040220_185958_27.dat" reads: "Sunset Orbit 2826, Optical Depth for UV, measurement starts at 2004/02/20 18:59:58UTC, using action table 27". The file names after Aug. 10, 2005 18:10UTC have an extra 'B' character before the two-digit action table number. This denotes the phase "B" measurement after that time when MAESTRO adopted a new sampling scheme. For the corresponding VISIBLE optical depth data, the sub-string "odu" is replaced by "odv". For the SunRise data, the first two letters are "sr". 3.2 Optical Depth data format Both UV and VISIBLE optical depth data have the same format. The structure is as follows: i) Rows 1-2: Two header lines of the file, just skip them. ii) Row 3: One header line for one spectrum measurement. In this line, three parameters after "TIME:" are important. They are date (yymmdd), time in UTC (hhmmss), elapsed kilo-seconds of the day. For example, in "ss2826_odu_040220_185958_27.dat", the third row contains "TIME: 040220 190042.080 68.442080", meaning "date at 2004/02/20, time at 19:00:42.08UTC, which is equivalent to the elapsed 68.442080 ksec in kilo-seconds". iii) Row 4: The tangent height in km at the time given in Row 3. Any missing altitude is filled with a default value of 999.9. iv) Rows 5 - 1029: The 1024 lines represent 1024 pixels of the optical depth. Each row is given by two columns: the first is the estimated wavelength in nm, the second the optical depth (unitless). The data gaps are filled with either infinite number of "1.#INF0e+000" or a Non-A-Number of "-1.#IND0e+000". v) Repeat ii) - iv) for N times. ================================================================================ 4. Ancillary data Ancillary data are those additional data associated with the measurement such as geolocation data. The linkage of the profile data or optical depth data with the ancillary data is through the common orbit number. The orbit number is the common key for linking all different types of data in ACE database. 4.1 Geolocation data Two files "SunriseTable.txt" and "SunsetTable.txt" are lookup tables of partial geolocation information for each occultation. Each file contains six columns. They are: -Orbit number -Date -Time in UTC at 30km tangent height -latitude at 30km tangent height -longitude at 30km tangent height -beta angle ================================================================================ 5. Reference The background of the instrument and the retrieval can be found in: McElroy C.T. (1995), A spectroradiometer for the measurement of direct and scattered solar spectral irradiance from on-board the NASA ER-2 high altitude research aircraft, Geophys. Res. Lett., 22, 1361-1364. McElroy C.T., C. Midwinter, D.V. Barton, and R.B. Hall (1995), A comparison of J-values estimated by the composition and photodissociative flux measurement with model calculation, Geophys. Res. Lett., 22, 1365-1368. Jason Zou jzou@atmosp.physics.utoronto.ca Tel: 416-9781297, Fax: 416-9788905