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Laboratory for Atmospheric and Space Physics

Level 4 Model

SEE Level 4 XPS Modeled Solar Irradiance Data

Download multiple days from the TIMED MDC

Level 4 XPS Calendar Access: Useful for finding data for a specific day.

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Level 4 XPS Data Directory– download any data file

XPS L4 Merged NetCDF file (single mission file) of the daily averaged XPS L4 data products

XPS L4A Merged NetCDF file (single mission file) of the observation averaged XPS L4 data products

Routine Time Series Plots


Detailed Level 4 XPS Model Description

README_SEE_XPS_L4_011.TXT – information for using XPS_L4 data

The SEE XPS Level 4 data are derived from the XPS Level 1 data products. The XPS Level 4 processing algorithm uses reference CHIANTI spectral models to generate a higher spectral resolution (0.1 nm) estimate of the solar XUV irradiance by scaling the model reference spectra to match the XPS photometer currents (signal). The CHIANTI Quiet Sun (QS) spectrum and Active Region (AR) spectrum are used with a scaling of the AR spectrum to match the minimum signal on each day, and then a CHIANTI isothermal flare spectrum is scaled to match the signal above the daily minimum signal. The flare temperature is determined from the ratio of the GOES XRS 0.1-0.8 nm irradiance to the GOES XRS 0.05-0.4 nm irradiance. These scaling factors, flare temperature, and resulting model spectrum in the 0-40 nm range in 0.1 nm intervals are in the XPS Level 4 data product for every measurement made by XPS photometer #1 or #2 (0.1-7 nm band).

A SEE XPS Level 4 data product is produced for each UT day, and these daily products are also merged into three different full mission data files:

  1. daily averages (24-hour)
  2. orbit averages (3-min about every 97 min)
  3. 1-minute averages (but with only about 3% duty cycle) available by request

The XPS Level 4 result in 0.1 nm intervals is also compressed into 1-nm intervals for use in the SEE Level 3 and Level 3A data products.

On-orbit instrument characterization is an ongoing effort, and the SEE team checks photometer degradation using redundant channels and underflight calibration rockets whose payload includes TIMED SEE prototype instruments.

The accuracy of the XPS Level 1 irradiance is 12%-26%, photometer dependent. There is additional uncertainty for applying the spectral model for the XPS Level 4 irradiances, and this estimated accuracy is 30% for the integrated XUV irradiance. The spectral distribution in the XPS Level 4 is from the CHIANTI model and not from direct measurements from XPS, a set of broadband photometers. The spectral distribution above 27 nm has been validated with the TIMED SEE EGS (27-190 nm, 0.4 nm resolution) measurements, so there is good confidence in the spectral distribution shortward of 27 nm.


Reading the Data with IDL

With read_netcdf.pro individual data files may be read using an IDL command such as:

read_netcdf,'xps_L4_2002022_011.ncdf',d,att

The data will then reside in the returned structure “d”, with each tag in the structure defined in the attributes array “att”. The wavelength for the model flux range from 0-40.0 nm in 0.1 nm intervals with 0.05 nm centers.


SEE Level 4 XPS Software

  • TIMED-SEE NetCDF README – Described IDL source code and gives examples using read_netcdf.pro and write_netcdf.pro
  • read_netcdf.pro – IDL procedure for reading NetCDF files as a structure
  • write_netcdf.pro – IDL procedure for writing a data structure (or array of structures) to a NetCDF file
  • plot_xps4.pro – IDL procedure for plotting a time series of SEE XPS Level 4 data.

SEE Level 4 XPS Model Solar Irradiance Data Format

Each data file contains an array of structures with as many elements as valid integration from XPS channel 1.

L4_XPS_DATA     STRUCT    = ->  Array[31]

Each L4_XPS_DATA structure has the following form:

** Structure <354828>, 14 tags, length=1652, data length=1650, refs=1:
   DATE            LONG           2002022
   TIME            FLOAT           1130.15
   XPS_QS          FLOAT           1.00000
   XPS_AR          FLOAT          0.211338
   XPS_FLARE       FLOAT       -0.00110218
   GOES_QS         FLOAT           1.00000
   GOES_AR         FLOAT         0.0229278
   GOES_FLARE      FLOAT         0.0451341
   FMTEMP          FLOAT           6.53379
   FMINDEX         INT             11
   FMWEIGHT        FLOAT          0.331066
   ERR_ABS         FLOAT          0.759908
   ERR_MEAS        FLOAT         0.0140824
   MODELFLUX       FLOAT     Array[400]

NetCDF file attributes for day 2002022

GLOBAL:

    Title = SEE XPS Level 4 Data Product - 1 nm spectrum

    Source = SEE POC at LASP / CU

    Mission = TIMED

    Data_product_type = XPS Level 4

    Data_product_version = 011

    Data_product_revision = 01

    Product_format_version = 001

    Software_version = 11.01

    Software_name = write_netCDF.pro called from xps_temp_model.pro

    Calibration_version = 11.01

    Description = Spectral XUV irradiance model based on calibrated XPS data and
      flare plasma temperature derived from GOES XRS

    History = 06/28/06 Don Woodraska Initial creation.

    Filename =
      /titus/timed/testing/data/science_dp/level4/xps_L4_2002022_011.ncdf

    Date_generated = Tue Aug 21 08:44:50 2012

DATE:

    Units = YYYYDOY

    Description = Year and day-of-year for the observation

TIME:

    Units = Seconds

    Description = Seconds of day for the center of the observation

XPS_QS:

    Units = None

    Description = Daily quiet-sun scale factor derived from XPS-1,-2 daily minimum
      (usually 1.0)

XPS_AR:

    Units = None

    Description = Daily active-region scale factor derived from XPS-1,-2 daily
      minimum (usually < 0.1)

XPS_FLARE:

    Units = None

    Description = Flare scale factor for each XPS-1,-2 integration with large
      numbers (> 2) indicating modest and large flares

GOES_QS:

    Units = None

    Description = Daily quiet-sun scale factor derived from GOES XRS-B daily
      minimum

GOES_AR:

    Units = None

    Description = Daily active-region scale factor derived from GOES XRS-B daily
      minimum

GOES_FLARE:

    Units = None

    Description = Flare scale factor for each GOES XRS-B integration with large
      numbers (> 2) indicating modest and large flares

FMTEMP:

    Units = Log10(K)

    Description = Flare model temperature derived from ratio of GOES XRS-B to
      XRS-A

FMINDEX:

    Units = None

    Description = Index into flare model table (indicating the temperature in
      model below the "fmtemp" value)

FMWEIGHT:

    Units = None

    Description = Weight parameter for the flare model at the "fmindex"
      temperature

ERR_ABS:

    Units = Fractional

    Description = Total combined standard uncertainty of the "modelflux" irradiance
      results (accuracy)

ERR_MEAS:

    Units = Fractional

    Description = Count-rate based combined standard uncertainty of the XPS-1,-2
      measurement (precision)

MODELFLUX:

    Units = W / m^2 / nm

    Description = Array of solar irradiances in 0.1 nm bins from 0 to 40 nm (on
      0.05 nm centers) based on scaling the Chianti spectral irradiance models using
      the calibrated XPS data and flare plasma temperature derived from GOES XRS