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_012.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:
- daily averages (24-hour)
- orbit averages (3-min about every 97 min)
- 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_012.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
