News and Status
Terra was launched on December 18, 1999.
- Features of the new MOPITT Version 5 product are described in a recently published JGR paper titled "MOPITT Multispectral CO Retrievals: Origins and Effects of Geophysical Radiance Errors" (J. Geophys. Res., 116, D15303, doi:10.1029/2011JD015703). The paper describes the cause and characteristics of geophysical noise, as well as modifications to the MOPITT retrieval algorithm required to fully exploit MOPITT's near-infrared observations.
- The MOPITT multispectral CO product has recently been applied to analyze emissions of both CO and CO2 during the 2008 Beijing Summer Olympics. The results suggest that urban traffic controls instituted during the Olympics significantly reduced emissions of CO and CO2. A manuscript (authored by Helen Worden) describing this pioneering work has recently been submitted to Geophysical Research Letters.
- May, 2013: The MOPITT Version 6 Level 2 product is now available for the year 2008. This represents a preliminary release of the V6 product. Features of the V6 product include (1) correction of the geolocation bias in V4 and V5 products, (2) updated a priori based on the CAM-Chem model for 2000-2009, and (3) MERRA reanalysis for temperature and water vapor profiles, and a priori surface temperature. A preliminary User's Guide for the V6 product is available here. As described in the V6 User's Guide, the V6 data products are being released in HDF-EOS5 format and therefore will not be readable with tools developed for previous MOPITT products without significant revisions. Sample IDL code for opening and reading the V6 Level 2 product files is included as an Appendix in the V6 User's guide. While the V6 Level 2 product has been evaluated and is considered technically superior to the V5 product, the MOPITT Algorithm Development Team strongly encourages feedback from the user community with respect to both the content and format of the V6 product. Provided that the feedback is positive, we expect to release the V6 Level 2 and Level 3 products for the entire mission within a few months.
- December, 2012: As previously announced, V4 processing will officially end at the end of this month. Processing and deliveries of the V5-TIR, V5-NIR, and V5 TIR/NIR products will continue for the foreseeable future. A manuscript presenting validation results for the V5 products has been submitted to JGR. The V6 product, now in development, will feature: (1) correction of the geolocation bias in V4 and V5 products, (2) updated a priori based on the CAM-Chem model for 2000-2009, and (3) MERRA reanalysis for temperature and water vapor profiles, and a priori surface temperature. Users interested in evaluating the new V6 product prior to the official release should contact Merritt Deeter at firstname.lastname@example.org.
- June 2012: Processing and deliveries of MOPITT Version 4 ('V4') Level 1, 2, and 3 products will cease at the end of 2012. The MOPITT V4 product is based solely on thermal infrared (TIR) radiances, and is therefore similar to the newer Version 5 TIR-only product. However, unlike the V4 product, the V5 TIR-only product benefits from (1) explicit modeling of long-term changes in the correlation radiometer gas cells, thus reducing retrieval bias drift, (2) a new method for quantifying radiance uncertainties which accounts for the effects of geophysical noise, and (3) additional diagnostics, such as the retrieval error covariance matrix. Details of these changes can be found in the V5 User's Guide. Current users of the V4 product are encouraged to prepare for this change well in advance. Questions regarding differences between V4 and V5 products should be directed to Merritt Deeter at email@example.com.
A small systematic error in the MOPITT geolocation values (latitude and longitude) has been identified. A detailed report analyzing this effect and describing a correction method is available here. This issue affects both current (V4 and V5) and previous (V3) MOPITT operational products. In MOPITT daytime (descending) overpasses, reported longitudes (contained in the Level 1 and Level 2 data files) appear to be systematically biased by approximately 0.35 degrees to the west of MOPITT's actual field of view. Reported latitudes in daytime overpasses do not appear to be significantly biased. The longitudinal error is similar to the size of a single MOPITT field of view (~22 km). Longitudinal errors increase at high latitudes where lines of longitude converge. Geolocation errors for nighttime (ascending) overpasses are different than errors for daytime overpasses.
This data issue should be recognized particularly by researchers applying MOPITT products to study CO concentrations on fine spatial scales (e.g., tens of km). A method for eliminating this geolocation error at the initial stage of data processing is described in this report and will be implemented in the next operational MOPITT product (Version 6). For users of current MOPITT Level 2 and Level 3 products, the geolocation error can be corrected to first order using a latitude-dependent table of zonal-mean geolocation bias values included in this report.
Users of the MOPITT Version 5 (V5) product should be aware of several recent developments.
1. As detailed below, the V5 Level 1 and Level 2 products originally processed for the period March, 2000 - 2009 were affected by several minor processing problems; these products have been reprocessed and have been delivered to the NASA data archives. V5 Level 1 and Level 2 products for 2010 - present have also been delivered to the NASA data archives. New V5 Level 2 products for these two different periods (2000 - 2009 and 2010 - present) have been processed in a consistent manner. This reprocessing does not affect the maturity (e.g., 'provisional' or 'beta') of any of the products.
2. V5 Level 3 products for the entire mission (March, 2000 - present) have been generated and delivered to the NASA data archives.
3. 'Quick-look' daily and monthly images for MOPITT V5 products are now available on the MOPITT website.
Reasons for reprocessing V5 products. The initial production and delivery of MOPITT V5 products covered observations made from March, 2000 through the end of 2009. After delivering the original V5 L1 and L2 products, MOPITT SIPS personnel became aware of several minor processing problems. First, a software module called the 'Post-preprocessor' had been inadvertently disabled. This code implements a minor correction to the Level 0 data for MOPITT's PMC measurements (Channels 3 and 7). Second, the version of MOPFAS used to process the original V5 product for observations during 2009 was based on slightly inaccurate instrument parameters, producing a small radiance bias in Channel 7 radiances. Finally, it was determined that some MOPITT observations (up to several percent each day) were being discarded based on irrelevant instrument parameters. While the MOPITT team believes these technical problems would only concern a small number of MOPITT data users, these issues could conceivably cause larger problems in the future as the instrument slowly degrades. Filenames of the L1 and L2 products include the processing version number and therefore can be used to distinguish the original V5 products and the reprocessed V5 products. The original L1 filenames included the text string 'L1V3.36' whereas the reprocessed L1 files include 'L1V3.37'. The original L2 filenames included the text string 'L2V10.0' whereas the reprocessed L2 files include 'L2V10.1'.
Users of the MOPITT Version 4 (V4) product should be aware of a recent minor instrumental reconfiguration. Because of this issue, the MOPITT L2V8.1 product for March 26-29, 2011, is invalid and has been replaced by the L2V8.2 product.
In October, 2009, one of MOPITT's molecular sieve heaters malfunctioned and became inoperable. Processing algorithms were then revised so that the sieve heater problem did not affect the V4 retrieval products. Following the hot calibration and decontamination performed in mid-March, 2011, this same sieve heater appears to be again functioning normally.
Just as in 2009, data processing algorithms have been revised to account for the slight change in cell pressure resulting from the action of the sieve heater; the consistency of retrieval results before and after the recent hot calibration/decontamination has been verified. Beginning March 26, 2011, the valid MOPITT Version 4 Level 2 product is labeled as L2V8.2 (as in the file MOP02-20110326-L2V8.2.2.prov.hdf). The previous MOPITT product (for the period between October 4, 2009 and March 13, 2011) is labeled L2V8.1.
For a brief period, the L2V8.1 product was generated for MOPITT observations between March 26 and March 29, 2011 and was made available at the DAAC. Any users who might have downloaded the L2V8.1 files for these dates should delete them and replace them with the L2V8.2 product.
- April 2011: The MOPITT V5 product (described below and in the V5 User's Guide) is now available for 2000-2009 through both the NASA ECHO/Reverb system and the ASDC Data Pool.
The 'Version 5' MOPITT product is now being processed and will become publicly available during the first quarter of 2011. This product will, for the first time, include information from the MOPITT near-infrared (NIR) channels in addition to the thermal-infrared (TIR) channels. As a result, the new 'multispectral' TIR/NIR MOPITT product features improved sensitivity to CO near the surface than the V3 and V4 TIR-based products. (See Worden et al., 2010).
The new product also benefits from an improved cloud detection algorithm and is better suited to climate studies than the earlier V3 and V4 products because it exploits a time-dependent radiative transfer model which accounts for long-term instrumental degradation.
Processing of the MOPITT V4 product will continue at least until the summer of 2011.
To serve the diverse needs of MOPITT's users, three different products will be generated based on different subsets of the MOPITT observations. Each of these products will be made available as both swath-format Level 2 data and daily and monthly gridded Level 3 data. (Level 3 data products may become available after the L2 data become available.)
The new V5 products will include:
- A TIR-only product, similar to the MOPITT V4 product. This product will initially be released as 'provisionally validated.' Compared to V4, this product offers improved long-term stability and more accurately accounts for random errors due to geophysical noise.
- A new NIR-only product, qualitatively similar to the ENVISAT SCIAMACHY CO product. This 'beta' product will be available only for daytime observations over land. Users should be very cautious in using this product, and are encouraged to collaborate with MOPITT science team members to exploit it properly. Compared to earlier TIR-based MOPITT products, this product exhibits larger random errors and may require significant spatial and/or temporal averaging.
- A new multispectral TIR/NIR product, featuring the maximum sensitivity to near-surface CO. In this 'beta' product, information from the NIR channels is limited to daytime observations over land. Users should be very cautious in using this product, and are encouraged to collaborate with MOPITT science team members to exploit it properly. Compared to earlier TIR-based MOPITT products, this product exhibits larger random errors and may require significant spatial and/or temporal averaging.
An update to the MOPITT V4 User's Guide to assist users with the V5 product is being prepared. The V5 HDF files will contain all of the V4 data types in addition to new diagnostics, such as the 'a posteriori' retrieval error covariance matrix and more detailed cloud information. The new V5 products will employ the same 10-level retrieval grid used for V4, but the association between retrieval levels and atmospheric layers has been modified. Specifically, for V5 products, each retrieval 'level' in fact corresponds to a uniformly-weighted layer immediately above that level. For example, the V5 surface-level retrieval product corresponds to the mean volume mixing ratio over the layer between the surface and 900 hPa. Quantitatively, this change may be important when comparing MOPITT products to model output or in-situ data exhibiting strong vertical gradients in the CO profile.
- January 2010:
Near real-time MOPITT L2 and L3 products are being
produced near for
applications that need faster access to the data than our normal
operational products via the ASDC. There are two types of NRT
- 2-hour (NRT2): two-hour granule level 2 only products with about a six hour delay from real-time
- daily (NRT): daily level 2 and level 3 products six hours after the last granule is received
- October 2009: Near the end of October 3, a backup system employing a molecular sieve to control the pressure in one of MOPITT's Length Modulation Cells (LMCs) became unresponsive. The associated LMC is shared by radiometers for Channels 5 and 6. The apparent failure of the sieve heater led to a weak drop in operating pressure from about 68.5 kPa to 65.3 kPa in a span of about six hours. The effect of this pressure drop on the calibrated radiances and retrieval products was quickly evaluated and the data processing software revised accordingly. Comparisons of data products just before and after the failure of the sieve heater exhibit no observable discontinuities. Since Level 2 data products for the period after the sieve heater failure are not yet fully validated, they are currently labeled as 'provisional' and are identifiable with the string 'L2V8.0.8' in the filename (e.g., 'MOP02-20091004-L2V8.0.8.prov.hdf').
- September 2009: After extensive modeling and analysis of the cooler malfunction, MOPITT was restarted on September 28 with slightly reduced amplitude for the displacer unit on the malfunctioning cooler. Following a cool-down period, science-quality data began flowing again on September 30. Analysis of engineering data, calibrated radiances and retrieval products reveal no measurable degradation of the MOPITT products following MOPITT's idle period between July 28 and September 28. No MOPITT products will be available for this period since the instrument was not operating in science mode.
- July 2009: On July 28, one of the two coolers of the MOPITT instrument developed a malfunction causing the instrument to turn itself off. It was soon determined that no permanent damage had been suffered by the instrument but that operating parameters of the malfunctioning cooler would require some adjustments before the instrument could be returned to operations.
The MOPITT Version 4 product, released as a 'provisional' product in April, is now officially 'validated.' This means that the algorithm used to produce the V4 product is final. V4 validation results will soon be posted on the
page. Users will notice that the Level 2 files now include the string 'val' instead of 'prov' (e.g., 'MOP02-20030303-L2V8.0.2.val.hdf' instead of 'MOP02-20030303-L2V8.0.2.prov.hdf').
Processing of the MOPITT Version 3 product will cease on July 31, 2009.
Users of the V4 product should also obtain the latest revision of the Version 4 User's Guide (updated May 28, 2009) on the Publications page. (Significant revisions include a fuller discussion of array dimensioning issues, and a correction in Appendix 7.4 related to the calculation of the total column averaging kernel.)
The MOPITT Science Team at the National Center of Atmospheric Research announces the availability of the Version 4 product for tropospheric carbon monoxide.
This product is currently 'provisional' and is available both from the
NASA Langley Data Pool
New Level 2 and Level 3 (gridded) products are available.
Users of the new V4 product should obtain the new V4 User's Guide available at the
or through the Langley Data Pool.
Processing of the current V3 product will cease this summer.
The retrieval algorithm used to generate the V4 product benefits from significant advances in radiative transfer modeling, state vector representation, and a priori statistics. Differences between the V3 and V4 products are generally significant and are detailed in the V4 User's Guide. Retrieval performance has been improved in many respects, particularly in regions of very low and very high CO concentrations. Problems with long-term bias drift are also evidently weaker in V4 than in V3. The new V4 product also includes new diagnostics, including the retrieval averaging kernels.