MYD07_L2 - MODIS/Aqua Temperature and Water Vapor Profiles 5-Min L2 Swath 5km

" The MODIS Level-2 Atmospheric Profile product consists of several parameters: total-ozone burden, atmospheric stability, temperature and moisture profiles, and atmospheric water vapor. All of these parameters are produced day and night at 5x5 1-km pixel resolution when at least 9 FOVs are cloud free. There are two MODIS Atmosphere Profile data product files: MYD07_L2, containing data collected from the Terra platform; and MYD07_L2, containing data collected from the Aqua platform.

The MODIS total-ozone burden is an estimate of the total-column tropospheric and stratospheric ozone content. The MODIS atmospheric stability consists of three daily Level-2 atmospheric stability indices. The Total Totals (TT), the Lifted Index (LI), and the K index (K) are each computed using the infrared temperature- and moisture-profile data, also derived as part of MYD07. The MODIS temperature and moisture profiles are produced at 20 vertical levels. A clear-sky synthetic regression retrieval algorithm is used, where regression coefficients are derived by using a fast radiative transfer model with atmospheric characteristics taken from a dataset of global (radiosonde and model) profiles. The MODIS atmospheric water-vapor product is an estimate of the total column water vapor made from integrated MODIS infrared retrievals of atmospheric moisture profiles in clear scenes.

Ozone-retrieval methods used were developed using the NOAA polar-orbiting High Resolution Infrared Radiometer Sounders (HIRS). A first-guess perturbation method and radiances from MODIS channel 30 (9.6 µm) are used to solve the radiative transfer equation. The perturbations are with respect to some a priori conditions that may be estimated from climatology, regression, or more commonly, from an analysis or forecast provided by a numerical model. The MODIS cloud-mask product (MYD35_L2) is also be used to screen for clouds.

Atmospheric-stability estimates are derived from the MODIS temperature and moisture retrievals contained in this product. Layer temperature and moisture values may be used to estimate the temperature lapse rate of the lower troposphere and the low-level moisture concentration.

Temperature and moisture profile retrieval algorithms are adapted from the International TOVS Processing Package (ITPP), taking into account the lack of stratospheric channels and far higher horizontal resolution of MODIS. The profile retrieval algorithm requires calibrated, navigated, and co-registered 1-km FOV radiances from MODIS channels 25, 27-29, and 30-36. The MODIS cloud mask (MYD35_L2) is used for cloud screening. The algorithm also requires NCEP analysis of surface pressure.

Several algorithms exist for determining atmospheric water vapor, or precipitable water. It is most directly achieved by integrating the moisture profile through the atmospheric column. Split-window methods also exist, which use the difference in water-vapor absorption that exists between channel 31 (11 µm) and channel 32 (12 µm). Data validation is conducted by comparing results to in situ radiosonde, microwave radiometer and GPS measurements, GOES sounder operational retrievals, NCEP analyses, and retrievals from the AIRS/AMSU-A/HSB instrument package on the Aqua platform. Quality control will consist of manual and automatic inspections, with regional and global mean temperatures at 300, 500, and 700 hPa monitored weekly, along with 700 hPa dew-point temperatures and atmospheric water vapor. For total ozone, data validation will consist of comparing the TOMS retrievals to the MODIS retrievals.

For additional details see the MODIS Atmospheres web site page on Collection 6.1 Updates. "