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Atmosphere Profile Product
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Introduction

Product Description

The MODIS Atmospheric Profile product consists of several parameters: they are total-ozone burden, atmospheric stability, temperature and moisture profiles, and atmospheric water vapor. All of these parameters are produced day and night for Level 2 at 5x5 1-km pixel resolution when at least 9 FOVs are cloud free. There are two MODIS Atmosphere Profile data product files: MOD07_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 MOD07. 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.

Research and Application

Total-column ozone estimates at MODIS resolution are required by MODIS investigators developing atmospheric correction algorithms. This information is crucial for accurate land and ocean-surface-parameter retrievals. Furthermore, strong correlations have been found to exist between the meridional gradient of total ozone and the wind velocity at tropopause levels, providing the potential to predict the position and intensity of jet streams. Total-column ozone monitoring is also important due to the potential harm to the environment caused by anthropogenic depletion of ozone.

Atmospheric instability measurements are predictors of convective-cloud formation and precipitation. The MODIS instrument offers an opportunity to characterize gradients of atmospheric stability at high resolution and greater coverage. Radiosonde-derived stability indices are limited by the coarse spacing of the point-source data, too large to pinpoint local regions of probable convection.

Atmospheric temperature and moisture sounding data at high spatial resolution from MODIS and high spectral resolution sounding data from AIRS will provide a wealth of new information on atmospheric structure in clear skies. The profiles will be used to correct for atmospheric effects for some of the MODIS products (e.g., sea-surface and land-surface temperatures, ocean aerosol properties, water-leaving radiances, and PAR) as well as to characterize the atmosphere for global greenhouse studies.

Total-column precipitable-water estimates at MODIS resolution are required by MODIS investigators developing atmospheric-correction algorithms. This information is crucial for accurate land and ocean surface-parameter retrievals. MODIS will also provide finer horizontal-scale atmospheric water vapor gradient estimates than are currently available from the POES satellites.

Data Set Evolution

One of two ozone-retrieval methods developed using the HIRS will be chosen as best suited for application with MODIS data. Both use a first-guess perturbation method and radiances from MODIS channel 30 (9.6 µm) 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 (MOD35_L2) will also be used to screen for clouds.

Atmospheric-stability estimates will be 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 coregistered 1-km FOV radiances from MODIS channels 25, 27-29, and 30-36. The MODIS cloud mask (MOD35_L2) is used for cloud screening. The algorithm also requires NCEP analysis of surface pressure.

Several algorithms for determining atmospheric water vapor, or precipitable water, exist. It is most directly achieved by integrating the moisture profile through the atmospheric column. Other, split-window, methods also exist. This class of techniques uses the difference in water-vapor absorption that exists between channel 31 (11 µm) and channel 32 (12 µm). Data validation will be 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.

Additional Information

Coverage: Global, clear-sky only

Spatial/Temporal Characteristics: 5 km

Key Science Applications:

  • Ozone: atmospheric correction, predic-tion of cyclogenesis, anthropogenic ozone depletion
  • Atmospheric stability: atmospheric correction, prediction of convective cloudiness and precipitation, characterization of the atmosphere
  • Soundings: atmospheric correction algorithm development and use, characterization of the atmosphere
  • Total-column water vapor: atmospheric-correction algorithm development and use, characterization of the atmosphere

Key Geophysical Parameters: Total-column ozone, atmospheric stability (Total Totals, Lifted Index, and K index), atmospheric profiles of temperature and moisture, atmospheric total-column water vapor

Processing Level: 2

Product Type: Standard, at-launch

Maximum File Size: 28 MB

File Frequency: 288/day

Primary Data Format: HDF-EOS

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