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Johnson, L. R.

Publications and source records attributed to Johnson, L. R..

4 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Rain volume estimation over areas using satellite and radar data

The analysis of 18 convective clusters demonstrates that the extension of the Area-Time-Integral (ATI) technique to the use of satellite data is possible. The differences of the internal structures of the radar reflectivity features, and of the satellite features, give rise to differences in estimating rain volumes by delineating area; however, by focusing upon the area integrated over the lifetime of the storm, it is suggested that some of the errors produced by the differences in the cloud geometries as viewed by radar or satellite are minimized. The results are good and future developments should consider data from different climatic regions and should allow for implementation of the technique in a general circulation model.

Doneaud, Andre A.↗
NASA NTRS1984

Rain Volume Estimation over Areas Using Satellite and Radar Data

The application of satellite data to a recently developed radar technique used to estimate convective rain volumes over areas on a dry environment (the northern Great Plains) is discussed. The area time integral technique (ATI) provides a means of estimating total rain volumes over fixed and floating target areas of the order of 1,000 to 100,000 km(2) for clusters lasting 40 min. The basis of the method is the existence of a strong correlation between the area coverage integrated over the lifetime of the storm (ATI) and the rain volume. One key element in this technique is that it does not require the consideration of the structure of the radar intensities inside the area coverage to generate rain volumes, but only considers the rain event per se. This fact might reduce or eliminate some sources of error in applying the technique to satellite data. The second key element is that the ATI once determined can be converted to total rain volume by using a constant factor (average rain rate) for a given locale.

Doneaud, A. A.↗
NASA NTRS1984

An attempt to extend the ATI technique to estimate convective rain volumes using satellite data

Digital satellite and radar data of a thunderstorm event that occurred on June 12, 1981 are examined. The processing of both data sets is described. Cumulative area versus count values, and threshold count values for IR and visible satellite data for 13 consecutive time steps are analyzed. The IR and visible satellite images are compared. The relation between radar reflectivity, temperature, and echo height is studied.

Doneaud, A. A.↗