| Calculating Dropwindsonde Location and Time from TEMP-DROP Messages for Accurate Assimilation and Analysis - :17966 | Office of Oceanic and Atmospheric Research (OAR)
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Calculating Dropwindsonde Location and Time from TEMP-DROP Messages for Accurate Assimilation and Analysis
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  • Description:
    Current practice is to transmit dropwindsonde data from aircraft using the TEMP-DROP format, which provides only the release location and time with 0.1 degrees latitude x 0.1 degrees longitude (about 11 km) and 1-h resolutions, respectively. The current dropwindsonde has a fall speed of approximately 15 ms s(-1), so the instrument will be advected faster horizontally than it will descend if thewind speed exceeds this value. Where wind speeds are greatest, such as in tropical cyclones, this will introduce large errors in the location of the observations, especially near the surface. A technique to calculate the correct time and location of each observation in the TEMP-DROP message is introduced. The mean differences between the calculated and reported locations are about 0.5 km for distance and 15 s for time, or <1% of the error size for distance and <10% for time.

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