ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Impact of Sounding Balloon Drift on Temperature Differences between Microwave Radiometer and Radiosonde
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Abstract:
To evaluate the reliability of the atmospheric temperature profiles retrieved by the Microwave Radiometer (MWR) and the impact of sounding balloon drift on the temperature difference (δT) between MWR and radiosonde, more than two years of temperature profile derived from MWR are tested against those from radiosondes. A method for quantitative assessment of bias in radiosonde temperature caused by the drift of sounding balloon has been proposed. It is demonstrated that: (1) There are significant temporal and spatial changes in the consistency of the temperatures acquired by MWR (TMWR) and radiosonde (TSONDE). The correlation coefficients between TMWR and TSONDE are found to be higher in spring and autumn than in summer and winter, and better correlation is always detected at lower altitude for all seasons. (2) At a given altitude, the δT is significantly negatively correlated with the ambient temperature represented by TSONDE. The higher the temperature, the more obvious the underestimation of the temperature by the MWR, and vice versa, leading to a phenomenon of "overestimating low temperature and underestimating high temperature", which is more obvious at high altitudes than at low altitudes, and in winter and summer than in spring and autumn. (3) The drift of sounding balloon causes the sounding temperature to be higher than the actual temperature right above the radiosonde sites in all seasons, and the biases in radiosonde temperature records are negatively correlated with the environmental temperature. Therefore, sounding balloon drift causes MD to be overestimated, and the degree of dispersion in δT to be underestimated, resulting in underestimation of the correlation between δT and ambient temperature as well as the severity of "overestimating low temperature and underestimating high temperature" of MWR. Overall, the influence of sounding balloon drift on the standard deviation of δT and root mean square deviation of the microwave radiometer and radiosonde temperature is below 2%, and its contribution to δT is much smaller than that of the retrieval algorithm.
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