Zewen Wu, Xin Liu, Yunkai He, Haoyu Jiang, Bo Peng, Ke Huang. Corrections of shipboard GPS radiosonde soundings and applications on historical records in the eastern tropical Indian Ocean and South China Sea[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-024-2361-4
Citation:
Zewen Wu, Xin Liu, Yunkai He, Haoyu Jiang, Bo Peng, Ke Huang. Corrections of shipboard GPS radiosonde soundings and applications on historical records in the eastern tropical Indian Ocean and South China Sea[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-024-2361-4
Zewen Wu, Xin Liu, Yunkai He, Haoyu Jiang, Bo Peng, Ke Huang. Corrections of shipboard GPS radiosonde soundings and applications on historical records in the eastern tropical Indian Ocean and South China Sea[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-024-2361-4
Citation:
Zewen Wu, Xin Liu, Yunkai He, Haoyu Jiang, Bo Peng, Ke Huang. Corrections of shipboard GPS radiosonde soundings and applications on historical records in the eastern tropical Indian Ocean and South China Sea[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-024-2361-4
State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
2.
Hubei Key Laboratory of Marine Geological Resources, China University of Geosciences, Wuhan 430074, China
3.
Guangzhou Cigarette Factory of China Tobacco Guangdong Industrial Co., LTD., Guangzhou 510385, China
4.
Institute for Environmental and Climate Research, Jinan University, Guangzhou 511443, China
5.
Fujian Provincial Key Laboratory of Marine Physical and Geological Processes, Xiamen 361000, China
Funds:
The Second Tibetan Plateau Scientific Expedition and Research (STEP) program under contract No. 2019QZKK0102-02; the National Natural Science Foundation of China under contract Nos 42230402, 92158204, 42176026, 42076201, 41049903, 41149908, 41249906, 41249907, and 41249910; the Guangdong Basic and Applied Basic Research Foundation under contract No. 2022A1515240069; the Marine Economic Development Special Program of Guangdong Province (Six Major Marine Industries): Research and Demonstration of Critical Technologies for Comprehensive Pevention and Control of Natural Disaster in Offshore Wind Farms, China under contract No. 29[2023]; the Fund of Fujian Provincial Key Laboratory of Marine Physical and Geological Processes under contract No. KLMPG-22-02.
Shipboard radiosonde soundings are important for detecting and quantifying the multiscale variability of atmosphere-ocean interactions associated with mass exchanges. This study evaluated the accuracies of shipboard global positioning system (GPS) soundings in the eastern tropical Indian Ocean and South China Sea through a simultaneous balloon-borne inter-comparison of different radiosonde types. Our results indicate that the temperature and relative humidity (RH) measurements of GPS-TK radiosonde (used at most stations before 2012) have larger biases than those of CF-06-A radiosonde (widely used in current observation) when compared to reference data from Vaisala RS92-SGP radiosonde, with a warm bias of 5℃ and dry bias of 10% during daytimes, and a cooling bias of –0.8℃ and a moist bias of 6% during nighttime. These systematic biases are primarily attributed to the radiation effects and altitude deviation. An empirical correction algorithm was developed to retrieve the atmospheric temperature and RH profiles. The corrected profiles agree well with that of RS92-SGP, except for uncertainties of CF-06-A in the stratosphere. These correction algorithms were applied to the GPS-TK historical sounding records, reducing biases in the corrected temperature and RH profiles when compared to radio occultation data. The correction of GPS-TK historical records illustrated an improvement in capturing the marine atmospheric structure, with more accurate atmospheric boundary layer height, convective available potential energy, and convective inhibition in the tropical ocean. This study contributes significantly to improving the quality of GPS radiosonde soundings and promotes the sharing of observation in the eastern tropical Indian Ocean and South China Sea.
Figure 1. Geographical maps of GPS-TK (a) and CF-06-A (b) historical radiosonde records over the ETIO and SCS. colored symbols represent the various years when the datasets were collected.
Figure 2. Temperature (a) and RH (c) profiles of RS92-SGP (red), CF-06-A (blue) and GPS-TK (black) launched at (0°N, 86°E) at 13:33, 5 April 2012; temperature (b) and RH (d) profiles launched at (0.026°N, 84°E) at 19:38, 4 April 2012; horizontal and vertical axes in (a, b) represent temperature (℃) and altitude (km) and in (c, d) represent RH (%) and altitude (km); schematic on the simultaneous inter-comparison soundings (e). LT: lower troposphere; UT: upper troposphere; LS: lower stratosphere; MS: middle stratosphere.
Figure 3. Comparisons of GPS-TK radiosonde with COSMIC: mean (red) (a) and root mean square (RMS) (blue) (b) of GPS-TK temperature difference in daytime; comparisons of GPS-TK radiosonde with COSMIC: mean (red) (c) and root mean square (RMS) (blue) (d) of GPS-TK RH difference in daytime; comparisons of GPS-TK radiosonde with COSMIC: mean (red) (e) and root mean square (RMS) (blue) (f) of GPS-TK temperature difference in nighttime; comparisons of GPS-TK radiosonde with COSMIC: mean (red) (g) and root mean square (RMS) (blue) (h) of GPS-TK RH difference in nighttime. The collocation of COSMIC is within 3 h and 400 km. Gray lines: individual GPS-TK difference. LT: lower troposphere; UT: upper troposphere.
Figure 4. Mean (a) and RMS (b) of GPS-TK temperature differences in daytime; mean (c) and RMS (d) of CF-06-A temperature differences in daytime; mean (e) and RMS (f) of GPS-TK temperature differences in nighttime; mean (g) and RMS (h) of CF-06-A temperature differences in nighttime. Red lines: mean biases; gray lines: Individual differences; blue lines: RMS. LT: lower troposphere; UT: upper troposphere; LS: lower stratosphere; MS: middle stratosphere. Updated figure of Xie et al. (2014).
Figure 5. Mean (a) and RMS (b) of GPS-TK RH differences in daytime; mean (c) and RMS (d) of CF-06-A RH differences in daytime; mean (e) and RMS (f) of GPS-TK RH differences in nighttime; mean (g) and RMS (h) of CF-06-A RH differences in nighttime. Red lines: mean biases; gray lines: Individual differences; blue lines: RMS. LT: lower troposphere; UT: upper troposphere; LS: lower stratosphere; MS: middle stratosphere. Updated figure of Xie et al. (2014).
Figure 6. The around clock biases of temperature (a), RH (b), altitude (c), and refractivity (d) derived from GPS-TK minus RS92-SGP (blue line) and CF-06-A minus RS92-SGP (red line). The green line represents the daytime and nighttime demarcation line in local time. Rose-color values represent: temperature (a, ℃), RH (%) (b, %), altitude (c, m), and refractivity (d, %).
Figure 7. Temperature errors of GPS-TK (a) and CF-06-A (b) radiosondes in daytime and nighttime. Shown are: the mean nighttime error profile (blue), the mean sunrise time profile (green), the mean noontime profile (red), and the mean sunset time profile (purple).
Figure 8. RH errors of GPS-TK (a) and CF-06-A (b) radiosondes in daytime and nighttime. Shown are: the mean nighttime profile (blue), the mean sunrise-time profile (green), the mean noontime profile (red) and the mean sunset-time profile (purple).
Figure 9. Temperature errors of GPS-TK and CF-06-A corrected measurements by comparing to RS92-SGP. a and b. Mean and RMS temperature errors of corrected GPS-TK in daytime; c and d. mean and RMS temperature error sof corrected CF-06-A in daytime; e and f. mean and RMS temperature errors of corrected GPS-TK in nighttime; g and h. mean and RMS temperature error of CF-06-A in nighttime. Red line: mean error.
Figure 10. The RH errors of GPS-TK and CF-06-A corrected measurements by comparing to RS92-SGP. a and b. Mean and RMS RH errors of corrected GPS-TK in daytime; c and d. mean and RMS RH errors of corrected CF-06-A in daytime; e and f. mean and RMS RH errors of corrected GPS-TK in nighttime; g and h. mean and RMS RH errors of CF-06-A in nighttime. Red line: mean error.
Figure 11. Inter-comparison of GPS-TK historical records with COSMIC temperature measurements before and after correction. a and b. Mean and RMS temperature differences of GPS-TK in daytime before correction; c and d. mean and RMS temperature differences of GPS-TK in daytime after correction; e and f. mean and RMS temperature differences of GPS-TK in nighttime before correction; g and h. mean and RMS temperature differences of GPS-TK in nighttime after correction. The collocation of COSMIC is 3 h and 400 km.
Figure 12. Inter-comparison of GPS-TK historical records with COSMIC RH measurements before and after correction. a and b. Mean and RMS RH differences of GPS-TK in daytime before correction; c and d. mean and RMS RH differences of GPS-TK in daytime after correction; e and f. mean and RMS RH differences of GPS-TK in nighttime before correction; g and h. mean and RMS of GPS-TK RH differences in nighttime after correction. The collocation of COSMIC is 3 h and 400 km.
Figure 13. The atmospheric boundary layer height derived from RS92-SGP (red), GPS-TK (black) and CF-06-A (blue) in daytime (a, b) and nighttime (c, d) flights. Horizontal ordinate represents the release sample number. (a and c are derived from measurements before corrections; b and d are after corrections.)
Figure 14. Histograms of CAPEs (a) and CINs (b) derived from GPS-TK historical soundings during the JJA (June, July and August, 2006–2011) before (blue) and after (red) corrections.
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