Comparisons of the temperature and humidity profiles of reanalysis products with shipboard GPS sounding measurements obtained during the 2018 Eastern Indian Ocean Open Cruise

摘要

TIt is important to be able to characterize the thermal conditions over the equatorial Indian Ocean for both weather forecasting and climate prediction. This study compared the equatorial eastern Indian Ocean (EEIO) temperature and relative humidity profiles from three reanalysis products (JRA-55, MERRA2, and FGOALS-f2) with shipboard global positioning system (GPS) sounding measurements obtained during the Eastern Indian Ocean Open Cruise in spring 2018. The FGOALS-f2 reanalysis product is based on the initialization module of a sub-seasonal to seasonal prediction system with a nudging-based data assimilation method. The results indicated that: (1) both JRA-55 and MERRA2 were reliable in characterizing the temperature profile from 850 to 600 hPa, with a maximum deviation of about <0.5°C. Both datasets showed a large negative deviation below 825 hPa, with a maximum bias of about 2°C at 1000 hPa and 1.5°C at 900 hPa, respectively. (2) JRA-55 showed good performance in characterizing the relative humidity profile above 850 hPa, with a maximum deviation of < 8%, while it showed much wetter conditions below 850 hPa. MERRA2 overestimated the relative humidity in the middle to lower troposphere, with a maximum deviation of about 15% at 925 hPa. (3) The FGOALS-f2 reanalysis product more accurately reproduced the temperature profile in the marine atmospheric boundary layer over the EEIO than that in JRA-55 and MERRA2, but showed much wetter conditions than the GPS sounding observations, with a maximum deviation of up to 20% at 600 hPa. Future applications of GPS sounding datasets are discussed.摘要本研究利用2018年春季东印度洋科学考察航次采集的GPS探空数据集，分析了三套再分析资料（JRA-55、MERR2和FGOALS-f2）对赤道东印度洋对流层中低层大气温湿廓线的模拟能力。结果表明：JRA-55和MERRA2能合理地再现850-600hPa之间的温度廓线的特征，最大偏差小于0.5度，但在850hPa以下的偏差增大，最底层的偏差分别达到了2和1.5度；两套再分析资料对850-600hPa之间的湿度扩线也具备较好的再现能力，但在850hPa以下JRA55和MERRA2再分析资料高估了相对湿度，最大湿度偏差可达15%。相对而言，FGOALS-f2分析资料对温度廓线再现能力最好，边界层内的温度偏差明显小于其它两套再分析资料；但FGOALS-f2也存在整层偏湿的问题，最大偏差在600hPa附近，误差接近20%。