GPS大气掩星技术在全球气候变化研究中的应用

Application of GPS Radio occultation data in global climate change study

人类活动引起全球变暖,衡量全球气候变化的指标有陆地、大气和海洋温度,水汽含量等等.研究对流层底层大气温度和水汽含量变化的传统方法是用数值天气预报模型和微波声纳,尚未实现用全球均匀覆盖的数据来做精确的定量研究.和GNSS系列卫星计划比较,最近发射的COSMIC卫星气象探测数据的空间、时间以及垂直分辨率都大大提高.采用COSMIC数据可以改进和量化南极洲的大气压力模型,并综合GNSS系列卫星测量的水汽和温度剖面研究全球气候变化.用一维协方差算法估计南极洲及附近海洋的大气压、温度和湿度剖面.把COSMIC卫星密集测量期间演算得到的大气折射率和GNSS系列卫星的结果进行比较.再和独立测量数据进行比较,包括南极洲自动气象观测站资料,数值天气预报模型资料,多种测高卫星水汽资料和海洋表面温度资料以及区域GPS水汽图.上述工作将改进发展中的气象遥感技术并应用于天气预报和空间天气预报及全球气候变化研究.

Land, air and ocean temperature, atmospheric water vapor content, and sea level rise are among the key indicators of global climate change as a result of anthropogenic warming. The lack of in situ observations has resulted in significant errors in Numerical Weather Prediction （NWP） models over the polar region, especially over Antarctica and its surrounding ocean. While contemporary studies of atmospheric （lower troposphere） temperature and water vapor variability have been based on NWP models and passive microwave sounders, while quantifications using an accurate and homogeneous global data set have not yet been unavailable. The recently launched constellation of 6-satellite COSMIC satellites in addition to CHAMP, GRACE and SAC C, provides an opportunity for global atmospheric observations via radio occultation fRO） including water vapor, temperature, and pressure profiles with improved spa- tial, temporal and vertical resolutions. Our primary scientific objective is to improve and quantify the pressure field modeling over Antarctic for mass balance studies, and to study the feasibility of using RO-derived water vapor and temperature profiles from the constellations of GNSS satellites （COSMIC, CHAMP, SAC-C） for climate change studies. We propose to validate RO retrieved atmospheric observations including refractivity （N）, and evaluate 1-D VAR algorithms to optimally estimate pressure, temperature and humidity profiles, focusing on Antarctica and surrounding seas, where air is largely dry with temperature 〈250°K. We will inter-compare retrieved N from COSMIC satellites during the Intensive Verification Period, and with CHAMP and SAC-C data. The external data products to be used include Automatic Weather Stations in Antarctica, NWPs （ECMWF, NCEP and Polar MM5s）, radar altimeter mission （TOPEX, ENVISAT, GFO, JASON） radiometer-measured integrated water vapor and NOAA-AMSU, and other radiometers, OSTIA sea surface temperature, and selected regional GPS-slant range derived water vapor tomography maps. The broader impacts of the study are its direct relevance to climate change studies, improving advanced remote sensing technologies for weather and space weather forecasting.