IASI(Infrared Atmospheric Sounding Interferometer)是搭载在欧洲METOP.A卫星上,采用干涉分光技术的新一代超高光谱红外大气探测仪器,其光谱测量范围涵盖了多个吸收带,可用于反演大气、海洋、云和大气成分,为地球大气遥感、气象业务和科学研究提供了丰富的遥感资料,是各国学者关注的又一热点。为深入了解IASI在国内的云产品情况,本文利用2008年10月15日~12月15日期间IASI在安徽寿县地区的云参数观测资料和中美[美国能源部大气辐射测量(ARM)计划]联合在安徽省寿县进行大气辐射综合观测试验期间,相同时段云雷达[ARMW-band(95 GHz)Cloud Radar,WACR]的观测资料进行了对比分析和验证。在以寿县ARM移动观测设施(AMF)为中心,半径为20km的范围内,IASI(2次/d)共有有效观测129次,其中与WACR(1次/2S)匹配的IASI有效观测共80时次。结果表明:对于单层云,二者云高相关系数为0.8312,标准差为1.8423km;对于双层及多层云,IASI反演云顶高结果绝大多数在WACR的最上和最下层云之间,且靠近较厚的云层。对比结果显示,一般情况下,IASI反演云顶高结果明显低于WACR;IASI反演云顶高结果受到视场中云量、云层厚度及云层中粒子浓度大小的影响:视场中云量越大,云层越厚,云层中粒子浓度越大,IASI反演云高的结果越接近真实云高。
The Infrared Atmospheric Sounding Interferometer (IASI) is a new-generation super-high-spectrum sounding instrument based on the Michelson interferometer and is loaded on the METOP-A European meteorological polar-orbit satellite. IASI covers multiple absorption bands to retrieve atmosphere, ocean, cloud, and atmosphere components toprovide a wealth of remote sensing data for earth-atmosphere remote sensing, meteorological operations, and scientific research. Therefore, this instrument has gained increasing attention. To fully understand the applicability of IASI, a comparison is made in this study between the cloud top height products from IASI over Shouxian, Anhui Province, China, recorded from October 15 to December 15, 2008, and the cloud parameter information from W-band (95 GHz) Cloud Radar (WACR) supplied by the Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) deployed in Shouxian. Within 20 km of AMF, a total of 129 measurements were synchronously made by the two instruments, 80 of which by IASI matched the data from WACR at the nearest distance. For the single-layer, the correlation coefficient and the standard deviations of the differences between IASI and WACR were 0.8312 and 1.8423 km, respectively. Moreover, for two- or three-layered measurements, the cloud top heights by IASI were, on average, within the WACR top and bottom cloud boundaries and close with thicker clouds. The comparison reveals that the cloud top heights by IASI are lower than by WACR in most cases. With increasing cloud cover, cloud thickness in the field of view, and the concentration of particles in the clouds, the result from IASI approach the true value.