FY-3B与FY-3C/MWRI交叉定标及雪深算法应用

Intercalibrating FY-3B and FY-3C/MWRI for Synergistic Implementing to Snow Depth Retrieval Algorithm

FY-3C/MWRI于2015年7月30日开始业务运行,与FY-3B/MWRI对地表微波辐射进行联合观测。为保证MWRI亮温数据的可靠性、一致性以及综合双星MWRI观测数据应用雪深业务算法,利用地面近似稳定目标格陵兰岛冰盖与亚马逊热带雨林,对双星MWRI亮温数据进行交叉定标。分析了交叉定标前后FY-3B与FY-3C/MWRI雪盖面积及雪深反演结果的一致性,并以2013~2014年冬季气象站点的雪深观测数据评价了交叉定标对雪深反演精度的影响。结果表明:FY-3C/MWRI亮温数据与FY-3B/MWRI数据一致性较好,二者各通道的亮温平均偏差介于-0.87~2.05K之间,前者多数通道略偏"暖";绝对值大于3K的偏差比例在18H、36V、86H及86V等通道略高(10%~18%),其他通道比例均较低;FY-3B与FY-3C/MWRI雪盖面积及雪深估算结果一致性较好,交叉定标对雪盖面积反演影响较小,交叉定标后FY-3C/MWRI雪深反演误差(RMSE)略微降低,MWRI雪深反演结果更加稳定。

FY-3C/MWRI has been in operation since 30 July 2015,thus measuring microwave radiation of the Earth＇s surface jointly with FY-3B/MWRI.To ensure the reliability and consistency of MWRI data and synergistic implementation to snow depth retrieval algorithm, brightness temperatures at all channels from FY-3C/MWRI are calibrated against FY-3B/MWRI based on pseudo-invariant targets, i.e., the Greenland ice sheet and Amazon rain forest.Then snow depths and snow covered areas over China are estimated by u- tilizing FY-3B/MWRI operational algorithm from FY-3B, FY-3C, and calibrated FY-3C/MWRI data, of those consistency analyses are conducted separately.And impact of intercalibration on snow depth retrieval is evaluated with in situ observations acquired by meteorological stations during 2013-2014 winter.It is in- dicated that FY-3B and FY-3C/MWRI data performs good consistency, though brightness temperatures from FY-3C/MWRI are little warmer than that from FY-3B/MWRI at most channels.The average relative bias between FY-3C and FY-3B MWRI are generally ranging from --0.87 to 2.05 K depending on channels. In addition,a little high percent （10% - 18%） of absolute bias greater than 3K occurs at 18H, 36V, 89H and 89V channels.Evaluations show that FY-3B and FY-3C/MWRI generate similar snow covered area and snow depth data,and that intercalibration has little impact on snow covered area estimating.FY-3C/MWRI derives snow depth a bit more accurately and MWRI snow depth retrieval is more robust after intercalibra- tion.