气象科技进展
氣象科技進展
기상과기진전
Advances in Meteorological Science and Technology
2013年
4期
50-59
,共10页
风云三号B星(FY-3B)%微波湿度计(MWHS)%微波湿度计(MHS)%主成分分析方法
風雲三號B星(FY-3B)%微波濕度計(MWHS)%微波濕度計(MHS)%主成分分析方法
풍운삼호B성(FY-3B)%미파습도계(MWHS)%미파습도계(MHS)%주성분분석방법
Fengyun-3B (FY-3B)%MicroWave Humidity Sounder (MWHS)%Microwave Humidity Sounder (MHS)%principal component analysis (PCA)
风云三号A星和B星上的微波湿度计（MWHS）在183GHz附近有3个水汽探测通道（通道3～5）。搭载在MetOp和NOAA卫星上的微波湿度计（MHS）在相同频率上也有3个水汽探测通道。MWHS和MHS都是跨轨扫描仪器。通过对比MWHS观测亮温和用辐射传输模式模拟得到的亮温，发现在这3个通道的观测中都存在着沿轨道方向、随扫描角变化的直线形噪音。即使对足够长时间里的大量资料进行平均分析，该噪音也没有消除，说明噪音并不是由大气或地表的自然变化引起的。通道3～5噪音的大小分别是0.3，0.2和0.2K。用主成分分析方法（PCA）对MWHS一个月的资料进行研究，发现MWHS的直线形噪音主要存在于第一模态中，MWHS的直线形噪音叠加在该模态所主要描述的观测亮温随扫描角变化特征，即跨轨仪器的主要特性。对于这3个水汽探测通道，第一主成分解释了超过99.91%的总方差。将第一主成分进行5点平滑再对原观测数据重构可以有效地去除MWHS资料中的噪音。重构后的资料随扫描角的变化变得比较平滑，与MHS偏差随扫描角的变化特征一致。
風雲三號A星和B星上的微波濕度計（MWHS）在183GHz附近有3箇水汽探測通道（通道3～5）。搭載在MetOp和NOAA衛星上的微波濕度計（MHS）在相同頻率上也有3箇水汽探測通道。MWHS和MHS都是跨軌掃描儀器。通過對比MWHS觀測亮溫和用輻射傳輸模式模擬得到的亮溫，髮現在這3箇通道的觀測中都存在著沿軌道方嚮、隨掃描角變化的直線形譟音。即使對足夠長時間裏的大量資料進行平均分析，該譟音也沒有消除，說明譟音併不是由大氣或地錶的自然變化引起的。通道3～5譟音的大小分彆是0.3，0.2和0.2K。用主成分分析方法（PCA）對MWHS一箇月的資料進行研究，髮現MWHS的直線形譟音主要存在于第一模態中，MWHS的直線形譟音疊加在該模態所主要描述的觀測亮溫隨掃描角變化特徵，即跨軌儀器的主要特性。對于這3箇水汽探測通道，第一主成分解釋瞭超過99.91%的總方差。將第一主成分進行5點平滑再對原觀測數據重構可以有效地去除MWHS資料中的譟音。重構後的資料隨掃描角的變化變得比較平滑，與MHS偏差隨掃描角的變化特徵一緻。
풍운삼호A성화B성상적미파습도계（MWHS）재183GHz부근유3개수기탐측통도（통도3～5）。탑재재MetOp화NOAA위성상적미파습도계（MHS）재상동빈솔상야유3개수기탐측통도。MWHS화MHS도시과궤소묘의기。통과대비MWHS관측량온화용복사전수모식모의득도적량온，발현재저3개통도적관측중도존재착연궤도방향、수소묘각변화적직선형조음。즉사대족구장시간리적대량자료진행평균분석，해조음야몰유소제，설명조음병불시유대기혹지표적자연변화인기적。통도3～5조음적대소분별시0.3，0.2화0.2K。용주성분분석방법（PCA）대MWHS일개월적자료진행연구，발현MWHS적직선형조음주요존재우제일모태중，MWHS적직선형조음첩가재해모태소주요묘술적관측량온수소묘각변화특정，즉과궤의기적주요특성。대우저3개수기탐측통도，제일주성분해석료초과99.91%적총방차。장제일주성분진행5점평활재대원관측수거중구가이유효지거제MWHS자료중적조음。중구후적자료수소묘각적변화변득비교평활，여MHS편차수소묘각적변화특정일치。
MicroWave Humidity Sounder (MWHS) onboard both Fengyun-3A (FY-3A) and FY-3B satellites have three channels (channels 3-5) near the 183-GHz water-vapor absorption line. These channel frequencies are also used in other instruments such as Advanced Microwave Sounding Unit-B (AMSU-B) and Microwave Humidity Sounder (MHS) onboard MetOp and NOAA satellites. Both MWHS and MHS are cross-track scanners. In this paper, a comparison between the simulated brightness temperatures with MWHS measurements clearly shows that MWHS observations from the three sounding channels contain a scan-angle-dependent cohesive noise along the instrument scanline. This noise does not cancel out when a large amount of data over a sufifciently long period of time is averaged, which eliminates the possibility of such a noise to arise from the natural variability of the atmosphere and the surface. The noises are around 0.3, 0.2, and 0.2 K for channels 3-5, respectively. A principle component analysis is used for the characterization of this cohesive noise using one-month FY-3B MWHS data. It is shown that the MWHS cohesive noise is primarily contained in the ifrst principal component (PC) mode, which mainly describes a scan-angle-dependent brightness temperature variation, i.e., a unique feature of the cross-tracking instrument. The ifrst PC accounts for more than 99.91%total variance in the three MWHS sounding channels. A ifve-point smoother is then applied to the ifrst PC, which effectively removes such a data noise in the MWHS data. The reconstruction of the MWHS radiance spectra using the noise-ifltered ifrst PC component is of good quality. The scan-angle-dependent bias from the reconstructed MWHS data becomes more uniform and is consistent with the NOAA-18 MHS data.
