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1.
Results are presented from the on-orbit calibration of the Jason Microwave Radiometer (JMR). The JMR brightness temperatures (TBs) are calibrated at the hottest and coldest ends of the instrument's dynamic range, using Amazon rain forest and vicarious cold on-Earth theoretical brightness temperature references. The retrieved path delay values are validated using collocated TOPEX Microwave Radiometer and Radiosonde Observation path delay (PD) values. Offsets of 1–4 K in the JMR TBs and 8–12 mm in the JMR PDs, relative to TMR measurements, were initially observed. There were also initial TB offsets of 2 K between the satellite's yaw state. The calibration was adjusted by tuning coefficients in the antenna temperature calibration algorithm and the antenna pattern correction algorithm. The calibrated path delay values are demonstrated to have no significant bias or scale errors with consistent performance in all nonprecipitating weather conditions. The uncertainty of the individual path delay measurements is estimated to be 0.74 cm ± 0.15, which exceeds the mission goal of 1.2 cm RMS. 相似文献
2.
Jason Microwave Radiometer Performance and On-Orbit Calibration 总被引：2，自引：0，他引：2
Results are presented from the on-orbit calibration of the Jason Microwave Radiometer (JMR). The JMR brightness temperatures (TBs) are calibrated at the hottest and coldest ends of the instrument's dynamic range, using Amazon rain forest and vicarious cold on-Earth theoretical brightness temperature references. The retrieved path delay values are validated using collocated TOPEX Microwave Radiometer and Radiosonde Observation path delay (PD) values. Offsets of 1-4 K in the JMR TBs and 8-12 mm in the JMR PDs, relative to TMR measurements, were initially observed. There were also initial TB offsets of 2 K between the satellite's yaw state. The calibration was adjusted by tuning coefficients in the antenna temperature calibration algorithm and the antenna pattern correction algorithm. The calibrated path delay values are demonstrated to have no significant bias or scale errors with consistent performance in all nonprecipitating weather conditions. The uncertainty of the individual path delay measurements is estimated to be 0.74 cm ± 0.15, which exceeds the mission goal of 1.2 cm RMS. 相似文献
3.
Three- dimensional vector modeling and restoration of flat finite wave tank radiometric measurements
In this paper, a three-dimensional Fourier transform inversion method describing the interaction between water surface emitted radiation from a flat finite wave tank and antenna radiation characteristics is reported. The transform technique represents the scanning of the antenna mathematically as a correlation. Computation time is reduced by using the efficient and economical fast Fourier transform algorithm. To verify the inversion method, computations have been made and compared with known data and other available results. The technique has been used to restore data of the finite wave tank system and other available antenna temperature measurements made at the Cape Cod Canal. The restored brightness temperatures serve as better representations of the emitted radiation than the measured antenna temperatures. 相似文献
4.
Dual-polarized ratio algorithm for retrieving Arctic sea ice concentration from passive microwave brightness temperature 总被引：1，自引：0，他引：1
We present a new algorithm for retrieving sea ice concentration from the AMSR-E data, the dual-polarized ratio (DPR) algorithm. The DPR algorithm is developed using vertically and horizontally polarized brightness temperatures at the same channel of 36.5 GHz. It depends on the ratio of dual-polarized emissivity, α, which is determined empirically at about 0.92 by remotely sensed brightness temperature in winter and used for the other seasons as well. The ice concentration retrieved by the DPR is compared with those by the NT2 and ABA algorithms. Since the main difference among these algorithms takes place in marginal ice zones, 17 marginal ice zones are chosen. The retrieved ice concentrations in these zones are examined by the ice concentration obtained by the MODIS data. The mean error, root-mean-square error and mean absolute error of the DPR algorithm are relatively better than those from the other two algorithms. The results of this study illustrate that the DPR algorithm is a more accurate algorithm for retrieving sea ice concentration from the AMSR-E brightness temperature, and can be used for operational purposes. 相似文献
5.
针对全球降水测量（Global Precipitation Measurement,GPM）卫星上搭载的微波成像仪（GPM Microwave Imager,GMI）,建立了陆面亮温数据的射频干扰（radio frequency interference,RFI）校正算法,同时提出了适用于GMI的综合指数雨强反演算法,即极化订正温度及散射指数（polarization corrected temperature-scattering index,PCT-SI）综合指数法,估算了2021年第6号强台风“烟花”登陆后,江苏及周边地区的雨强,与同时期双频降水测量雷达（Dual-frequency Precipitation Radar,DPR）的近地面雨强产品进行对比分析,并比较了RFI校正前、后的近地面雨强反演精度。进而用强台风“梅花”和一次江淮气旋检验了该雨强反演算法的精度以及RFI校正算法对提高反演精度的有效性。结果表明,GMI的高频观测与降水强度大小密切相关,利用低频组合拟合89.00 GHz通道亮温获得大气散射指数,散射指数越大,雨强越大;RFI信号对微波资料反演近地面雨强的影响显著,所提出的校正方法可以有效地校正陆面上受RFI污染的GMI观测数据。研究结果有助于揭示微波传感器多通道亮温资料和降水强度之间的相关性,提高微波反演陆面降水的精度,并为陆面降水反演和预报提供参考。 相似文献
6.
相比于实孔径微波辐射计,一维综合孔径微波辐射计具有高空间分辨率和多入射角观测特点。本文提出采用观测频率为6.9,10.65,18.7,23.8和36.5 GHz,且入射角范围为0°~65°的一维综合孔径微波辐射计遥感大气海洋环境要素。基于构建的微波大气海洋辐射传输正演模型,分析了辐射计亮温对大气海洋环境要素的敏感性,为辐射计关键指标确定和大气海洋环境要素反演算法设计提供技术支撑。结果表明：一维综合孔径微波辐射计的垂直和水平极化亮温对大气海洋环境要素的敏感性表现出不同特性,且敏感性随入射角的改变而变化显著;6.9和10.65 GHz对海面温度的敏感性较大,且随着入射角的增大,垂直极化亮温的敏感性增大,水平极化亮温的敏感性减小;10.65和18.7 GHz对海面风速的敏感性相对较大,且敏感性最大的风速区间位于10~20 m/s;23.8 GHz对大气水汽含量最敏感,且水汽含量较低、入射角较大时,敏感性越大;36.5 GHz对云液态水含量最敏感,随着入射角的增大,垂直极化亮温的敏感性减小,水平极化的敏感性增大,但两者均在液态水含量较小时表现出较大的敏感性。 相似文献
7.
藻胆体是红、蓝藻特有的光合作用捕光天线复合物。别藻蓝蛋白(APC)是组成藻胆体高效能量传递的核心结构的主要成分。本文以基因重组的别藻蓝蛋白(rAPC)的单体和三聚体为材料,通过稳态光谱、圆二色光谱以及超快时间分辨光谱研究了rAPC的结构构象和能量传递过程。结果表明,rAPC在测试条件下能保持和天然APC一致的光谱特性和活性构象;rAPC单体组装成三聚体后,其α84PCB和β84PCB可以组成激子色素对,通过激子分裂提高三聚体的能量传递效率;超快时间分辨光谱结果显示,在rAPC三聚体中,能量从620 nm传至650 nm的时间为300～600 fs,同时存在着19 fs的激子态的电子退相干过程。这些结果为揭示藻胆体的高效能量传递机制提供了数据基础。 相似文献
8.
Monitoring Measurements from the Jason-1 Microwave Radiometer and Independent Validation with GPS 总被引：1，自引：0，他引：1
The Jason-1 Microwave Radiometer (JMR) provides measurements of the wet troposphere content to correct the altimetric range measurement for the associated path delay. Various techniques are used to monitor the JMR wet troposphere path delays, with measurements of zenith troposphere content from terrestrial GPS sites used as an independent verification technique. Results indicate that an unexpected offset of approximately +4.1 ± 1.2 mm (drier) emerged in the JMR measurements of wet path delay between cycles 28-32 of the Jason-1 mission, and that the measurements may be drifting at a rate of approximately -0.5 mm/year. These anomalies are shown to be caused by a -0.7 K offset in 23.8 GHz brightness temperatures between cycles 28-32, and a 0.16 ± 0.04 and -0.45 ± 0.08 K/year drift in the 18.7 and 34.0 GHz brightness temperatures, respectively. Intercomparison of the 3-Hz JMR brightness temperature measurements show that they have been drifting with respect to each other, and that a dependence on yaw-steering regime is present in these measurements. An offset of 0.5 m/s between cycles 28-32 and a drift of approximately 0.5 m/s/year in the JMR wind speed measurements is also associated with these anomalies in the 1-Hz brightness temperatures. These errors in JMR wind speeds presently have a negligible impact on the retrieved JMR path delays. 相似文献
9.
Monitoring Measurements from the Jason-1 Microwave Radiometer and Independent Validation with GPS 总被引：1，自引：1，他引：0
The Jason-1 Microwave Radiometer (JMR) provides measurements of the wet troposphere content to correct the altimetric range measurement for the associated path delay. Various techniques are used to monitor the JMR wet troposphere path delays, with measurements of zenith troposphere content from terrestrial GPS sites used as an independent verification technique. Results indicate that an unexpected offset of approximately +4.1 ± 1.2 mm (drier) emerged in the JMR measurements of wet path delay between cycles 28–32 of the Jason-1 mission, and that the measurements may be drifting at a rate of approximately ?0.5 mm/year. These anomalies are shown to be caused by a ?0.7 K offset in 23.8 GHz brightness temperatures between cycles 28–32, and a 0.16 ± 0.04 and ?0.45 ± 0.08 K/year drift in the 18.7 and 34.0 GHz brightness temperatures, respectively. Intercomparison of the 3-Hz JMR brightness temperature measurements show that they have been drifting with respect to each other, and that a dependence on yaw-steering regime is present in these measurements. An offset of 0.5 m/s between cycles 28–32 and a drift of approximately 0.5 m/s/year in the JMR wind speed measurements is also associated with these anomalies in the 1-Hz brightness temperatures. These errors in JMR wind speeds presently have a negligible impact on the retrieved JMR path delays. 相似文献
10.
Vertically polarized antenna temperatures of ore boats and their wakes were measured with a 35-GHz radiometer from a helicopter platform. The signatures of the boats appear to be independent of viewing angle at a temperature which is about 40 K cooler than the surrounding water. The signatures of the wakes show a dependence on viewing angle. Models for the antenna temperature are presented which fit the measured data to within the accuracy of the measurement and model parameters. These models are useful in themselves for predicting the antenna temperatures of targets in terms of parameters such as viewing angle, beam fill factor (BFF), antenna main beam efficiency, and target emissivity. 相似文献
11.
星载微波辐射计外定标的关键问题是通过辐射传输方程计算天线入瞳处亮温。根据辐射传输方程,海面成份对亮温的影响包括海面的微波辐射和对下行大气辐射的反射,其中的关键参数分别为海面发射率ep和海表面反射率R。文中对平静海面Fresnel反射率模式和粗糙海面反射率模式进行了研究分析,在此基础上着重研究了海面温度TS、海面盐度SS、海面风速W、以及观测角度θ等物理参数对海面发射率ep的影响,进而分析了这些物理参数的测量误差对亮温的计算精度的影响。 相似文献
12.
In the context of the sea level survey at the mm level, it is necessary all along the lifetime of the altimeter mission to survey the quality of the products from the microwave radiometer. The calibration of the brightness temperatures has been validated using reference brightness temperatures over selected continental areas as well as simulations for a wide range of oceanic and atmospheric situations. The validation of the wet path delay is performed by comparison with radiosonde measurements and pointed out that both the JMR and the TMR estimate wet path delay around 5 mm higher than the one measured by radiosondes. Furthermore, it appeared that the correction of the TMR drift degrades the product with respect to radiosonde measurements. The monitoring of the brightness temperatures since launch shows a mean drift around +0.1 K/year for the 18.7 GHz, ?0.6 K/year for the 23.8 GHz channel, and around ?0.4 K/year for the 34 GHz channel. 相似文献
13.
Compared with traditional real aperture microwave radiometers, one-dimensional synthetic aperture microwave radiometers have higher spatial resolution. In this paper, we proposed to retrieve sea surface temperature using a one-dimensional synthetic aperture microwave radiometer that operates at frequencies of 6.9 GHz, 10.65 GHz,18.7 GHz and 23.8 GHz at multiple incidence angles. We used the ERA5 reanalysis data provided by the European Centre for Medium-Range Weather Forecasts and a radiation transmission forward model to calculate the model brightness temperature. The brightness temperature measured by the spaceborne one-dimensional synthetic aperture microwave radiometer was simulated by adding Gaussian noise to the model brightness temperature.Then, a backpropagation(BP) neural network algorithm, a random forest(RF) algorithm and two multiple linear regression algorithms(RE1 and RE2) were developed to retrieve sea surface temperature from the measured brightness temperature within the incidence angle range of 0°–65°. The results show that the retrieval errors of the four algorithms increase with the increasing Gaussian noise. The BP achieves the lowest retrieval errors at all incidence angles. The retrieval error of the RE1 and RE2 decrease first and then increase with the incidence angle and the retrieval error of the RF is contrary to that of RE1 and RE2. 相似文献
14.
In the context of the sea level survey at the mm level, it is necessary all along the lifetime of the altimeter mission to survey the quality of the products from the microwave radiometer. The calibration of the brightness temperatures has been validated using reference brightness temperatures over selected continental areas as well as simulations for a wide range of oceanic and atmospheric situations. The validation of the wet path delay is performed by comparison with radiosonde measurements and pointed out that both the JMR and the TMR estimate wet path delay around 5 mm higher than the one measured by radiosondes. Furthermore, it appeared that the correction of the TMR drift degrades the product with respect to radiosonde measurements. The monitoring of the brightness temperatures since launch shows a mean drift around +0.1 K/year for the 18.7 GHz, -0.6 K/year for the 23.8 GHz channel, and around -0.4 K/year for the 34 GHz channel. 相似文献
15.
射频干扰RFI(Radio-Frequency Interference)的校正和抑制一直是微波遥感研究领域的重要问题之一。本文基于SMAP卫星2015年5月1日至5日L波段辐射计亮温数据对中国近海及沿岸的射频干扰进行了特征分析。研究发现RFI分布不均匀,主要集中在城市群及其周边地区;通过对比辐射计天线接收的亮温数据与射频干扰校正和抑制后的数据,发现研究区域主要的射频干扰(95%)的平均值为1.4 K,整体射频干扰平均值为2.5 K,标准差为6.5;研究区域中不同波段和极化的数据受到射频干扰影响较为相似,受射频干扰影响最大的是升轨的垂直极化数据,受影响最小的是升轨的水平极化数据。 相似文献
16.
HY-2A is the first one of the Chinese HY-2 ocean satellite series carrying a microwave radiometer(RM)to measure sea surface temperature,sea surface wind speed,atmospheric water vapor,cloud liquid water content,and rain rate.We verified the RM level 1B brightness temperature(T B)to retrieve environmental parameters.In the verification,TB that simulated using the ocean-atmosphere radiative transfer model(RTM)was used as a reference.The total bias and total standard deviation(SD)of the RM level 1B TB,with reference to the RTM simulation,ranged-20.6-4.38 K and 0.7-2.93 K,respectively.We found that both the total bias and the total SD depend on the frequency and polarization,although the values for ascending and descending passes are different.In addition,substantial seasonal variation of the bias was found at all channels.The verification results indicate the RM has some problems regarding calibration,e.g.,correction of antenna spillover and antenna physical emission,especially for the 18.7-GHz channel.Based on error analyses,a statistical recalibration algorithm was designed and recalibration was performed for the RM level 1B TB.Validation of the recalibrated TB indicated that the quality of the recalibrated RM level 1B TB was improved significantly.The bias of the recalibrated T B at all channels was reduced to<0.4 K,seasonal variation was almost eradicated,and SD was diminished(i.e.,the SD of the 18.7-GHz channel was reduced by more than 0.5K). 相似文献
17.
Akira Shibata 《Journal of Oceanography》2006,62(3):351-359
A wind speed retrieval algorithm was developed using 6 and 10 GHz h-pol (6H and 10H) data of the Advanced Microwave Scanning
Radiometer (AMSR) aboard the Advanced Earth Observation Satellite-II (ADEOS-II) and AMSR-E aboard AQUA, for the purpose of
retrieving wind speed inside rainstorms, primarily hurricanes and typhoons. The h-pol was used rather than the v-pol, because
the brightness temperature sensitivity to the ocean wind at h-pol is larger than v-pol. The microwave emission change of 6H
and 10H corresponding to ocean wind was evaluated in no-rain areas by combining AMSR and SeaWinds data aboard the ADEOS-II
(SeaWinds was NASA’s scatterometer), and it was found that the ratio of the two 6H to 10H increments due to ocean wind is
0.9. Assuming that this result also holds with higher wind speeds and under rainy conditions, the brightness temperatures
at 6H and 10H were simulated using a microwave radiative transfer model. A parameter W6 (unit; Kelvin) was then defined, representing
an increment at 6H due to ocean wind. W6 is applicable to rainy areas, and to all ranges of sea surface temperature. W6 was
compared with wind speed reported by the National Hurricanes Center for several hurricanes in the Western Atlantic Ocean during
three years (2002 to 2004). W6 averaged around centers of hurricanes was found to exhibit a sensitivity to wind speed, such
as increasing from 22 K to 65 K as the wind speed rose from 65 to 140 knots (33 to 72 m/s), and an empirical relationship
relating the averaged W6 to wind speed in hurricanes was derived. 相似文献
18.
SARAL carried onboard a radar altimeter that provides very precise measurements of the sea surface height (SSH). Like other altimetric missions, SARAL carries a passive microwave radiometer (PMR) for wet tropospheric correction to SSH. In the present study, new algorithms are developed for the retrieval of cloud liquid water (CLW) and total precipitable water vapor (TPW) over the global oceans from PMR measurements of the brightness temperatures. A radiative transfer and genetic algorithm based retrieval scheme is proposed for the estimation of CLW and TPW from SARAL PMR. The comparisons of CLW from PMR with independent measurements from GPM-GMI and SSMIS within and outside ±40° latitudes show correlation (R) of 0.86 and 0.83, bias of 0.7 and ?3.61?mg/cm2, and root mean square error (RMSE) of 8.42 and 8.07?mg/cm2, respectively. Similarly, TPW from PMR with GPM-GMI and SSMIS show R of 0.99 and 0.98, bias of ?0.04 and ?0.03?g/cm2 and RMSE of 0.17 and 0.17?g/cm2, respectively. The retrieval accuracy of CLW and TPW from the new algorithms is compared with these parameters provided in the SARAL geophysical data records as finished products, which showed substantial improvement in the quality of the parameters from the new algorithm. 相似文献
19.
The accuracy of sea surface temperatures (SSTs) derived from the Advanced Very High Resolution Radiometer (AVHRR)/NOAA-11 is examined by comparison with sea-truth SSTs obtained from ocean data buoys durings November 1988 through December 1989. We made a 122 point data set of buoy SSTs from the oceans around Japan and the corresponding brightness temperatures of channels 4 and 5 during cloud free periods. The satellite temperatures are corrected for atmospheric effects using the NOAA Multi-Channel SST (MCSST) and Cross Product SST (CPSST) algorithms. The two algorithms give similar results for our data set and result in biases of about –0.1°C with rms errors of about 0.6°C relative to buoy SSTs. It is found that MCSSTs and CPSSTs tend to be higher than SSTs from the buoy in the Japan Sea in summer. New coefficients for the MCSST equations suitable for our data set are determined and the resultant rms error is 0.49°C. If we eliminate the cluster of anomalous summer data in the Japan Sea, the rms error becomes 0.43°C. 相似文献
20.
The effect of the four major surface types in Finland (forests, boglands, farmlands, and water (ice)) on the microwave brightness temperature of snow-covered areas is investigated. Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) data are employed to derive the response of each surface type. An algorithm to retrieve the water equivalent of snow cover from Nimbus-7 SMMR data is tested in different dry snow conditions. 相似文献