Comparison of precipitable water vapor derived from radiosonde, GPS, and Moderate-Resolution Imaging Spectroradiometer measurements
Comparison of precipitable water vapor derived from radiosonde, GPS, and Moderate-Resolution Imaging Spectroradiometer measurements
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DOI：
10.1029/2003jd003372
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发表时间：
2003-10-29
影响因子：
4.4
通讯作者：
Cross, P
中科院分区：
文献类型：
--
作者：
Li, ZH;Muller, JP;Cross, P
[1]大气水蒸气在整个地球的空间和时间上都是高度可变的，了解水蒸气的分布对于了解天气和全球气候是必不可少的。此外，高精度干涉合成孔径雷达(InSAR)的应用需要了解大气中的水蒸汽量，因为它对微波信号有重大影响，这是本研究的主要动机。为了评估不同仪器，即无线电探空仪(RS)、全球定位系统(GPS)和中分辨率成像光谱仪(MODIS)的性能以及测量可降水量(PWV)的性能，使用在大平原南部大气辐射测量站点和Herstmonceux站点8-11个月期间收集的重合观测数据进行时间序列相互比较。在这项研究中，研究了Terra MODIS近红外水汽产品(集合3)。此外，首次使用覆盖整个德国的数据进行了MODIS PWV和GPS PWV的空间比较，该数据由GeoForschungsZentum Potsam提供。无线电探空仪和GPS的PWV时间序列比较表明，无线电探空仪和GPS的PWV标度因子一致为4%，相关系数大于0.98，标准偏差约为1 mm。与GPS PWV相比，Vaisala RS90无线电探空仪的昼夜差异显著，夜间发射的比例因数增加了4%，但总体上符合得更好。GPS PWV和RS PWV与MODIS PWV的一致性较好，MODIS PWV相对于GPS和RS PWV的差异大于GPS PWV和RS PWV。MODIS PWV似乎高估了相对RS的PWV，比例因子从1.14到1.20，标准偏差从1.6到2.2 mm。相对于GPS，MODIS PWV似乎高估了PWV，比例因子在1.07到1.14之间，时间序列的标准偏差在0.8到1.4 mm之间。相对于MODIS PWV的较大差异可能是由于MODIS反演的光谱数据库中的不确定性、MODIS测量的辐射的校准不确定性、三个系统的操作差异以及GPS和MODIS PWV反演中采用的不同测绘函数造成的。我们建立了一个线性拟合模型来标定MODIS PWV，并在空间上取得了与GPS PWV更好的一致性。这表明，MODIS PWV产品在应用于校正InSAR测量之前，应使用线性拟合模型进行更新或校准。此外，还评估了来自英国气象局和怀俄明大学的标准分辨率(重采样)无线电探空仪数据的潜在准确性。这表明，在使用标准分辨率数据时需要注意一些问题。
[1] Atmospheric water vapor is highly variable in both space and time across the Earth, and knowledge of the distribution of water vapor is essential in understanding weather and global climate. In addition, knowledge of the amount of atmospheric water vapor is required for high-precision interferometric synthetic aperture radar (InSAR) applications due to its significant impact on microwave signals, which is the principal motivation for this study. In order to assess the performance of different instruments, i.e., radiosondes (RS), Global Positioning System (GPS), and the Moderate- Resolution Imaging Spectroradiometer ( MODIS) and for measuring precipitable water vapor (PWV), coincident observations collected at the Atmospheric Radiation Measurement Southern Great Plains site and at the Herstmonceux site over a 8 - 11 month period are used for time series intercomparisons. In this study, the Terra MODIS near-infrared water vapor products ( Collection 3) were examined. In addition, a first spatial comparison of MODIS PWV and GPS PWV was performed using data covering all of Germany and kindly supplied by the GeoForschungsZentrum Potsdam. Time series comparisons of PWV between radiosondes and GPS show that the scale factors of PWV from radiosondes and GPS agreed to 4% with correlation coefficients higher than 0.98 and standard deviations about 1 mm. A significant day-night difference was found for Vaisala RS90 radiosondes in comparison with GPS PWV, with nighttime launches having a scale factor 4% larger, but agreeing overall better. It is also shown that GPS PWV and RS PWV agreed better with each other than with MODIS PWV, and the differences of MODIS PWV relative to GPS or RS were larger than those between GPS PWV and RS PWV. MODIS PWV appeared to overestimate PWV against RS, with scale factors from 1.14 to 1.20 and standard deviations from 1.6 to 2.2 mm. MODIS PWV appeared to overestimate PWV against GPS, with scale factors from 1.07 to 1.14 and standard deviations varying from 0.8 to 1.4 mm in time series. The larger differences relative to MODIS PWV are likely to be caused by uncertainties in the spectroscopic database for the MODIS retrievals, calibration uncertainties in the radiances measured by MODIS, operational differences of the three systems, and different mapping functions adopted in GPS and MODIS PWV retrievals. We derived a linear fit model to calibrate MODIS PWV, and better agreements between calibrated MODIS PWV and GPS PWV in space have been achieved. This indicates that MODIS PWV products should be updated or calibrated using a linear fit model before being applied to correct InSAR measurements. Also, the potential accuracy of standard resolution ( resampled) radiosonde data from the UK Met Office and the University of Wyoming has been assessed. It is demonstrated that some caution needs to be exercised when using standard resolution data.