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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Retrieval and characterization of cloud liquid water path using airborne passive microwave data during INDOEX
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Retrieval and characterization of cloud liquid water path using airborne passive microwave data during INDOEX

机译：在INDOEX期间使用机载无源微波数据检索和表征云状液态水路径

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During the 1999 intensive observation period of the Indian Ocean Experiment (INDOEX), the Airborne Imaging Microwave Radiometer (AIMR) was deployed on the National Center for Atmospheric Research (NCAR) C-130 aircraft to measure upwelling microwave radiation that can be used to retrieve cloud liquid water path (LWP). In this study, we present a LWP retrieval algorithm that is optimized for tropical atmospheric conditions, typical of conditions observed in INDOEX. Radiative transfer modeling and error analysis are conducted for the four AIMR channels, to guide selection of AIMR. channels used for the LWP retrievals. Results show that the horizontal polarization channels outperform vertical 2 polarization channels at both 37 and 90 GHz. Additionally, for LWP less than similar to 300 g m(-2) the best results are expected from the 90 GHz horizontal polarization channel, while the 37 GHz horizontal polarization channel performs better for higher LWPs. On the basis of these findings we formulated the LWP retrieval algorithm from the combination of the retrievals of 37 and 90 GHz horizontal polarization channels. Results of several indirect validations show that in nearly clear condition the LWP retrievals have essentially no bias and a random error of about 28 g m(-2) The image of the retrieved LWP compares well with observations by a 0.64 mum visible channel, and the magnitude of the retrieved LWP for large convective cells is comparable to the estimation based on in situ measurements. It is also shown that the retrieved LWPs for convective cells are smaller than those estimated by assuming adiabatic process while the two have a similar trend in the LWP versus cloud top temperature diagram. By analyzing all available AIMR observations, it is found that the mean LWP for cloudy pixels measured during the INDOEX experiment is about 50 g m(-2). A significant north-south gradient of the mean LWP is found in INDOEX domain during this period, with the mean LWP in the region south of 5 degreesS being twice as high as that in the region north of 5 degreesN, The LWP frequency distribution shows that clouds with larger LWPs occur more often in the southern region than in the northern region. [References: 22]
机译：在印度洋实验（INDOEX）的1999年密集观察期中，机载成像微波辐射仪（AIMR）被部署在美国国家大气研究中心（NCAR）的C-130飞机上，用于测量上升流的微波辐射，该辐射可用于获取云液态水路径（LWP）。在这项研究中，我们提出了一种LWP检索算法，该算法针对热带大气条件（在INDOEX中观察到的典型条件）进行了优化。对四个AIMR通道进行了辐射传递建模和误差分析，以指导AIMR的选择。用于LWP检索的通道。结果表明，在37 GHz和90 GHz频率下，水平极化信道均优于垂直2极化信道。此外，对于小于300 g m（-2）的LWP，可以从90 GHz水平极化信道获得最佳结果，而对于更高的LWP，37 GHz水平极化信道的性能更好。在这些发现的基础上，我们结合了37 GHz和90 GHz水平极化信道的检索结果，制定了LWP检索算法。几次间接验证的结果表明，在近乎清晰的条件下，LWP取回基本没有偏差，随机误差约为28 gm（-2）。所取回的LWP的图像与0.64毫米可见通道的观测值比较好，其幅值大型对流单元的LWP取值与基于原位测量的估计值相当。还显示，对流单元的检索到的LWP小于假定绝热过程估计的LWP，而两者在LWP与云顶温度关系图中的趋势相似。通过分析所有可用的AIMR观测值，发现在INDOEX实验期间测得的浑浊像素的平均LWP约为50 g m（-2）。在此期间，在INDOEX域中发现了平均LWP的明显的南北梯度，其中5°S以南地​​区的平均LWP是5°N以北地区的平均LWP的两倍，LWP频率分布表明：具有较大LWP的云在南部地区比北部地区更常见。 [参考：22]

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