Cloud Liquid Water Path Retrieval Products over the Pacific Ocean and Their Climate Change Characteristics
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摘要: 基于极轨卫星NOAA-15上的微波温度计AMSU-A(Advanced Microwave Sounding Unit-A)多年亮温观测资料,建立了全球海洋上的云液态水路径反演产品,并通过对比ERA5和FNL/NCEP再分析资料的云水路径产品,分析了反演产品对云液态水路径气候变化特征的再现能力,进一步通过线性回归和EEMD(Ensemble Empirical Mode Decomposition)方法分别分析了太平洋地区大气云水路径的线性和非线性气候变化趋势特征。结果表明,云水路径反演资料可以很好的再现多年平均空间分布特征及相应的气候变化趋势,云水路径气候趋势表现出明显的纬度带特征,增多和减小趋势随纬度带间隔出现,而且在北半球东太平洋地区,云水路径气候趋势的纬度带特征有向北迁移的现象。相比而言,反演产品的气候趋势与ERA5再分析资料有更好的相似性,而FNL资料对趋势的纬度带特征,尤其是纬度带特征的北移现象未能很好的再现,只是表现为赤道地区水汽减少,而两侧云水路径显著增加的特征。Abstract: Based on the multi-year brightness temperature observation data of the AMSU-A (Advanced Microwave Sounding Unit-A) on the polar-orbiting satellite NOAA-15, a product of cloud liquid water path on the global ocean has been established and compared with ERA5 and FNL/NCEP. We analyzed the ability of retrieval products to reproduce the climate change characteristics of cloud liquid water path, and further analyzed the linear and nonlinear climate change trend characteristics of cloud water path in the Pacific region through linear regression and EEMD (Ensemble Empirical Mode Decomposition) methods. The results show that the CLWP (Cloud Liquid Water Path) inversion data can well reproduce the average spatial distribution characteristics of the years and the corresponding climate change trend. The CLWP climate trend shows obvious latitude zone characteristics, and the increasing and decreasing trends appear with the latitude zone interval. Moreover, in the eastern Pacific region of the northern hemisphere, the latitude zone characteristic of the climatic trend of the CLWP has a phenomenon of migration northward. In contrast, the climatic trend of the inversion product has better similarity with the ERA5 reanalysis data. While the latitude zone characteristics of the trend, especially the northward movement of the latitude zone characteristics, cannot be reproduced well by the FNL data. It is characterized by a decrease in water vapor in the equatorial region, and a significant increase in cloud liquid water paths on both sides.
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图 4 2000~2020年太平洋地区不同区域平均CLWP的逐月变化(蓝线:反演1;红线:ERA5/CLWP产品):(a)(0°~10°S,120°~130°W);(b)(0°~10°N,110°~120°W);(c)(35°~45°N,170°~180°E)
Figure 4. Monthly variation of average CLWP in different regions of the Pacific from 2000 to 2020: (a) (0°–10°S, 120°–130°W); (b) (0°–10°N, 110°–120°W); (c) (35°–45°N, 170°–180°E). Blue lines: inversion 1; red lines: CLWP products from ERA5
图 6 2000~2020年太平洋上不同纬度带上CLWP的线性趋势。黑色实线:反演1,红色实线:反演2,黑色虚线:FNL的CLWP产品,红色虚线:ERA5的CLWP产品
Figure 6. Linear trend of CLWP at different latitudes in the Pacific from 2000 to 2020. Black solid line: inversion 1, red solid line: inversion 2, black dash line: CLWP products from FNL, red dash line: CLWP product from ERA5
表 1 NOAA15/AMSU-A的各通道参数特征
Table 1. parameter characteristics of each channel of NOAA15/AMSU-A
通道 各通道参数 频率/GHz 辐射温度灵敏度/K 带宽/MHz 波束宽度 1 23.800 0.211 270 3.53° 2 31.400 0.265 180 3.41° 3 50.300 0.219 180 3.76° 4 52.800 0.143 400 3.72° 5 53.596±0.115 0.148 170 3.70° 6 54.400 0.154 400 3.68° 7 54.940 0.132 400 3.61° 8 55.500 0.141 330 3.63° 9 f0=57.290344 0.236 330 3.51° 10 f0±0.217 0.250 78 3.51° 11 f0±0.322±0.048 0.280 36 3.51° 12 f0±0.322±0.022 0.400 16 3.51° 13 f0±0.322$ \pm $0.010 0.539 8 3.51° 14 f0±0.322±0.0045 0.914 3 3.51° 15 89.000 0.166 6000 3.80° -
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