To implement continuous and reliable rainfall retrieval, based on the satellite retrieval algorithm of 10-min rain rate, this study proposes an immediate tracking and continuous accumulation technique (ITCAT) of halfhour rainfall retrieval by further combining the cross-correlation method. The ITCAT includes two steps. 1) The cross-correlation method is applied to track cloud-motion currents and establish 10-min-interval image sequences. 2) A continuous retrieval of 10-min rain rates is conducted with the image sequences, and finally a total half-hour rainfall is determined by accumulations. The satellite retrieval tests on the typical precipitation processes in the summer of 2008 show that, compared with the previous direct rainfall retrieval for half-hour to one-hour, this rainfall retrieval technique significantly improves the retrieval accuracy of rainfall scope and rainfall intensity ranging from slight rain to rainstorm for both real-time monitoring or nowcasting processes. This technique is more effective than the previous algorithm, and the fundamental reason lies in its consideration of the movement of cloud clusters. On this basis, coverage duration of rainfall clouds can be reliably estimated. It is of significance to the retrieval of deep convective cloud rainfall with rapid movement speed and drastic intensity variation. This technique also provides a feasible idea for improving the accuracy of rainfall nowcasting.

This study develops a method for both precipitation area and intensity retrievals based on multispectral geostationary satellite images. This method can be applied to continuous observation of large-scale precipitation so as to solve the problem from the measurements of rainfall radar and rain gauge. Satellite observation is instantaneous, whereas the rain gauge records accumulative data during a time interval. For this reason, collocated 10-min rain gauge measurements and infrared (IR) and visible (VIS) data from the FengYun-2C (FY-2C) geostationary satellite are employed to improve the accuracy of satellite rainfall retrieval. First of all, the rainfall probability identification matrix (RPIM) is used to distinguish rainfall clouds from nonrainfall clouds. This RPIM is more efficient in improving the retrieval accuracy of rainfall area than previous threshold combination screening methods. Second, the multispectral segmented curve-fitting rainfall algorithm (MSCFRA) is proposed and tested to estimate the 10-min rain rates. Rainfall samples taken from June to August 2008 are used to assess the performance of the rainfall algorithm. Assessment results show that the MSCFRA improves the accuracy of rainfall estimation for both stratiform cloud rainfall and convective cloud rainfall. These results are practically consistent with rain gauge measurements in both rainfall area division and rainfall intensity grade estimation. Furthermore, this study demonstrates that the temporal resolution of satellite detection is important and necessary in improving the precision of satellite rainfall retrieval.

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In predator-prey interactions, various factors affect the prey's perception of risk and decision to ee. Gaze sensitivity, the ability to react to the presence, direction, or movement of the head and eyes, has been reported in many birds and they could recognise not only the head direction but the subtle difference in eye direction. But few studies focused on variation in sensitivity to human gaze in relation to other risks and costs. Here, we studied the in uence of human gaze on the escape behaviour of Azure-winged magpies (Cyanopica cyanus) and investigated the effects of breeding state and directness of approach on gaze sensitivity. In Experiment 1, we tested whether magpies showed different sensitivity to human gaze according to age class and breeding state when being approached directly. The results showed that the breeding state could affect the ight initiation distance (FID), with adults in the breeding season having a shorter FID. Meanwhile, only adults were found to be averse to direct human gaze and juveniles showed no sensitivity, implying that gaze aversion was not innate. In Experiment 2, we conducted three different gaze treatments on adult magpies in the breeding season under three bypass distances (0m, 2.5m, 5m). The results showed that directness of approach had no effects on FID, while the sensitivity to human gaze differed under three bypass distances. Adults could clearly recognise human head and eye direction at a certain bypass distance (2.5m). Our study reveals the cognitive ability of Azure-winged magpies to human head and eye direction and the effects of additional cost and risk, which may provide further insights into human-wildlife interactions, especially for birds in urban habitats.