9 research outputs found

    Impact of Indian Ocean Dipole on Atlantic Niño predictive skill

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    Recent studies suggest that tropical Indian Ocean sea surface temperature (SST) anomalies, especially those associated with the Indian Ocean Dipole (IOD), may trigger Atlantic Niño through atmospheric teleconnection. However, it remains unclear whether the former has an impact on the prediction skill of the latter. This work applies hindcasts from 21 operational seasonal forecast systems based on dynamical climate models to verify the impact of the IOD in boreal autumn on the predictive skill of the Atlantic Niño in the following winter. The results indicate that the prediction skills of both the IOD and Atlantic Niño show pronounced seasonality, with a peak in the target season of boreal autumn for the former and in the following winter for the latter. The models with a stronger connection between the boreal autumn IOD and the following winter Atlantic Niño appear to have a higher skill in predicting the latter when compared to the weaker connection models. This leads to a significant in-phase relationship between the prediction skills of the boreal winter Atlantic Niño and the strength of the IOD–Atlantic Niño connection among the models. When compared to the weaker connection models, the stronger connection models tend to simulate a warmer climatological mean of SST in the tropical Indian Ocean during boreal autumn and winter. The warmer climatological mean of SST benefits a stronger atmospheric circulation response to the underlying SST forcing associated with the IOD. This suggests that mean state bias in the tropical Indian Ocean plays a role in modulating the strength of the simulated IOD–Atlantic Niño connection and thus prediction skill of the Atlantic Niño in boreal winter

    Remarkable Impacts of Indian Ocean Sea Surface Temperature on Interdecadal Variability of Summer Rainfall in Southwestern China

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    During the boreal summer from June to August, rainfall in Southwestern China shows substantial interdecadal variabilities on timescales longer than 10 years. Based on observational analyses and numerical modeling, we investigated the characteristics of interdecadal Southwestern China summer rainfall (SWCSR) and its dynamic drivers. We find that the SWCSR is markedly impacted by the interdecadal Indian Ocean basin mode (ID-IOBM) of the sea surface temperature (SST), which may induce anomalous inter-hemispheric vertical circulation. During the cold phase of the ID-IOBM, an enhanced lower-level divergence and upper-level convergence exist over the tropical Indian Ocean. The simultaneous lower-level outflow anomalies further converge over the Indo-China peninsula, resulting in an anomalous ascending motion and a lower-level cyclone that contribute to strengthening the eastward moisture transport from the Bay of Bengal to Southwestern China. The joint effects of the anomalous ascending motion and the above-normal moisture transport play a key role in increasing the SWCSR. In summers during the warm phase of the ID-IOBM, the situation is approximately the same, but with opposite polarity. After the beginning of the 1970s, the impacts of interdecadal Indian Ocean dipole (ID-IOD) on SWCSR is strengthening. The anomalous vertical circulation associated with the positive (negative) phase of ID-IOD is in favor of decreased (increased) rainfall in SWC. However, the impacts of ID-IOD on SWCSR is relatively weak before the 1970s, indicating that the ID-IOD is the secondary driver of the interdecadal variability of SWCSR. Modeling results also indicate that the ID-IOBM of SST anomalies is the main driver of interdecadal variability of SWCSR

    Why was the heat wave in the Yangtze River valley abnormally intensified in late summer 2022?

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    A record-breaking heat wave hit the Yangtze River valley during the boreal summer of 2022, and caused severe social and economic losses. One prominent feature of this long-lived heat event was its persistence and abnormal intensification in August. This study investigated the physical mechanisms be responsible for the intensification of this heat event in late summer under the background of a La Niña event. The prolonged heat event was directly related to the intensification and westward extension of the western North Pacific subtropical high (WNPSH), which can be attributed to the synergistic effects of an anomalous western North Pacific (WNP) anticyclone and the eastward extension of the South Asian high (SAH) in the upper troposphere. The anomalous anticyclone in the WNP, which was induced by negative sea surface temperature anomalies in the central tropical Pacific, strengthened in August. The positive sea surface temperature anomaly in the western Pacific warm pool and enhanced in-situ convection led to anomalous high pressure over the Yangtze River valley via the local meridional circulation. Atmospheric convergence and descending motion over the Yangtze River valley was amplified in August as a result of the zonal shift in the SAH from the Iranian Plateau to the Tibetan Plateau. The Silk Road pattern (SRP) index of August 2022 was the lowest since the 1990s. The abnormal negative phase of the SRP contributed to both the zonal shift in the SAH and the westward extension of the WNPSH, which led to the abnormal intensification of the heat event over the Yangtze River valley in August 2022

    The Sixth Visual Object Tracking VOT2018 Challenge Results

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    The Visual Object Tracking challenge VOT2018 is the sixth annual tracker benchmarking activity organized by the VOT initiative. Results of over eighty trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in the recent years. The evaluation included the standard VOT and other popular methodologies for short-term tracking analysis and a “real-time” experiment simulating a situation where a tracker processes images as if provided by a continuously running sensor. A long-term tracking subchallenge has been introduced to the set of standard VOT sub-challenges. The new subchallenge focuses on long-term tracking properties, namely coping with target disappearance and reappearance. A new dataset has been compiled and a performance evaluation methodology that focuses on long-term tracking capabilities has been adopted. The VOT toolkit has been updated to support both standard short-term and the new long-term tracking subchallenges. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The dataset, the evaluation kit and the results are publicly available at the challenge website (http://votchallenge.net).Funding agencies: Slovenian research agencySlovenian Research Agency - Slovenia [P2-0214, P2-0094, J2-8175]; Czech Science FoundationGrant Agency of the Czech Republic [GACR P103/12/G084]; WASP; VR (EMC2); SSF (SymbiCloud); SNIC; AIT Strategic Research Programme 2017 Visua</p