The Predictability of Ocean Environments that Contributed to the 2020/21 Extreme Cold Events in China:2020/21 La Niña and 2020 Arctic Sea Ice Loss

Several consecutive extreme cold events impacted China during the first half of winter 2020/21,breaking the low-temperature records in many cities.How to make accurate climate predictions of extreme cold events is still an urgent issue.The synergistic effect of the warm Arctic and cold tropical Pacific has been demonstrated to intensify the intrusions of cold air from polar regions into middle-high latitudes,further influencing the cold conditions in China.However,climate models failed to predict these two ocean environments at expected lead times.Most seasonal climate forecasts only predicted the 2020/21 La Niña after the signal had already become apparent and significantly underestimated the observed Arctic sea ice loss in autumn 2020 with a 1-2 month advancement.In this work,the corresponding physical factors that may help improve the accuracy of seasonal climate predictions are further explored.For the 2020/21 La Niña prediction,through sensitivity experiments involving different atmospheric-oceanic initial conditions,the predominant southeasterly wind anomalies over the equatorial Pacific in spring of 2020 are diagnosed to play an irreplaceable role in triggering this cold event.A reasonable inclusion of atmospheric surface winds into the initialization will help the model predict La Niña development from the early spring of 2020.For predicting the Arctic sea ice loss in autumn 2020,an anomalously cyclonic circulation from the central Arctic Ocean predicted by the model,which swept abnormally hot air over Siberia into the Arctic Ocean,is recognized as an important contributor to successfully predicting the minimum Arctic sea ice extent.

The extremely cold 2009-2010 winter and its relationship with the Arctic oscillation

The Northern-Hemisphere high-latitude continents experienced extremely cold weathers in winter 2009 2010. In the present paper, we show that the cold winter was associated with the activity of tile Arctic oscillation （AO）, which demonstrated the strongest negative polarity over the past six decades and persisted from December, 2009 to March, 2010. It is found that variations of the surface AO was closely linked to stratospheric polar vortex anomalies, and that the surface AO phases followed downward propagation of stratospheric Northern-Hemisphere Annular mode （NAM） anomalies during the winter. The case of 2009-2010 winter provides us with a typical example that anomalous stratospheric signals can be used to improve skills of long-range weather forecast and intra-seasonal climate prediction in winter time. We also show that the E1 Nifio event, which started developing from May 2009, might contribute the formation of exceptionally negative and persistent AO and stratospheric NAM, particularly over North Pacific and North America.

Clathrin-dependent endocytosis predominantly mediates protein absorption by fat body from the hemolymph in Bombyx mori

During insect larval-pupal metamorphosis,proteins in the hemolymph are absorbed by the fat body for the maintenance of intracellular homeostasis;however,the type of proteins and how these proteins are internalized into the fat body are unclear.In Bombyx mori,the developmental profiles o f total proteins in the hemolymph and fat body showed that hemolymph-decreased protein bands(55-100 kDa)were in accordance with those protein bands that increased in the fat body.Inhibition o f clathrin-dependent endocytosis predominantly blocked the transportation o f 55-100 kDa proteins from the hemolymph into the fat body,which was further verified by RNA interference treatment o f Bmclathrin.Six hexamerins were shown to comprise〜90%of the total identified proteins in both the hemolymph and fat body by mass spectrum(MS)analysis.In addition,hemolymphspecific proteins were mainly involved in material transportation,while fat body-specific proteins particularly participated in metabolism.In this paper,four hexamerins were found for the first time,and potential proteins absorbed by the fat body from the hemolymph through clathrin-dependent endocytosis were identified.This study sheds light on the protein absorption mechanism during insect metamorphosis.