Contributors to linkage between Arctic warming and East Asian winter climate

Previous modelling and observational studies have shown discrepancies in the interannual relationship of winter surface air temperature (SAT) between Arctic and East Asia, stimulating the debate about whether Arctic change can influence midlatitude climate. This study uses two sets of coordinated experiments (EXP1 and EXP2) from six different atmospheric general circulation models. Both EXP1 and EXP2 consist of 130 ensemble members, each of which in EXP1 (EXP2) was forced by the same observed daily varying sea ice and daily varying (daily climatological) sea surface temperature (SST) for 1982–2014 but with different atmospheric initial conditions. Large spread exists among ensemble members in simulating the Arctic–East Asian SAT relationship. Only a fraction of ensemble members can reproduce the observed deep Arctic warming–cold continent pattern which extends from surface to upper troposphere, implying the important role of atmospheric internal variability. The mechanisms of deep Arctic warming and shallow Arctic warming are further distinguished. Arctic warming aloft is caused primarily by poleward moisture transport, which in conjunction with the surface warming coupled with sea ice melting constitutes the surface-amplified deep Arctic warming throughout the troposphere. These processes associated with the deep Arctic warming may be related to the forcing of remote SST when there is favorable atmospheric circulation such as Rossby wave train propagating from the North Atlantic into the Arctic.publishedVersio

The Role of Mid-latitude Westerly Jet in the Impacts of November Ural Blocking on Early-Winter Warmer Arctic-Colder Eurasia Pattern

Based on statistical analysis using observations and idealized model simulations, previous studies have revealed the potential response of early-winter atmospheric circulation and temperature anomalies to November Ural blocking (UB) anomalies. Using a large number of coupled simulations, this study found that the response is sensitive to the intensity of November mid-latitude westerly jet over Eurasia. Stronger-than-normal November UB without a significantly weakened westerly jet could not cause significant atmospheric response in early-winter. By contrast, stronger-than-normal November UB with a significantly weakened jet would be followed by a warmer Arctic-colder Eurasia (WACE) pattern in December. The significantly weakened westerly jet favors stronger upward propagation of planetary waves, which causes stronger weakening and longer persistence of the stratospheric polar vortex. This stratospheric response persists into December and propagates downward into the troposphere interfering with planetary waves (especially wavenumber-1). The lead-lag UB-WACE linkage modulated by mid-latitude jet may have implications for sub-seasonal predictability.publishedVersio

Oceanic forcing of the global warming slowdown in multi-model simulations

Abstract Concurrent with the slowdown of global warming during 2002–2013, the wintertime land surface air temperatures over Eurasia, North America, Africa, Australia, South America, and Greenland experienced notable cooling trends. The oceanic effects on the continental cooling trends are here investigated using two sets of uncoupled experiments with six different climate models. Daily and annually varying sea ice is prescribed for both sets of experiments, while daily and annually varying SST is used in the first set (EXP1) and daily and annually repeating climatological mean SST in the second set (EXP2). All six models capture the slowdown of global-mean land surface air temperature during 2002–2013 winters in EXP1 only. The slowdown concurs with a negative phase of the Pacific Decadal Oscillation (PDO), indicating that PDO plays an important role in modulating the global warming signal. Not all ensemble members capture the cooling trends over the continents, suggesting additional contribution from internal atmospheric variability. KEYWORDS continental cooling, global warming, multi-model simulations, Pacific Decadal Oscillationpublished versio

Research on Acquisition and Communication Technology of Marine Equipment Fault Diagnosis Information for Vessels in Inland Rivers

Abstract: This study describes a system for the analysis of the fault diagnosis of marine equipments in inland rivers. Since the normal operation of the marine equipments significantly influences the ship safety, this study develops an efficient fault diagnosis information system for the condition monitoring and fault diagnosis of marine equipments. In this new system, field bus and ship-to-shore communication technologies have been integrated for the fault diagnosis information acquisition. Then the application of network bus, including CAN and RS485, has been employed to connect the fault diagnosis information with Ethernet in the ship. Lastly, for the real time and wireless transmission of the fault information, the Automatic Identification System (AIS) technology has been adopted to provide accurate and reliable fault diagnosis information transmission from ships to onshore diagnosis center. A comprehensive study of the application of proposed fault diagnosis information system has been implemented for remote diagnosis of marine equipments. The analysis results demonstrate that the newly developed fault diagnosis information system can enhance the fault diagnosis precision and hence is competent for the condition monitoring and fault diagnosis of marine equipments in inland rivers

Effects of precipitation variation and trampling disturbance on seedling emergence of annual plants in a semi-arid grassland

Precipitation change and grazing are the main factors influencing vegetation structure and dynamics in semi-arid grassland. However, the effects of precipitation variation and livestock trampling on the seedling emergence patterns of plants remain largely unknown. In this study, an experiment with four gradients of trampling (no-trampling, light, moderate, and heavy) and three precipitation treatments (ambient precipitation, +30% precipitation, and −30% precipitation) was conducted to assess the effects of trampling disturbance and precipitation variation on seedling emergence of annual plants. The results showed that an increase in precipitation significantly improved total seedling emergence by 3.5–3.6 times and seedling density of grasses by more than 4.1 times under trampling conditions, while significantly improving total seedling emergence and density of forbs under no-trampling conditions. Moreover, +30% precipitation significantly improved the seedling proportion of grasses under light, moderate, and heavy trampling, while decreasing the seedling proportion of forbs. Seedling emergence of forbs was more sensitive to trampling disturbance, and seedling emergence of grasses was more sensitive to precipitation changes, especially under trampling conditions. Light and moderate trampling with a +30% precipitation increase promoted seedling emergence of grasses, and no trampling with a +30% precipitation increase improved seedling emergence of forbs. Thus, targeted grazing management measures should be implemented for plant communities dominated by either grasses or forbs under changing precipitation conditions