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In recent years, studies have found that drought can occur rapidly under anomalous atmospheric circulation patterns and underlying surface conditions. This type of drought is defined as "flash drought". It is more sensitive to global warming compared to traditional drought and may become a common drought phenomenon in the future and require intensive research. But the characteristics and development mechanism of flash drought in northern China has been studied much less than in southern China, and thus deserve further study. Based on the daily station data and GLDAS grid data from 1978 to 2020, this paper identified the flash drought in northern China, analyzed its evolution of temporal-spatial characteristics and explored the meteorological driving factors of flash drought. The main results are as follows: (1)The frequency of flash drought in the year is the highest in WNW (West of Northwest), followed by ENW (East of Northwest), NC (North China) and NE (Northeast China), while the frequency in the plant growing season is the highest in the south of NE and the south of NC, and low in the other regions. (2)The hotspot areas of flash drought showed an obvious eastward trend from WNW to ENW in northern China from the 1980s to 2010s. (3) There is a good relationship between soil moisture and precipitation in WNW and ENW, while the soil moisture is affected by both temperature and precipitation in NC and NE. (4) Flash drought could occur all through the year in WNW and NC, while it mainly occurred in the summer half-year and summer in EWN and NE. The main high occurrence period of flash drought in each region is in late spring and early summer, while a second high occurrence period appears from early September to late October in WNW. (5) From the perspective of the driving of water vapor changes, the flash drought in WNW and ENW is mainly driven by water vapor advection, while that in NC and NE is mainly driven by wind field divergence. • The hotspot areas of flash drought showed an obvious eastward movement from WNW to ENW in northern China. • The main high occurrence period is around early May to early July in northern China, with a second one in WNW. • Flash drought in WNW and ENW (NC and NE) is mainly driven by water vapor advection (wind field divergence). [ABSTRACT FROM AUTHOR]

Two atmospheric circulation systems, i.e., the mid-latitude Westerlies and the East Asian summer monsoon (EASM), dominate climate change in the NE Tibetan Plateau. However, controversy remains with regard to the climatic boundary between these westerly and monsoon regimes. In this paper, detailed rock magnetic and geochemical Rb/Sr analyses for a larger number of surface soils from a wide area in the NE Tibetan Plateau are presented. They show that surface soils in this region evince relatively significant regional variations in magnetic properties and geochemical characteristics. The magnetic parameters χ fd, χ ARM and geochemical Rb/Sr ratios exhibit higher values in EASM-controlled (humid) areas, and lower values in Westerlies-influenced (arid) areas. These characteristics indicate that such variations in χ fd, χ ARM and Rb/Sr ratios can be regarded as effective indicators of the degree of pedogenesis and weathering in the NE Tibetan Plateau. Our results also demonstrate that the climatic boundary between the westerly and monsoon regimes approximately overlaps with the boundary of highland meadow and temperate steppe desert/desert in NW China. [ABSTRACT FROM AUTHOR]

Abstract: This paper reviews the current understanding of the effect of climate change on extreme sea levels in the South Pacific region. This region contains many locations that are vulnerable to extreme sea levels in the current climate, and projections indicate that this vulnerability will increase in the future. The recent publication of authoritative statements on the relationship between global warming and global sea level rise, tropical cyclones and the El Niño-Southern Oscillation phenomenon has motivated this review. Confident predictions of global mean sea level rise are modified by regional differences in the steric (density-related) component of sea level rise and changing gravitational interactions between the ocean and the ice sheets which affect the regional distribution of the eustatic (mass-related) contribution to sea level rise. The most extreme sea levels in this region are generated by tropical cyclones. The intensity of the strongest tropical cyclones is likely to increase, but many climate models project a substantial decrease in tropical cyclone numbers in this region, which may lead to an overall decrease in the total number of intense tropical cyclones. This projection, however, needs to be better quantified using improved high-resolution climate model simulations of tropical cyclones. Future changes in ENSO may lead to large regional variations in tropical cyclone incidence and sea level rise, but these impacts are also not well constrained. While storm surges from tropical cyclones give the largest sea level extremes in the parts of this region where they occur, other more frequent high sea level events can arise from swell generated by distant storms. Changes in wave climate are projected for the tropical Pacific due to anthropogenically-forced changes in atmospheric circulation. Future changes in sea level extremes will be caused by a combination of changes in mean sea level, regional sea level trends, tropical cyclone incidence and wave climate. Recommendations are given for research to increase understanding of the response of these factors to climate change. Implications of the results for adaptation research are also discussed. [Copyright &y& Elsevier]

Abstract: Recent studies have pointed out that persistence of the atmospheric circulation over Europe, as measured by residence times of circulation types, has increased since the mid-1980s in all seasons and for most groups of the types. The greater persistence may affect surface climatic anomalies, particularly the frequency and severity of heat and cold waves associated with severe impacts on society and environment. In this paper, relationships between the persistence of circulation types over Europe and extreme surface air temperature anomalies are studied over the 20th century using the Hess–Brezowsky catalogue of large-scale circulation patterns and long-term temperature series at stations covering most of the European continent. Types significantly conducive to heat and cold waves are identified, and temperature anomalies are linked to their persistence. It is shown that more persistent circulation enhances the severity of temperature extremes over the whole area, which is slightly more important for warm than cold temperature anomalies. The changes in both frequencies and residence times of circulation patterns have been supporting sharply rising trends in warm temperature extremes observed over Europe in recent decades, and the circulation changes may also contributed to the fact that trends in cold temperature extremes have been less pronounced or absent in the same period. The findings also emphasize the need for taking into account the persistence of circulation types together with their frequencies when evaluating links between the atmospheric circulation and the surface climate. In global warming context, the effects of the future climate change on the occurrence and severity of temperature extremes may be exacerbated by a more persistent circulation related to a decreased cyclone activity over mid-latitudes and a northward shift of storm tracks. [Copyright &y& Elsevier]