Possible Impact of the Summer North Atlantic Oscillation on Extreme Hot Events in China

This paper reveals that the summer North Atlantic Oscillation (SNAO) is closely related to the extreme hot event (EHE) variability in China during the period of 1979 2009, with a positive-phase (negative-phase) SNAO corresponding to less (more) EHEs in northern China. The summer circulation anomalies associated with the SNAO give further confirmation of the above relationship. In a positive-phase (negative-phase) SNAO year, there is an anomalous cyclone (anticyclone) over central East Asia, which can increase (decrease) the total cloud cover over this region. Such changes of the total cloud cover can then decrease (increase) the solar radiation reaching the surface, which is consequently unfavorable (favorable) to the formation of EHEs over northern China.

Interdecadal variability of the large-scale extreme hot event frequency over the middle and lower reaches of the Yangtze River basin and its related atmospheric patterns

Based on daily maximum temperature data from Chinese weather stations for the period 1960- 2013, the characteristics of the interdecadal variability of large-scale extreme hot event （EHE） frequency over the middle and lower reaches of the Yangtze River basin （MLYR） are analyzed. It is found that the frequency of large-scale EHE over the MLYR experiences two significant interdecadal changes, around the early 1970s and early 2000s, having a more-less-more variability shape during the past half century. Furthermore, the EHE frequency interdecadal variability-related atmospheric circulation patterns are diagnosed. The results indicate the western Pacific subtropical high could not be the dominant atmospheric circulation associated with the interdecadal variability of the large-scale EHE frequency over the MLYR. In contrast, the dominant teleconnection pattern over the Eurasian continent, which is represented by the second empirical orthogonal function mode of the 200 hPa geopotential height, is closely related to the interdecadal variability of the EHE frequency over the MLYR. The results of this study deepen our understanding of the variability of the EHE frequency over the MLYR and its possible mechanism.

The Extremely Hot and Dry Climatic Events and Potash Enrichment in Salt Lakes of the Jiangling Depression, Jianghan Basin

Objective A total of 820 million tons of potash reserves are predicted to exist in the Palaeocene-Eocene of the Jianghan Basin. However, the basin history is still unclear concerning the potash enriching conditions and mechanism. The Well SKDI is the first exploration well drilled in the Paleogene of Jianghan Basin with continuous coring, which was implemented in the south-central Jiangling Basin in 2013. It is essential to study the Palaeocene-Eocene paleoclimate, to further constrain the extreme draught events and the potash forming conditions.

Influence of the Boreal Summer Intraseasonal Oscillation on Extreme Temperature Events in the Northern Hemisphere

The impact of the boreal summer intraseasonal oscillation （BSISO） on extreme hot and cool events was investig-ated, by analyzing the observed and reanalysis data for the period from 1983 to 2012. It is found that the frequency of the extreme events in middle and high latitudes is significantly modulated by the BSISO convection in the tropics, with a 3-9-day lag. During phases 1 and 2 when the BSISO positive rainfall anomaly is primarily located over a northwest-southeast oriented belt extending from India to Maritime Continent and a negative rainfall anomaly ap- pears in western North Pacific, the frequency of extreme hot events is 40% more than the frequency of non-extreme hot events. Most noticeable increase appears in midlatitude North Pacific （north of 40°N） and higher-latitude polar region. Two physical mechanisms are primarily responsible for the change of the extreme frequency. First, an upper-tropo-spheric Rossby wave train （due to the wave energy propagation） is generated in response to a negative heating anom-aly over tropical western North Pacific in phases 1 and 2. This wave train consists of a strong high pressure anomaly center northeast of Japan, a weak low pressure anomaly center over Alaska, and a strong high pressure anomaly cen-ter over the western coast of United States. Easterly anomalies to the south of the two strong midlatitude high pres-sure centers weaken the climatological subtropical jet along 40°N, which is accompanied by anomalous subsidence and warming in North Pacific north of 40°N. Second, an enhanced monsoonal heating over South Asia and East Asia sets up a transverse monsoonal overturning circulation, with large-scale ascending （descending） anomalies over trop-ical Indian （Pacific） Ocean. Both the processes favor more frequent extreme hot events in higher-latitude Northern Hemisphere. An anomalous atmospheric general circulation model is used to confirm the tropical heating effect.