Trends in graded precipitation in China from 1961 to 2000

Daily precipitation rates observed at 576 stations in China from 1961 to 2000 were classified into six grades of intensity, including trace （no amount）, slight （≤ 1 mm d^-1）, small, large, heavy, and very heavy. The last four grades together constitute the so called effective precipitation （〉 1 mm d^-1）. The spatial distribution and temporal trend of the graded precipitation days are examined. A decreasing trend in trace precipitation days is observed for the whole of China, except at several sites in the south of the middle section of the Yangtze River, while a decreasing trend in slight precipitation days only appears in eastern China. The decreasing trend and interannual variability of trace precipitation days is consistent with the warming trend and corresponding temperature variability in China for the same period, indicating a possible role played by increased surface air temperature in cloud formation processes. For the effective precipitation days, a decreasing trend is observed along the Yellow River valley and for the middle reaches of the Yangtze River and Southwest China, while an increasing trend is found for Xinjiang, the eastern Tibetan Plateau, Northeast China and Southeast China. The decreasing trend of effective precipitation days for the middle- lower Yellow River valley and the increasing trend for the lower Yangtze River valley are most likely linked to anomalous monsoon circulation in East China. The most important contributor to the trend in effective precipitation depends upon the region concerned.     

Interdecadal variation of precipitation days in August in the Korean Peninsula

The present study examines a climate regime shift in the time series of the number of rainy days during August in the Korean Peninsula. The statistical change-point analysis indicates that a significant shift occurred in the time series around 1998, providing a rationale to divide it into two parts: 1975–1997 for the shorter rainy-day period and 1998–2012 for the longer rainy-day period. To examine the cause of recent rapid increases in the number of days with precipitation in August in the Korean Peninsula, differences in the averages of large-scale environments between the 1998–2012 period and the 1975–1997 period were analyzed.The differences in stream flows showed that anomalous cyclones were reinforced in the East Asian continent while anomalous anticyclones were reinforced in the western North Pacific at all layers of the troposphere. The anomalous anticyclones reinforced in the western North Pacific were associated with the western North Pacific subtropical high (WNPSH) developed a little more toward the Korean Peninsula recently. Consequently, the Korean Peninsula has been affected by anomalous south westerlies that supplied warm and humid airs from low tropical regions to the Korean Peninsula. The vertical thermal instability (warm anomaly at lower-level and cold anomaly at middle and upper-level) developed near the Korean Peninsula. In addition, upper tropospheric jets were reinforced further recently near the Korean Peninsula to provide good environments for development of upward flows. The frequency of TCs that affect the Korean Peninsula in August also increased rapidly since 1998.     

青海玉树7.1级大震的预测讨论

讨论了2010年4月14日青海玉树大震的震源组合模式。用临界慢化的观点讨论了玉树大震的前震。以异年倍九律与磁暴二倍法相配讨论了玉树大震的发生日期。     

广东沿海夏季降水年代际变化成因分析

利用零降水日对广东沿海夏季降水的年代际变化成因进行统计相关分析,结果表明:南海表层海温(SST)对次年夏季广东沿海地区降水有明显影响,并且这种影响作用在20世纪70年代有一个明显的年代际变异;南海SST影响广东省夏季降水的敏感区域在不同的年代际阶段都非常靠近广东省,局地性非常明显。局地的海气相互作用对广东沿海夏季降水的短期气候预测有显著的意义。     

DISCHARGE AND SEDIMENT-LOAD CHARACTERISTICS OF THE HILDA ROCK-GLACIER STREAM,CANADIAN ROCKY MOUNTAINS,ALBERTA

Water discharge and sediment load characteristics of the Hilda rock-glacier stream are described for portions of the 1985 and 1986 ablation seasons. Covering an area of 1.5 km², the Hilda rock glacier yields a relatively consistent flow, generally low in suspended sediments and relatively high in total dissolved solids during the ablation season. The seasonal hydrograph shows decreasing discharge and suspended sediment load and increasing dissolved loads through the ablation season as snowmelt water sources are depleted. Superimposed on this is a diurnal hydrograph showing that daily peaks in discharge lag several hours behind daily temperature maxima. Rain events produce hydrograph anomalies and act to flush sediment, elevating suspended loads, while diluting dissolved loads. These data suggest that rock-glacier hydrological systems are more responsive to short-term and transient meteorological conditions than previously suggested in the literature. Nonetheless, the data indicate that the Hilda rock glacier is more conservative in both water and sediment yield than glacier systems of comparable size and in the same environment.     

山西高温天气的环流特征及流型配置研究

利用1958年-2008年高低空气象观测资料以及山西省气象信息中心归档的109站1958年-2008年的原始气象记录月报表及其信息化产品资料,分别以最高气温≥35℃、≥37℃、≥40℃为指标,研究山西高温日的时空分布、变化趋势及环流特征。结果表明：a）山西高温日最早出现在4月中旬,最晚出现在9月中旬,≥35℃、≥37℃和≥40℃的高温日6月下旬最多;b）高温日数有随纬度、随海拔的升高而减少,有西部多于东部、南部多于北部、盆地多于山区的空间分布特征。≥40℃的高温区域主要集中在运城和临汾地区;C）1984年-2008年,35℃以上的高温日数整体呈上升趋势;1979年-2008年,30年间高温站次以153站次,10a的趋势增多。20世纪90年代以后,不仅高温日数增多,而且高温持续时间、强度、范围都有增强趋势;d）影响山西高温的500hPa环流形势主要有副高纬向性、副高经向型以及大陆高压（脊）控制型3类。在特定的流型配置下,T850≥25℃、T700≥13℃,T850≥26℃、T700≥14℃,T850≥28℃、T700≥15℃,T850≥32℃、T700≥16℃是山西省不同区域、不同风向影响时,≥35℃、≥37℃、≥40℃高温天气预报的临界值。     

Analysis of the Trends of Thunderstorms in 1951–2007 in Jiangsu Province

Based on the 1951–2007 thunderstorms in Jiangsu, a study is conducted for their climate trends, periodicity, spatiotemporal patterns, and the distributions of the first and last days of the thunderstorms at different guarantee rates (GRs) using climate tendency rate, wavelet analysis, and GR for diagnosis. Results suggest that the inter-annual number of thunderstorm days (TSDs) exhibits a decreasing trend in this province. The trend is displayed mainly in the decreasing TSD number in summer and autumn except in spring, when the variation is not significant in the study period. In this province, the TSD number declines by ~2 days per 10 years. On an inter-annual basis, the pronounced positive departures of the number take place chiefly in the early 1960s, the late 1960s to the early-mid-1970s, the late 1980s, and the late 1990s compared with the negative anomalies dominant in the late 1970s to the mid-1980s, the mid-to-late-1990s, and the late 1990s to 2007. There are vast differences in the initial and ending days at diverse GRs in different areas of the province. At 50% GR, the earliest (last) days occur from mid-March to early April (early to late September) while at 80% GR, the initial (last) days are from late March to early May (early to late October). For the distribution of periods, the periods >8–10 years are relatively stable for the entire province. Based on 1951–2007 period analysis, the region north (south) of the Huaihe River experiences TSDs less (more) than normal days in recent years.     

Spatial and Temporal Distribution and Variations in the Near-surface Soil Freezing Days across China, 1956-2006

Using surface soil daily minimum temperature from 845 meteorological stations across China, the long-term (1971-2000) mean and spatial distribution of the near-surface soil freezing days were estimated with annual values of the number of near surface soil freezing days. The time series for the number of freezing days were constructed and compared with air temperatures in the same period.Resultsshowed that long term mean value in the number of the near surface soil freezing days increased with the increasing latitudes and altitudes over China. Near-surface soils were frozen for more than 200 days in the Qinghai Tibet Plateau, northern Xinjiang and northeast of China. The boundaries of permafrost zones coincide with the contour of (220±10) days of near-surface soil freezing. Using the mean number of 15 days of near-surface soil freezing as criterion, we found that the southern boundary of seasonally frozen ground is around the 25°N line, and the regions south of 22°N are essentially unfrozen regions. The time series of the number of freezing days showed a significant linear trend with change with a slope of -0.22days/year over a period from 1956 through 2006. After the 1990s, the linear slope was up to -1.02 days / year, indicating that the rate of decrease in the number of near-surface soil freezing days has accelerated. Changes in the number of near surface soil freezing were in a negative correlation with air temperature, i.e., the number of near-surface soil freezing days decreases with increase in air temperature.Backgroundcolor represents the contour values of the departure of near-surface soil freezing days from the 1971-2000 mean; Black dashed line is the boundary of permafrost regions, red dashed line is the boundary between frozen and unfrozen ground regions in China     

Spatial distributions and interannual variations of snow cover over China in the last 40 years

By using the observational snow data of more than 700 weather stations,the interannual temporal and spatial characteristics of seasonal snow cover in China were analyzed.The results show that northern Xinjiang,northeastern China-Inner Mongolia,and the southwestern and southern portions of Tibetan Plateau are three regions in China with high seasonal snow cover and also an interannual anomaly of snow cover.According to the trend of both the snow depth and snow cover days,there are three changing patterns for the seasonal snow cover:The first type is that both snow depth and snow cover days simultaneously increase or decrease;this includes northern Xinjiang,middle and eastern Inner Mongolia,and so on.The second is that snow depth increases but snow cover days decrease;this type mainly locates in the eastern parts of the northeastern plain of China and the upper reaches of the Yangtze River.The last type is that snow depth decreases but snow cover days increase at the same time such as that in middle parts of Tibetan Plateau.Snow cover in China appears to have been having a slow increasing trend during the last 40 years.On the decadal scale,snow depth and snow cover days slightly increased in the 1960s and then decreased in the 1970s;they again turn to increasing in the 1980s and persist into 1990s.     

我国沙尘暴发生日数的空间分布格局

根据全国近30 a的沙尘暴记录,运用分形分析得出,在不同的降水量区域,沙尘暴的发生规律明显不同。中国北方沙尘暴发生日数平均为4.4 d·a-1。年降水量≤305 mm的地区沙尘暴发生日数最多,平均为9.9 d·a-1,这是荒漠和半荒漠地区,主要是我国传统的畜牧区;305 mm<年降水量<570 mm的地区平均为4.0 d·a-1,这是草原区,主要是传统的农牧交错带。年降水量≥570 mm的地区为0.4 d·a-1,主要是我国的农耕区。305 mm<年降水量<570 mm的区域,沙尘暴发生的频率随降水的变化幅度最大,为4.1,年降水量≤305 mm地区,沙尘暴随降水的变化幅度最小,为0.3。分析认为,我国沙尘暴危害的防治需要构建牧区—农牧交错带—农区生态农业体系。