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喀什市1952-2006年日照时数时间变化特征 总被引：3，自引：0，他引：3
阿布都克日木&#;阿巴司 《沙漠与绿洲气象(新疆气象)》2008,2(3):22-24
利用喀什市1952--2006年日照时数实测资料,分析了喀什市日照时数年代际、年际和各季的气候变化特征,并根据喀什市的降水资料及总、低云量资料,对照时数减少的成因做了分析。结果表明：近55a来喀什市的年、季日照时数均呈减少趋势。各季减少的气候倾向率不同,减少幅度最多的是夏季,最少的是秋季。 相似文献
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Rainfall intensity–duration–frequency (IDF) relationships describe rainfall intensity as a function of duration and return period, and they are significant for water resources planning, as well as for the design of hydraulic constructions. In this study, the two‐parameter lognormal (LN2) and Gumbel distributions are used as parent distribution functions. Derivation of the IDF relationship by this approach is quite simple, because it only requires an appropriate function of the mean of annual maximum rainfall intensity as a function of rainfall duration. It is shown that the monotonic temporal trend in the mean rainfall intensity can successfully be described by this parametric function which comprises a combination of the parameters of the quantile function a(T) and completely the duration function b(d) of the separable IDF relationship. In the case study of Aegean Region (Turkey), the IDF relationships derived through this simple generalization procedure (SGP) may produce IDF relationships as successfully as does the well‐known robust estimation procedure (REP), which is based on minimization of the nonparametric Kruskal–Wallis test statistic with respect to the parameters θ and η of the duration function. Because the approach proposed herein is based on lower‐order sample statistics, risks and uncertainties arising from sampling errors in higher‐order sample statistics were significantly reduced. The authors recommend to establish the separable IDF relationships by the SGP for a statistically favorable two‐parameter parent distribution, because it uses the same assumptions as the REP does, it maintains the observed temporal trend in the mean additionally, it is easy to handle analytically and requires considerably less computational effort. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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基于2001-2018年广东省86个国家自动气象站逐小时降水资料,分析了广东省不同历时降水的时空分布特征.结果表明：1）除粤北山区外,基本符合年均降水时数越多,累积降水量越大的规律.年均小时降水强度从南部沿海向北部内陆呈减弱趋势.2）汛期降水事件以短历时为主,占全年降水事件65.3%;累积降水量上,长历时降水量占汛期56.7%.前汛期短历时降水多发生在粤西;中历时降水多发生在珠三角两侧和粤西北地区;长历时降水多发生在粤东和粤北地区.后汛期短历时降水多发生在内陆,出现频次自西北向东南递减;中历时降水分布不均;长历时降水多发生在沿海.3）汛期降水时数日变化呈双峰型变化特征,小时降水强度日变化呈单峰型变化特征.小时降水强度峰值易出现在下午的站点多分布在内陆,小时降水强度峰值易出现在下半夜至上午时段的站点则多分布在沿海、部分山区和珠三角地区. 相似文献
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Information on the Arctic sea ice climate indicators is crucial to business strategic planning and climate monitoring. Data on the evolvement of the Arctic sea ice and decadal trends of phenology factors during melt season are necessary for climate prediction under global warming. Previous studies on Arctic sea ice phenology did not involve melt ponds that dramatically lower the ice surface albedo and tremendously affect the process of sea ice surface melt. Temporal means and trends of the Arctic sea ice phenology from 1982 to 2017 were examined based on satellite-derived sea ice concentration and albedo measurements. Moreover, the timing of ice ponding and two periods corresponding to it were newly proposed as key stages in the melt season. Therefore, four timings, i.e., date of snow and ice surface melt onset (MO), date of pond onset (PO), date of sea ice opening (DOO), and date of sea ice retreat (DOR); and three durations, i.e., melt pond formation period (MPFP, i.e., MO–PO), melt pond extension period (MPEP, i.e., PO–DOR), and seasonal loss of ice period (SLIP, i.e., DOO–DOR), were used. PO ranged from late April in the peripheral seas to late June in the central Arctic Ocean in Bootstrap results, whereas the pan-Arctic was observed nearly 4 days later in NASA Team results. Significant negative trends were presented in the MPEP in the Hudson Bay, the Baffin Bay, the Greenland Sea, the Kara and Barents seas in both results, indicating that the Arctic sea ice undergoes a quick transition from ice to open water, thereby extending the melt season year to year. The high correlation coefficient between MO and PO, MPFP illustrated that MO predominates the process of pond formation. 相似文献
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封育是推广范围最广的草地恢复措施之一. 为研究不同封育年限高寒草甸植被、土壤碳密度变化, 对1 a、6 a和16 a不同封育年限样地监测结果进行分析.结果表明: 不同封育年限高寒草甸植被现存碳密度表现出封育16 a>封育1 a>封育6 a, 分别为1 522.57 gC·m-2、1 323.12 gC·m-2和1 148.17 gC·m-2, 但不同封育年限之间植被现存碳密度差异不显著(P>0.05). 土壤碳密度垂直分布明显, 0~5 cm和5~10 cm土层有机碳密度较高, 随土层深度增加土壤有机碳密度明显下降, 土壤容重上升;不同封育年限之间0~40 cm层次土壤碳密度和土壤容重差异性均不显著, 但仍可表现出土壤碳密度封育1 a>封育6 a>封育16 a, 分别为28 636.32 gC·m-2、26 570.92 gC·m-2和26 060.71 gC·m-2;同时, 土壤容重随封育时间延长而下降. 对7月下旬到10月上旬净生态系统CO2交换率(NEE)监测来看, 封育1 a植被土壤碳吸收速率显著高于封育16 a(P<0.05);而排放率与封育16 a样地接近, 差异不显著(P>0.05). 相似文献
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利用新疆伊犁河谷高密度地面自动站逐小时降水观测资料,对2010-2022年暖季（5-9 月）短时强降水（flash heavy rain,FHR）逐1h、3h和6h时空分布特征进行分析,结果发现:伊犁河谷暖季不同历时短时强降水阈值空间分布具有一致性,1h、3h和6h极端降水阈值的平均值分别为 8.5mm?h-1 、12.6mm?（3h）-1和16.8mm?（6h）-1。不同历时FHR集中发生在5月中旬至8月中旬,其中6月最多,7月次之;不同历时FHR频次发生在中午13：00至下午18：00。不同历时FHR事件最大小时雨强的月分布与发生站次略有差异,除1h最大为62.6mm?h-1出现在7月外,其他雨强均出现在6月分别为89.9mm?（3h）-1、104.5mm?（6h）-1,较大值位于河谷东部和南部。伊犁河谷暖季不同历时FHR空间分布具有明显的不对称性特征,总体呈东高西低的分布格局,在南北方向上1h短时强降水呈北高南低,3h、6h短时强降水均无明显变化趋势。不同历时FHR降水贡献和发生频率的局地差异明显,存在多个大值中心,主要出现在新源县、昭苏县偏北地区、霍城县偏北地区、特克斯县偏西地区、尼勒克县偏西地区及伊宁县中部等地。FHR频次各站虽有显著差异,但未发生明显离散,地形对FHR的增幅作用显著。 相似文献
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In order to analyze the differences between the two snow cover data, the snow cover data of 884 meteorological stations in China from 1951 to 2005 are counted. The data include days of visual snow observation, snow depth, and snow cover durations, which vary according to different definitions of snow cover days. Two series of data, as defined by "snow depth" and by "weather observation," are investigated here. Our results show that there is no apparent difference between them in east China and the Xinjiang region, but in northeast China and the Tibetan Plateau the "weather observation" data vary by more than 10 days and the "snow depth" data vary by 0.4 cm. Especially in the Tibetan Plateau, there are at least 15 more days of "weather observation" snow in most areas (sometimes more than 30 days). There is an obvious difference in the snow cover data due to bimodal snowfall data in the Tibetan Plateau, which has peak snowfalls from September to October and from April to May. At those times the temperature is too high for snow cover formation and only a few days have trace snow cover. Also, the characteristics and changing trends of snow cover are analyzed here based on the snow cover data of nine weather stations in the northeast region of the Tibetan Plateau, by the Mann-Kendall test. The results show significantly fewer days of snow cover and shorter snow durations as defined by "snow depth" compared to that as defined by "weather observation." Mann-Kendall tests of both series of snow cover durations show an abrupt change in 1987. 相似文献
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溶蚀作用是喀斯特地区最根本的作用过程之一,与水密切相关,极易受到干旱的影响。过去研究表明,干旱对喀斯特溶蚀有重要的影响,但具体影响有多大尚不清楚。论文采用标准溶蚀试片法并通过野外控制试验的方式,定量地给出了12种不同持续时间干旱对黔中地区林地、灌草地和耕地及其地下不同土层深度喀斯特溶蚀的影响,并初步分析了其影响过程机理。研究表明：① 不同持续时间干旱对林地、灌草地和耕地喀斯特溶蚀的影响程度分别达到30.61%~83.33%、38.45%~88.82%和66.76%~95.14%,均随干旱持续时间的增加而呈明显的上升趋势;② 干旱对不同土层喀斯特溶蚀的影响不一致,较短持续时间干旱对林地、灌草地和耕地中下层喀斯特溶蚀的影响较大,而长持续时间干旱则对表层喀斯特溶蚀的影响较大;③ 土壤水分是干旱影响喀斯特溶蚀的关键要素,土壤pH随土壤水分变化而变化,而土壤有机质对喀斯特溶蚀的干旱影响则有一定的减缓作用。 相似文献
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