分类: 地球科学 >> 水文学 提交时间: 2023-10-17 合作期刊: 《干旱区科学》
摘要: The wide valley of the Yarlung Zangbo River is one of the most intense areas in terms of aeolian activity on the Tibetan Plateau, China. In the past, the evaluation of the intensity of aeolian activity in the QuxuSangri section of the Yarlung Zangbo River Valley was mainly based on data from the old meteorological stations, especially in non-sandy areas. In 2020, six new meteorological stations, which are closest to the new meteorological stations, were built in the wind erosion source regions (i.e., sandy areas) in the QuxuSangri section. In this study, based on mathematical statistics and empirical orthogonal function (EOF) decomposition analysis, we compared the difference of the wind regime between new meteorological stations and old meteorological stations from December 2020 to November 2021, and discussed the reasons for the discrepancy. The results showed that sandy and non-sandy areas differed significantly regarding the mean velocity (8.3 (0.3) versus 7.7 (0.3) m/s, respectively), frequency (12.9% (6.2%) versus 2.9% (1.9%), respectively), and dominant direction (nearly east or west versus nearly north or south, respectively) of sand-driving winds, drift potential (168.1 (77.3) versus 24.0 (17.9) VU (where VU is the vector unit), respectively), resultant drift potential (92.3 (78.5) versus 8.7 (9.2) VU, respectively), and resultant drift direction (nearly westward or eastward versus nearly southward or northward, respectively). This indicated an obvious spatial variation in the wind regime between sandy and non-sandy areas and suggested that there exist problems when using wind velocity data from non-sandy areas to evaluate the wind regime in sandy areas. The wind regime between sandy and non-sandy areas differed due to the differences in topography, heat flows, and their coupling with underlying surface, thereby affecting the local atmospheric circulation. Affected by large-scale circulations (westerly jet and Indian monsoon systems), both sandy and non-sandy areas showed similar seasonal variations in their respective wind regime. These findings provide a credible reference for re-understanding the wind regime and scientific wind-sand control in the middle reaches of the Yarlung Zangbo River Valley.
分类: 地球科学 >> 大气科学 提交时间: 2023-05-30 合作期刊: 《干旱区研究》
摘要: 为了改进短时暴雨预报方程,提高短时暴雨预报准确率,综合评价多种大气环境参数对甘肃河东短时暴雨预报的影响权重是十分必要的。本文利用甘肃河东20132018年汛期降水量资料,采用百分位法计算了甘肃河东68月短时暴雨阈值,根据阈值挑选出甘肃河东92个短时暴雨个例,使用ECMWF 0.250.25再分析资料,分析大气环境参数发现,K指数、700 hPa相对湿度、大气可降水量等参数对甘肃河东短时暴雨有较好的指示意义;基于模糊数学的方法,考虑显著性及适度性,构建了28个大气环境参数的综合评价方案,得出不同时段大气环境参数权重,综合分析表明:甘肃河东汛期发生短时暴雨时,各时段大气环境参数权重排序不同,预报短时暴雨时需考虑其所处气候时段大气环境参数的权重,并对权重排序较前的参数进行重点考虑。
分类: 地球科学 >> 地理学 提交时间: 2021-09-08 合作期刊: 《干旱区科学》
摘要: River runoff plays an important role in watershed ecosystems and human survival, and it is controlled by multiple environmental factors. However, the synergistic effects of various large-scale circulation factors and meteorological factors on the runoff on different time-frequency scales have rarely been explored. In light of this, the underlying mechanism of the synergistic effects of the different environmental factors on the runoff variations was investigated in the Yellow River Basin of China during the period 1950–2019 using the bivariate wavelet coherence (WTC) and multiple wavelet coherence (MWC) methods. First, the continuous wavelet transform (CWT) method was used to analyze the multiscale characteristics of the runoff. The results of the CWT indicate that the runoff exhibited significant continuous or discontinuous annual and semiannual oscillations during the study period. Scattered inter-annual time scales were also observed for the runoff in the Yellow River Basin. The meteorological factors better explained the runoff variations on seasonal and annual time scales. The average wavelet coherence (AWC) and the percent area of the significant coherence (PASC) between the runoff and individual meteorological factors were 0.454 and 19.89%, respectively. The circulation factors mainly regulated the runoff on the inter-annual and decadal time scales with more complicated phase relationships due to their indirect effects on the runoff. The AWC and PASC between the runoff and individual circulation factors were 0.359 and 7.31%, respectively. The MWC analysis revealed that the synergistic effects of multiple factors should be taken into consideration to explain the multiscale characteristic variations of the runoff. The AWC or MWC ranges were 0.320–0.560, 0.617–0.755, and 0.819–0.884 for the combinations of one, two, and three circulation and meteorological factors, respectively. The PASC ranges were 3.53%–33.77%, 12.93%–36.90%, and 20.67%–39.34% for the combinations one, two, and three driving factors, respectively. The combinations of precipitation, evapotranspiration (or the number of rainy days), and the Arctic Oscillation performed well in explaining the variability in the runoff on all time scales, and the average MWC and PASC were 0.847 and 28.79%, respectively. These findings are of great significance for improving our understanding of hydro-climate interactions and water resources prediction in the Yellow River Basin.
分类: 地球科学 >> 空间物理学 提交时间: 2017-03-10
摘要: High-energy electron precipitation in the high latitude regions enhances the ionization of the atmosphere, and subsequently increases the atmospheric conductivities and the vertical electric field of the atmosphere near the ground as well. The high-energy electron flux (HEEF) data measured by the Feng-Yun III meteorological satellite are analyzed together with the data of near-surface atmospheric vertical electric field measured at the Russian Vostok Station. Three HEEF enhancements are identified and show that when the HEEF increases to a certain level, the local atmospheric vertical electric field near the ground can increase substantially than usual. The time of the response of the electric field to the HEEF enhancement is about 3.7 to 4 days (delay time).
分类: 地球科学 >> 空间物理学 提交时间: 2017-01-22
摘要: High-energy electron precipitation in the high latitude regions enhances the ionization of the atmosphere, and subsequently increases the atmospheric conductivities and the vertical electric field of the atmosphere near the ground as well. The High-Energy Electron Flux (HEEF) data measured by the Fengyun-3 meteorological satellite are analyzed together with the data of nearsurface atmospheric vertical electric field measured at the Russian Vostok Station. Three HEEF enhancements are identified and it is shown that when the HEEF increases to a certain level, the local atmospheric vertical electric field near the ground can increase substantially than usual. The response time of the electric field to HEEF enhancement is about 3.7 to 4 days.
分类: 地球科学 >> 空间物理学 提交时间: 2016-05-03
摘要: The paper develops a passive sub-millimeter atmospheric profile and precipitation retrievals algorithm for Microwave Humidity and Temperature Sounder (MWHTS) onboard the Chinese Feng Yun 3C (FY-3C) satellite. The retrieval algorithm employs a number of neural network estimators trained and evaluated using the validated global reference physical model NCEP/WRF/ARTS, and works for land and seawater with latitude between -30 to 30 degree. To simply the calculation procedure and save the training time, principle component analysis was adapted to filter out the redundancy caused by scanning angle and surface effects, as well as system noise. NCEP data per 6 hours are downloaded to run the Weather Research and Forecast model WRF, and derive the typical precipitation data from the whole world. The Atmospheric Radiative Transfer Simulator ARTS is feasible for performing simulations of atmospheric radiative transfer.