Diurnal Variation Of Summer Precipitation Research Articles

The characteristics and mechanisms on diurnal variation of summer precipitation over the Tibetan Plateau

The characteristics and mechanisms on diurnal variation of summer precipitation over the Tibetan Plateau

Diurnal variation of summer precipitation modulated by air pollution: observational evidences in the beijing metropolitan area

Studying precipitation diurnal variation characteristics is crucial to better understand their formation mechanism. Moreover, it is fundamental in assessing regional climate variability and to validate the effectiveness of cloud and precipitation parameterization schemes in weather and climate models. Based on observational data from 2008 to 2017, this manuscript objective is to assess the aerosol effects on summer precipitation on an hourly-scale diurnal variation basis in the Beijing metropolitan area. The results put in evidence that the precipitation frequency and duration on polluted days were 25.0% and 14.8% lower with respect to clean days. No significant differences were observed in total daily accumulated rainfall between clear and polluted days. While heavy precipitation mean intensity on polluted days increased by 13.5%, which is potentially linked with aerosol microphysical effects. Note that precipitation occurs earlier on polluted days, with peak time of 1 ∼ 2-hour in advance compared with clean days over the urban areas of Beijing, which may be primarily ascribed to the influence of advanced turning local circulation of mountain-valley breezes and urban heat island circulation due to aerosol-radiation effects.

Diurnal Variations of Summer Precipitation Linking to the Topographical Conditions over the Beijing-Tianjin-Hebei Region

The Beijing-Tianjin-Hebei (BTH) region of above 110 million people, located in North China, is confronted with high risks of precipitation-related disasters during the summer. Efforts to better understand diurnal variation characteristics of summer precipitation and associated physical driving processes are of vital importance to accurate forecast of short-time precipitation. Based on hourly gridded precipitation data at a fine resolution of 0.1° newly developed by China Meteorological Administration (CMA), we investigate diurnal variations of summer precipitation and their linkages with the topographical conditions in the BTH region for the period of 2008–2018. Summer precipitation amounts are shown to nonlinearly change with the topographical height, the largest values occurring at the altitudes of around 350 m in the BTH region. As a whole, diurnal variation of summer mean precipitation in the BTH region exhibits an S-shape structure with the peak appearing around 20:00 LST. While the mountainous precipitation largely triggers the precipitation peak with contribution from coastal and plain areas, the large precipitation in early morning is dominated by the precipitation over coastal and plain areas. Heavy and very heavy precipitation frequencies generally decrease with topographical height while light precipitation frequency increases in a nonlinear manner. The physical processes explaining the tight precipitation-topography linkages are also discussed. Our findings are expected to provide useful information for the improvement of short-time precipitation forecast over the BTH region.

Diurnal Variations of Summer Precipitation over the Qilian Mountains in Northwest China

Based on the high-density hourly rain-gauge data from 265 stations over the Qilian Mountains in Northwest China, climatic mean diurnal variations of summer rainfall over different topographies of this area are investigated. Influences of the gauge elevations on the diurnal variation of rainfall are also revealed. Distinct regional features of diur-nal variations in rainfall are observed over the Qilian Mountains. Rainfall over the Qinghai Lake areas shows a single nocturnal peak. A dominant, late-afternoon peak of rainfall occurs over the mountain tops. Over the northeastern and southeastern slopes, a dominant diurnal peak appears in the late afternoon, and an evident second peak is found in the early morning, respectively. The strengths of the early-morning peaks in the rainfall frequency are closely related to the rainfall events with different durations over the two slopes. The early-morning peak is dominant across plains with low elevations. From the mountain tops to the plains, the diurnal peaks of rainfall gradually vary from the domi-nant late-afternoon peak to the dominant early-morning peak with the enhanced early-morning peak in concurrent with the decreasing gauge elevation over the northeastern and southeastern slopes. Further examination indicates that the rainfall at higher elevations over the northeastern and southeastern slopes occurs more readily in the afternoon, compared to the lower elevations. This phenomenon corresponds to the result that the proportion of the rainfall frequency occurring during the early-morning period decreases with increasing elevations over the two slopes.

Diurnal variations of summer precipitation over the regions east to Tibetan Plateau

Based on the hourly gauge-satellite merged precipitation product with the horizontal resolution of 0.1° latitude/longitude during 2008–2014, diurnal variations of the summer precipitation amount (PA), frequency (PF), and intensity (PI) with different duration time over the regions east to Tibetan Plateau have been systematically revealed in this study. Results indicate that the eight typical precipitation diurnal patterns identified by the cluster analysis display pronounced regional features among the plateaus, basins, plains, hilly and coastal areas. The precipitation diurnal cycles are significantly affected by the sub-grid terrain fluctuations. The PA, PF and PI of the total rainfall show much more pronounced double diurnal peaks with the sub-grid topography standard deviation (SD) decreased. Meanwhile, the diurnal peaks of PA and PF (PI) strengthen (weaken) with the sub-grid topography SD enhanced. Over the elevated mountain ranges, southeastern hilly and coastal regions, the PA and PF diurnal patterns of the total rainfall generally show predominant late-afternoon peaks, which are closely associated with the short-duration (leqslant , 3 h) rainfall. Along the Tibetan Plateau to its downstream, the diurnal peaks of PA, PF and PI for the total rainfall all exhibit obvious eastward phase time delay mainly due to the diurnal evolutions of long-duration (> 6 h) rainfall. However, the 4–6 h rainfall leads to the eastward phase time delay of the total rainfall along the Taihang Mountains to its downstream. Further mechanism analysis suggests that the midnight to morning diurnal evolution of the long-duration rainfall is closely associated with the diurnal variations of the upward branches of thermally driven mountain-plain solenoids and the water vapor transport associated with the accelerated nocturnal southwesterly winds. The late-afternoon peak of the short-duration PA over the southeastern hilly and coastal regions is ascribed to the strong local thermal convections due to the solar heating in afternoon, while the early-evening peak of the short-duration PA over the elevated mountain ranges is significantly contributed by the upward warm-moist wind from the surrounding low-lying basins or plains.

Diurnal Variation of Summer Precipitation across the Central Tian Shan Mountains

AbstractThe climatic features of the diurnally varying summer precipitation over and around the central Tian Shan Mountains are investigated. Both the hourly rainfall data observed at eight stations along a transect across the mountains and the convective index derived from the satellite data show that there are three distinct regimes: the early morning peak at stations to the south of the mountains, the late afternoon peak at stations on the mountains, and the night peak at stations to the north of the mountains. The relation between regimes of diurnal variation is analyzed. By defining the regional rainfall event (RRE), the initial stations of each RRE are recorded. The early morning rainfall in the southern periphery of the mountains is triggered locally in the southern basin. Both the late afternoon peak over the mountains and the night peak in the northern periphery are influenced by mountain-originated rainfall events. These rainfall events appear over the mountains in the afternoon, and some of them move northward and lead to the nocturnal rainfall in the northern basin. The triggering of convection in the afternoon over the mountains and that in the early morning in the southern basin is related to the diurnally varying wind and thermodynamic conditions over and around the mountains. Low-level convergence with thermodynamic instability appears at noon (night) over the mountains (in the southern basin) just before the start of the convection.

Assessment of diurnal variation of summer precipitation over the Qilian Mountains based on an hourly merged dataset from 2008 to 2014

To investigate the diurnal variation of summer precipitation in the Qilian Mountains in the northeast Tibetan Plateau, the hourly precipitation amount for this region during the summers of 2008–2014 are analyzed using an hourly merged precipitation product at 0.1°×0.1° resolution. The main results are as follows. (1) The spatial distribution and temporal variation of mean hourly precipitation amount and frequency are generally similar and hourly precipitations in the eastern and middle portions are larger and more frequent than that in the western portion. The high value area of precipitation intensity is obviously different from that of precipitation amount and frequency. (2) The spatial distribution of daytime precipitation is generally similar to that of nighttime precipitation, and the daytime precipitation is heavier than the nighttime precipitation. (3) The change rate of precipitation has a maximum at 20:00 Beijing time, and a minimum at 12:00. The hourly precipitation amount significantly correlated with frequency, especially for the middle and eastern portions.

Precipitation Spectra Analysis Over China With High-Resolution Measurements From Optimally-Merged Satellite/Gauge Observations—Part II: Diurnal Variability Analysis

Timing and diurnal variation of summer precipitation is analyzed over China using a new high-resolution ( $0.1^\circ,\text{hourly}$ ) satellite-gauge merged surface rainfall dataset that spans from 2008 through 2013. The results show that: 1) both precipitation amount (PA) and frequency (PF) show strong diurnal cycles with local solar time (LST); 2) peak times of PA (PAPT) primarily occur from 15 LST to 00 LST in most parts of the Tibet Plateau (TP), Xinjiang (XJ), Northwestern China (NW), Northeastern China (NE), and Southern China (SC), and the PAPT occurs from 00 LST to 09 LST in southern TP, Eastern XJ, western NW, southern NE, eastern Northern China (NC), and most parts of Southwestern China (SW); 3) the PAPT transitions eastward with time, occurring at ${\sim}15\; \text{LST}$ in central TP, at midnight in SW, and at 15–18 LST in the eastern coastal regions that are in the lower reach of Yangtze River and in the north side of Wuyi Mountains; 4) peak times of PF (PFPT) show a similar spatial pattern with PAPT, but with a small temporal (1–2 h) lead; 5) peak times of precipitation intensity (PIPT) occur during the 18–00 LST time frame in the southeastern TP and central SW regions. The PIPT along the upper Yangtze River valley occurs around 00–06 LST. The PIPT occurs in the morning at around 06–09 LST in the mid-lower Yangtze River valley and most parts of SC. This study on the diurnal cycle of precipitation over China can be used as a reference to validate atmospheric and hydrologic models, and also to guide hydrometerological research and applications.

Numerical Examination of the Diurnal Variation of Summer Precipitation over Southern China

Numerical Examination of the Diurnal Variation of Summer Precipitation over Southern China

Diurnal variation of summer precipitation over the Tibetan Plateau: a cloud-resolving simulation

Abstract. In this study, the Weather Research and Forecasting model was used to simulate the diurnal variation in summer precipitation over the Tibetan Plateau (TP) at a cloud-resolving scale. Compared with the TRMM, precipitation data shows that the model can well simulate the diurnal rainfall cycle with an overall late-afternoon maximum precipitation in the central TP and a nighttime maximum in the southern edge. The simulated diurnal variations in regional circulation and thermodynamics are in good correspondence with the precipitation diurnal cycles in the central and southern edge of TP, respectively. A possible mechanism responsible for the nocturnal precipitation maximum in the southern edge has been proposed, indicating the importance of the TP in regulating the regional circulation and precipitation.

Diurnal variations of summer precipitation over the Asian monsoon region as revealed by TRMM satellite data

Climatological characteristics of diurnal variations in summer precipitation over the Asian monsoon region are comprehensively investigated based on the Tropical Rainfall Measuring Mission (TRMM) satellite data during 1998–2008. The topographic influence on the diurnal variations and phase propagations of maximum precipitation are identified according to spatiotemporal distributions of the amplitude and peak time of the diurnal precipitation. The amplitude and phase of diurnal precipitation show a distinct geographical pattern. Significant diurnal variations occur over most of continental and coastal areas including the Maritime Continent, with the relative amplitude exceeding 40%, indicating that the precipitation peak is 1.4 times the 24-h mean. Over the landside coasts such as southeastern China and Indochina Peninsula, the relative amplitude is even greater than 100%. Although the diurnal variations of summer precipitation over the continental areas are characterized by an afternoon peak (1500–1800 Local Solar Time (LST)), over the central Indochina Peninsula and central and southern Indian Peninsula the diurnal phase is delayed to after 2100 LST, suggesting the diurnal behaviors over these areas different from the general continental areas. The weak diurnal variations with relative amplitudes less than 40% exist mainly over oceanic areas in the western Pacific and most of Indian Ocean, with the rainfall peak mainly occurring from midnight to early morning (0000–0600 LST), indicating a typical oceanic regime characterized by an early morning peak. However, apparent exceptions occur over the South China Sea (SCS), Bay of Bengal (BOB), and eastern Arabian Sea, with the rainfall peak occurring in daytime (0900–1500 LST). Prominent meridional propagations of the diurnal phase exist in South Asia and East Asia. Along the eastern Indian Peninsula, there is not only the southward phase propagation with the peak occurring around 25°N but also the northward phase propagation with the peak beginning with the southernmost continent, and both reach the central Indian continent to finish. Along the same longitudes where southern China and Kalimantan are located, the diurnal phase of the former propagates from the oceanic area (northern SCS) toward the inland continent, while the phase of the latter propagates from the land area toward the outside sea, showing a landward or seaward coastal diurnal regime. A distinct zonal propagation of the diurnal phase is observed over the BOB oceanic area. The maximum precipitation zone originates from the land-sea boundary of the eastern coast of the Indian peninsula at around 0300 LST, and then propagates eastward with increasing time to reach the eastern coast of the BOB on 1800 LST, finally migrates into the Indochina continent on about 2100 LST.

Diurnal variations of summer precipitation in the Beijing area and the possible effect of topography and urbanization

The present study examined the diurnal variations of summer precipitation in the Beijing area by using subdaily precipitation and wind observations. A combined effect of topography and urbanization on the characteristics of diurnal variations was suggested. It was shown that stations located in the plain area exhibited typical night rain peaks, whereas those in the mountainous area exhibited clear afternoon peaks of precipitation diurnal variations. The precipitation peaks were associated with wind fields around the Beijing area, which were found to be highly modulated by mountain-valley circulation and urban-country circulation. The lower-tropospheric wind exhibited a clear diurnal shift in its direction from north at 0800 LST to south at 2000 LST, which reflected mountain-valley circulation. The transitions from valley to mountain wind and the opposite generally happened after sunset and sunrise, respectively, and both occurred earlier for the stations located closer to mountains. By comparing the diurnal variations of precipitation at stations in a northeast suburb, an urban area, and a southwest suburb, it was revealed that the northeast suburb group had the highest normalized rainfall frequency, but the southwest group had the lowest from late afternoon to late evening. On the contrary, in the early morning from about 0200 to 1000 LST, the southwest group and urban group had the highest normalized rainfall frequency. This pattern might originate from the combined effects of mountain-valley topography and urbanization.

Diurnal variation in summer monsoon precipitation during active and break periods over central India and southern Himalayan foothills

The diurnal variations of summer precipitation over central India and the southern Himalayan foothills are investigated using Tropical Rainfall Measuring Mission (TRMM) data for July–August from 1998 to 2007. The TRMM precipitation radar (PR) and Lightning Imaging Sensor (LIS) data are used to understand characteristics of precipitation. Daily data from TRMM/3B42 are used to determine active and break periods in central India on the basis of rainfall characteristics. Diurnal variation in rain rate, frequency of rain, conditional rain rate, storm height, and occurrence of convective rain is analyzed using TRMM/PR data (0.1° × 0.1° resolution). Diurnal variation in total lightning flashes is analyzed using TRMM/LIS data. The precipitation over central India during wet periods is characterized by a large amount of rainfall with a high frequency of rain and a secondary morning peak. The precipitation in dry periods is characterized by a strong diurnal variation with convective rainfall and enhanced electrical activity over central India. Characteristics of wet and dry periods over central India are generally supported over the southern Himalayan foothills.

Diurnal variations of summer precipitation in Beijing

Climatic characteristics and secular trends of diurnal variations of summer precipitation in Beijing are studied using hourly self-recording rain-gauge data during 1961–2004. The results show that both rainfall amount and rainfall frequency present high values from late afternoon to early morning and reach the minima around noon. Two separate peaks can be identified in the high value period, one in the late afternoon and the other in the early morning. Taking the rainfall duration into account, it is found that the rainfall during late afternoon to midnight mainly comes from the short-duration rainfall events (an event of 1–6 hours in duration), while the rainfall during midnight to early morning is accumulated mostly by the long-duration rainfall events (an event that lasts longer than 6 hours). In the recent 40 years, the summer precipitation in Beijing has been considerably restructured. The total rainfall amount of short-duration events has increased significantly, while the total rainfall amount of long-duration events has decreased.

Diurnal variations of summer precipitation over contiguous China

Diurnal variations of summer precipitation over contiguous China are studied using hourly rain‐gauge data from 588 stations during 1991–2004. It is found that summer precipitation over contiguous China has large diurnal variations with considerable regional features. Over southern inland China and northeastern China summer precipitation peaks in the late afternoon, while over most of the Tibetan Plateau and its east periphery it peaks around midnight. The diurnal phase changes eastward along the Yangtze River Valley, with a midnight maximum in the upper valley, an early morning peak in the middle valley, and a late afternoon maximum in the lower valley. Summer precipitation over the region between the Yangtze and Yellow Rivers has two diurnal peaks: one in the early morning and another in the late afternoon.