scholarly journals Diurnal Variations of Warm Season Rainfall Affected By Complex Topography Based On High-Density Stations Observation In Chongqing Over Southwest China

2021 ◽  
Author(s):  
Qiang Li ◽  
Yongguang Zheng ◽  
Guobing Zhou ◽  
Yan Zhu ◽  
Chao Liu
Keyword(s):  
Southwest China ◽  
Warm Season ◽  
Early Morning ◽  
Rainfall Amount ◽  
Diurnal Variations ◽  
High Density ◽  
Observation Data ◽  
Complex Topography ◽  
Morning Peak ◽  
Surrounding Areas

Abstract Located in the eastern edge of the Sichuan Basin (SCB) in the southwest China, Chongqing is a mountainous region with typical complex topographic features. Using the hourly precipitation observation data of high-density 1686 meteorological stations in Chongqing during warm season from 2009 to 2016, the diurnal characteristics of precipitation effected by complex topography are investigated. The mountainous terrain has a significant impact on distinct regional features of rainfall amount, frequency, and intensity, and stations located in the higher complex mountainous areas are larger than those in the lower surrounding areas. In addition, the detailed characteristics of the rainfall amount and frequency over four study regions further show that the values at higher elevations are larger than those at the lower elevations, and the rainfall amount and frequency significantly increase, especially in the area that terrain heights sharply increase along mountains extending direction. The diurnal characteristics of the rainfall amount has dual structure with a dominant early-morning peak appearing at approximately 0700 LST (23 UTC), and a weaker secondary late-afternoon peak is found at approximately 1600 LST (08 UTC). The rainfall amount and frequency peaks during early-morning accounts for 81.9% and 88.1% of all stations, respectively. However, the rainfall frequency has single early-morning peak diurnal characteristics. The gauge elevation has a significant impact on the diurnal variations of the early-morning rainfall. With elevation increasing in four study regions, the proportions of the rainfall amount (frequency) that occurs during early-morning periods decrease. Different duration hours of rainfall events have distinct diurnal variation and phase features.

Diurnal Variations of Warm-Season Precipitation over Northern China

2010 ◽  
Vol 138 (4) ◽  
pp. 1017-1025 ◽  
Author(s):  
Huizhong He ◽  
Fuqing Zhang
Keyword(s):  
High Resolution ◽  
North China ◽  
Warm Season ◽  
Northern China ◽  
Early Morning ◽  
Diurnal Variations ◽  
Broad Area ◽  
Mountain Ranges ◽  
Low Level ◽  
Nocturnal Jet

Abstract This study examines the diurnal variations of the warm-season precipitation over northern China using the high-resolution precipitation products obtained from the Climate Prediction Center’s morphing technique (CMORPH) during May–August of 2003–09. The areas of focus are the Yanshan–Taihangshan Mountain ranges along the east peripheries of the Loess and Inner Mongolian Plateaus and the adjacent North China Plains. It is found that the averaged peak in local precipitation begins early in the afternoon near the top of the mountain ranges and propagates downslope and southeastward at a speed of ∼13 m s−1. The peak reaches the central North China Plains around midnight and the early morning hours resulting in a broad area of nocturnal precipitation maxima over the plains. The diurnal precipitation peak (minimum) is closely collocated with the upward (downward) branch of a mountain–plains solenoid (MPS) circulation. Both the MPS and a low-level southwesterly nocturnal jet are likely to be jointly responsible for the nighttime precipitation maxima over the plains.

Cattle Foraging Behavior in Leafy Spurge (Euphorbia esula)-Infested Rangeland

1987 ◽  
Vol 1 (4) ◽  
pp. 314-318 ◽  
Author(s):  
Rodney G. Lym ◽  
Donald R. Kirby
Keyword(s):  
Warm Season ◽  
Economic Loss ◽  
Leafy Spurge ◽  
High Density ◽  
Euphorbia Esula ◽  
Low Density ◽  
Forage Production ◽  
Grazing Season ◽  
Grazing Cattle ◽  
Early Fall

Leafy spurge causes economic loss by reducing both herbage production and use. Herbage use by grazing cattle in various densities of leafy spurge (Euphorbia esulaL. #3EPHES) was evaluated over a 3-yr period in North Dakota. Forage production and disappearance were estimated in four density classes of leafy spurge. Use of cool- and warm-season graminoids, forbs, and leafy spurge was estimated during the middle and the end of each grazing season. Cattle used 20 and 2% of the herbage in the zero and low density infestations, respectively, by mid-season. Moderate and high density infestations were avoided until the milky latex in leafy spurge disappeared in early fall, and herbage availability in zero and low density infestations declined. Herbage use in moderate and high density infestations increased to an average of 46% by the end of the grazing season compared to 61% in zero and low density infestations. An annual herbage loss of at least 35% occurred in pasture infested with 50% density or more of leafy spurge.

scholarly journals First simultaneous measurements of peroxyacetyl nitrate (PAN) and ozone at Nam Co in the central Tibetan Plateau: impacts from the PBL evolution and transport processes

2017 ◽  
Author(s):  
Xiaobin Xu ◽  
Hualong Zhang ◽  
Weili Lin ◽  
Ying Wang ◽  
Shihui Jia
Keyword(s):  
Long Range ◽  
Early Morning ◽  
Diurnal Variations ◽  
Long Range Transport ◽  
Nam Co ◽  
Monsoon Period ◽  
Air Masses ◽  
Upper Troposphere ◽  
Central Tibetan Plateau ◽  
Range Transport

Abstract. Both peroxyacetyl nitrate (PAN) and ozone (O3) are key photochemical products in the atmosphere. Most of the previous in-situ observations of both gases have been made in polluted regions and at low altitude sites. Here we present first simultaneous measurements of PAN and O3 at Nam Co (NMC, 90°57′ E, 30°46′ N, 4745 m  a.s.l.), a remote site in the central Tibetan Plateau (TP). The observations were made during summer periods in 2011 and 2012. The PAN concentrations averaged 0.36 ppb (range: 0.11–0.76 ppb) and 0.44 ppb (range: 0.21–0.99 ppb) during 16–25 August 2011 and 15 May to 13 July 2012, respectively. The O3 concentration varied from 27.9 ppb to 96.4 ppb, with an average of 60.0 ppb. Profound diurnal cycles of PAN and O3 were observed, with minimum values around 05:00 LT, steep rises in the early morning, and broader platforms of high values during 09:00–20:00 LT. We find that the evolution of planetary boundary layer (PBL) played a key role in shaping the diurnal patterns of both gases, particularly the rapid increases of PAN and O3 in the early morning. Air entrainment from the free troposphere into the PBL seemed to cause the early morning increase and be a key factor of sustaining the daytime high concentrations of both gases. The days with higher daytime PBL (about 3 km) showed stronger diurnal variations of both gases and were mainly distributed in the drier pre-monsoon period, while those with shallower daytime PBL (about 2 km) showed minor diurnal variations of both gases and were mainly distributed in the humid monsoon period. Episodes of higher PAN levels were observed occasionally at NMC. These PAN episodes were caused either by rapid downward transport of air masses from the middle/upper troposphere or by long-range transport of PAN plumes from North India. The PAN level in the downward transport cases ranged from 0.5 ppb to 0.7 ppb and may indicate the PAN abundance in the middle/upper troposphere. In the long-range transport case, the PAN level varied in the range of 0.6–1.0 ppb. This long-range transport process influenced most of the western and central TP region for about a week in early June 2012. Our results suggest that polluted air masses from South Asia can significantly enhance the PAN level over the TP. As PAN act as a reservoir of NOx, the impacts of pollution transport from South Asia on tropospheric photochemistry over the TP region deserve further studies.

scholarly journals Chemical characteristics of inorganic ammonium salts in PM<sub>2.5</sub> in the atmosphere of Beijing (China)

2011 ◽  
Vol 11 (21) ◽  
pp. 10803-10822 ◽  
Author(s):  
A. Ianniello ◽  
F. Spataro ◽  
G. Esposito ◽  
I. Allegrini ◽  
M. Hu ◽  
...  
Keyword(s):  
Fine Particulate Matter ◽  
Early Morning ◽  
Temporal Variations ◽  
Diurnal Variations ◽  
Local Source ◽  
Particle Interactions ◽  
Atmospheric Conditions ◽  
Fine Particulate ◽  
Annular Denuder ◽  
Beijing China

Abstract. The atmospheric concentrations of gaseous HNO3, HCl and NH3 and their relative salts have been measured during two field campaigns in the winter and in the summer of 2007 at Beijing (China), as part of CAREBEIJING (Campaigns of Air Quality Research in Beijing and Surrounding Region). In this study, annular denuder technique used with integration times of 2 and 24h to collect inorganic and soluble PM2.5 without interferences from gas–particle and particle–particle interactions. The results were discussed from the standpoint of temporal and diurnal variations and meteorological effects. Fine particulate Cl−, NH4+ and SO42− exhibited distinct temporal variations, while fine particulate NO3− did not show much variation with respect to season. Daily mean concentrations of fine particulate NH4+ and SO42− were higher during summer (12.30 μg m−3 and 18.24 μg m−3, respectively) than during winter (6.51 μg m−3 and 7.50 μg m−3, respectively). Daily mean concentrations of fine particulate Cl− were higher during winter (2.94 μg m−3) than during summer (0.79 μg m−3), while fine particulate NO3− showed similar both in winter (8.38 μg m−3) and in summer (9.62 μg m−3) periods. The presence of large amounts of fine particulate NO3− even in summer are due to higher local and regional concentrations of NH3 in the atmosphere available to neutralize H2SO4 and HNO3, which is consistent with the observation that the measured particulate species were neutralized. The composition of fine particulate matter indicated the domination of (NH4)2SO4 during winter and summer periods. In addition, the high relative humidity conditions in summer period seemed to dissolve a significant fraction of HNO3 and NH3 enhancing fine particulate NO3− and NH4+ in the atmosphere. All measured particulate species showed diurnal similar patterns during the winter and summer periods with higher peaks in the early morning, especially in summer, when humid and stable atmospheric conditions occurred. These diurnal variations were affected by wind direction suggesting regional and local source influences. The fine particulate species were correlated with NOx and PM2.5, supporting the hypothesis that traffic may be also an important source of secondary particles.

scholarly journals Image Processing of Radar Mosaics for the Climatology of Convection Initiation in South China

2020 ◽  
Vol 59 (1) ◽  
pp. 65-81 ◽  
Author(s):  
Lanqiang Bai ◽  
Guixing Chen ◽  
Ling Huang
Keyword(s):  
South China ◽  
Numerical Models ◽  
Early Morning ◽  
Moist Convection ◽  
Late Night ◽  
Morning Peak ◽  
Spatial Modes ◽  
Triggering Mechanisms ◽  
Deep Moist Convection ◽  
Convection Initiation

AbstractA dataset of convection initiation (CI) is of great value in studying the triggering mechanisms of deep moist convection and evaluating the performances of numerical models. In recent years, the data quality of the operationally generated radar mosaics over China has been greatly improved, which provides an opportunity to retrieve a CI dataset from that region. In this work, an attempt is made to reveal the potential of applying a simple framework of objective CI detection for the study of CI climatology in China. The framework was tested using radar mosaic maps in South China that were accessible online. The identified CI events were validated in both direct and indirect ways. On the basis of a direct manual check, nearly all of the identified CI cells had an organized motion. The precipitation echoes of the cells had a median duration of approximately 2.5 h. The CI occurrences were further compared with rainfall estimates to ensure physical consistency. The diurnal cycle of CI occurrence exhibits three major modes: a late-night-to-morning peak at the windward coasts and offshore, a noon-to-late-afternoon peak on the coastal land, and an evening-to-early-morning peak over the northwestern highland. These spatial modes agree well with those of rainfall, indirectly suggesting the reliability of the CI statistics. By processing radar mosaic maps, such a framework could be applied for studying CI climatology over China and other regions.

scholarly journals Seasonal and Diurnal Variations in the Priestley–Taylor Coefficient for a Large Ephemeral Lake

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 849 ◽  
Author(s):  
Guojing Gan ◽  
Yuanbo Liu ◽  
Xin Pan ◽  
Xiaosong Zhao ◽  
Mei Li ◽  
...  
Keyword(s):  
Poyang Lake ◽  
High Water ◽  
Diurnal Variations ◽  
Observation Data ◽  
Available Energy ◽  
Diurnal Patterns ◽  
Ephemeral Lakes ◽  
Seasonal And Diurnal Variations ◽  
Daily Scale ◽  
Mean Square Errors

The Priestley–Taylor equation (PTE) is widely used with its sole parameter (α) set as 1.26 for estimating the evapotranspiration (ET) of water bodies. However, variations in α may be large for ephemeral lakes. Poyang Lake, which is the largest freshwater lake in China, is water-covered and wetland-covered during its high-water and low-water periods, respectively, over a year. This paper examines the seasonal and diurnal variations in α using eddy covariance observation data for Poyang Lake. The results show that α = 1.26 is overall feasible for both periods at daily and subdaily scales. No obvious seasonal trend was observed, although the standard deviation in α for the wetland was larger than that for the water surface. The mean bias in evaporation estimations using the PTE was less than 5 W·m−2 during both periods, and the root mean square errors were much smaller than the average evaporation measurements at daily scale. U-shaped diurnal patterns of α were found during both periods, due partly to the negative correlation between α and the available energy (A). Compared to the vapor pressure deficit (VPD), wind speed (u) exerts a larger contribution to these variations. In addition, u is positively correlated with α during both periods, however, VPD was positively and negatively correlated with α during the high-water and low-water periods, respectively. Subdaily α exhibited contrasting clusters in the (u, VPD) plane under the same available energy ranges. Our study highlights the seasonal and diurnal course of α and suggests the careful use of PTE at subdaily scales.

scholarly journals Volcano Monitoring from Space Using High-Cadence Planet CubeSat Images Applied to Fuego Volcano, Guatemala

2019 ◽  
Vol 11 (18) ◽  
pp. 2151 ◽  
Author(s):  
Aldeghi ◽  
Carn ◽  
Escobar-Wolf ◽  
Groppelli
Keyword(s):  
Morphological Change ◽  
Volcanic Hazard ◽  
Volcano Monitoring ◽  
Lava Flows ◽  
Observation Data ◽  
Density Currents ◽  
Fuego Volcano ◽  
Earth Observation Data ◽  
Surrounding Areas ◽  
High Cadence

Fuego volcano (Guatemala) is one of the most active and hazardous volcanoes in the world. Its persistent activity generates lava flows, pyroclastic density currents (PDCs), and lahars that threaten the surrounding areas and produce frequent morphological change. Fuego’s eruption deposits are often rapidly eroded or remobilized by heavy rains and its constant activity and inaccessible terrain makes ground-based assessment of recent eruptive deposits very challenging. Earth-orbiting satellites can provide unique observations of volcanoes during eruptive activity, when ground-based techniques may be too hazardous, and also during inter-eruptive phases, but have typically been hindered by relatively low spatial and temporal resolution. Here, we use a new source of Earth observation data for volcano monitoring: high resolution (~3 m pixel size) images acquired from a constellation of over 150 CubeSats (‘Doves’) operated by Planet Labs Inc. The Planet Labs constellation provides high spatial resolution at high cadence (<1–72 h), permitting space-based tracking of volcanic activity with unprecedented detail. We show how PlanetScope images collected before, during, and after an eruption can be applied for mapping ash clouds, PDCs, lava flows, or the analysis of morphological change. We assess the utility of the PlanetScope data as a tool for volcano monitoring and rapid deposit mapping that could assist volcanic hazard mitigation efforts in Guatemala and other active volcanic regions.

Sign in / Sign up

Export Citation Format

Share Document