Multiannual study of convective and stratiform situations associated to wet deposition of desert dust in the Sahelian band

2021 ◽  
Author(s):  
Thomas Audoux ◽  
Benoit Laurent ◽  
Béatrice Marticorena ◽  
Gilles Bergametti ◽  
Jean Louis Rajot ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wet Deposition ◽  
Precipitation Amount ◽  
Dilution Effect ◽  
Rainfall Rate ◽  
Event Scale ◽  
Deposition Fluxes ◽  
Convective Systems ◽  
Intense Precipitation ◽  
Sahel Region

<p>In the semi-arid Sahel region, wet deposition can represent more than half of the total annual deposition and are associated to different rainfall types, from stratiform precipitation to convective systems. Surface parameters such as temperature, wind speed, wind direction as well as rainfall rate can be used to distinguish these situations. We investigate the behaviour of dust wet deposition at the event-scale based on a multiannual (2007 to 2016) monitoring of wet deposition fluxes, PM10 concentration, precipitation and meteorological parameters in two Sahelian stations Banizoumbou (Niger, 13.54°N, 2.66 E) and Cinzana (Mali, 13.28°N, 5.93°W) of the INDAAF network. Rainfall events have been classified into three types: (i) stratiform, convective associated with (ii) weak precipitation or (iii) intense precipitation. This classification is based on selected criteria regarding evolutions of surface temperature, of wind speed and direction before and after the rainfall onset as well as on the event rainfall rate. Based on an interpretation of hundreds of single events, almost 25% of wet deposition events are associated with non-convective situation, more than 40% with atmospheric convective situation and weak precipitation, and more than 35% events with atmospheric convective situation combined with intense precipitation. This exhaustive work over a long-time period of measurements illustrates the predominance of convective situations regarding wet deposition in the two Sahelian stations. Washout ratios (WR) have been computed from PM10 concentrations, precipitation and deposition fluxes for each kind of events when data were concomitant. The dependency of WR to precipitation amount is shown to differ depending on the rain types. For instance, the decreasing dependency of WR with the precipitation amount of non-convective events has been quantified and could be explained by a dilution effect of the deposition. On the contrary, no clear dependency of WR with the precipitation has been observed for atmospheric convective conditions associated with intense rainfall rate.</p>

scholarly journals Atmospheric Thermal and Dynamic Vertical Structures of Summer Hourly Precipitation in Jiulong of the Tibetan Plateau

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 505
Author(s):  
Yonglan Tang ◽  
Guirong Xu ◽  
Rong Wan ◽  
Xiaofang Wang ◽  
Junchao Wang ◽  
...  
Keyword(s):  
Wind Speed ◽  
Tibetan Plateau ◽  
Precipitation Amount ◽  
Summer Precipitation ◽  
The Tibetan Plateau ◽  
Hourly Precipitation ◽  
Air Convection ◽  
Precipitation Variation ◽  
Long Term Observation

It is an important to study atmospheric thermal and dynamic vertical structures over the Tibetan Plateau (TP) and their impact on precipitation by using long-term observation at representative stations. This study exhibits the observational facts of summer precipitation variation on subdiurnal scale and its atmospheric thermal and dynamic vertical structures over the TP with hourly precipitation and intensive soundings in Jiulong during 2013–2020. It is found that precipitation amount and frequency are low in the daytime and high in the nighttime, and hourly precipitation greater than 1 mm mostly occurs at nighttime. Weak precipitation during the daytime may be caused by air advection, and strong precipitation at nighttime may be closely related with air convection. Both humidity and wind speed profiles show obvious fluctuation when precipitation occurs, and the greater the precipitation intensity, the larger the fluctuation. Moreover, the fluctuation of wind speed is small in the morning, large at noon and largest at night, presenting a similar diurnal cycle to that of convective activity over the TP, which is conductive to nighttime precipitation. Additionally, the inverse layer is accompanied by the inverse humidity layer, and wind speed presents multi-peaks distribution in its vertical structure. Both of these are closely related with the underlying surface and topography of Jiulong. More studies on physical mechanism and numerical simulation are necessary for better understanding the atmospheric phenomenon over the TP.

scholarly journals Djankuat glacier station in the North Caucasus, Russia: a database of glaciological, hydrological, and meteorological observations and stable isotope sampling results during 2007–2017

2019 ◽  
Vol 11 (3) ◽  
pp. 1463-1481 ◽  
Author(s):  
Ekaterina P. Rets ◽  
Viktor V. Popovnin ◽  
Pavel A. Toropov ◽  
Andrew M. Smirnov ◽  
Igor V. Tokarev ◽  
...  
Keyword(s):  
Wind Speed ◽  
Precipitation Amount ◽  
Turbulent Fluxes ◽  
Water Runoff ◽  
North Caucasus ◽  
Time Step ◽  
Glacier Surface ◽  
The North ◽  
Meteorological Observations ◽  
The Impact

Abstract. This study presents a dataset on long-term multidisciplinary glaciological, hydrological, and meteorological observations and isotope sampling in a sparsely monitored alpine zone of the North Caucasus in the Djankuat research basin. The Djankuat glacier, which is the largest in the basin, was chosen as representative of the central North Caucasus during the International Hydrological Decade and is one of 30 “reference” glaciers in the world that have annual mass balance series longer than 50 years (Zemp et al., 2009). The dataset features a comprehensive set of observations from 2007 to 2017 and contains yearly measurements of snow depth and density; measurements of dynamics of snow and ice melting; measurements of water runoff, conductivity, turbidity, temperature, δ18O, δD at the main gauging station (844 samples in total) with an hourly or sub-daily time step depending on the parameter; data on δ18O and δ2H sampling of liquid precipitation, snow, ice, firn, and groundwater in different parts of the watershed taken regularly during melting season (485 samples in total); measurements of precipitation amount, air temperature, relative humidity, shortwave incoming and reflected radiation, longwave downward and upward radiation, atmospheric pressure, and wind speed and direction – measured at several automatic weather stations within the basin with 15 min to 1 h time steps; gradient meteorological measurements to estimate turbulent fluxes of heat and moisture, measuring three components of wind speed at a frequency of 10 Hz to estimate the impulse of turbulent fluxes of sensible and latent heat over the glacier surface by the eddy covariance method. Data were collected during the ablation period (June–September). The observations were halted in winter. The dataset is available from PANGAEA (https://doi.org/10.1594/PANGAEA.894807, Rets et al., 2018a) and will be further updated. The dataset can be useful for developing and verifying hydrological, glaciological, and meteorological models for alpine areas, to study the impact of climate change on hydrology of mountain regions using isotopic and hydrochemical approaches in hydrology. As the dataset includes the measurements of hydrometeorological and glaciological variables during the catastrophic proglacial lake outburst in the neighboring Bashkara valley in September 2017, it is a valuable contribution to study lake outbursts.

scholarly journals Wet and dry deposition of mineral dust particles in Japan: factors related to temporal variation and spatial distribution

2013 ◽  
Vol 13 (8) ◽  
pp. 21801-21835
Author(s):  
K. Osada ◽  
S. Ura ◽  
M. Kagawa ◽  
M. Mikami ◽  
T. Y. Tanaka ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Mineral Dust ◽  
Temporal Variations ◽  
Dust Particles ◽  
Insoluble Residue ◽  
Spatial Distributions ◽  
Dust Deposition ◽  
Deposition Fluxes ◽  
Deposition Amount

Abstract. Data of temporal variations and spatial distributions of mineral dust deposition fluxes are very limited in terms of duration, location, and processes of deposition. To ascertain temporal variations and spatial distributions of mineral dust deposition by wet and dry processes, weekly deposition samples were obtained at Sapporo, Toyama, Nagoya, Tottori, Fukuoka, and Cape Hedo (Okinawa) in Japan during October 2008–December 2010 using automatic wet and dry separating samplers. Mineral dust weights in water-insoluble residue were estimated from Fe contents measured using an X-ray fluorescence analyzer. For wet deposition, highest and lowest annual dust fluxes were found at Toyama (9.6 g m−2 yr−1) and at Cape Hedo (1.7 g m−2 yr−1) as average values in 2009 and 2010. Higher wet deposition fluxes were observed at Toyama and Tottori, where frequent precipitation (>60% days per month) was observed during dusty seasons. For dry deposition among Toyama, Tottori, Fukuoka, and Cape Hedo, the highest and lowest annual dust fluxes were found respectively at Fukuoka (5.2 g m−2 yr−1) and at Cape Hedo (2.0 g m−2 yr−1) as average values in 2009 and 2010. Although the seasonal tendency of the monthly dry deposition amount roughly resembled that of monthly days of Kosa dust events, the monthly amount of dry deposition was not proportional to monthly days of the events. Comparison of dry deposition fluxes with vertical distribution of dust particles deduced from Lidar data and coarse particle concentrations suggested that the maximum dust layer height or thickness is an important factor for controlling the dry deposition amount after long-range transport of dust particles. Size distributions of refractory dust particles were obtained using four-stage filtration: >20, >10, >5, and >1 μm diameter. Weight fractions of the sum of >20 μm and 10–20 μm (giant fraction) were higher than 50% for most of the event samples. Irrespective of the deposition type, the giant dust fractions were decreasing generally with increasing distance from the source area, suggesting the selective depletion of larger giant particles during atmospheric transport. Because giant dust particles are an important mass fraction of dust accumulation, especially in the north Pacific where is known as a high-nutrient, low-chlorophyll (HNLC) region, the transport height of giant dust particles is an important factor for studying dust budgets in the atmosphere and their role in biogeochemical cycles.

scholarly journals Assimilation of Satellite-Derived Soil Moisture for Improved Forecasts of the Great Plains Low-Level Jet

2020 ◽  
Vol 148 (11) ◽  
pp. 4607-4627
Author(s):  
Craig R. Ferguson ◽  
Shubhi Agrawal ◽  
Mark C. Beauharnois ◽  
Geng Xia ◽  
D. Alex Burrows ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Wind Speed ◽  
Data Assimilation ◽  
Great Plains ◽  
Wrf Model ◽  
Added Value ◽  
Low Level ◽  
Convective Systems ◽  
South Central ◽  
Mesoscale Convective

AbstractIn the context of forecasting societally impactful Great Plains low-level jets (GPLLJs), the potential added value of satellite soil moisture (SM) data assimilation (DA) is high. GPLLJs are both sensitive to regional soil moisture gradients and frequent drivers of severe weather, including mesoscale convective systems. An untested hypothesis is that SM DA is more effective in forecasts of weakly synoptically forced, or uncoupled GPLLJs, than in forecasts of cyclone-induced coupled GPLLJs. Using the NASA Unified Weather Research and Forecasting (NU-WRF) Model, 75 GPLLJs are simulated at 9-km resolution both with and without NASA Soil Moisture Active Passive SM DA. Differences in modeled SM, surface sensible (SH) and latent heat (LH) fluxes, 2-m temperature (T2), 2-m humidity (Q2), PBL height (PBLH), and 850-hPa wind speed (W850) are quantified for individual jets and jet-type event subsets over the south-central Great Plains, as well as separately for each GPLLJ sector (entrance, core, and exit). At the GPLLJ core, DA-related changes of up to 5.4 kg m−2 in SM can result in T2, Q2, LH, SH, PBLH, and W850 differences of 0.68°C, 0.71 g kg−2, 59.9 W m−2, 52.4 W m−2, 240 m, and 4 m s−1, respectively. W850 differences focus along the jet axis and tend to increase from south to north. Jet-type differences are most evident at the GPLLJ exit where DA increases and decreases W850 in uncoupled and coupled GPLLJs, respectively. Data assimilation marginally reduces negative wind speed bias for all jets, but the correction is greater for uncoupled GPLLJs, as hypothesized.

scholarly journals Atmospheric wet and litterfall mercury deposition in typical rural and urban areas in China

2016 ◽  
Author(s):  
Xuewu Fu ◽  
Yang Xu ◽  
Xiaofang Lang ◽  
Jun Zhu ◽  
Hui Zhang ◽  
...  
Keyword(s):  
Urban Areas ◽  
Wet Deposition ◽  
Arid Zone ◽  
Atmospheric Mercury ◽  
Urban Site ◽  
Cloud Base ◽  
Subtropical Zone ◽  
Deposition Fluxes ◽  
Precipitation Depth ◽  
Rural Sites

Abstract. Mercury (Hg) concentrations and deposition fluxes in precipitation and litterfall were measured at multiple sites (six rural sites and an urban site) across a broad geographic area in China. The annual deposition fluxes of Hg in precipitation at rural sites and an urban site were 2.0 to 7.2 µg m−2 yr−1 and 12.6 ± 6.5 µg m−2 yr−1, respectively. Wet deposition fluxes of Hg at rural sites showed a clear regional difference with elevated deposition fluxes in the subtropical zone, followed by the temporal zone and arid/semi-arid zone. Precipitation depth is the primary influencing factor causing the variation of wet deposition. Hg fluxes through litterfall ranged from 22.8 to 62.8 µg m−2 yr−1, higher than the wet deposition by a factor of 3.9 to 8.7 fluxes and representing approximately 75 % of the total Hg deposition at the forest sites in China. This suggests that uptake of atmospheric Hg by foliage is the dominant pathway to remove atmospheric mercury in forest ecosystems in China. Wet deposition fluxes of Hg at rural sites of China were generally lower compared to those in North America and Europe, possibly due to a combination of lower precipitation depth, lower GOM concentrations in the troposphere and the generally lower cloud base heights at most sites that washout a smaller amount of GOM and PBM during precipitation events.

scholarly journals Elemental carbon in snow at Changbai Mountain, northeastern China: concentrations, scavenging ratios, and dry deposition velocities

2014 ◽  
Vol 14 (2) ◽  
pp. 629-640 ◽  
Author(s):  
Z. W. Wang ◽  
J. C. Gallet ◽  
C. A. Pedersen ◽  
X. S. Zhang ◽  
J. Ström ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Radiative Forcing ◽  
Elemental Carbon ◽  
Northeastern China ◽  
Snow Surface ◽  
Deposition Fluxes ◽  
The Mean ◽  
Deposition Processes ◽  
Scavenging Ratio

Abstract. Light-absorbing aerosol – particularly elemental carbon (EC) – while mixed with snow and ice is an important climate driver from the enhanced absorption of solar radiation. Currently, considerable efforts are being made to estimate its radiative forcing on a global scale, but several uncertainties remain, particularly those regarding its deposition processes. In this study, concurrent measurements of EC in air and snow are performed for three years (2009–2012) at Changbai station, northeastern China. The scavenging ratio and the wet- and dry-deposition fluxes of EC over the snow surface are estimated. The mean EC concentration in the surface snow is 1000 ± 1500 ng g−1, ranging from 7 to 7640 ng g−1. The mean value of the scavenging ratio of EC by snow is 140 ± 100, with a median value of 150, which is smaller than that reported in Arctic areas. A non-rimed snow process is a significant factor in interpreting differences with Arctic areas. Wet-deposition fluxes of EC are estimated to be 0.47 ± 0.37 μg cm−2 month−1 on average over the three snow seasons studied. Dry deposition is more than five times higher, with an average of 2.65 ± 1.93 μg cm−2 month−1; however, only winter period estimation is possible (December–February). During winter in Changbai, 87% of EC in snow is estimated to be due to dry deposition, with a mean dry deposition velocity of 6.44 × 10−3 m s−1 and median of 8.14 × 10−3 m s−1. Finally, the calculation of the radiative effect shows that 500 ng g−1 of dry-deposited EC to a snow surface absorbs three times more incoming solar energy than the same mass mixed in the snow through wet deposition. Deposition processes of an EC-containing snow surface are, therefore, crucial to estimate its radiative forcing better, particularly in northeastern China, where local emission strongly influences the level and gradient of EC in the snowpack, and snow-covered areas are cold and dry due to the atmospheric general circulation. Furthermore, this study builds on the knowledge to characterize the conditions in the snow-laden Chinese rural areas better as well as to constrain transport of EC to the Arctic better.

Aggregation of Selected Three-Day Periods to Estimate Annual and Seasonal Wet Deposition Totals for Sulfate, Nitrate, and Acidity. Part I: A Synoptic and Chemical Climatology for Eastern North America

1995 ◽  
Vol 34 (2) ◽  
pp. 297-325 ◽  
Author(s):  
Jeffrey R. Brook ◽  
Perry J. Samson ◽  
Sanford Sillman
Keyword(s):  
North America ◽  
Wet Deposition ◽  
Atmospheric Transport ◽  
Precipitation Amount ◽  
Statistical Correlation ◽  
Eastern North America ◽  
Time Of Year ◽  
Transport Patterns

Abstract Running 3-day periods from 1979 to 1985 were categorised into one of 20 meteorological categories. These categories were developed through the cluster analysis of 3-day progressions of 85-kPa wind flow over eastern North America. The purpose for developing the categories was to identify recurring atmospheric transport patterns that were associated with differing amounts of wet sulfate (SO2−4) and nitrate (NO−3) deposition at a variety of locations in eastern North America. Identification of these patterns was necessary to facilitate the selection of time periods for simulation by the Regional Acid Deposition Model and in the development of a method for estimating long-term acidic deposition over eastern North America from a limited number of model runs. The effectiveness of this method (referred to as the aggregation method) was expected to be dependent on the ability of the categories to separate structure in wet deposition patterns. This paper describes the determination of the 20 meteorological categories and demonstrates that there were differences in their meteorological and chemical behavior and in their frequency of occurrence. Observations of precipitation and wet SO2−4 and NO−3 deposition from 22 sites in eastern North America and multiple regression models were used to demonstrate that there were statistically significant differences in deposition among categories and that knowledge of meteorological category explained some of the variation in wet deposition. The best statistical correlation, which was based upon precipitation amount, time of year, and meteorological category, explained 35%–83% (28%– 76%) of the observed variation in wet SO2−4 (NO−3) deposition depending on location. On average, across all sites and for both SO2−4 and NO−3, knowledge of category accounted for about 4% of the variation. The minimum amount explained by category was 1% and the maximum was 13%.

Comparison of annual dry and wet deposition fluxes of selected pesticides in Strasbourg, France

2009 ◽  
Vol 157 (1) ◽  
pp. 303-312 ◽  
Author(s):  
Nathalie Sauret ◽  
Henri Wortham ◽  
Rafal Strekowski ◽  
Pierre Herckès ◽  
Laura Ines Nieto
Keyword(s):  
Wet Deposition ◽  
Deposition Fluxes ◽  
Dry And Wet Deposition
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