scholarly journals Attribution of dry and wet climatic changes over Central Asia

2021 ◽  
pp. 1-57
Keyword(s):  
Surface Water ◽  
Vapor Pressure ◽  
Central Asia ◽  
Land Surface ◽  
Water Budget ◽  
Water Resource Management ◽  
Vapor Pressure Deficit ◽  
Moisture Flux ◽  
Dry Season ◽  
Wet Season

Abstract Central Asia (CA: 35°-55°N, 55°-90°E) has been experiencing a significant warming trend during the past five decades, which has been accompanied by intensified local hydrological changes. Accurate identification of variations in hydroclimatic conditions and understanding the driving mechanisms are of great importance for water resource management. Here, we attempted to quantify dry/wet variations by using precipitation minus evapotranspiration (P–E) and attributed the variations based on the atmosphere and surface water balances. Our results indicated that the dry season became drier while the wet season became wetter in CA for 1982–2019. The land surface water budget revealed precipitation (96.84%) and vapor pressure deficit (2.26%) as the primary contributing factors for the wet season. For the dry season, precipitation (95.43%), net radiation (3.51%), and vapor pressure deficit (−2.64%) were dominant factors. From the perspective of the atmospheric water budget, net inflow moisture flux was enhanced by a rate of 72.85 kg m−1 s−1 in the wet season, which was mainly transported from midwestern Eurasia. The increase in precipitation induced by the external cycle was 11.93 mm/6month. In contrast, the drying trend during the dry season was measured by a decrease in the net inflow moisture flux (74.41 kg m−1 s−1) and reduced external moisture from midwestern Eurasia. An increase in precipitation during the dry season can be attributed to an enhancement in local evapotranspiration, accompanied by a 4.69% increase in the recycling ratio. The compounding enhancements between wet and dry seasons ultimately contribute to an increasing frequency of both droughts and floods.

scholarly journals Examining the Value of Global Seasonal Reference Evapotranspiration Forecasts to Support FEWS NET’s Food Insecurity Outlooks

2017 ◽  
Vol 56 (11) ◽  
pp. 2941-2949 ◽  
Author(s):  
Shraddhanand Shukla ◽  
Daniel McEvoy ◽  
Mike Hobbins ◽  
Greg Husak ◽  
Justin Huntington ◽  
...  
Keyword(s):  
Food Insecurity ◽  
Central Asia ◽  
East Africa ◽  
Central America ◽  
Southern Africa ◽  
Early Warning ◽  
Reference Evapotranspiration ◽  
Dry Season ◽  
Wet Season ◽  
Skill Evaluation

AbstractThe Famine Early Warning Systems Network (FEWS NET) team provides food insecurity outlooks for several developing countries in Africa, central Asia, and Central America. This study describes development of a new global reference evapotranspiration (ET0) seasonal reforecast and skill evaluation with a particular emphasis on the potential use of this dataset by FEWS NET to support food insecurity early warning. The ET0 reforecasts span the 1982–2009 period and are calculated following the American Society for Civil Engineers formulation of the Penman–Monteith method driven by seasonal climate forecasts of monthly mean temperature, humidity, wind speed, and solar radiation from the National Centers for Environmental Prediction CFSv2 model and the National Aeronautics and Space Administration GEOS-5 model. The skill evaluation, using deterministic and probabilistic scores, focuses on the December–February (DJF), March–May (MAM), June–August (JJA), and September–November seasons. The results indicate that ET0 forecasts are a promising tool for early warning of drought and food insecurity. Globally, the regions where forecasts are most skillful (correlation > 0.35 at leads of 2 months) include the western United States, northern parts of South America, parts of the Sahel region, and southern Africa. The FEWS NET regions where forecasts are most skillful (correlation > 0.35 at lead 3) include northern sub-Saharan Africa (DJF; dry season), Central America (DJF; dry season), parts of East Africa (JJA; wet season), southern Africa (JJA; dry season), and central Asia (MAM; wet season). A case study over parts of East Africa for the JJA season shows that ET0 forecasts in combination with the precipitation forecasts would have provided early warning of recent severe drought events (e.g., in 2002, 2004, 2009) that contributed to substantial food insecurity in the region.

scholarly journals Overview: Precipitation characteristics and sensitivities to environmental conditions during GoAmazon2014/5 and ACRIDICON-CHUVA

2018 ◽  
Vol 18 (9) ◽  
pp. 6461-6482 ◽  
Author(s):  
Luiz A. T. Machado ◽  
Alan J. P. Calheiros ◽  
Thiago Biscaro ◽  
Scott Giangrande ◽  
Maria A. F. Silva Dias ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Land Surface ◽  
Rain Rate ◽  
Vertical Motion ◽  
Cloud Droplet ◽  
Dry Season ◽  
Wet Season ◽  
Aerosol Loading ◽  
Dry Seasons ◽  
Wet And Dry Seasons

Abstract. This study provides an overview of precipitation processes and their sensitivities to environmental conditions in the Central Amazon Basin near Manaus during the GoAmazon2014/5 and ACRIDICON-CHUVA experiments. This study takes advantage of the numerous measurement platforms and instrument systems operating during both campaigns to sample cloud structure and environmental conditions during 2014 and 2015; the rainfall variability among seasons, aerosol loading, land surface type, and topography has been carefully characterized using these data. Differences between the wet and dry seasons were examined from a variety of perspectives. The rainfall rates distribution, total amount of rainfall, and raindrop size distribution (the mass-weighted mean diameter) were quantified over both seasons. The dry season generally exhibited higher rainfall rates than the wet season and included more intense rainfall periods. However, the cumulative rainfall during the wet season was 4 times greater than that during the total dry season rainfall, as shown in the total rainfall accumulation data. The typical size and life cycle of Amazon cloud clusters (observed by satellite) and rain cells (observed by radar) were examined, as were differences in these systems between the seasons. Moreover, monthly mean thermodynamic and dynamic variables were analysed using radiosondes to elucidate the differences in rainfall characteristics during the wet and dry seasons. The sensitivity of rainfall to atmospheric aerosol loading was discussed with regard to mass-weighted mean diameter and rain rate. This topic was evaluated only during the wet season due to the insignificant statistics of rainfall events for different aerosol loading ranges and the low frequency of precipitation events during the dry season. The impacts of aerosols on cloud droplet diameter varied based on droplet size. For the wet season, we observed no dependence between land surface type and rain rate. However, during the dry season, urban areas exhibited the largest rainfall rate tail distribution, and deforested regions exhibited the lowest mean rainfall rate. Airplane measurements were taken to characterize and contrast cloud microphysical properties and processes over forested and deforested regions. Vertical motion was not correlated with cloud droplet sizes, but cloud droplet concentration correlated linearly with vertical motion. Clouds over forested areas contained larger droplets than clouds over pastures at all altitudes. Finally, the connections between topography and rain rate were evaluated, with higher rainfall rates identified at higher elevations during the dry season.

Study on the Contamination of NH3-N and Total Phosphorus in the Seasonal River

2013 ◽  
Vol 864-867 ◽  
pp. 79-82
Author(s):  
Xue Ying Song ◽  
Xiao Jun Hu ◽  
Ru Jing Liang ◽  
Yu Shuang Liang ◽  
Wen Juan Sun
Keyword(s):  
Surface Water ◽  
Total Phosphorus ◽  
Industrial Wastewater ◽  
Quality Standards ◽  
Domestic Sewage ◽  
Dry Season ◽  
Main Stream ◽  
Wet Season ◽  
Permissible Levels ◽  
Taizi River

Water samples were collected from the upstream to the downstream of a seasonal river, the Taizi River, and its main tributaries in dry season, normal season, and wet season. The variations of NH3-N, and total phosphorus (TP) within a hydrological year were analyzed, aimed to study the pollution characteristics and sources of the water bodies. It was found that the tributaries of the Taizi River were heavily contaminated by NH3-N, with 83.8%, 100% and 100% of the sampling sites exceeding the fifth level in the dry season, wet season and normal season, respectively. The concentration of TP in the dry season fluctuated wildly, which was much higher than those in the wet and normal season. Compared with the permissible levels set by the environmental quality standards for surface water standard (GB3838-2002) of China, 57.1% of the sampling sites in the main stream and tributaries of the Taizi River belong to the fifth level or exceed the fifth level in the dry season, and only 7.1% of the sampling sites were belonging to the fifth level or exceed the fifth level in the wet and normal season. Overall, the waterbody of Taizi River was more seriously polluted by urban domestic sewage and point source of industrial wastewater.

scholarly journals Hydrogeological, hydrochemical, and natural isotopes evaluation of groundwater and surface water interactions in the alluvial plain, tropical region of southeastern Brazil

2021 ◽  
Author(s):  
Waldilene Correa ◽  
Sueli Pereira ◽  
Joaquim Ernesto Bernardes ◽  
Paulo Ricardo Pereira
Keyword(s):  
Surface Water ◽  
Groundwater Flow ◽  
Rainy Season ◽  
Dry Season ◽  
Alluvial Plain ◽  
Morphological Features ◽  
Southeastern Brazil ◽  
Wet Season ◽  
Natural Isotopes ◽  
Abandoned Meanders

Groundwater-Surface water interactions in alluvial plains facing morphological features are the subject of the study. Considered transitions zones, alluvial plains have different morphological features interfering with groundwater flow and hydrochemistry. The alluvial plain of Mogi Guaçu river (southeastern Brazil) presented topography-controlled groundwater flow, nevertheless, natural levees, wet fields, oxbow lakes, and abandoned meanders can control local flow and interfere in discharges points of the main river. Two sampling water campaigns were done in the dry and wet season for physicochemical and natural isotopes analysis, collecting in total 44 groundwaters samples from monitoring wells and eight water samples from the river, creek, and lake. The groundwaters in wet fields and terraces, and surface waters from creek and lake presented low mineralization (EC from 8 to 37 μS.cm), pH acidic (4.98 to 5.8), and essentially Ca and Na-HCO composition. River waters samples presented pH between 5.92 e 7.69 (acidic in the rainy season and basic in the dry season), and EC from 24.2 and 181.1 μS/cm (lower values in the wet season), Na-HCO and Na-HCO-SO (dry season) and Ca-HCO and Na-HCO (rainy season) compositions. In dry season groundwaters composition showed evolution from sodium mixed (SO – HCO) to bicarbonate waters and higher mineralization; in wet season waters varied from Ca to Na-HCO composition and low mineralization, denoting dilution due to rainwater infiltration. Closer to the river margins, in abandoned meanders and oxbows, the groundwaters have increased values of EC and major ions indicating GW-SW mixtures, and effluent-influent changes (descendent and ascendent flux) in wet and dry seasons, respectively. Natural isotopes in groundwaters imply meteoric origin, without evaporation during recharge and high d-excess can be influenced by continental air masses and Amazonia Basin low-level jet. Shallow water table, permeable silty-sand material of vadose zone, flat terrain, and pristine conditions can contribute to direct infiltration of rainwaters, recharging the shallow aquifer.

scholarly journals Investigating basin-scale water budget dynamics in 18 rivers across Tibetan Plateau through multiple datasets

2017 ◽  
Author(s):  
Wenbin Liu ◽  
Fubao Sun ◽  
Yanzhong Li ◽  
Guoqing Zhang ◽  
Yan-Fang Sang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Water Budget ◽  
Water Resource Management ◽  
Management Practices ◽  
Yellow River ◽  
Aridity Index ◽  
Surface Model ◽  
The Tibetan Plateau ◽  
Basin Scale

Abstract. The dynamics of basin-scale water budgets are not well understood nowadays over the Tibetan Plateau (TP) due to the lack of hydro-climatic observations. In this study, we investigate seasonal cycles and trends of water budget components (e.g., precipitation-P, evapotranspiration-ET and runoff-Q) in eighteen TP river basins during the period 1982–2011 through the use of multi-source datasets (e.g., in situ observations, satellite retrievals, reanalysis outputs and land surface model simulations). A water balance-based two-step procedure, which considers the changes in basin-scale water storage at the annual scale, is also adopted to calculate actual ET. The results indicated that precipitation (mainly snowfall from mid-autumn to next spring), which mainly concentrated during June–October (varied among different monsoons-impacted basins), was the major contributor to the runoff in TP basins. Increased P, ET and Q were found in most TP basins during the past 30 years except for the upper Yellow River basin and some sub-basins of Yalong River, which were mainly affected by the weakening East Asian Monsoon. Moreover, the aridity index (PET/P) and runoff coefficient (Q/P) decreased in most basins, which were in agreement with the warming and moistening climate in the Tibetan Plateau. The results obtained demonstrated the usefulness of integrating multi-source datasets to hydrological applications in the data-sparse regions. More generally, such approach might offer helpful insights towards understanding the water and energy budgets and sustainability of water resource management practices of data-sparse regions in a changing environment.

scholarly journals Evaluation of the JULES land surface model in simulating catchment hydrology in Southern Africa

2013 ◽  
Vol 10 (8) ◽  
pp. 11093-11128 ◽  
Author(s):  
N. C. MacKellar ◽  
S. J. Dadson ◽  
M. New ◽  
P. Wolski
Keyword(s):  
Southern Africa ◽  
Land Surface ◽  
River Discharge ◽  
Water Resource Management ◽  
River Flow ◽  
Land Surface Model ◽  
Dry Season ◽  
Surface Model ◽  
Runoff Generation ◽  
Subsurface Runoff

Abstract. Land surface models (LSMs) are advanced tools which can be used to estimate energy, water and biogeochemical exchanges at regional scales. The inclusion of a river flow routing module in an LSM allows for the simulation of river discharge from a catchment and offers an approach to evaluate the response of the system to variations in climate and land-use, which can provide useful information for regional water resource management. This study offers insight into some of the pragmatic considerations of applying an LSM over a regional domain in Southern Africa. The objectives are to identify key parameter sensitivities and investigate differences between two runoff production schemes in physically contrasted catchments. The Joint UK Land Environment Simulator (JULES) LSM was configured for a domain covering Southern Africa at a 0.5° resolution. The model was forced with meteorological input from the WATCH Forcing Data for the period 1981–2001 and sensitivity to various model configurations and parameter settings were tested. Both the PDM and TOPMODEL sub-grid scale runoff generation schemes were tested for parameter sensitivities, with the evaluation focussing on simulated river discharge in sub-catchments of the Orange, Okavango and Zambezi rivers. It was found that three catchments respond differently to the model configurations and there is no single runoff parameterization scheme or parameter values that yield optimal results across all catchments. The PDM scheme performs well in the upper Orange catchment, but poorly in the Okavango and Zambezi, whereas TOPMODEL grossly underestimates discharge in the upper Orange and shows marked improvement over PDM for the Okavango and Zambezi. A major shortcoming of PDM is that it does not realistically represent subsurface runoff in the deep, porous soils typical of the Okavango and Zambezi headwaters. The dry-season discharge in these catchments is therefore not replicated by PDM. TOPMODEL, however, simulates a more realistic seasonal cycle of subsurface runoff and hence improved dry-season flow.

scholarly journals Spatial Assessment of Land Surface Temperature and Emissivity in the Tropical Littoral City of Port Harcourt, Nigeria

2019 ◽  
pp. 88-103 ◽  
Author(s):  
P. Nwaerema ◽  
Ojeh N. Vincent ◽  
C. Amadou ◽  
Atuma, I. Morrison
Keyword(s):  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Dry Season ◽  
Wet Season ◽  
City Center ◽  
Multiple Wavelength ◽  
Port Harcourt ◽  
Land Surfaces ◽  
The City

The study examined Land Surface Temperature (LST) and Land Surface Emissivity (LSE) in a tropical coastal city of Port Harcourt and its environs. Satellite remote sensing of multiple-wavelength origin was employed to derive data from the Landsat Enhance Thematic Mapper (ETM+). Statistical mean and range were used to show pattern of LST and LSE. The study established the relationship and characteristics of land use land cover, built-up area and influence of population on land surfaces. With population of over 3,095,342 persons occupying surface area of approximately 458,28 Km2, rapid vegetal and water body lost have put the city area under pressure of 4.7°C heat bias at the interval of 15 years. From rural fringes to the city center, LST varies with 9.3°C in wet season and 4.8°C in the dry season. During the dry season, LSE is severe in the southern part of the city contributed by water bodies, more vegetal cover and urban pavement materials. Emissivity in the wet season varied with 0.0136 and 0.0006 during the dry season but differs with 0.0165 between the two seasons. One critical finding is that LSE decreases from the rural fringes to the city center and LST increases from the rural fringes to the city center. It is recommended that urban greening at the city center should be practiced and the rural fringes should be explored by decongesting activities at the city center to the outskirts in order to ameliorate the effects of urban heat bias without further delay.

Seasonal Variations of the Regular Indices of the Surface Water in the Taizi River

2014 ◽  
Vol 513-517 ◽  
pp. 4486-4489
Author(s):  
Xiao Jun Hu ◽  
Li Qi Sun ◽  
Xue Ying Song ◽  
Wen Juan Sun ◽  
Ru Jing Liang
Keyword(s):  
Surface Water ◽  
Seasonal Variations ◽  
Dry Season ◽  
Liaoning Province ◽  
Wet Season ◽  
Ph Values ◽  
Northeast Of China ◽  
Taizi River

The regular indices of the surface water of the Taizi River, Liaoning Province, northeast of China, were investigated. Samples were collected from upstream to downstream locations of the mainstream, and also from the tributaries of the Taizi River in dry season, wet season, and normal season, respectively. The DO values of the surface water ranged from 3.35 mg/L to 18.73 mg/L, 0.09 mg/L to 13.44mg/L, and 3.49 mg/L to 16.9 mg/L, respectively, in the dry season, wet season, and normal season, respectively. The seasonal variations of the pH values of the surface water were in the order of dry season >wet season >normal season.

scholarly journals Overview: Precipitation Characteristics and Sensitivities to the Environmental Conditions during GoAmazon2014/5 and ACRIDICON-CHUVA

2017 ◽  
Author(s):  
Luiz A. T. Machado ◽  
Alan J. P. Calheiros ◽  
Thiago Biscaro ◽  
Scott Giangrande ◽  
Maria A. F. Silva Dias ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Land Surface ◽  
Rain Rate ◽  
Vertical Motion ◽  
Cloud Droplet ◽  
Dry Season ◽  
Wet Season ◽  
Dry Seasons ◽  
The Mean ◽  
Wet And Dry Seasons

Abstract. Abstract. This is study provides an overview of precipitation processes and their sensitivities to environmental conditions, in the Central Amazon Basin, during the GoAmazon2014/5 and ACRIDICON-CHUVA experiments. Taking advantage of the numerous measuring platforms and instruments systems operating during both campaigns sampling cloud structure and environmental conditions during 2014 and 2015, the rainfall variability among seasons, aerosol loading, land surface type, and topography have carefully been characterized. Differences between the wet and dry seasons were examined from a variety of different perspectives. The rain rate distribution, the total amount of rainfall, and the raindrop size distribution (the mean mass-weighted diameter) were quantified for the two seasons. The dry season has a higher average rain rate than the wet season and reflects more intense rain. While the cumulative wet season rainfall amount was four times larger than the total dry season rainfall, reflecting in large total rainfall accumulation. The typical size and life cycle of the Amazon cloud clusters (observed by satellite) and rain cells (observed by radar) were examined, as well their differences among the seasons. Moreover, we analyse the monthly mean thermodynamical and dynamical variables, measured by radiosondes to elucidate the differences in rainfall characteristics during the wet and dry seasons. The sensitivity of rainfall to the atmospheric aerosol loading is discussed with regard to the mean mass-weighted diameter and rain rate. This topic was evaluated during the wet season only due to the insignificant statistics of rainfall events for different ranges of aerosol loadings and the low frequency of precipitation events during the dry season. The aerosol impacts on the cloud droplet diameter is different for small and large drops. For the wet season, we observe no dependence on land surface type on the rain rate. However, during the dry season, urban areas exhibit the largest rain rate tail distribution, and deforested regions have the lowest mean rain rate. Airplane measurements were performed to characterize and contrast cloud microphysical properties and processes over forested and deforested regions. The vertical motion turned out to be uncorrelated with cloud droplet sizes, but the cloud droplets number concentration revealed a linear relationship to the vertical motion. Clouds over forest exhibit larger droplets than clouds over pastures at all cloud levels. Finally, the connections between topography and rain rate were evaluated, showing a higher rain rate over higher elevations for the dry season.

Sign in / Sign up

Export Citation Format

Share Document