scholarly journals Assessing the Roles of Terrestrial Stilling and Solar Dimming in Land Surface Drying/Wetting across China

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1996
Author(s):  
Kai Duan ◽  
Jiali Guo ◽  
Tiesong Hu ◽  
Xianxun Wang ◽  
Yadong Mei
Keyword(s):  
Wind Speed ◽  
Land Surface ◽  
River Basins ◽  
Evaporative Demand ◽  
The Past ◽  
The North ◽  
Attribution Analysis ◽  
Huai River ◽  
Surface Drying ◽  
Spatially Varying

Decreases in wind speed (i.e., terrestrial stilling) and radiation (i.e., solar dimming) have been identified as important causes of aridity change both globally and regionally. To understand how their roles have varied across different natural and socioeconomic circumstances in China, this study presents a nationwide attribution analysis of land surface drying/wetting across the ten first-level river basins. The results suggest that consistent warming and reductions in relative humidity have significantly enhanced atmospheric evaporative demand and driven the land surface to become drier over the past six decades. However, the widespread terrestrial stilling and solar dimming have largely offset such trends by suppressing evaporation. While spatially varying changes in precipitation were the most influential driver of aridity change over half of the 713 used climate sites, decreasing wind speed and radiation were identified as the dominant cause of wetting at 15% and 13% of the sites, respectively. The impacts of terrestrial stilling and solar dimming were generally more prominent in the north (e.g., the Liao River, Songhuajiang, Hai River, and Huai River basins) and south (e.g., the Southeast, Pearl River, and Yangtze River basins) respectively, which could be associated with the weakening monsoon and intensified anthropogenic disturbances such as ecological restoration, urbanization, and air pollution. We conclude that more attention needs to be paid to the independent and combined climatological impacts of global- and regional-level human activities to develop proactive adaptation strategies of water and land management.

scholarly journals The Evaporative Demand Drought Index. Part I: Linking Drought Evolution to Variations in Evaporative Demand

2016 ◽  
Vol 17 (6) ◽  
pp. 1745-1761 ◽  
Author(s):  
Michael T. Hobbins ◽  
Andrew Wood ◽  
Daniel J. McEvoy ◽  
Justin L. Huntington ◽  
Charles Morton ◽  
...  
Keyword(s):  
Land Surface ◽  
Drought Index ◽  
Drought Indices ◽  
Evaporative Demand ◽  
The North ◽  
Physically Based ◽  
Surface Drying ◽  
American Society ◽  
Land Data Assimilation System ◽  
Reference Et

Abstract Many operational drought indices focus primarily on precipitation and temperature when depicting hydroclimatic anomalies, and this perspective can be augmented by analyses and products that reflect the evaporative dynamics of drought. The linkage between atmospheric evaporative demand E0 and actual evapotranspiration (ET) is leveraged in a new drought index based solely on E0—the Evaporative Demand Drought Index (EDDI). EDDI measures the signal of drought through the response of E0 to surface drying anomalies that result from two distinct land surface–atmosphere interactions: 1) a complementary relationship between E0 and ET that develops under moisture limitations at the land surface, leading to ET declining and increasing E0, as in sustained droughts, and 2) parallel ET and E0 increases arising from increased energy availability that lead to surface moisture limitations, as in flash droughts. To calculate EDDI from E0, a long-term, daily reanalysis of reference ET estimated from the American Society of Civil Engineers (ASCE) standardized reference ET equation using radiation and meteorological variables from the North American Land Data Assimilation System phase 2 (NLDAS-2) is used. EDDI is obtained by deriving empirical probabilities of aggregated E0 depths relative to their climatologic means across a user-specific time period and normalizing these probabilities. Positive EDDI values then indicate drier-than-normal conditions and the potential for drought. EDDI is a physically based, multiscalar drought index that that can serve as an indicator of both flash and sustained droughts, in some hydroclimates offering early warning relative to current operational drought indices. The performance of EDDI is assessed against other commonly used drought metrics across CONUS in Part II.

Two parameters are required for a Budyko function to describe the land-atmosphere interaction

2021 ◽  
Author(s):  
Daeha Kim ◽  
Jong Ahn Chun
Keyword(s):  
Land Surface ◽  
River Basins ◽  
Control Surface ◽  
Primary Control ◽  
Evaporative Demand ◽  
Atmosphere Interaction ◽  
The Mean ◽  
Two Parameters ◽  
Two Parameter ◽  
Surface Changes

<p>While the Budyko framework has been a simple and convenient tool to assess runoff (Q) responses to climatic and surface changes, it has been unclear how parameters of a Budyko function represent the vertical land-atmosphere interactions. Here, we explicitly derived a two-parameter equation by correcting a boundary condition of the Budyko hypothesis. The correction enabled for the Budyko function to reflect the evaporative demand (E<sub>p</sub>) that actively responds to soil moisture deficiency. The derived two-parameter function suggests that four physical variables control surface runoff; namely, precipitation (P), potential evaporation (E<sub>p</sub>), wet-environment evaporation (E<sub>w</sub>), and the catchment properties (n). We linked the derived Budyko function to a definitive complementary evaporation principle, and assessed the relative elasticities of Q to climatic and land surface changes. Results showed that P is the primary control of runoff changes in most of river basins across the world, but its importance declined with climatological aridity. In arid river basins, the catchment properties play a major role in changing runoff, while changes in E<sub>p</sub> and E<sub>w</sub> seem to exert minor influences on Q changes. It was also found that the two-parameter Budyko function can capture unusual negative correlation between the mean annual Q and E<sub>p</sub>. This work suggests that at least two parameters are required for a Budyko function to properly describe the vertical interactions between the land and the atmosphere.</p>

Analysis of the past and future water resources of the Pyrenees by means of a land-surface simulation

2020 ◽  
Author(s):  
Pere Quintana-Seguí ◽  
Anaïs Barella-Ortiz ◽  
Omar Cenobio-Cruz ◽  
Jean-Philippe Vidal ◽  
Ane Zabaleta
Keyword(s):  
Water Resources ◽  
Land Surface ◽  
Water Cycle ◽  
National Level ◽  
River Basins ◽  
Surface Model ◽  
Future Evolution ◽  
Daily Streamflow ◽  
The Past ◽  
Monthly Streamflow

<p>The Pyrenees are the "Water Towers" of several key river basins in France, Andorra and Spain, being the Adour-Garonne and the Ebro the largest ones. The water of these basins is used by agricultural and industrial economic sectors which have a significant socioeconomic impact. Furthermore, the water of these rivers also sustains ecosystems which have an intrinsic value and provide ecosystem services to society. For this reason, an assessment of the past and future evolution of the water resources of the Pyrenees is necessary. Until now, these assessments have often been done at the basin or at the national level, but never the water resources of the Pyrenees were assessed as a whole. This is the main aim of the PIRAGUA project, within which we develop our research.</p><p>In order to simulate the continental water cycle of the Pyrenees we have used the SASER (SAFRAN-SURFEX-Eaudyssée-RAPID) modeling chain. SAFRAN is a meteorological analysis system, that allows us to create a gridded dataset of all the variables needed by the SURFEX land-surface model. SURFEX’s outflows (runoff and drainage) are used by Eaudyssée and RAPID to calculate streamflow.</p><p>Until now there were two separate implementation of SAFRAN in France (8 km resolution) and Spain (5 km resolution). For this project we have taken the climatic zone level SAFRAN data of both countries and interpolated it to a new common grid at a resolution of 2.5 km. The dataset covers a domain that includes the Adour-Garonne, the Ebro and all other Pyrenean river basins, its time period is 1979/80-2014/15 (which will be extended to 2016/17). The RAPID river routing scheme has been implemented in the simulation domain using HydroSheds to describe the river network.</p><p>In order to simulate the future evolution of the continental water cycle we use the Pyrenean climate scenarios developed within the CLIMPY project. These include precipitation and maximum and minimum temperature. SURFEX needs other variables too, such as wind speed, relative humidity and radiation. We solve this problem using an analog based approach similar to Clemins et al (2019).</p><p>The simulated streamflow is compared to observed streamflow of natural basins. The results show that 18 (out of 38) non influenced stations present a KGE of daily streamflow larger than 0.5. For monthly streamflow, KGE is larger than 0.5 on 22 stations (out of 38).</p><p>The next steps of our research are to quantify the improvement due to the increased resolution (comparing to a lower resolution simulation), calculate trends of relevant variables at the sub-bassin scale and compared them to the observed ones in the past, and analyze future trends of these variables. Finally, we will assess the impacts of these changes on water resources.</p><p>This research is funded by the EFA210/16-PIRAGUA project, within the INTERREG V-A España-Francia-Andorra POCTEFA2014-2020 program.</p>

scholarly journals What Drives the Variability of Evaporative Demand across the Conterminous United States?

2012 ◽  
Vol 13 (4) ◽  
pp. 1195-1214 ◽  
Author(s):  
Michael Hobbins ◽  
Andrew Wood ◽  
David Streubel ◽  
Kevin Werner
Keyword(s):  
United States ◽  
Wind Speed ◽  
Time Scales ◽  
Land Surface ◽  
Longwave Radiation ◽  
Mean Value ◽  
Specific Humidity ◽  
Shortwave Radiation ◽  
Evaporative Demand ◽  
System Variables

Abstract To understand the sources of temporal and spatial variability of atmospheric evaporative demand across the conterminous United States (CONUS), a mean-value, second-moment uncertainty analysis is applied to a spatially distributed dataset of daily synthetic pan evaporation for 1980–2009. This evaporative demand measure is from the “PenPan” model, which is a combination equation calibrated to mimic observations from U.S. class-A evaporation pans and here driven by six North American Land Data Assimilation System variables: temperature, specific humidity, station pressure, wind speed, and downwelling shortwave and longwave radiation. The variability of evaporative demand is decomposed across various time scales into contributions from these drivers. Contrary to popular expectation and much hydrologic practice, temperature is not always the most significant driver of temporal variability in evaporative demand, particularly at subannual time scales. Instead, depending on the season, one of four drivers (temperature, specific humidity, downwelling shortwave radiation, and wind speed) dominates across different regions of CONUS. Temperature generally dominates in the northern continental interior. This analysis assists land surface modelers in balancing parameter parsimony and physical representativeness. Patterns of dominant drivers are shown to cycle seasonally, with clear implications for modeling evaporative demand in operational hydrology or as a metric of climate change and variability. Depending on the region and season, temperature, specific humidity, downwelling shortwave radiation, and wind speed must together be examined, with downwelling longwave radiation as a secondary input. If any variable may be ignored, it is atmospheric pressure. Parameterizations of evaporative demand based solely on temperature should be avoided at all time scales.

scholarly journals The distribution and trends of fog and haze in the North China Plain over the past 30 years

2014 ◽  
Vol 14 (11) ◽  
pp. 16123-16149 ◽  
Author(s):  
G. Q. Fu ◽  
W. Y. Xu ◽  
R. F. Rong ◽  
J. B. Li ◽  
C. S. Zhao
Keyword(s):  
Wind Speed ◽  
North China Plain ◽  
North China ◽  
Formation Mechanisms ◽  
The Past ◽  
The North ◽  
The North China Plain ◽  
Low Visibility ◽  
Increasing Trends ◽  
Fog Days

Abstract. Frequent low visibility, haze and fog events were found in the North China Plain (NCP). Data throughout the NCP during the past 30 years were examined to determine the horizontal distribution and decadal trends of low visibility, haze and fog events. The impact of meteorological factors such as wind and RH on those events was investigated. Results reveal distinct distributions of haze and fog days, due to their different formation mechanisms. Low visibility, haze and fog days all display increasing trends of before 1995, a steady stage during 1995–2003 and a drastically drop thereafter. All three events occurred most frequently during the heating season. Benefiting from emission control measures, haze and fog both show decreasing trends in winter during the past 3 decades, while summertime haze displays continuous increasing trends. The distribution of wind speed and wind direction as well as the topography within the NCP has determinative impacts on the distribution of haze and fog. Weakened south-easterly winds in the southern part of the NCP has resulted in high pollutant concentrations and frequent haze events along the foot of the Taihang Mountains. The orographic wind convergence zone in the central band area of the southern NCP is responsible for the frequent fog events in this region. Wind speed has been decreasing throughout the entire southern NCP, resulting in more stable atmospheric conditions and weaker dispersion abilities, calling for harder efforts to control emissions to prevent haze events. Haze events are strongly influenced by the ambient RH. RH values associated with haze days are evidently increasing, suggesting that an increasing fraction of haze events are caused by the hygroscopic growth of aerosols, rather than simply by high aerosol loadings.

Estimating Gridded Domestic Water Demand and Assessing its Vulnerability over South-East Asian Countries

2021 ◽  
Author(s):  
Manas Ranjan Panda ◽  
Yeonjoo Kim
Keyword(s):  
Water Demand ◽  
Land Surface ◽  
East Asian ◽  
River Basins ◽  
Living Standard ◽  
Asian Countries ◽  
Domestic Water ◽  
Domestic Water Demand ◽  
The Past ◽  
Mega Cities

<p>During the past three decades, the over-growing population of the south-east Asian countries is becoming a threat to the available potential water sources. This region also includes many developed as well as developing countries including Korea, China, Japan and India, and the higher rate of GDP growth also enhanced the living standard of people. As a result, the water scarcity has been increasing in various mega-cities of the region. Here, we present the assessment of grid-scale domestic water demand of each country by evaluating the gridded Domestic Structural Water Intensity (DSWI) over a period of 1995-2015 at a spatial resolution of 0.5°. We estimated yearly grid-scale DSWI with using the past economic development based on GDP and the population. Considering the gridded water demand, we assessed the vulnerability of major river basins of the region and the few cities having more than one million population. A few mega-cities in India located in arid and semi-arid regions of the river basins are already experiencing water stress. Developing such gridded dataset will give a better shape to project the future water demand by integrating the datasets within a water demand module of any land surface models.</p><p><strong>Acknowledgements</strong></p><p>This work was supported by a grant from the National Research Foundation of Korea funded by the Ministry of Science, ICT & Future Planning (2020R1A2C2007670).</p>

scholarly journals The distribution and trends of fog and haze in the North China Plain over the past 30 years

2014 ◽  
Vol 14 (21) ◽  
pp. 11949-11958 ◽  
Author(s):  
G. Q. Fu ◽  
W. Y. Xu ◽  
R. F. Yang ◽  
J. B. Li ◽  
C. S. Zhao
Keyword(s):  
Wind Speed ◽  
North China Plain ◽  
North China ◽  
Formation Mechanisms ◽  
The Past ◽  
The North ◽  
The North China Plain ◽  
Low Visibility ◽  
Increasing Trends ◽  
Fog Days

Abstract. Frequent low visibility, haze and fog events were found in the North China Plain (NCP). Data throughout the NCP during the past 30 years were examined to determine the horizontal distribution and decadal trends of low visibility, haze and fog events. The impact of meteorological factors such as wind and relative humidity (RH) on those events was investigated. Results reveal distinct distributions of haze and fog days, due to their different formation mechanisms. Low visibility, haze and fog days all display increasing trends of before 1995, a steady stage during the period 1995–2003 and a drastically drop thereafter. All three events occurred most frequently during the heating season. Benefiting from emission control measures, haze and fog both show decreasing trends in winter during the past 3 decades, while summertime haze displays continuous increasing trends. The distribution of wind speed and wind direction as well as the topography within the NCP has determinative impacts on the distribution of haze and fog. Weakened south-easterly winds in the southern part of the NCP have resulted in high pollutant concentrations and frequent haze events along the foot of the Taihang Mountains. The orographically generated boundary layer wind convergence line in the central area of the southern NCP is responsible for the frequent fog events in this region. Wind speed has been decreasing throughout the entire southern NCP, resulting in more stable atmospheric conditions and weaker dispersion abilities, calling for harder efforts to control emissions to prevent haze events. Haze events are strongly influenced by the ambient RH. RH values associated with haze days are evidently increasing, suggesting that an increasing fraction of haze events are caused by the hygroscopic growth of aerosols, rather than simply by high aerosol loadings.

Interrogating the Constitutionality of Federal Character Principle in Nigeria

2018 ◽  
Vol 9 (07) ◽  
pp. 20492-20498
Author(s):  
Aborisade Olasunkanmi ◽  
Christopher Agulanna
Keyword(s):  
Ethnic Groups ◽  
Research Work ◽  
National Unity ◽  
The Past ◽  
The North ◽  
Inhibiting Factors

This work interrogates federal character principle (FCP) in Nigeria. The FCP was designed to fundamentally address the striking features of Nigeria politics of intense struggles for power among the different ethnic groups in the country between the elites from the North and their Southern counterparts and the various segments, but the practice of FCP in Nigeria so far raises curiosity and doubts. Given the outcome of the interrogation, this research work discovered and conclude that federal character has not indeed achieve its objective in the Nigeria, the study finds that Ethnocentrism, Elitism, Mediocrity, Mutual suspicion amongst others accounts for some inhibiting factors of the FCP in Nigeria. Like many other provisions of the Constitution, the Federal Character principle was meant to correct some imbalances experienced in the past, but it has created more problems than it has attempted to solve. Rather than promote national unity, it has disunited Nigerians. There is an urgent need to use more of professionals and result oriented Nigerians to carry out national tasks, than to use unprogressive people due to this "Federal character" issue. Nigeria should be a place where one's track records and qualifications are far greater than just "where they come from" or their lineage if Nigerian truly want to progress.

Colchicum autumnale (Colchicaceae) w okolicach Krakowa – dawne i obecne rozmieszczenie

2019 ◽  
pp. 15-27
Author(s):  
Magdalena Zarzyka-Ryszka
Keyword(s):  
Adjacent Area ◽  
Colchicum Autumnale ◽  
The Past ◽  
The North ◽  
North Eastern ◽  
New Localities ◽  
Present Distribution ◽  
The 19Th Century ◽  
North Eastern Part

The paper describes the past and present distribution of Colchicum autumnale in the vicinity of Cracow, highlights the role of Stanisław Dembosz (who published the first locality of C. autumnale near Igołomia in 1841). Gives information about the occurrence of C. autumnale in Krzeszowice in the 19th century (reported by Bronisław Gustawicz), presents new localities noted in 2012–2014 in meadows in the north-eastern part of the Puszcza Niepołomicka forest and adjacent area (between the Vistula and Raba rivers), and gives a locality found in Cracow in 2005 (no longer extant).

Changing Characteristic of Land Surface Evapotranspiration and Soil Moisture in China during the Past 30 Years

2012 ◽  
Vol 14 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Longfei BING ◽  
Hongbo SU ◽  
Quanqin SHAO ◽  
Jiyuan LIU
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
The Past
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