Hillslope Form and Process: History 1960− 2000+

2021 ◽  
pp. M58-2021-8
Author(s):  
Mike Kirkby
Keyword(s):  
Land Surface ◽  
Drainage Density ◽  
Cold Climate ◽  
Lower Atmosphere ◽  
Tectonic Activity ◽  
Significant Advance ◽  
Mass Movements ◽  
Solution Processes ◽  
Process Understanding ◽  
Rapid Mass

AbstractThe study of hillslopes has been dominated by the expansion of studies into process rates and mechanisms. Perhaps the greatest volume of work has been on the ‘wash’ processes of soil erosion, but there has also been significant work on the diffusive mass movements of linear and non-linear ‘creep’ that shape the convexity of hilltops, on more rapid mass movements and on solution processes. There has also been fresh work on distinctive processes in coastal, arid and cold-climate environments.Accompanying and integrated with process understanding, and made possible by ubiquitous computational power, modelling has developed from soluble mathematical simplifications to complex simulations that incorporate much of our understanding of process and climate.Particular topics that have seen significant advance include a more complete understanding of drainage density and texture, and a broadening of interest to encompass the ‘critical zone’ that constructively unifies the land surface with the lower atmosphere, the biosphere and the regolith. There has also been a change of focus towards steeplands, dominated by mass movements, supply limited removal and tectonic activity.Most recently, and now incorporated into the concept of the ‘Anthropocene’, human impact is now receiving increasing attention as we acknowledge its accelerating role in changing landscapes and their relationships.

scholarly journals Sensitivity of land surface and Cumulus schemes for Thunderstorm prediction

2016 ◽  
Vol XLI-B8 ◽  
pp. 271-275
Author(s):  
Dinesh Kumar ◽  
U. C. Mohanty ◽  
Krishan Kumar
Keyword(s):  
Land Surface ◽  
Process Model ◽  
Atmospheric Condition ◽  
Surface Fluxes ◽  
Lower Atmosphere ◽  
Freezing Process ◽  
Precipitation Process ◽  
Convective System ◽  
Cumulus Schemes ◽  
Physical Parameterizations

The cloud processes play an important role in all forms of precipitation. Its proper representation is one of the challenging tasks in mesoscale numerical simulation. Studies have revealed that mesoscale feature require proper initialization which may likely to improve the convective system rainfall forecasts. Understanding the precipitation process, model initial condition accuracy and resolved/sub grid-scale precipitation processes representation, are the important areas which needed to improve in order to represent the mesoscale features properly. Various attempts have been done in order to improve the model performance through grid resolution, physical parameterizations, etc. But it is the physical parameterizations which provide a convective atmosphere for the development and intensification of convective events. Further, physical parameterizations consist of cumulus convection, surface fluxes of heat, moisture, momentum, and vertical mixing in the planetary boundary layer (PBL). How PBL and Cumulus schemes capture the evolution of thunderstorm have been analysed by taking thunderstorm cases occurred over Kolkata, India in the year 2011. PBL and cumulus schemes were customized for WSM-6 microphysics because WSM series has been widely used in operational forecast. Results have shown that KF (PBL scheme) and WSM-6 (Cumulus Scheme) have reproduced the evolution of surface variable such as CAPE, temperature and rainfall very much like observation. Further, KF and WSM-6 scheme also provided the increased moisture availability in the lower atmosphere which was taken to higher level by strong vertical velocities providing a platform to initiate a thunderstorm much better. Overestimation of rain in WSM-6 occurs primarily because of occurrence of melting and freezing process within a deeper layer in WSM-6 scheme. These Schemes have reproduced the spatial pattern and peak rainfall coverage closer to TRMM observation. It is the the combination of WSM-6, and KF schemes which have preformed reasonably well to reproduce the right atmospheric condition for a thunderstorm leading to improved spatial and temporal rainfall over the study domain. Thus the parameterization schemes of WMS-6 and KF have shown significant improvement by capturing the location, intensity and surface meteorological parameters closer to observed details.

Late Quaternary aggradation and incision in the headwaters of the Yangtze River, eastern Tibetan Plateau, China

2021 ◽  
Author(s):  
Yang Yu ◽  
Xianyan Wang ◽  
Shuangwen Yi ◽  
Xiaodong Miao ◽  
Jef Vandenberghe ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Yangtze River ◽  
Late Quaternary ◽  
Cold Climate ◽  
Luminescence Dating ◽  
Tectonic Activity ◽  
The Yangtze River ◽  
Eastern Tibetan Plateau ◽  
Sedimentary Process ◽  
Fluvial Terraces

River aggradation or incision at different spatial-temporal scales are governed by tectonics, climate change, and surface processes which all adjust the ratio of sediment load to transport capacity of a channel. But how the river responds to differential tectonic and extreme climate events in a catchment is still poorly understood. Here, we address this issue by reconstructing the distribution, ages, and sedimentary process of fluvial terraces in a tectonically active area and monsoonal environment in the headwaters of the Yangtze River in the eastern Tibetan Plateau, China. Field observations, topographic analyses, and optically stimulated luminescence dating reveal a remarkable fluvial aggradation, followed by terrace formations at elevations of 55−62 m (T7), 42−46 m (T6), 38 m (T5), 22−36 m (T4), 18 m (T3), 12−16 m (T2), and 2−6 m (T1) above the present floodplain. Gravelly fluvial accumulation more than 62 m thick has been dated prior to 24−19 ka. It is regarded as a response to cold climate during the last glacial maximum. Subsequently, the strong monsoon precipitation contributed to cycles of rapid incision and lateral erosion, expressed as cut-in-fill terraces. The correlation of terraces suggests that specific tectonic activity controls the spatial scale and geomorphic characteristics of the terraces, while climate fluctuations determine the valley filling, river incision and terrace formation. Debris and colluvial sediments are frequently interbedded in fluvial sediment sequences, illustrating the episodic, short-timescale blocking of the channel ca. 20 ka. This indicates the potential impact of extreme events on geomorphic evolution in rugged terrain.

Geomorphic impacts of large and rapid mass movements: a review

2009 ◽  
Vol 15 (1) ◽  
pp. 4764 ◽  
Author(s):  
Monique Fort ◽  
Etienne Cossart ◽  
Philip Deline ◽  
Marc Dzikowski ◽  
Gérard Nicoud ◽  
...  
Keyword(s):  
Mass Movements ◽  
Rapid Mass

scholarly journals About this title - Subaqueous Mass Movements and their Consequences: Advances in Process Understanding, Monitoring and Hazard Assessments

10.1144/sp500 ◽  
2020 ◽  
Vol 500 (1) ◽  
pp. NP-NP
Author(s):  
A. Georgiopoulou ◽  
L. A. Amy ◽  
S. Benetti ◽  
J. D. Chaytor ◽  
M. A. Clare ◽  
...  
Keyword(s):  
Mass Movements ◽  
Submarine Landslides ◽  
Global Database ◽  
Spatial And Temporal Scales ◽  
Indonesian Archipelago ◽  
Process Understanding ◽  
Landslide Processes ◽  
New Research ◽  
Global Datasets

This volume focuses on underwater or subaqueous landslides with the overarching goal of understanding how they affect society and the environment. The new research presented here is the result of significant advances made over recent years in directly monitoring submarine landslides, in standardizing global datasets for quantitative analysis, constructing a global database and from leading international research projects. Subaqueous Mass Movements demonstrates the breadth of investigation taking place into subaqueous landslides and shows that, while events like the recent ones in the Indonesian archipelago can be devastating, they are at the smaller end of what the Earth has experienced in the past. Understanding the spectrum of subaqueous landslide processes, and therefore the potential societal impact, requires research across all spatial and temporal scales. This volume delivers a compilation of state-of-the-art papers covering topics from regional landslide databases to advanced techniques for in situ measurements, to numerical modelling of processes and hazards.

scholarly journals Urban heat island: Aerodynamics or imperviousness?

2019 ◽  
Vol 5 (4) ◽  
pp. eaau4299 ◽  
Author(s):  
Dan Li ◽  
Weilin Liao ◽  
Angela J. Rigden ◽  
Xiaoping Liu ◽  
Dagang Wang ◽  
...  
Keyword(s):  
Green Infrastructure ◽  
Rural Areas ◽  
Land Surface ◽  
Urban Heat Islands ◽  
Lower Atmosphere ◽  
Geographic Variations ◽  
Heat Islands ◽  
Urban Heat ◽  
The Difference ◽  
Urban And Rural Areas

More than half of the world’s population now live in cities, which are known to be heat islands. While daytime urban heat islands (UHIs) are traditionally thought to be the consequence of less evaporative cooling in cities, recent work sparks new debate, showing that geographic variations of daytime UHI intensity were largely explained by variations in the efficiency with which urban and rural areas convect heat from the land surface to the lower atmosphere. Here, we reconcile this debate by demonstrating that the difference between the recent finding and the traditional paradigm can be explained by the difference in the attribution methods. Using a new attribution method, we find that spatial variations of daytime UHI intensity are more controlled by variations in the capacity of urban and rural areas to evaporate water, suggesting that strategies enhancing the evaporation capability such as green infrastructure are effective ways to mitigate urban heat.

Surveillance of Vrancea active seismic region in Romania through time series satellite data

2014 ◽  
Vol 6 (2) ◽  
Author(s):  
Maria Zoran ◽  
Roxana Savastru ◽  
Dan Savastru
Keyword(s):  
Time Series ◽  
Satellite Data ◽  
Land Surface ◽  
Main Shock ◽  
Tectonic Activity ◽  
Wave Radiation ◽  
Outgoing Long Wave Radiation ◽  
Seismic Region ◽  
Long Wave ◽  
Long Wave Radiation

AbstractCumulative stress energy in active seismic regions caused by tectonic forces creates various earthquake precursors. This energy transformation may result in enhanced transient thermal infrared (TIR) emission, which can be detected through satellites equipped with thermal sensors like MODIS (Terra/Aqua) and AVHRR (NOAA). Satellite time-series data, coupled with ground based observations, where available, can enable scientists to survey pre-earthquake signals in the areas of strong tectonic activity. This paper presents observations made using time series MODIS and NOAA-AVHRR satellite data for derived multi-parameters including land surface temperature (LST), outgoing long-wave radiation (OLR), and mean air temperature (AT) for the moderate, 5.9 magnitude earthquake, which took place on the 27th of October, 2004, inthe seismic region of Vrancea, in Romania. Anomalous thermal infrared signals, reflected by a rise of several degrees celsius (°C) in LSTs, and higher OLR values were seen several days before the earthquake. AT values in the epicentral area also increased almost two days prior to the earthquake and intensified three days after the main shock. Increases in LSTs and OLR disappeared three days after the main shock. The survey and joint analysis of geospatial and in-situ geophysical information on land surface temperatures and outgoing long-wave radiation provides new insights into the field of seismic hazard assessment in Vrancea, a significant area of tectonic activity in Romania and Europe.

Upscaling runoff and evapotranspiration fluxes in the Little Washita watershed using physically-based hillslope models

2020 ◽  
Author(s):  
Fanny Picourlat ◽  
Emmanuel Mouche ◽  
Claude Mugler
Keyword(s):  
Land Surface ◽  
Reference Model ◽  
Drainage Density ◽  
Equivalent Model ◽  
Distributed Model ◽  
Climatic Data ◽  
Good Prediction ◽  
Surface Models ◽  
Physically Based ◽  
Physically Based Models

<p>Several authors in the literature, such as Khan (2014) and Loritz (2017), have previously suggested that 3D catchment hydrology can be predicted from 2D hillslope simulations. Following this idea, we propose an upscaling methodology for runoff and evapotranspiration fluxes. The first step consists of a geomorphic analysis of the studied watershed. The average mean slope and hillslope length are then used to build a 2D equivalent-hillslope model. The validity of the methodology is tested by comparing the resulting water balance with a 3D physically-based distributed model. 2D fluxes of the equivalent hillslope are converted into 3D by using the drainage density. This upscaling methodology is applied to the Little Washita (LW) watershed (Oklahoma, USA). Both the 3D reference model and the 2D equivalent model are built with the physically-based distributed code HydroGeoSphere, which is forced by LW reanalysis climatic data. Two decades are simulated. Regarding the evapotranspiration, the upscaling methodology with only one equivalent hillslope gives a good prediction of 3D fluxes. However, a combination of several hillslopes is needed for simulating the 3D flow rate at the basin’s outlet. This work on the decrease of model dimensionality is a first step in the upscaling process from 3D physically-based models to 1D column models used in global Land Surface Models.</p>

scholarly journals Building a field- and model-based climatology of local water and energy cycles in the cultivated Sahel – annual budgets and seasonality

2014 ◽  
Vol 11 (5) ◽  
pp. 4753-4808 ◽  
Author(s):  
C. Velluet ◽  
J. Demarty ◽  
B. Cappelaere ◽  
I. Braud ◽  
H. B.-A. Issoufou ◽  
...  
Keyword(s):  
Land Surface ◽  
Regional Climate ◽  
Surface Fluxes ◽  
Process Understanding ◽  
Land Use Types ◽  
Physically Based ◽  
Data Imprecision ◽  
Local Water ◽  
Physical Laws ◽  
And Storage

Abstract. In the African Sahel, energy and water cycling at the land surface is pivotal for regional climate, water resources and land productivity, yet it is still extremely poorly documented. As a step towards a comprehensive climatological description of surface fluxes in this area, this study provides estimates of average annual budgets and seasonal cycles for two main land use types of the cultivated Sahelian belt, rainfed millet crop and fallow bush. These estimates build on the combination of a 7 year field dataset from two typical plots in southwestern Niger with detailed physically-based soil-plant-atmosphere modelling, yielding a continuous, comprehensive set of water and energy flux and storage variables over the 7 year period. In this study case in particular, blending field data with mechanistic modelling is considered as making best use of available data and knowledge for such purpose. It extends observations by reconstructing missing data and extrapolating to unobserved variables or periods. Furthermore, model constraining with observations compromises between extraction of observational information content and integration of process understanding, hence accounting for data imprecision and departure from physical laws. Climatological averages of all water and energy variables, with associated sampling uncertainty, are derived at annual to subseasonal scales from the 7 year series produced. Similarities and differences in the two ecosystems behaviors are highlighted. Mean annual evapotranspiration is found to represent ~82–85% of rainfall for both systems, but with different soil evaporation/plant transpiration partitioning and different seasonal distribution. The remainder consists entirely of runoff for the fallow, whereas drainage and runoff stand in a 40–60% proportion for the millet field. These results should provide a robust reference for the surface energy- and water-related studies needed in this region. The model developed in this context has the potential for reliable simulations outside the reported conditions, including changing climate and land cover.

scholarly journals Geomorphological study of Kleinovitikos stream drainage network (Trikala prefecture - western Thessaly)

2018 ◽  
Vol 40 (3) ◽  
pp. 1365
Author(s):  
G. D. Bathrellos ◽  
H. D. Skilodimou ◽  
G. Livaditis ◽  
E. Verikiou-Papaspiridakou
Keyword(s):  
Quantitative Analysis ◽  
Drainage Density ◽  
Tectonic Activity ◽  
Mountain Range ◽  
Drainage Network ◽  
Drainage Pattern ◽  
Tectonic Structure ◽  
Tectonic Structures ◽  
Secondary Cracks ◽  
Prevailing Direction

The Kleinovitikos stream is a tributary ofPineios River in the Western Thessaly. Its basin drainages parts of mountain range of Southern Pindos as well as the mountain of Koziaka. In this study a quantitative analysis of drainage network was accomplished and the relation of tectonics features with the watershed and the channels of drainage network were investigated. The main channel of the drainage network is of 6th order, while the dominated type of the network is the trellis drainage pattern. The morphological slopes of the basin show various fluctuations. The gentle slopes express erosional landforms while the steep ones represent geological and tectonic structures. It was noted by the quantitative analysis of the drainage network that the geological and tectonic structure of the area affects in its evolution. Moreover, the outcrop of heterogeneous lithological formations in the basin affects the values of drainage density and frequency. The lithology and the secondary cracks involve in the prevailing direction of the watershed. The streams of 1st -3r order are controlled by the younger cracks; the younger cracks as well as the older Alpine cracks have an influence on the streams of 4' and 5' order, and the Alpine tectonic activity affects the stream of 6' order.

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