A simple and efficient model for orographic precipitation

Hergarten, Stefan; Robl, Jörg

doi:10.5194/gmd-2021-179

Cited by 4 publications

(3 citation statements)

References 29 publications

(64 reference statements)

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“…During the summer, heating of the atmosphere in the south of the CH (Terai) region amplifies atmospheric instability due to orographic lifting, resulting in deep convective events in that region [34]. Previous studies using the orographic moisture flux (OMF) and evapotranspiration showed that orographic lifting influences precipitation significantly [3,41,42]. Trapero et al (2013) argued that the OMF values were high in a conditionally unstable environment (high CAPE) [42].…”

Section: Resultsmentioning

confidence: 99%

Modeling Lightning Activity in the Third Pole Region: Performance of a km-Scale ICON-CLM Simulation

Singh,

Ahrens

2023

Atmosphere

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The Third Pole region, especially the Himalayas, is a lightning hotspot. Predicting lightning activity in this region is difficult due to the complex monsoon and westerly circulations, as well as the complex orography. Km-scale simulations can explicitly, without parameterization, tackle deep convective phenomena. A year-long (October 2019–September 2020) ICON-CLM simulation was performed with a km-scale horizontal grid spacing of 3.3 km to assess the region’s lightning activity and evaluate the model ICON-CLM. The simulated lightning potential index (LPI) was compared against the lightning proxy CAPE × PREC (CP) derived from ICON-CLM and reanalysis ERA5. In addition, the LPI was evaluated against the TRMM lightning climatology and observed flashes from the International Space Station Lightning Imaging Sensor (ISS-LIS). The LPI reproduced the major spatial, seasonal, and diurnal features of lightning activity as represented in the TRMM climatology. In contrast, the CP from both ICON-CLM and ERA5 performed less well regarding the location of events and the diurnal features. Taking the mean values of the LPI and CP of all the grids within 90 km × 90 km around the ISS-LIS detected lightning event, we found that over 80% of lightning events were recorded using the ICON-CLM simulation. Analysis of individual cases showed that the LPI predicted localization of lightning events better, but flash counts were slightly lower than the CP. Therefore, the combined use of ICON-CLM’s simulated LPI and CP can be a valuable predictor for lightning events over the Third Pole region.

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Section: Resultsmentioning

confidence: 99%

Modeling Lightning Activity in the Third Pole Region: Performance of a km-Scale ICON-CLM Simulation

Singh,

Ahrens

2023

Atmosphere

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“…Code and data availability. All codes are available in a Zenodo repository at https://doi.org/10.5281/zenodo.10473156 (Hergarten, 2024b). This repository also contains the data obtained from the numerical simulations.…”

Section: Discussionmentioning

confidence: 99%

A simple model for faceted topographies at normal faults based on an extended stream-power law

Hergarten

2024

Preprint

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Abstract. Faceted topographies at normal faults have been studied for more than a century. Since the dip angle of the facets is typically much lower than the dip angle of the fault, it is clear that the facets are not just the exhumed footwall, but have been eroded considerably. It has also been shown that a constant erosion rate in combination with a constant rate of displacement can explain the occurrence of planar facets. Quantitatively, however, the formation of faceted topographies is still not fully understood. In this study, the shared stream-power model for ﬂuvial erosion and sediment transport is used in combination with a recently published extension for hillslopes. As a major theoretical result, it is found that the ratio of the tangent of the facet angle and the dip angle of the fault as well as the ratio of baseline length and horizontal width of perfect triangular facets mainly depends on the ratio of the horizontal rate of displacement and the hillslope erodibility. Numerical simulations reveal that horizontal displacement is crucial for the formation of triangular facets. For vertical faults, facets are rather polygonal and much longer than wide. While the sizes of individual facets vary strongly, the average size is controlled by the ratio of hillslope erodibility and ﬂuvial erodibility.

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“…The open-source landform evolution model OpenLEM (http://hergarten.at/openlem) is employed for all numerical simulations. Since focus is on a minimum scenario, none of the components of OpenLEM beyond fluvial erosion and sediment transport, such as lithospheric flexure and orographic precipitation (Hergarten and Robl, 2021), are used. The fluvial model implemented in OpenLEM is presumably the simplest model of large-scale fluvial erosion and sediment transport.…”

Section: Introductionmentioning

confidence: 99%

Theoretical and numerical considerations of rivers in a tectonically inactive foreland

Hergarten

2022

Preprint

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Abstract. Recent advances in the numerics of fluvial landform evolution models allow for large-scale simulations of erosion and sediment transportover time spans of several million years. This study aims at finding out fundamental properties of rivers in a tectonically inactive foreland of a mountain range by investigating a simple reference scenario. This scenario consists of a mountain range and a foreland in a quasi-steady state where the material eroded in the mountain range is routed through the foreland. In order to understand the properties of foreland rivers, a subdivision into two classes – carriers and redistributors – is introduced. Carriers originate in the mountain range and are thus responsible for the large-scale sediment transport to the ocean. In turn,redistributors are rivers whose entire catchment is located in the foreland. Using the concept of carriers and redistributors, it is shown that the drainage network in the foreland permanently reorganizes, so that a steady state in the strict sense is impossible. However, the longitudinal profiles of carriers are described well by a steady-state approximation. Their concavity index is considerably greater than that of rivers in the mountain range. Carriers are predominantly depositing sediment at high rates, while redistributors are eroding at much lower rates. Despite the low erosion rates, the sediment flux from redistributors into carriers is a major component of the overall sediment budget and finally the main driver of the highly dynamic behavior of the carriers.

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A simple and efficient model for orographic precipitation

Cited by 4 publications

References 29 publications

Modeling Lightning Activity in the Third Pole Region: Performance of a km-Scale ICON-CLM Simulation

Modeling Lightning Activity in the Third Pole Region: Performance of a km-Scale ICON-CLM Simulation

A simple model for faceted topographies at normal faults based on an extended stream-power law

Theoretical and numerical considerations of rivers in a tectonically inactive foreland

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